'91 Stallling on Acceleration/No Codes

[GJarrett]

I tried a search for stall no code and it wouldn't compute. My brother's '91 (109,000 miles) has new MAS, new fuel pressure regulator, new plugs.

When cold the engine idles higher about 1200-1300 rpm so when he starts from a dead stop there's no problem. Once warm when the idle settles at 700 rpm or so, when he gives it gas to take off from a stop it will stall and sometimes completely dies. Last time he had to wait a half hour to restart it. Seems to me almost similar to vapor-lock symptoms. The kicker is that the diagnostic test is throwing no codes whatsoever to help point to the problem.

He is supposed to join us in Moab but obviously unless this gets fixed pronto he cannot chance taking the trip. Does anyone have any ideas? His mechanic has tried every trick he knows and it still does it.

 

[mdrut]

do a vacuum test, could be a blown gasket at the throtle body or intake, also do a fuel pressure test, could be a clogged filter..

 

[Paul Gagnon]

It could possibly be a problem with the computer. I had a similar problem with mine and after spend a ton of money troubleshooting the rest of the ignition system it turned out to be the computer. You will not get any codes because the computer is basically shutting itself down and wiping the codes. If you have a friend who has a similar truck try swapping computers to see if it goes away. If that solves the problem then get one from Ford because you never know when a junkyard computer is going to decide to fail too.

 

[SteveVB]

gerald,

Check the IAC valve and throttle body, and the throttle body gasket. Clean them, and check the IAC operation. Reset the computer.

One other thought- the MAF thats you said is new- did the MAF get put on and the problem started or you just saying its been replaced lately??

 

[DougSilverblade]

Same stalling problem!!!!!!!!!!!!!!!

I have trouble with stalling also! Bought my '97 xlt 4.0 ohv w/36k off a lease. Great shape strong runner. Problem is a quick out of the blue stall that doesnt kill the engine100%. Only happens when warm/accelerating (off line or out of corners). The motor never shuts down and it happens in a fraction of a second. I've changed all fluids and filters (oil,tranny,front&rear diff.,coolant,fuel filter&injectors) also coil pak new plugs and wires from accel. I've also cleaned the MAS. Xklunker has seen FORD but they didnt want to spend my $$ on testing since I have no test light showing up????? Could anyone please help? If so you'll be #1 on Xmas list!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Paul Gagnon]

Re: Same stalling problem!!!!!!!!!!!!!!!

Originally posted by DougSilverblade
I have trouble with stalling also! Bought my '97 xlt 4.0 ohv w/36k off a lease. Great shape strong runner. Problem is a quick out of the blue stall that doesnt kill the engine100%. Only happens when warm/accelerating (off line or out of corners). The motor never shuts down and it happens in a fraction of a second. I've changed all fluids and filters (oil,tranny,front&rear diff.,coolant,fuel filter&injectors) also coil pak new plugs and wires from accel. I've also cleaned the MAS. Xklunker has seen FORD but they didnt want to spend my $$ on testing since I have no test light showing up????? Could anyone please help? If so you'll be #1 on Xmas list!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

This is a completely separate issue. There is actually a TSB(technical service bulletin) on this. It is fixed by the dealer reprogramming the shift points for the transmission. If you do a search you should be able to find more infomation and the actual TSB number. If you are not getting any satisfaction from your dealer take it to another. This is a free fix.

 

[JoeC5]

Speaking of no codes. This week my truck got 150 to a full tank of gas. This would be highway driving to. My gas mileage situation is getting worse every day. Took it to the mechanic and there are no codes. I dont know what to do. He did notice that there is something funny going on with the way the computer is recognizing the temp of the engine. Hmmm, oh and its not the t-stat, just replaced it. And its not the coolant temp sensor, replaced that also.

 

[overseer]

check the injector O rings. When air passes the injectors due to faulty O rings, the truck will stall.

 

[mrboyle]

JoeC5, don't overlook that it COULD be the t-stat. I have installed several brand new t-stats (from every aftermarket company) that were bad. Therefore I now only run Ford t-stats in my personal vehicles.

 

[JoeC5]

Really, I am going to look into that now. Thanks. How much does a t-stat run from ford??

 

[GJarrett]

Thanks for all the suggestions. I just got through talking with his mechanic who has tried everything you've suggested except he used aftermarket MAS and computer. He will try a Ford MAS tomorrow and then try a Ford computer per Paul's suggestion if that doesn't work. He's replaced, tested, and/or cleaned just about everything and it still does it. The maddening thing is sometimes it does and sometimes it doesn't.

If he can't get this fixed within the next day or so I'll be looking for a roommate in Moab....

 

[overseer]

Have you tried checking your Catilitic converter? I have heard that they sometimes break down and restrict air flow from the engine. Remember Beverly hills cop and the bananas in the tail pipe? same thing!

 

[mrboyle]

Gerald,
I guess it wasn't the TPS? Sorry. I still am stumpped. Have they attempted to determine if it is loosing fuel or spark? That could narrow it downand at least get them in the ballpark.

Joe,
Last I remember they were something like $15.

 

[Big E]

Before you buy a computer go to auto parts store and buy a can or carb and choke cleaner. Then go to the bathroom and grab your sisters tooth brush. Next go back out to your truck. Take the rubber hose off the intake. With the engine OFF. Squirt the cleaner all over the throttle plate. Then open it up then take the tooth brush and clean it really good. You will noitice some pretty nasty stuff coming off. Then take the IAC off of the upper intake and clean it really good. This might help. If it is ideling at 1200-1400 when you start it up this sound like the IAC is not working. Oh one more thing. Make sure the little hole is clean in the throttle plate. This will affect the idle big time.

Eric

 

[FAKRWEE]

Hi Gerald,
I had the same problem when we went to Moab last year. Remember I had to turn back from one of the trail and limp into town. I had changed and cleaned everything but still had the same problem. The only thing I hadn't replaced was the fuel pump. I installed a new one in town and the problem was solved. Hope this helps.

Tom FAKRWEE

 

[mrboyle]

Gerald,
Any luck fixing the problem? Just wanted to see if they had figured it out yet.

 

[Rhett]

JoeC5: Have you replaced the O2 sensors? Sometimes they don't throw codes even if they are worn out.

 

[jemail]

I had a similar problem on my '91 and changed the fuel pressure regulator.
This solved the problem for a few days, then the problem showed back up again.
So I hooked up my pressure gauge/injector cleaner hose to clean the injectors and found that my pressure was actually 52 psi (30-40 is normal).
So I exchanged the regulator, lucky it is a mechanical item and can be exchanged with the receipt.
That fixed the problem.