1986 B2 2.9L acceleration hesitation

[Jbrownjr]

Sorry, your last reply came in while I was typing. If extra fuel didnt change it, then we are looking at ignition or base engine. The O2 sensor might not have been warm enough during your check.
Sounds like everything in the ign system has been changed.
It sounds a bit (from your last description) like a cracked spark plug or plug/coil wire leak. (Arcing) but not if everything is new.
Is the capacitor on the coil power wire still there? It should be bolted to the coil mount frame and plugged into the grey one wire connector that connects to the red on the coil. (It controls voltage spikes from the ignition coil in the primary (12v) side)
Did you check for a partially restricted exhaust as Tiha suggested earlier?
Use a vacuum guage on a manifold port (the one on the fuel press reg will work)
Read it at idle and then around 2000rpm in neutral, (get it to run as smooth as you can when its revved up.) the vac should be 1-3”hg better at 2000 eg. 18”hg @idle and 21”hg at 2000.
If it drops and was running smooth, you probably have A plugged muffler or resonator.
If it wont run fairly smooth, dont trust the vacuum reading.
Good luck
Cheers

• Checked each spark plug (replaced within a year ago). None broken/damaged. One was slightly oil fouled. We cleaned it. No change.
• I used wire ties to make sure every wire was at least 1/4" apart at all times. No change.
• Capacitor on the coil power wire is there and bolted to the coil mount frame, and plugged into the grey connector.
• Cat and muffler are removed. Only the exhaust manifold and exhaust piping up to the point they join (right after the O2 sensor)

Interesting result from checking each wire with the timing gun...(see response to good01boydws below)

 

[Jbrownjr]

Now that you've done so much to eliminate possibilities:

If its still not running smoothly through MOST of the rpm range and only gets WORSE when accellerating, I'd suspect either a fairly significant cylinder (or cylinders) misfire or incorrect**** INITIAL timing. Both are easy to check.

(I forgot if you said the heads have ever been off that you know of, or the timing chain and gears replaced. If either have not, they could both potentially contribute to the problem.)

(Again, I misremember:
If you haven't already done so, double check a piston mechanically to see if TDC on the timing mark comb is where its supposed to be.)

Follow the adjustment procedure and try backing the distributor off a couple degrees at a time and after each adj, see if it has any effect. Then advance it back to where you started. Now move it forwards a couple degrees at a time and see how that effects it.

Even new wires can be marginal or less-than-optimally-routed, and possibly causing or helping to cause misfiring or cross firing.

Use a timing light on every sparkplug wire, stare into it and watch for a steady flashing rate at idle and also as you accelerate. Any misfiring will be seen as a break in the steady rate of flashing, which it should have (no matter what is going on fuel-wise) and would tell you where to concentrate.

****After XYZ thousand miles (especially if its been burning any significant amount of oil), there could be enough build up of deposits in the combustion chambers of some or all cylinders to raise the compression rate in those cylinders to the point that the "normal" ignition setting isn't what they want to see.

• Heads have not been removed since we've owned it. Timing gears were replaced about 4 months ago.
• We rotated the engine until Piston #1 was visually TDC, and the timing mark comb was at 0. (The pointer, not the circle view finder)
• I wire-tied each spark wire to ensure no contact. No change.
• I used the timing gun on each wire and could observe a ~1 second period of no light, which was almost immediately followed by a stumble. Every wire had the same pattern. We tend tested the wire coming from the coil to the distributor and saw the same behavior. Since we had an extra coil (warranty replacement a few months back when troubleshooting suggested that might be a fault, which it wasn't so we have two good ones (I think).

Ran out of time tonight to play with the distributor, but last time I adjusted it we got it running as smoothly as possible at the right timing mark. We can play with that again tomorrow evening.

Interesting observation off the coil pack. If we can't blame the coil pack for inconsistent firing, is there something upstream from there that may be at fault?

 

[L\Bronco]

• Heads have not been removed since we've owned it. Timing gears were replaced about 4 months ago.
• We rotated the engine until Piston #1 was visually TDC, and the timing mark comb was at 0. (The pointer, not the circle view finder)
• I wire-tied each spark wire to ensure no contact. No change.
• I used the timing gun on each wire and could observe a ~1 second period of no light, which was almost immediately followed by a stumble. Every wire had the same pattern. We tend tested the wire coming from the coil to the distributor and saw the same behavior. Since we had an extra coil (warranty replacement a few months back when troubleshooting suggested that might be a fault, which it wasn't so we have two good ones (I think).

Ran out of time tonight to play with the distributor, but last time I adjusted it we got it running as smoothly as possible at the right timing mark. We can play with that again tomorrow evening.

Interesting observation off the coil pack. If we can't blame the coil pack for inconsistent firing, is there something upstream from there that may be at fault?

If it was an old points system, I'd say the condenser was bad. But thats a TFI system, so all the coil controls are in the module. I think you said the distributor was replaced though. (Could be a bad module or pickup out of the box. (I always change them together)
Weird one for sure.
Cheers

 

[goodO1boydws]

• Heads have not been removed since we've owned it. Timing gears were replaced about 4 months ago.
• We rotated the engine until Piston #1 was visually TDC, and the timing mark comb was at 0. (The pointer, not the circle view finder)
• I wire-tied each spark wire to ensure no contact. No change.
• I used the timing gun on each wire and could observe a ~1 second period of no light, which was almost immediately followed by a stumble. Every wire had the same pattern. We tend tested the wire coming from the coil to the distributor and saw the same behavior. Since we had an extra coil (warranty replacement a few months back when troubleshooting suggested that might be a fault, which it wasn't so we have two good ones (I think).

Ran out of time tonight to play with the distributor, but last time I adjusted it we got it running as smoothly as possible at the right timing mark. We can play with that again tomorrow evening.

Interesting observation off the coil pack. If we can't blame the coil pack for inconsistent firing, is there something upstream from there that may be at fault?

You wrote:

Timing gears were replaced about 4 months ago.
(I assume you replaced the chain at the same time.)

From a performance standpoint, its possible to have a very noticible problem if the cam is out of time with the crank, (and that's fairly easy to do when replecing the gear and chain set) but it would NOT explain the uniform one second ignition drop out on all cylinders.

One second in electronics is a very long time.
Unless it is only part of a series of steps in a process or more than one thing going on at once, that results in the drop out-at least one of of which is NOT electronic.

That long of a delay, and its uniformity, THAT HAPPENS ONLY WHEN ACCELLERATING, is interesting. It almost sounds like something including vacuum.

AT IDLE, have you tried very short burst of carb cleaner directed, one at a time with pauses between, at all of the vacuum connections and hoses, to see if the idle speed picks up?

Also, as to initial timing,check this out.
Its a stepwise list of how to set the initial timing and note what it says in step 3. Did you do that when setting the itiming?

How to Set the Timing on a Ford 2.9L

The Ford 2.9-liter, V-6 engine was built in Cologne, Germany and thus nicknamed the Ford Cologne engine. The Ford 2.9-liter engine was used on the Ford Bronco II, a compact SUV. The engine's ignition timing determines when a spark will occur to start the engine. The 2.9-liter engine has an...

itstillruns.com

 

[Jbrownjr]

You wrote:

Timing gears were replaced about 4 months ago.
(I assume you replaced the chain at the same time.)

From a performance standpoint, its possible to have a very noticible problem if the cam is out of time with the crank, (and that's fairly easy to do when replecing the gear and chain set) but it would NOT explain the uniform one second ignition drop out on all cylinders.

One second in electronics is a very long time.
Unless it is only part of a series of steps in a process or more than one thing going on at once, that results in the drop out-at least one of of which is NOT electronic.

That long of a delay, and its uniformity, THAT HAPPENS ONLY WHEN ACCELLERATING, is interesting. It almost sounds like something including vacuum.

AT IDLE, have you tried very short burst of carb cleaner directed, one at a time with pauses between, at all of the vacuum connections and hoses, to see if the idle speed picks up?

Also, as to initial timing,check this out.
Its a stepwise list of how to set the initial timing and note what it says in step 3. Did you do that when setting the itiming?

How to Set the Timing on a Ford 2.9L

The Ford 2.9-liter, V-6 engine was built in Cologne, Germany and thus nicknamed the Ford Cologne engine. The Ford 2.9-liter engine was used on the Ford Bronco II, a compact SUV. The engine's ignition timing determines when a spark will occur to start the engine. The 2.9-liter engine has an...

itstillruns.com

We suspected the timing gears about 6 months ago and took it to a local (ex-Ford) mechanic. He took off the front-end and verified everything was copasetic there. (Replaced gears while he was in there) I don't recall if he replaced or just validated the timing chain. Waiting for a response from him now.

I remember that vacuum test at some point a year or so ago. That was before the main wiring harness was replaced. We can run through that again. (as well as playing with the distributor)

Those timing instructions...we did remove the spout connector, but what is "Engage the warm idle speed option on the idle speed control valve located by the engine."?
I am also unfamiliar with "Disconnect the distributor vacuum hose and plug it into the electronic spark computer. [Use jumper cables](https://itstillruns.com/use-jumper-cables-4500480.html) to ground the carburetor switch."?

 

[goodO1boydws]

This was the quickest link I could find to the 2.9L engine, and ididn't read it closely enough to notice that it was covering many years and applications of the 2.9L. Sorrry about that.

Mainly wanted to see if you had removed the spout connector-some people don't and the initial timing can be off significantly because of it.

It would be kinda surprising if the chain wasn't changed by an ex-Ford mech at the same time as the gears since he was in there. Plus the tensioner/gears/chain/guide set isn't that much than only the gear set. Just looked for it on rockauto and the 5 piece Melling set including the tensioner/gears/chain/guide is about $62.00 vs $26. for the 3-pc Melling gears and chain.

 

[Jbrownjr]

It's been a while, so here's an update:

Replaced the TPS after voltage reads were inconsistent with what is expected.
It was still accelerating rough, but running well enough for a short drive within the neighborhood.
Sunday a friend approached me after noticing our B2 in the driveway. Seems he picked up an '85 B2 which had the 5.0 engine swapped and a number of other after-market mods. His had just blown the transaxle seal, but it was good to find another B2 fan so close. We had planned to drive by yesterday (and drop off a fluid pump so he could fill his enough to limp to a tranny shop)...but ours wouldn't start.

Saturday my son and a friend were attempting to remove the ICM to have it tested, but were unsuccessful. (without loosening the distributor hold-down bolt, thinking one of the screws was stripped) He was adamant that they didn't touch anything else, but was sure I had tugged too ******* the main wiring harness a week ago which "probably" contributed.

Today he found an after-market fusible link had a blown fuse and replaced it. (The connectors he used to install it were not taped/exposed, and at least once I noticed a soft 'zap' over the past week or two.) That's been replaced and covered with heat-shrink tubing. Chasing down what appeared to be a no-spark condition, we found nothing on spark wires, nothing coming out of the ignition coil (neither with a timing light nor a grounded spark plug) and proper voltage and ground at the coil.

I stumbled onto another thread were a guy had similar symptoms to ours, and replaced his (black) ICM with a gray one. (He said the pins seemed thicker on the gray one and it made a world of difference). In our case, we had purchased a gray one a year or so ago, but when swapping the (AutoZone) distributor assembly under warranty, my son left the gray ICM on the old one and received a black ICM with the replacement distributor assembly. Thought nothing of it at the time...but we've been struggling with this for months. My son decided earlier today to buy one. Another $85 out-of-pocket, but this one has a 5-year warranty (the same carparts.com source this guy bought and had success with) which will arrive this Friday.

As my son was cranking this evening, (actually during a KOEO moment) I was pushing/pulling on the ICM just to make sure it was tight, and I noticed the fuel injectors activated for a few seconds at a time as I pushed. This time I applied pressure toward the firewall while he cranked, and it wanted to start. (spark) Ah-ha!

Took that (black/Autozone) ICM off (this time loosening the distributor hold-down bolt, no stripped ***** after all) and had AutoZone test it. (FAIL)

SO...another case of a failed ICM it seems. Who knows if the gray ICM we bought a year ago was perfectly good, but we accidentally let it go with the distributor assembly "core". Sure seems like another AutoZone (black) ICM which was defective (or failed prematurely). This weekend he'll swap that out with the carparts.com gray ICM, re-time it and cross our fingers!

 

[Tiha]

Brand new parts, bad. That is the worst thing. That has to be the most frustrating thing. Thinking we fixed something and really just wasted time.

 

[goodO1boydws]

It's been a while, so here's an update:

Replaced the TPS after voltage reads were inconsistent with what is expected.
It was still accelerating rough, but running well enough for a short drive within the neighborhood.
Sunday a friend approached me after noticing our B2 in the driveway. Seems he picked up an '85 B2 which had the 5.0 engine swapped and a number of other after-market mods. His had just blown the transaxle seal, but it was good to find another B2 fan so close. We had planned to drive by yesterday (and drop off a fluid pump so he could fill his enough to limp to a tranny shop)...but ours wouldn't start.

Saturday my son and a friend were attempting to remove the ICM to have it tested, but were unsuccessful. (without loosening the distributor hold-down bolt, thinking one of the screws was stripped) He was adamant that they didn't touch anything else, but was sure I had tugged too ******* the main wiring harness a week ago which "probably" contributed.

Today he found an after-market fusible link had a blown fuse and replaced it. (The connectors he used to install it were not taped/exposed, and at least once I noticed a soft 'zap' over the past week or two.) That's been replaced and covered with heat-shrink tubing. Chasing down what appeared to be a no-spark condition, we found nothing on spark wires, nothing coming out of the ignition coil (neither with a timing light nor a grounded spark plug) and proper voltage and ground at the coil.

I stumbled onto another thread were a guy had similar symptoms to ours, and replaced his (black) ICM with a gray one. (He said the pins seemed thicker on the gray one and it made a world of difference). In our case, we had purchased a gray one a year or so ago, but when swapping the (AutoZone) distributor assembly under warranty, my son left the gray ICM on the old one and received a black ICM with the replacement distributor assembly. Thought nothing of it at the time...but we've been struggling with this for months. My son decided earlier today to buy one. Another $85 out-of-pocket, but this one has a 5-year warranty (the same carparts.com source this guy bought and had success with) which will arrive this Friday.

As my son was cranking this evening, (actually during a KOEO moment) I was pushing/pulling on the ICM just to make sure it was tight, and I noticed the fuel injectors activated for a few seconds at a time as I pushed. This time I applied pressure toward the firewall while he cranked, and it wanted to start. (spark) Ah-ha!

Took that (black/Autozone) ICM off (this time loosening the distributor hold-down bolt, no stripped ***** after all) and had AutoZone test it. (FAIL)

SO...another case of a failed ICM it seems. Who knows if the gray ICM we bought a year ago was perfectly good, but we accidentally let it go with the distributor assembly "core". Sure seems like another AutoZone (black) ICM which was defective (or failed prematurely). This weekend he'll swap that out with the carparts.com gray ICM, re-time it and cross our fingers!

Its very hot location (mounted on the distributor's body) is the usual cause for this particular Ford product ICM failure (once its been on a while). The metal back plate is a heat sink. Unfortunately, the V-6 distributor is located in a very hot area, sometimes (especially on shut down) the distributor can transfer ITS heat to the module instead.

Keeping as much air flow space as you can around the ICM and distributor will help, as the cooler they are the longer they tend to last.

In case it didn't come with the distributor or module, make sure that there is heat sink grease on the ICM's back plate.

I hope it was the whole distributor that you paid $85 for, not just the module.

A new distrib with the grey module (according to their website photos) and lifetime warranty is about $93 at Advance. The grey module with a 5 year warranty starts at about $26. at Rockauto.

 

[Jbrownjr]

Its very hot location (mounted on the distributor's body) is the usual cause for this particular Ford product ICM failure (once its been on a while). The metal back plate is a heat sink. Unfortunately, the V-6 distributor is located in a very hot area, sometimes (especially on shut down) the distributor can transfer ITS heat to the module instead.

Keeping as much air flow space as you can around the ICM and distributor will help, as the cooler they are the longer they tend to last.

In case it didn't come with the distributor or module, make sure that there is heat sink grease on the ICM's back plate.

I hope it was the whole distributor that you paid $85 for, not just the module.

A new distrib with the grey module (according to their website photos) and lifetime warranty is about $93 at Advance. The grey module with a 5 year warranty starts at about $26. at Rockauto.

$85 for just the module.
Autozone charged as much for the distro assembly (black module)
RockAuto has been our other "go-to", but with a 'testimonial' for the CarParts.com version, we jumped on that bandwagon. (Are all "gray" modules created equal?)
I see the same Standard ICM is $56 with a 5-year warranty. Lesson learned! (https://www.rockauto.com/en/moreinfo.php?pk=49702&cc=1106154&pt=7172&jsn=930)

 

[goodO1boydws]

$85 for just the module.
Autozone charged as much for the distro assembly (black module)
RockAuto has been our other "go-to", but with a 'testimonial' for the CarParts.com version, we jumped on that bandwagon. (Are all "gray" modules created equal?)
I see the same Standard ICM is $56 with a 5-year warranty. Lesson learned! (https://www.rockauto.com/en/moreinfo.php?pk=49702&cc=1106154&pt=7172&jsn=930)

I take testimonials with more than a grain of salt in most cases now-sometimes even if I know the person (or BECAUSE I do).

My brother turned me onto Rockauto years ago and its the place I look first for parts now, if only to get an idea of what is a reasonable price for a part and to know if I'm getting um.....threaded, from buying at a chain store. Rock often has parts that chain stores say are no longer made, are "special order" or ARE made but they can't order them.
I have yet to find another place that consistantly has a selection of (most) parts in more than one brand in GOOD multiple price ranges-often from different places*. I've even found their NEW parts prices to be less than boneyard used parts at times.

*A minor gripe is that, since they ship from different warehouses, any order including several items, say for a complete brake job-master cylinder, wheel cylinders and/or calipers, rotors and/or drums, pads and/or shoes, hardware, etc. can have high shipping costs as a result of coming from 3,4, or 5 places, even though the parts prices themselves are USUALLY enough less to justify ordering. Its frustrating when a left side part come from one warehouse and the right side mate comes from another.

 

[Jbrownjr]

And the story resumes...

New ICM/TFI installed a few weeks ago. Started right up, idled OK; so we focused on timing. She was purring at idle! Acceleration seemed much better. Ended the day on a high note!

A few days later, it wouldn't start. I was holding the TFI (installed) adjusting the distro and noticed the TFI was loose. My son use a few 'standard' bolts which didn't quite fit it seems. A few days later he found the right bolts from a donor at the salvage yard and snugged up the TFI. Still wouldn't start.

Yesterday we finally got back to it and I observed no spark. (Timing light at a few different plug wires). Focusing next on the Ignition coil. confirmed there's 12v at the red and green wires, and the ground is also good. Used an old spark plug on the distro end of the coil wire, and despite grounding I got nothing. (I did the same test a month or so ago, and there was a good 1 1/2" arc.) We happened to have another coil and swapped them out, but no change.

(Assuming there's no (newly) failed parts and no wires that shorted out - which is always the dreaded result when we seem to take 2 steps forward and one step back...)

Between the last time it ran/idled well the TFI was removed/tightened with new bolts. Timing shouldn't have changed during that process (but could have), which is why I also tried adjusting it yesterday as my son cranked. No sign of spark. SO...what else contributes to the coil sparking other than the coil?

Otherwise I go back to re-checking the obvious:

• Bench-test TFI
• Pull (KOEO) codes

 

[Tiha]

I would bench test the TFI again.

It's mounting is the heat sink. If it was loose it could have over heated and failed already.

No timing will not change.

Not sure what else affects spark.

 

[goodO1boydws]

I agree with Tiha.
The last part being installed incorrectly is the likely culprit.

Without the heat sink being in good contact they do fry quickly.
Of course, its connector may only have gotten loosened and not snugged again.

While you're checking things, be certain there is a thin coating of dielectric compound in place to protect the control module to to heat sink connection from debris or corrosion.

(At least you should be well within the warranty period for the module.)

 

[Motech]

First go back and observe your Check Engine light:

• Is it off KOEO?
  • Back to power relay basic

If it's on, watch it while cranking:

• Is it still on cranking?
  • It's a bad PIP
• Does it turn off while cranking?
  • Move along

For grins, when checking for spark at coil wire, disconnect SPOUT connector, try again and see if you get any spark, no matter how weak.

• Got some now?
  • It's your PIP
• Still no juice?
  • Reconnect SPOUT and check that coil primary again

KOEO, connect your 12v test light clip to battery negative and then probe both positive and negative coil terminals with the other end:

• Hot on +, not on -?
  • Replace your coil
• Hot on both?
  • Check trigger as follows:

Switch your 12v test light clip to battery positive this time, probe the negative coil terminal and crank it.

• Does it flash fairly bright?
  • Replace your coil
• No flash at all while cranking?
  • It's your PIP

As has been mentioned here before, lack of a secure, well-grounded ICM can help cook it, as can a shorted coil, but you wouldn't even know it was shorted. (Frankly, I doubt coil or sloppy mount would fry ICM it so quickly, but you never know)
Sooo.... If it DOES turn out to be a bad TFI ICM, two things:

1. Make sure the correct fasteners are clamping it tightly, with that di-electric grease you smeared on the backside heat sink pooching out the edges
2. Replace ignition coil too (automatic in shops so they don't have to warranty that ICM next month)

 

[Jbrownjr]

First go back and observe your Check Engine light:

• Is it off KOEO?
  • Back to power relay basic

If it's on, watch it while cranking:

• Is it still on cranking?
  • It's a bad PIP
• Does it turn off while cranking?
  • Move along

For grins, when checking for spark at coil wire, disconnect SPOUT connector, try again and see if you get any spark, no matter how weak.

• Got some now?
  • It's your PIP
• Still no juice?
  • Reconnect SPOUT and check that coil primary again

KOEO, connect your 12v test light clip to battery negative and then probe both positive and negative coil terminals with the other end:

• Hot on +, not on -?
  • Replace your coil
• Hot on both?
  • Check trigger as follows:

Switch your 12v test light clip to battery positive this time, probe the negative coil terminal and crank it.

• Does it flash fairly bright?
  • Replace your coil
• No flash at all while cranking?
  • It's your PIP

As has been mentioned here before, lack of a secure, well-grounded ICM can help cook it, as can a shorted coil, but you wouldn't even know it was shorted. (Frankly, I doubt coil or sloppy mount would fry ICM it so quickly, but you never know)
Sooo.... If it DOES turn out to be a bad TFI ICM, two things:

1. Make sure the correct fasteners are clamping it tightly, with that di-electric grease you smeared on the backside heat sink pooching out the edges
2. Replace ignition coil too (automatic in shops so they don't have to warranty that ICM next month)

Motech - You caught my attention...

• KOEO - EMISS light stays on.
• Turn key to start - EMISS light goes off.
• Crank - EMISS light flickers (more on than off)

Just to double-check, I found a nice post where Seth had the same "no-start" problem on a full-size Bronco (remote ICM) and provided a similarly methodical approach to troubleshooting. Running through those tests, my test light on the passenger side of the ignition coil (green wire) stayed lit while cranking. He suggested at that point it's the PIP or ICM. Since we bench-tested the ICM...points to the PIP. We have consensus.

Thankfully the Distro assembly has a Limited Lifetime warranty from O'Reilly's, so we'll swap the assembly (less the known good ICM) and get the PIP replaced as part of the package. We've been here before...(Feb. 2021 we bought the distro assembly)

Why would the PIP fail again?

My fear is there's a short in one of the fusible links or another hidden wire in the main wiring harness and this will keep happening. For that reason we've started looking at non-contact voltage testers. Those seem to run >$100, but we found a few for something less on Amazon...just not sure of the quality/reliability.

Might be another week, but we'll get that distro swapped and report back.

 

[Motech]

Why would the PIP fail again?

Because they sometimes do not get replaced in the remanned distributors. If they look acceptable and ohm test OK, they may reuse them.

But as The Borg has taught us all...

Resistance is Futile

 

[Motech]

Crank - EMISS light flickers (more on than off)

This indicates a weak PIP.

Try unplugging your SPOUT (timing) connector and cranking again. It might try to fire, and your PIP diagnosis would be even stronger.

 

[Jbrownjr]

Good call on the PIP.

Finally got to warranty-exchange the distributor assembly, and minus the spout she's running well!
Adding the SPOUT...not-so-much.

Son's headed off to college next week, and hoping to get this thing running/driving so it can be sold.
(After putting so much love into it...kind of disappointing, but he found an E350 customized for a 'vagabond' and that's his gig on weekends)

I'll jump on the accelerator within the next few days and make sure it's just the SPOUT that's amiss, but I vaguely recall that introduced the computer to dynamic timing adjustments. The computer was replaced weeks ago, so hopefully it's not that. So any obvious clues on why connecting the SPOUT will cause it to run rough and die?

 

[Motech]

So any obvious clues on why connecting the SPOUT will cause it to run rough and die?

That's almost always a weak PIP signal. I've never seen anything else cause that as unplugging SPOUT reverts to base timing with no advance, so it's a pig that wakes back up with SPOUT plugged back in.

ICM is a possibility. One of it's jobs is converting analog PIP signal to digital that PCM ccan process. But if I've ever seen it, I don't remember. (And I've rebuilt a ton of TFI distributors for bad PIP)