I have a '93 F150 w/ 5.0 automatic. When I come to a stop, the truck idles up & down for a minute or so before it smoothes out. It seems to be worse if I come to a quick stop. Any ideas?
Thanks,
Plaidad

 

Have you disconnected the battery cable recently? Done a battery swap?

The computer needs to relearn the Idle again. If the IAC (Idle Air Control) solenoid are gunked up or bad, then you'll have an erratic Idle. Remove the IAC and clean it with a throttle body cleaner and clean the spot where you have removed the IAC from.

IDLE RE-LEARN PROCEDURE:
Disconnect the battery cable and leave it disconnected for at least 15 minutes.

Reconnect the battery cable and start the engine "do not press the gas pedal" but just crank the engine and let the engine running.

If the engine does not start, then turn the ingition switch off and then start again and again "do not press the gas pedal at all".

Once the engine starts running, let it run for at least 15 minutes and turn if off.

Note: The engine RPM might be erratic during the idle re-learn because the computer is trying to find the right idle settings.


An FYI folks: The TPS is the most overlooked sensor with regards to erratic IDLE problems. Be careful when squirting cleaner solvent in the throttle body because the TPS will "fail" if it is saturated with that cleaner solvent.
Never attempt to clean the TPS with any chemical because you can't clean it and if you try to clean a good TPS then it will "fail". TPS is cheap so just replace it.

 

I have the same symptoms with my 89 351W. Every sensor on my truck has been changed and I even tried a different computer. Tried two new IAC sensors and even tried two modules. New dizzy and a new throttle body. I haven't been able to solve my problem yet but mine doesn't do it all the time and it some times likes to stall.

 

Hey RTM and plaidad,

if the re-learn isent the problem, on MAS air equipped vehicles even the slightest amount of air entering the intake stream after the MAS sensor will cause similar problems. So, check all hoses for leaks and assure that all clamps are fully tightened.

I'm not sure if either of your vehicles are mas equipped but if they are, I hope this is beneficial.

 

I have the good old speed density system and I have tried to find my leaks as best as I could. Some think I have a bad connection some where but I can't find it either.

 

I had an idle problem on my '88 302 also.

I just changed the timing chain and have no idle problem now. My truck only had 56K miles on it.

 

Test the sensor before you just go replacing things because of something that was said on here. Have you checked to see if there are any codes in the computer?

 

tadslc, did you have an idling problem every time you slowed down or was it random? Mine is random. I have about 5 degrees of backlash in my chain when I checked it. It could very well be a little more than 5 degrees.

 

RTM- It was random but at the same time happened much more often than not. It makes sense though that excessive play in the chain would effect the idle.

But as implied earlier, just don't start replacing parts because it corrected my problem. I was in the process of replacing a leaky water pump and had to take the front cover off to get at some broken studs. I changed the gears/chain while I had it apart.

Good Luck

 

Well I am already in the middle of changing the chain. It would be done already but Iwent to the drum store so I should have it done tonight.

I am going to change the heater core while I am in there. The truck is an 89 so this all can only help. The water pump looks orginal so I am replacing it also. It still had gray paint on it like everything else. The chain was loose and there is wear in the cam gear. If it doesn't help at least I know it's good.

I will try to remember to post the results on my idling problem.

 

I drove the truck with the new timing chain and no change. As soon as the truck idled down from the cold start it had the same miss and when I went to pull out of the garage it started to search like it always does. As soon as I stopped at the first light it was fine. The first stop for me is only 300 yards away. Drove it down the highway and back and it never acted up again. The down side to this is this is the exact same thing it does all the time. One minute it wants to search and then the next it's fine.

I am out of things to change. I don't know what to do now other than wait for what ever it is to show up with a code or something.

 

Hello. I just had the same problem, except for I also had the additional symptom of excessive fuel consumption. Mine was surging and using a bit more fuel than it normally did. My problem ended up being a faulty Fuel Flow Regulator. Instead of 35 lbs pressure, I was getting 120 lbs of pressure in the fuel rail. I changed that and the surging is gone and I am again back to my lovely 23 to 26 mpg/hwy.

I had cleaned out my BY-pass air/Idle Control Valve, and tested all my sensors to as well. But luckily, we have an awesome EFI shop in town and it took him 2 minutes to identify and confirm my problem. Unfortunately, the Allen screws that hold the regulator in place are a B*TCH to get at...LOL

 

I have replaced that as well already.

 

rip off the ISC-BPA, separate the ISC from the BPA, clean the dickens out of the BPA with carb cleaner and pipe cleaners, replace, relearn, drive in peace.

 

What are ISC-BPA? Do you mean the IAC sensor? If so I myself have a new throttle body and have had two new IAC sensors and still have the problem. I am very tired and can not think straight. I think I am catching a cold.