94 XLT No/Hard start when cold, fine when warm

My 94 XLT 4.0L Pushrod V6 has problems starting when the engine is cold or it is cool out. If the engine is warm or it is warm out it starts fine and runs great. When cold it takes 7-10 tries to start, turns over fine, almost catches but then dies. Lately I can't get it started in the mornings at all.

Things checked/replaced:
- Replaced the fuel pump after I noticed fuel pressure was low/out of range (I was told the pump was going out when I got it 10 years ago and figured now as a good time to replace it) Fuel pressure is good now at the fuel rail.
- Fuel Filter replaced a year ago.
- ECT Sensor tested and in range.
- Air Change Temp Senor replaced.
- Battery is fine.
- Spark is good (didn't check timing but assumed as ok since it runs great when warm).

When I can get it started (cold start) it seems to idle fairly well, occasionally a bit rough until its driven minimal distances.

I don't get any codes (no CEL) so nothing to really report there.

What I can tell from everything I've read is that it could be either the IAC or the intake plenum gaskets (i.e. when cold they are leaky, warm it swells). Apparently a crankshaft position sensor can also cause starting problems but since it runs fine when warm it doesn't seem to be the problem.

Any thoughts?

If it's the intake plenum gasket is that the same as the upper intake manifold on this engine? If so, any recommendations on replacement gasket type or just standard at autozone?

So apparently the IAC is the usual culprit for this problem. I've read that the gasket problem is more common with 2nd gens which is why I decided to try replacing the IAC.

I tried cleaning it per other threads but discovered that I instead got a whistling noise with only moderate improvement. Also cleaned the throttle body.

Replaced the IAC and will have to check to see if things work in the morning when hopefully it is cooler and I can try to duplicate the original problem.

Update: still didn't start this morning. Any help would be appreciated.

A week ago on Car Talk, they suggested these symptoms could be caused by dirty injectors. Warm the engine is very forgiving as far as the spray pattern. Cold, the engine needs a good spray pattern from the injectors.

I've seen too many people who report good fuel pressure only to find out they didn't check the pressure when it was hard to start. Are you checking the fuel pressure when it is hard to start?

Yeah I've checking the pressure when it is hard to start - actually haven't checked it when it is running, just KOEO and during cranking. Always around 30-40psi, even after 5min of sitting off.

Just cleaned the MAFS and that didn't seem to do anything either.

It seems odd to me that the spray pattern would be affected by a 10 to 20 deg temperature difference. Seems like I can't get it started if the outside temp is below approx 55 deg but can if it is higher - if the engine has set overnight.

Is there a way to test the injectors to know if they are dirty?

Oh, I've also done the seafoam thing in the vac line and fuel tank. Saw a bunch of smoke out the exhaust (no leaks that I noticed in the engine compartment). Not much changed in terms of how it runs, possibly smoother idle and definitely a bit lower rpms.

I'm starting to suspect I may have a vacuum leak somewhere now. After replacing the IAC i've noticed a very very high pitched whistle but I've been having problems locating it or even hearing it when I have the hood up. I tried some soapy water spray to see if the intake manifold had a leak and some hose locations but didn't find anything.

At this point I am ready to bring it to my mechanic and see if he can diagnose it. I want to fix it though, after all this I need some satisfaction!

Update:

Well, my mechanic says it is the crankshaft position sensor that is the problem. Apparently it just barely works when you are cranking, enough to send a pulse or two and then stops.

So about $400 later I will hopefully have the problem fixed. I could have replaced it myself but since they currently have the ex hooked up to all sorts of diagnostic equipment I decided to let them do it. Otherwise, if it didn't work I'd have to pay for diagnostics again.

Oh, and he said don't use the after-market CPS because you'll be right back in to replace it again. Guess the good ones cost about $80.

I'll keep everyone updated once I get it back to see how things work. Hope this helps anyone experiencing that same issue.

Update 2: Apparently that wasn't it. It is still hooked up to "life support" and they are still tracing circuits. Sounds like some sort of electrical problem now.

Final update: Turns out in the end it was the PCM. They replaced it with a used one and now it works! Hope no one else has to go through this.

crap...i am going throght this now.atleast i know what to check now.glad you got yours going good.

edoner said:

Final update: Turns out in the end it was the PCM. They replaced it with a used one and now it works! Hope no one else has to go through this.

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what a pcm please help

Power Control Module - it's the on-board computer. It's located behind the passenger kick-panel.

help

edoner said:

Power Control Module - it's the on-board computer. It's located behind the passenger kick-panel.

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ok here it is went the ford is cold it very hard to start, some time i have to use stating fliud to start it went it warm it start rigth up , please help it a 1992 Ford Explorer v-6, if any can help , that would be great, the pcm was replace

If you can find a different PCM from a junk yard or a friends explorer I'd try that to see if it corrects the problem. Otherwise have you checked everything listed above?

Fix

edoner said:

If you can find a different PCM from a junk yard or a friends explorer I'd try that to see if it corrects the problem. Otherwise have you checked everything listed above?

Click to expand...

Ty very much, problem cure, again ty in your debt, mike, it was the pcm

How do i know which PCM to buy? i have a 1992 explorer 4 door 4wd automatic tranny. i have a spare 91 2wd with manual transmission. Are they swappable?

@ Mr.smith: Sort of. The engine managements systems are similar enough between a '92 auto and a '91 manual that I would expect the engine should run and the truck should be driveable. There are a few differences -- most notably, the '91 manual PCM will likely not have the ability to command the 3-4 shift and TCC lockup, effectively turning your A4LD into a 3 speed transmission.

Because of these differences, I don't see it as a permanent fix. It could be useful as a diagnostic step to determine if the problem you are seeing on the '92 is a fault in the PCM or as a temporary fix to get it back on the road until you find the correct PCM.

Hi i'm new to this great forum! haha anyways I am having the same exact problem. and it just seems to slowly get worse and I think i'm going to try the ECM/PCM so I will post an update

Update: It was my fuel pump.