Hey guys, I need help. My 1992 F-150 5.0 is running weird and I need it by friday to take my boy camping. Ive promised him for weeks now. I went to the store tonight and did not let it warm up. The store is about a mile away. Half way there I stopped at a stop sign and the truck tried to die. I gave it gas and a hesitation followed and away I went. The next stop was about a 1/4 mile at the stop light. I stopped and again the truck tried to die again. When I pulled into the parking lot of the shopping center, I pressed the gas and let off real quick to see what happened. The rpm's dropped to nothing engine stumbled and quickly reved up again. Sorta surged is the best way to describe after it stumbled. I got home and remember the truck never did get to normal temp. I reved it in the driveway and let off and again it tried to die. Idle was all over the place. My question is would it be the Idle Air Control Valve or maybe the Throttle Position Sensor. I pulled the IAC off and it looked clean. The rod moved freely. I soaked it anyway for the night and will reinstall tomorrow. Any other ideas. Thanks I dont want to let my boy down, we need the truck to pull the camper this friday.

 

a "bump" for the kid.

 

If it runs fine going down the road and has a lack of power when accelerating and poor idle and trying to die then your EGR valve is more then likely stuck open.

 

I wondered about that. I got a new TPS and another IAC to put on. Can I clean the EGR or plug it off.

 

Sounds like a vacuum leak. Check for cracked vacuum lines, and have a look at the vacuum resovoir on the pass side fender well(juice can). You may have another on the drivers side as well. Pull the lines off the resovoir and put you finger over the ends, if the idle smooths out you found your problem. You can use the same technique to test the EGR for vacuum leaks.

 

Wouldn't a vacuum leak cause it to idle too high? I'd think that the most likely culprit would be the idle air control. EGR would make it run rough, but it should still idle even though it sounds like it's got a nasty big cam. I would run a self test and see if the computer has any codes stored. Instead of randomly guessing at what the problem is, there's a better chance of a code pointing in the right direction so you can make a more educated guess.

If you've never pulled codes yourself before, do a quick google search for "EEC-IV self test" click on one of the links and follow the instructions.

 

Hey guys thanks for all the help. I replaced the TPS and the IAC, cleaned the throttle body and the EGR valve. I started it up and it runs great, however the idle is about 1100 not the 800 im use to. I drive it all afternoon and it did not change the idle. Is this normal since I replaced so much stuff and cleaned the crap out of the manifold and the throttle body.

 

Make sure you put all the hoses back on that you took off, this is usually a vacuum leak and a hose off will cause it. Maybe the hose from the charcoal canister to the throttle body.

 

Also could be that the TPS is not adjusted properly.

 

Alz, the bolt holes in the TPS were not elongated. I dont think this TPS is adjustable.

 

Do you have a volt meter? If so, test the TPS output to make sure that closed throttle voltage is around 0.9V. Another thing to try is to reset the computer. It may have adapted to the old sensor and as a result it keeps the idle too high with the new one. If you get a chance, disconnect the battery for 10-15 minutes and see if it makes any difference.

 

What does the TPS have to do with idle speed?
Are you saying the TPS changes the timing and that will increase idle?

 

Cleaning the throttle body is a no no. You have to replace them, these throttle bodies must not be cleaned inside the bore, as this cleaning will impair the sensitive coating.

 

Since you said you replaced a bunch of sensors, someone also mentioned did you reset the computer. Just leave the battery unhooked over night and plug it back in so the computer can do a base check to see if the sensors are all in the right place.

If the truck still doesn't warm up consider replacing the thermostat. The engine coolant temperature sensor will keep the truck running at high idle to warm it up to ideal conditions. Look at fordfuelinjection.com to read all about the sensors that control idle and engine performance and it has handy listings about what is on spec for the sensors, as well as testing procedures to see if the sensor is good.

I would recommend the thermostat change if your truck is still not warming up due to a stuck open thermostat as well as unplugging the computer so that the keep alive memory clears itself due to loss of power.

 

Okay, Goood news. I unhooked the battery, left it. I hooked it up this morning and let it warm up in the driveway. Everything seems to be excellent! Guess the computer needed to get use to the new sensors and clean throttle body. Thanks guys for all your help!!!!! Ryan