1993 Bronco XLT 5.8L Resto Update

[Whipsaw]

Hi Everyone, its been a while since I've posted here. In the interim, with a new PCM installed, the Bronco has been running well. I do have a problem with high idle when it's warm out ( I think it's a vacuum leak, but I haven't looked that hard yet - if it's the plenum gasket, I'll get to that at some point. I have a replacement vacuum canister (coffee can), the old one is a little rusty, but I don't think its leaking. Turning off the engine and starting again fixes it for a time - if that might indicate what the problem could be). I did have it painted, stock emerald green, got it back from the body shop a few months ago - rust repaired, new front springs installed, new tailgate, new back glass. Looks great! I'll have to get a picture up soon.

The water pump seal just went (need to verify, coolant was running down the front of the engine, could be a cracked hose), if the pump is shot, will be replacing the timing set while I'm in there. After that is an Air Conditioning refit, and probably front wheel bearings.

 

[Motech]

Real simple to check if your high-idle issue is a vacuum leak or a command issue. Just unplug your IAC valve while idling high.
If idle drops (or stalls), it's a command issue.
If it stays high, it's either a vacuum leak or stuck IAC (doubtful).
At that point, give a sharp rap or two on the IAC valve with a screwdriver handle. If it drops then, you have a sticky IAC valve. If not, a vacuum leak somewhere.

EDIT:

Unlike Chrysler and GM Stepper-type IAC valves that stay put when unplugged, Ford's spring loaded IABP valve snaps back to closed when disconnected.

Also, if you have the IABP valve adjustable spacer, it might be opened up too much, and need to be adjusted.



Two more things too:

1. Could be pesky re-learning glitches that will self-correct if you've disconnected battery and erased Keep-Alive Memory recently, and
2. Also could be binding throttle linkage or weak return spring keeping throttle from returning full-closed sometimes. Next time it happens, give a sharp rap on the accelerator pedal and see if it drops back down.

 

[miesk5]

Yo Whipsaw,
Ignore ACT.

 

[Whipsaw]

Thanks! I've unplugged the IAC and the idle did drop to almost stall... so.. Motech, not sure what you mean by 'command issue?' Will work through the attachments above and see if I can isolate the problem. As for the coolant leak, its NOT from the water pump weep hole; it appears to be leaking from where the water pump attaches to the timing cover. Oil looks good, so no internal leakage. I'm going to try and snug the water pump bolts and see if that stops it. Otherwise it's a full court press to the timing set, along with a new water pump, timing cover if needed, gaskets of course, fan clutch and harmonic balancer. Anything else I should address while I'm in there? Thanks again!

 

[L\Bronco]

Thanks! I've unplugged the IAC and the idle did drop to almost stall... so.. Motech, not sure what you mean by 'command issue?'

Motech meant that if the idle drops when you unplug the IAC, then it is a command from the PCM, not a vacuum leak causing the high idle. The pcm is reacting to an input from somewhere.
That system used to reference closed throttle TPS as the lowest learned value, when you had an intermittent sensor failure (bad spot), the new closed throttle value would be near zero, making the pcm think it was at part throttle. This puts the IAC into dashpot mode and it sits around12-1800 RPM until the key is cycled and a new value is learned.
That's where I would look first based on your description.
If you have a scan tool that shows data, look for a PID called TPCT while its stuck idling high and see what it reads, then shut it off and re start and check it again and see if it reads higher. (It only takes .3-.4 volts to mess it up.) If you can't do that try a new TPS and see if its fixed.
I would also verify the base idle, (hard stop) with the IAC unplugged, fully warmed up, all accessories off , in park it should just run. (500ish RPM) Make sure your throttle body is clean. (be careful, yours might have teflon around the plates and a large bypass hole in the throttle plates.) If someone has "cleaned" the teflon coating off the base idle will be too high which can also cause an intermittent high idle.
That being said, I'd start with the TPS. (Especially if it resets with a key cycle.
Hope that helps
Cheers

 

[Motech]

I've unplugged the IAC and the idle did drop to almost stall... so.. Motech, not sure what you mean by 'command issue?

@L\Bronco covered that pretty good. Your test results are normal.

I would add:

Did you disconnect it while the idle was stuck high?

That's critical. If so, then yes, it's definitely a command issue, where PCM is seeing a false value that it believes to be true, and it's commanding higher idle from bad data.

Now then, if you didn't run that test when the idol was stuck high, wait for it to happen and do it again. Then if it still stays high, look at your throttle linkage.

 

[L\Bronco]

Did you disconnect it while the idle was stuck high?

Very good point!

 

[Whipsaw]

Hi everyone, I'm back, thanks for the replies - had a difficult spring in that my Mom took a bad fall and passed away in April. Everything else went on hold until a couple of weeks ago. I'm literally in the same place as my last post. With the coolant leak, I really can't run the engine to troubleshoot the high Idle as the coolant literally runs out of the front of the engine. Looking at a replacement timing cover on RockAuto, there is an opening at the bottom of where the water pump attaches, I'm guessing its leaking from there (the view is blocked by the balancer/pulley. The pump has a back panel, either that rusted through or the gasket blew out at the pump outlet. I haven't tried snugging up the water pump bolts yet, I should start there.

 

[Motech]

Well if you're going to do a pump, you're going to likely need a timing cover. Those pass through bolts going through pump and cover tend to rust up badly and break real easy. Whenever my older Windsor customers come in for a water pump, be it 289, 302 or 351, I prepare them for the cost of timing cover and timing chain replacement too just in case.

 

[miesk5]

Yo Whipsaw,
Know that your mom is always with you; first during your life journey and then in your memories of her.
Al

 

[wyo58]

Hi everyone, I'm back, thanks for the replies - had a difficult spring in that my Mom took a bad fall and passed away in April. Everything else went on hold until a couple of weeks ago. I'm literally in the same place as my last post. With the coolant leak, I really can't run the engine to troubleshoot the high Idle as the coolant literally runs out of the front of the engine. Looking at a replacement timing cover on RockAuto, there is an opening at the bottom of where the water pump attaches, I'm guessing its leaking from there (the view is blocked by the balancer/pulley. The pump has a back panel, either that rusted through or the gasket blew out at the pump outlet. I haven't tried snugging up the water pump bolts yet, I should start there.

Sorry to hear that Whipsaw, never easy losing a loved one. Good luck on your repair sounds like your headed in the right direction.

 

[Whipsaw]

Thank you all for the condolences, it is greatly appreciated. She's in a much better place, and still nearby when I bust a knuckle.

 

[Whipsaw]

Parts are arriving from RockAuto, Motech, I did get the timing cover - I ran into the exact problem you describe on my '01 Explorer 5.0:

https://www.explorerforum.com/forum...5-0-timing-set-water-pump-replacement.496664/

Just ordered a stainless bolt set from AlloyBoltz to swap out with the original fastners as this job proceeds.

 

[johnnyreb]

Hi everyone, I'm back, thanks for the replies - had a difficult spring in that my Mom took a bad fall and passed away in April. Everything else went on hold until a couple of weeks ago. I'm literally in the same place as my last post. With the coolant leak, I really can't run the engine to troubleshoot the high Idle as the coolant literally runs out of the front of the engine. Looking at a replacement timing cover on RockAuto, there is an opening at the bottom of where the water pump attaches, I'm guessing its leaking from there (the view is blocked by the balancer/pulley. The pump has a back panel, either that rusted through or the gasket blew out at the pump outlet. I haven't tried snugging up the water pump bolts yet, I should start there.

Sorry to hear about your mom passing away.

 

[Motech]

Parts are arriving from RockAuto, Motech, I did get the timing cover - I ran into the exact problem you describe on my '01 Explorer 5.0:

https://www.explorerforum.com/forum...5-0-timing-set-water-pump-replacement.496664/

Just ordered a stainless bolt set from AlloyBoltz to swap out with the original fastners as this job proceeds.

Good call @Whipsaw

Often times, I've had those through-bolts break inside the cover, corroded so badly they bond to the cover, making it real difficult to pull it off.

When that happens, there is typically no way that fastener is ever going to twist out of the engine block. It has become virtually welded into the threads.

In these cases, I'll grind the broken bolt down flush with the block and prep the whole surface, including cleanup of all the threads with thread chasers. Then I'll mock up the new cover with your new hardware, but no gaskets yet, and use it as a template to drill into the block where the broken bolt still lives. A larger bit works best to provide an initial pilot, one that fits smugly in the cover hole for best centering, 3/8" maybe, or 11/32", whichever works best. Just enough to cut a little divit to center your cutting bit.

You can then remove the cover or not. I've done both. Leaving it on helps to center your cutting bit if I'm not confident in my eyeball, but risks slipping and damaging the cover.

A 17/64" bit is typically the size needed for your 5/16 x 16 tap.



It will be rough drilling because you'll not likely be perfectly centered and may be drilling through brittle bolt remains and block surface. That can cause some chunky feedback, so go slow and use plenty of cutting oil. Do not be concerned with perfection on this point. There is plenty of space to accommodate a slightly offset threaded boss. Straight matters more than center. Just take it slow; controlled and deliberate. You don't want this job fuckered by a broken bit, or worse yet, a broken tap!

These types of repairs are dreaded, and maybe not even necessary if all goes well. But if you're prepared for the worst in your mind, taking your time no matter the obstacles, your mastery will prevail, and that beer (or Scotch, or cigar, or your vice of choice) will taste so much sweeter with success.

 

[Whipsaw]

Hi everyone, I tackled the waterpump (painted it red!) and timing chain a couple of weeks ago, disasembly went very smooth. Some of the bolts had corroded in the timing cover, but not enough to seize up. I was able to use the original timing cover again (I now have a new spare (Dorman) if anyone needs one), coated bolts with anti-seize. No leaks! Only problem was disconnecting the transmission cooler lines, one was stuck real good and I managed to twist the mount and tear the cooler (in the side tank, it looks like a paper towel roll - I had to cut it out to get the fittings; the new radiator from Advance Auto didn't come with the correct fittings, or any other hardware). I'll get pics up soon.

Back to the high idle problem... I had my mechanic install a new TPS from Carquest (he had the car to pump out the R12 for the upcoming A/C rebuild, and I was short on time). At any rate, the high idle problem appears to be fixed.

I have a new question I haven't found an answer to. Previously, since getting the vehicle, when starting from cold, the idle would go up to about 1000 RPM for about a minute, then slowly ramp down to a normal idle, every time, hot or cold out (hot start it didn't ramp up). Now it starts from cold and goes right to idle ~550-600 RPM. Is that normal? It hasn't gotten cold yet, so I don't know if that may be a problem this winter. Otherwise, seems to be running very well.

Mechanic said there was a good bit of gunk in the intake plenum, will get after that with Gumout and maybe Sea Foam.

 

[Motech]

Definitely clean that throttle bore. In fact, scold your mechanic for not doing it when he had it off to do the TPS. That should have been automatic, and that is half of your problem.

The other half is the long-term memory erase that occurs with the battery disconnect. When that happens, the computer starts at scratch with idle values. With limited airflow around those throttle plates due to the carbon buildup, it no doubt has a very low minimum air rate flow at this point.

Now the computer will relearn it's idle strategies and stop doing this over a little bit of time. But it's just compensating for the crud that's in there with new values.

The reason I say this is automatic when the throttle body is off is because of where that TPS lives. Being at the bottom of the throttle body, if you spray chemicals into your throttle bores to clean up that carbon in there, you risk damaging your new TPS as it seeps through the throttle shaft and into the potentiometer below. With that, to clean it on the truck, you need to be very careful and just use rags and brushes to clean those bores, being careful not to allow fluid indide the lower one.

Once you got it all cleaned out, and your engine is warmed up and idling, that is the time to adjust your minimum air rate to give your computer the ideal starting point with your idle adjusting. To do that, unplug your idle air control valve at hot idle. If the engine stalls, your air rate is too low, and you need to open up your throttle plates a little bit with the small scroo provided. Sometimes it's actually easier to bend the flap of steel that the throttle linkage rests against the scroo. Either way, plug the IAC valve back in again, fire it up, and once it's stable, unplug it again and see where it's at.

Keep doing this until your base idle speed without the valve connected is right around 450 to 500 RPM. Then plug your valve back in and disconnect the battery for 20 minutes to reset all your memories again, because you're TPS values will be a little bit higher now and they need to be erased.

After that, expect your idle quality, especially on cold starts, to be a little erratic the first few warm-up cycles. That's Ford's process of relearning the strategies, and it's perfectly normal. Except now, with a good minimum air rate, your udle will flare up higher than 1,000 RPM on startup, and it'll all settle in nicely a few days later.

 

[Motech]

I really can't run the engine to troubleshoot the high Idle as the coolant literally runs out of the front of the engine.

I somehow overshot this one.

When coolant gets low in these engines, an air pocket will often form around the Engine Coolant Temperature sensor. Doesn't take much either, just 5-6 inches low in the radiator. So ECT cannot measure air like it does fluid, and when this pocket forms, ECT sends false low signal to the computer. PCM is gullible enough to believe it, and it enriches fuel mix and ramps up idle speed in a perceived warmup cycle.

This is prevalent on Ford V engines with ECT located in the intake manifold coolant crossover, and especially so in the taller 351 Windsor block.

If this were the case with yours, it would also have some pig-rich, stanky exhaust.

 

[Whipsaw]

It's been a busy few months, as it turns out, that wonderful mechanic I use forgot to plug in the IAC when he installed the TPS, causing the low idle at start. The idle behavior is back to normal (high at cold start, ramps down to about 700 rpm now. Interestingly, I hadn't noticed this before, when in drive at the light the idle is normal; once moving it ramps up to about 1200 which will keep it going at 25 mph or so with foot off the gas (strong creep). When stopped, in or out of gear, idle is normal. Seems to be in a good, stable, running condition. Thanks for all the great input and advice. Next project is an Air-conditioning complete rebuild. Will start a new thread for that.

 

[Whipsaw]

Updating this thread with some photos:



This is probably the most useful tip in this entire thread, in order to get the crank bold out without the engine turning, I was able to brace the harmonic balancer against the frame with a sturdy piece of wood. Worked just as good when tightening the bolt as well - move the wood to the other side ;-) . Normally the crank bolt is a huge pain in the @$$.



I was able to remove the timing cover with out any broken bolts! Now I have an extra timing cover. This is the old timing set, it had the eccentric for the mechanical fuel pump - of which this vehicle is not equipped. Replaced with a Cloyes double roller set without the eccentric!



Assembly went well, until a few weeks went by anyway. I used a Permatex gasket prep that cross referenced to what is used by ford, then took two days torquing all the bolts as the gaskets compressed. A few weeks later, the coolant started to seep out around the pump, fortunately, a couple more rounds of torquing bolts locked it down. Folks may already know this... I recommend at least two more rounds of torquing the bolts after a week and then again a week later.



Upon reassembly and filling with coolant, this is what you don't want to see... Transmission fluid in the coolant. I knew immediately what was wrong (spun the transmission line fitting), got a new transmission and installed it. Autozone part, it seemed that parts were missing, at least the fitting adapters for my flavor of transmission lines weren't there, I had to extract them from the old radiator, among other things. It was sort of like an automotive autopsy! Here's a pic of the transmission cooler after cutting open the plastic end piece, I'd never seen one before. The fitting on the right spun and tore the cooler (see the crease in the pic), which is just a double walled tube to exchange the heat from the transmission to the engine coolant... Think about that, how hot does the transmission get to cool it down with hot engine coolant?! I may go for a temperature sensor kit at some point. Keep that transmission fluid changed regularly!!



I hope this helps a few folks out there!