Truck: 94 F150 4.9L Base Model Automatic 123K

Issue: The engine will randomly stall when first cranking it up. It may run a few seconds or a few minutes. It will start right back up and run smoothly until it stalls again. There is no change in RPMs before the engine stalls. It seems like a kill switch is flipped. If you press the gas pedal slightly, the engine will run smoothly and surge during the time it would typically stall, but it will remain running. After 5-10 minutes of running, the engine will run and drive smoothly until it has been shut off for 8 hours or so. There are no codes during KOEO or KOER. Prior to this issue, I had a 332 in continues memory. I replaced the EGR valve and replaced a clogged vacuum line. I then had a surge in RPMs while cursing in overdrive. I followed a thread and installed an EGR restrictor plate. The surge in RPMs while driving went away, but I am still left with the stalling issue.

Recent replacements: EGR valve, EGR solenoid, EGR sensor, EGR restrictor plate, plugs, wires

Distributor cap and rotor are in good shape with less than 20k on them. The fuels pumps are strong and I have tried both tanks. I feel like I may be losing spark, but the symptoms do not point me toward the coil or ignition control module. I had read all of the relevant posts, I am at a lost. Any suggestions would be appreciated.

Thanks, Justin

 

I have changed the IAC, coil, and ignition control module. No change in symptoms.

Any ideas?

 

My guess would be one of the sensors. Examples: throttle position sensor, engine coolant temperature sensor, MAP sensor, there are more sensors also. Most of the sensors can be tested with a multi-meter. The Haynes repair manual gives the specs.

 

If you don't have a haynes, you can goto www.oldfuelinjection.com to find out about testing them. Sounds like it could be a TPS, but check it before you replace it, no need to replace a good part.

 

I will test those sensors over the next few days and post my findings. Thanks for the direction.

JB

 

check ur timing my 4.9 did the same thing till i timed it no i got no problem but a leaky injector but thats a diffrent problem

and yes it ran fine drove down the road fine but cold start it would stall but start right back up
if i pressed the gass a little it just idle rough till u got going
i set the timing and it straitend right up

 

I do not have any experience with checking or setting the timing. I have read several posts and other links on the subject, but each post or link had a different take on how to check the timing and set it. Does anyone have a solid link that is straight forward? I do not have a timing light. Is this essential, or does anyone recommend setting the timing by finding TDC using the manual method?

 

You would need a timing light to check the timing. You also need to remove something called a spout connector before checking or setting timing, should be above the driver side fenderwell near the fender. I think the spec is 10 degrees BTDC before top dead center, I couldn't find it right offhand.

I just happened to read about someone with a 4.9 of this vintage with a problem like yours, and cleaning the throttle body solved their problem.

 

like he said remove the spout conector its a plug next to the distributer that had a gray block in the end

then get ur timming light conect red to positive of battery black to negitive and the claw to the #1 plug wire then start the truck

from the passenger side point the light between the smog pump and water pump and u will see the timing gauge. the gauge has a big notch for 10dbtdc like the notch on the ballancer to that notch and truck is in time

tip the lock nut holding the distribbuter down dont losten it to much just enough to b able to turn it by hand. too loose the rotation of the engine with turn the distributer back out of time

and when ur dun dont forget to tighten the distributer back up and plug the spout conector back in

 

I had all of the electrical systems tested at Autozone, and they tested fine. I changes the TPS last night. The truck ran fine after the change, but would not crank at all this morning. It spins over, but never tried to fire. I plan on doing some tracing tomorrow afternoon. Any ideas?

 

I would suspect a defective new TPS, beings that is what you just changed. Did you get the TPS at Autozone?

 

Test the tps with a multimeter, autozone does not test the system at all. They check for codes and that's it. Check them yourself, its very simple to do.

 

i would have your mass airflow sensor checked. my dad's 94 crown vic had the check engine light but no code. after taking it to 3 places, a fourth found that the mass airflow sensor was a little off when it was cold. and the CEL wouldnt show up until the car had been driven about 10 miles each time. it would start and run fine but when he put it in reverse, it would try to stall just once. after that one time, it was perfectly fine. the stalling would happen without the CEL on but after 10 mins or so it would come on and stay on. i fixed the CEL from coming on by flooring it up to about 110mph. must have cleaned something out too.CEL didnt come back for about a year but it still tried to stall within that timeframe. but 3 places didnt see anything wrong with the mass airflow sensor. the fourth found it was reading wrong. but they said it didnt NEED replaced unless it got worse.

 

94's are Speed Density, not Mass Air; there is no MAF sensor.

 

Well after pulling most of my hair out and some of my wife's, I took off the TPS I recently purchased (Autozone) and replaced it with my old one. The engine fired right up. I have purchased a new TPS (Autozone again) and plan to install it in the morning. It seems that I purchased a bad part on the first round. I am hope the new TPS will stop the stalling. The clerk asked if I had set the TPS before installing it. I am not sure he knows what he is talking about. The TPS does not appear to have a way to change the settings.
While in the parts store, the clerk also mentioned that it could be possible that the spout plug is bad. He stated that when the spout is unplugged, the computer runs a preset timing. He said I could unplug the spout to see how the engine ran, and if it ran good, it had a timing issue. Has anyone heard of this method?
I usually get my parts at Advance and Autozone to save some cash. Should I be getting electrical parts at NAPA or FORD? Does anyone use Oreillys?