I have been having problems with idle. Ford dealer replaced the fuel flter, IAC valve and did a complete tune up, After $400 still have problems. I bought a special cleaner and sprayed the MAC valve that looked absolutely spotless.

The check engine light is on again and the truck will not idle cold, have to keep the rpm's at around 1500 on cold start up. After the engine is warm it idles fine but of course check engine light is still on.
If I remove the posotive battery post and reset the computer, the check engine light goes off. Once the weather is cold again, same thing, no idle on start up and check engine light comes on again.
Any suggestions for what to do next??????????

 

You might want to find out what the check engine lite code means. That could be just about anything and it would help to maybe pinpoint your problem. Was the lite on before the work was done and what was the code then? Is it the same code? did the dealer miss the problem?

 

I recently did this repair on a Lincoln Town car. The customer said the car would start, but would stall immediately after. When I tried it the engine would only idle if I held my foot on the gas pedal is would not stall. I put the scan tool on it and the first thing I saw was the TPS was at 22% at closed throttle(idle). It should be 0% or very near 0% at idle. I swapped the TPS and it was somewhat better, but still stalled at times. I looked at the IAC counts and they were too low so I changed the IAC. That did it. Since the dealer has already changed your IAC and fuel filter I'd monitor the fuel pressure. If you can get the engine to run how does it perform at WOT?

 

I will see if I can get my neighbor to check the error code with his machine.

Help me out, what is TPS and WOT????

 

TPS:Throttle Position Sensor
WOT:Wide Open Throttle(pedal to the metal as truckers say it)
Since the parts I would have changed have already been swapped I'd check fuel pressure. If you have fuel injection the pressure has to be very close to or above the rated value. Just a couple pounds low will cause driveability issues. Do you have misfires at WOT and going up hill? This could be a result of insufficient fuel pressure. I would also check the ECT sensor. Are you going into closed loop? If not this could be due to the ECT not telling the PCM that you motor has warmed up enough to leave open loop and go closed. If you hold the gas pedal down when the engine stalls can you keep the engine running? If so, I'd look realy closely at the IAC to be sure it looks new since you say the dealership installed a new one and be sure it is properly connected.

 

The truck runs great after it is warmed up. No missing. Full throttle it runs great, lots of power. No missing at all when warm, uphill, downhill. The only problem is at cold start up, have to keep the rpms at 1500 until warm and then when warm, runs fine. Will not idle or stay running only when cold.
If I reset the check engine light it stays off until cold weather. When the temp outside falls below 60 degrees I get the check engine light. After the reset and the outside temp stays above 70 degrees no more check engine light until the next winter.
Given this situation, what would you check first or where would you start to trouble shoot the problem???

 

WHAT ABOUT HEGO OR O2 SENSORS??

 

From your description, I would say either a bad IAC and I know you have replaced it, or a MAF meter problem. The reason it might be the MAF meter is that the pcm will try to use it for about 120s seconds after start and if it cannot control the parameters, then it will "go back to the tables" and run off of known good value as we say in the biz. It will then ignore what that sensor says and run better "off the tables". But I still suspect the IAC.

 

I guess I will have to post back later. The neighbor brought home his NAPA computer and checked the engine with key on and running both. Got only two codes, P1116 and P1127, both not problem codes, just engine not warm enough, and ECT sensor out of range. He reset the engine and check engine light went off. I am sure it will be back on next cold start and we will check again hopefully with an error code.
Thanks for all your help and I am sure I will be back here soon.

 

I talked with a guy at Ford. He said with the codes I found that the probable culprit was the ECT sensor on the thermostat. Does this sound right or am I just changing out parts??????
He said it sounded like the temp sensor (ECT) and then looked up the codes The P1116 is the ECT (engine coolant temp) and p1127 is the O2 sensor (on exhaust). He said when the ECT goes bad it is telling the engine it is warm when it really is not so when it is cold on initial startup it will not go to high idle. It will also cause the O2 sensor to throw a fault code.