Bronco pulsing while driving

[Dingo0722]

I’ve noticed a slight pulsing while driving my 95 bronco 351W, at various speeds but definitely most noticeable when under a load like going up hill. Could this be the torque converter slipping Or the transmission? Truck has 138K on it

 

[miesk5]

Yo Dingo,
Check the double cardon joint on the rear driveshaft and the transmission mount.

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and if it can run long enough, greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up if you can, and shift thru all gears including Reverse.
Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch.
Then turn off engine, all accessories/lights (close driver's door) , etc.
Do KOEO test First
Post Code(s) here according to:
KOEO & KOER

For now, Table 8 Stumbles, Surges, etc

Quick Test is Self Test
Idle Air Flow is IAC:



See my Vacuum leak test in post #11 @ Help with dtc codes and idle

 

[Tiha]

That is a great place to start. Be sure to check for codes. Pending codes do not turn on the engine light.

I wouldn't jump to the transmission. I would be looking more at a bad ignition coil or weak fuel pump.

Does it only happen with cruise control on? Or all the time?

When is the last time it had a new set of spark plugs?

 

[Dingo0722]

I will definitely check for codes. I have had the bronco on the lift and the drive shaft seems solid and no play. The symptom occurs at all cruise speeds, more obvious under load no cruise control on. Plugs wires rotor cap and coil are of unknown age. Wires rotor and cap are not OEM. Cap and rotor have some spark erosion. First things first I will see what codes I can get it to put out and will report back

 

[wyo58]

I agree with both Miesk5 and Tiha, see if it gives you some codes and start from there. If the tranny was slipping you should notice slight rpm increases that match your Pulses. To me it sounds more ignition related or fuel related. Good Luck Dingo keep us informed of what you find.

 

[L\Bronco]

I will definitely check for codes. I have had the bronco on the lift and the drive shaft seems solid and no play. The symptom occurs at all cruise speeds, more obvious under load no cruise control on. Plugs wires rotor cap and coil are of unknown age. Wires rotor and cap are not OEM. Cap and rotor have some spark erosion. First things first I will see what codes I can get it to put out and will report back

Hey Dingo
Shorting plug wires or plugs will show up as a jerky hesitation most noticeable under light to medium load.
Commonly called fish bite in the drive-ability world as it feels like when a fish is biting at your bait.
A quick check is to get someone to put it in D (assuming automatic), and give it a medium load while you spray water from a squirt bottle, (like the nozzles you get with diff ****)
Spray directly at the plug/exh manifold area. You will know right away if your wires are bad. (Don’t load the engine for more that 15 to 20 seconds at a time or you will overheat the torque converter!)
Also, a new set of plugs is never a bad idea!
Cheers

 

[Dingo0722]

Hey Dingo
Shorting plug wires or plugs will show up as a jerky hesitation most noticeable under light to medium load.
Commonly called fish bite in the drive-ability world as it feels like when a fish is biting at your bait.
A quick check is to get someone to put it in D (assuming automatic), and give it a medium load while you spray water from a squirt bottle, (like the nozzles you get with diff ****)
Spray directly at the plug/exh manifold area. You will know right away if your wires are bad. (Don’t load the engine for more that 15 to 20 seconds at a time or you will overheat the torque converter!)
Also, a new set of plugs is never a bad idea!
Cheers

Wow that’s interesting. So two weeks ago I washed the engine compartment and after the truck would not start. I let it dry over night and it fired up with a little hesitation. I was planning in diving into checking for codes this weekend, but we have been hammered with tropical storms. Hope to get to it this week. Probably will just replace cap, rotor, wires and plugs anyways as their age is unknown. Any recommendations?

 

[L\Bronco]

Wow that’s interesting. So two weeks ago I washed the engine compartment and after the truck would not start. I let it dry over night and it fired up with a little hesitation. I was planning in diving into checking for codes this weekend, but we have been hammered with tropical storms. Hope to get to it this week. Probably will just replace cap, rotor, wires and plugs anyways as their age is unknown. Any recommendations?

Sounds like you are on the right track.
As far as brand goes, I don’t know what to suggest, there seems to be an alarming lack of quality across the board.
I am loyal to autolite spark plugs. As far as cap, rotor, and wires, my choice would be motorcraft (if available)
Good luck Dan
Cheers

 

[Dingo0722]

Sounds like you are on the right track.
As far as brand goes, I don’t know what to suggest, there seems to be an alarming lack of quality across the board.
I am loyal to autolite spark plugs. As far as cap, rotor, and wires, my choice would be motorcraft (if available)
Good luck Dan
Cheers

Since I was in HS, I’ve been told Autolite plugs for Ford. So if that is still holding true, that’s what I’ll do. For the rest, I’ll probably just just a brand name if OEM is not an option. Thank you for the help

 

[L\Bronco]

Since I was in HS, I’ve been told Autolite plugs for Ford. So if that is still holding true, that’s what I’ll do. For the rest, I’ll probably just just a brand name if OEM is not an option. Thank you for the help

Any time!
Cheers

 

[paul rondelli]

when my 1996 would hesitate under load ... I too replaced the usual electronic wear parts.

Finally after a few weeks ... It stumbled and almost shut off.

It immediately threw a code for a cam shaft sensor.

After some research

I found that the PIP sensor on the distributor.... was going bad.

The distributor shaft spins at high RPMs...... for the last 30 years.

Eventually the shaft starts to wear ... causing some heat buildup in the distributor assembly. This heat then causes the PIP to fail since it is mounted to the Distributor. It only happened after she was warmed up enough.... for a good amount of heat to build up in the assembly.

It only threw a code that one time.

I just went and replaced the entire distributor assembly. Less than $200 at AZ and she has ran great since.

The PIP also sends the RPM information to the tach. If your tach starts to act crazy ... usually a PIP replacement is in order.

 

[Motech]

OBD2 on this Windsor engine by design is very, very difficult to set misfire codes with. When you do, you'll probably just get a P0300 random misfire code. This is one of the main reasons that 96 was the only year for OBD2 Windsor engines.

I can't really add to any of the input here, I think it's pretty much all covered. I can add for brands though. Motorcraft spark plugs are very readily available, and try to avoid the temptation to upgrade. If yours calls for copper, keep it copper. Platinum will not help at all, and iridium is just so darned expensive that the cost negates the benefit.

If you can't find your other secondary ignition items in Motorcraft, NAPA's Belden plug wires and Echlin components are still high quality.

 

[Dingo0722]

OK so finally got a chance to do the test. Engine Off Key On I have a 33 and a 133. Engine On I have a 33. Does this make sense?

 

[wyo58]

Continuous Memory Code 33 indicates that the EGR valve did not open with the engine stabilized and with EVR solenoid duty cycle present sometime during vehicle operation. Possible cause: -- Obstructed or cracked hose to EGR valve. And I believe the 133 is this one? P0133 is an O2 sensor CKT slow to response, bank 1 ,sensor 1. Were you counting the flashes or actually using a code reader?

 

[wyo58]

No I'm wrong there does not seem to be a 133 code for the OBD1 might be getting the pass code and your reading it wrong?

 

[Dingo0722]

Yes counting flashes. First time doing this so I am trying to learn the patterns of the flashes. I suspected the Engine Running/on flashes might be a 111 followed by a 111.

 

[wyo58]

I believe that is a pass code

 

[Motech]

33 is your KOEO On Demand code. 1 is 10, the separator code between KOEO On Demand and Continuous (memory) mode, then 33 is your Continuous code.

But wait, that is for older EEC IV. Ford switched to 3 digit codes early nineties, and your 95 should have no 2 digit codes at all.

Code 133 means high EVR voltage. It will set in all three modes, and it is a very common code that typically gets ignored cuz it causes no grief and will not turn on the Check Engine light.

Back to flash counting for you because your 2 digit code is not possible.

 

[Dingo0722]

Wish I could post a video. Did the test again for KOEO and I got the same results. Unless I am not interpreting the timing of flashes correctly. Three light on light off. Timing of the on about the same as the off. 2 second delay to the next number in the code. 4 second delay starts the next number sequence.

 

[Motech]

Wish I could post a video.

That would be nice. Feel free to email one to me if you'd like:

[email protected]

(Fair warning: I've never flashed EEC IV codes before as I've always had scanners with Enhanced Ford protocols)

I did just check, and there definitely are no 2 digit codes in 1995. Only 3 digit.

Furthermore:

• There is no code 133 in your model
• Code 111 means "System Pass"
• Code 111 can potentially appear three times: twice during KOEO Self Tests, and once during KOER Self Test

How much clearer is it now?