Hi all,

Trying new approach...

1992, F150, 5.0, AT, 2wd, 180k, dual tanks

Here are the symptoms:

1.) Upon cold startup engine starts idles then dies (without giving gas), restart and it starts fine. Then it will idle ok, but at times seems like it is hunting for a correct idle, idle will go up and down a little before settling into the high idle before warming up where it will correctly idle down.

2.) Idles much rougher or with a miss in D and R. In P and N idle is pretty consistent and good with a hint of roughness/miss but not sure if that isn't the way it's always ran.

3.) When depressing gas pedal have a rough running/miss at certain rpm ranges. Maybe a 1k, 2k, and 3k (tach doesn't work below 2.5k)...however, rough running/miss goes away in between those ranges and truck runs fairly smooth.

4.) Can feel a rough running/miss when first accelerating and then again when quickly taking my foot off the pedal. This rough running/miss, in my opinion, occurs right after or right before the throttle plates open/close.

5.) Have plenty of power when accelerating and no signs of bogging down or missing.

6.) Truck has always had a rough running/miss right after switching gears when driving on the road...almost like bogging down.

7.) Symptoms are consistent when using either tank.

I have done numerous things to the truck recently, new coil, plugs, wires, fuel filter, dist. cap, rotor button and check numerous sensors for correct operation per DMM. The problems were far worse before changing coil, plugs, wires, dist. cap and rotor button.

Everyone has been great so far on here and a bunch of help. Just trying a different approach to resolve this last issue(s) before giving in...

Thanks,
Rick

 

No mention of pulling the codes..

 

The only codes are 111 and 111.

Additional observation today:

Truck has been sitting since Thursday. Started it up today (much cooler ambient temperature) and truck started and ran, without giving it gas, ok. Seemed to have a mild rough running condition, but key point is that it did not stall. Has stalled during cold start ups in warm weather...

Thanks,
Rick

 

As Conanski pointed out, you haven't pulled the codes- see fordfuelinjection.com for the procedure if you're not sure how to do it.

Otherwise, what all sensors have you checked? Was the TPS included in those checks? I'd also try giving all the battery connections a good cleaning.

Start there and keep us updated.

 

You may have a bad ECT or ACT sensor.

 

Codes were pulled, 111 and 111.

ACT, ECT, IAC, timing, and TPS all check out within specifications as per fordfuelinjection.com and Haynes.

Only codes that have been received on truck are 634 - MLPS and HEGO running rich. HEGO cleared up once I did the "tune-up", was getting cross-firing, and has not shown up since. I have not driven the truck on the road enough to get the MLPS code, yet. But, my shift points seem high, 10-15mph, 25-30mph, etc.

No vacuum leaks of any significance that I can tell, pulling 17in with 1/2in (max) needle bounce...at idle warm.

 

You say the TPS checks out to spec but that's usually just the open and closed positions. Do the measurements increase/decrease smoothly from closed to open with absolutely no glitches or dead spots? An old analog multimeter would be best for this test.. it's easier to see dead spots.

Another thing would be to disassemble and clean the IAC valve to ensure it operates smootly.

Is the exhaust system stock or otherwise?

 

You are correct on the testing of the TPS. I do not have analog meter only a digital one. I will see if I can get my hands on one to test the smoothness of the operation.

I did clean my IAC a while back, however I only sprayed TB cleaner onto and removed most of the crud in there. The spring controlling the valves did return when released. Is there a better way to clean it? Also, when disconnecting the IAC truck runs REALLY bad at idle.

The exhaust system is stock. New muffler and tailpipe last year.