I have a 1991 F-150 with 120000 miles on it. When I start my truck, it idles erratically, eventually stalling. If I push the gas while idling, it stalls almost every time. When I am driving at slow speeds the engine hesitates, causing the vehicle to jerk. If I am driving above 45 or 50 mph, the truck runs just fine. Every time I slow down to stop or turn a corner, the engine stalls. If I am driving slow (5-10 mph) the engine sometimes stalls. The truck is getting REALLY poor mileage and, when idling, you can smell gas. It started out only stalling occasionally at stop signs, but rapidly got worse. Check engine light comes on intermittently. Pulled the codes and it showed a 31, 32, 41 and 63 (EGR sensor, Throttle Position Sensor, Oxygen Sensor.) I tried a new EGR valve, but it made no difference. I checked the voltage on the EGR sensor and it was a little low, but voltage seems to change correctly as I push the pintle in (on the sensor.)What should my next step be? Thank you.

-warlord raven

 

One bad sensor may cause other good sensors to over compensate giving good sensors false readings. I would place bets on the O2 sensor being bad. But the sure way to check is to do the troubleshooting.
Someone else may have a clearer idea.

My input.

 

change the throttle positioning sensor and see what you get. this causes a lot of your problems.

 

A quick update on my problem... Last night I changed the Oxygen Sensor. This did not fix the problem so I can now rule out a faulty Oxygen Sensor as the culprit.

-warlord raven

 

tps sensor

 

I had the same sort of problem this summer and someone in this forum suggested cleaning the tps. I pulled the sensor and sure enough, it was filthy. It's as simple as removing two screws and cleaning the tip and reassembling. If I were you I'd try that before buying anymore sensors. Hope this helps.

 

Sorry warlord, I had a brainfart. I'm talking about the iac, NOT the tps. My truck would stall at idle sometimes and cutout at moderate speeds. After I cleaned it, I haven't had a problem and that was 3 months ago. Sorry for the confusion.

 

I had the same thing in my f-250 . Turned out to be bad Idle Air Control Motor. Replaced it - the easiest swap in the world. No problem. Thanks to the forum.

 

i am having the same prob with a 92-f150-302-4x4. ithink it is the idle air bypass valve. my question is sould this thing be very hard to get to break loose? i took the two bolts holding it on out but after tyring to break it loose with just my hand it didnt want to break loose.sould i tap on it with a hammer? i didnt want to damage it,thought i would try cleaning it first to see if this was the prob? thanks

 

Try twisting it slowly while pulling it out or you might want to use a large pliers and put some tape around on both sides of the pliers so it won't damage the IAC.

Clean both the IAC as well as the spot where the IAC goes in.

Since you also have an error pertaining to the EGR, it's time to clean the passage ways and the pipe to the EGR because it is more likely blocked and full of hardered carbon.

A lot of problem with engines is that it's full of gunk cargon blocking all sorts of passages ways and sensors.

Use a $6 Seafoam Motor Tune-Up. 1/3 in fuel tank, 1/3 in oil crankcase, 1/3 in intake vacuum (use the brake booster vacuum hose with a funnel while the engine running). Let it set for 30 minutes, the longer the better. I'd recommend driving it at night at less traffic highway and push the throttle at WOT for a few seconds. There would be a lot of smoke and the other driver thinks they have a fog situation. Get an oil change after that.

The sympton you are talking about could be also a clogged cat. If you have not replaced your spark plugs, try replacing it as well since they are cheap. Make sure you set the spark plugs to proper gap and then use a torque wrench to tighten the spark plugs and never use an anti-seize compound.

 

I am new at this, and my truck does the same thing. but only when it is cold and has been geting a little worse.
You said you found the codes.... how did you find the codes?
My dads Dodge van you turn the key off and on several times and the dash lights flash.
Is there something similar?
I have been told to clean this one thing.. cant think of the name... sits on top of the engine long and cylinder shaped?

 

Guys I'm reading along and trying to follow the story, but, I have one question ...Why was warlord raven smelling gas?? Is it spewing out the exhaust or is it leaking from the engine fuel/emissions systems somewhere??

 

it could be running to rich and not burning all the fuel