65mph+ miss

[mercurygm88]

Ok for several months now ive been having a slight miss every now and again at any constant speed. So last week I found out I had a code for a bad egr solenoid, replaced that and all was perfect for about two days. Now its back its a very slight miss only happens at speeds of 65+ and happens more often with the cruise set although it happens with the cruise off just not as often. If im going under 65 with or without cruise engaged it never happens. Its also not very consistent sometimes itll happen every few seconds, sometimes every two or three miles and sometimes it will only happen once or twice every fifty miles. Im just hoping somebody may have some ideas, ive talked to one mechanic who said it may be a faulty pip sensor but when I mentioned its been doing this for months he said that was highly unlikely it also seems to be getting better as it used to be a sudden jerk and its now so slight you can barely feel it any ideas?

Btw car has new plugs,wires,cap and rotor,tfi module, ignition coil, fuel filter, air cleaner, map sensor, and alternator all within the last 6 months also tps is set to .9 volts. Also code 11 both KOEO and KOER so nothing to go off there.

[1990LTD]

My first suggestion was going to be replace any ignition components that are 6+ months old. For whatever reason (I suspect due to the load) misfires on these cars have only appeared at speed.....and they're finicky with ignition parts that are even slightly worn. Might be the nature of the beast - 20+ yr old motor - but I can't say for sure.


Have you got a vacuum gauge to put on it?


Intermittent stuff like this is always the hardest to find.

[tjc78]

Could it be a very small head gasket leak? My 93 Taurus with the infamous 3.8 V6 had a miss under load that was eventually found to be the head gasket.

I also wonder if it is not a miss at all and possibly the A/C compressor cycling on and off? I have driven cars where you could feel it cycling on the highway if you were paying attention.

[1990LTD]

Has the filter/fluid ever been changed on the AOD?

[mercurygm88]

New fluid and filter 10000 miles ago. And I also wouldnt be surprised if maybe it is the a/c compressor cycling I always use the hi-lo function on the heater and I know that cycles the compressor. Ill take it for a drive after work with everything off and see if it does it then. I can tell you that it ia so slight of a miss yoi can barely feel it maybe I shoild ignore it like I did previously and come to think about it this did start happening right about the time I got my a/c fixed, and I know if your driving with the heater controls off and switch to a position that engages the compressor you can feel it kick in but wont know till I get home and get the chance to drive it.

[sly]

I vote for the AC compressor.

[mercurygm88]

Got it figured out it was the A/C compressor so looks like I have nothing to worry about and I need to stop looking for things to be bad. Took it down the road set cruise at 70 with controls off and no problem set to HI-LO and felt it kick in and noticed it several times over the next few miles. Turned around and came home with it on vent and never felt it once so I guess im all good.

[Lincolnmania]

3.73 gears will prob fix it lol

[mercurygm88]

3.73 gears will prob fix it lol

because ill be spinning 3500 rpm at 65 instead of 2500ish lol?

[Lincolnmania]

actually around 2200 at 65 in overdrive

[mercurygm88]

Looks like I got a lil too excited unfortunately it wasnt the A/C compressor. I had to go on about a 60 mile trip after work today and it was fairly warm so I had the heat off and it still did it every now and then. When I got home I found out the parking brake switch vac line was leaking so I plugged it no leaks coming from the cruise dump valve and no other vacuum leaks that I can determine. I talked to a guy at the local auto parts store who told me to spray carb cleaner around the throttle body, egr spacer and where the upper intake bolts to the lower and no leaks there. He also told me to take off the IAC separate it into two halves (which ive done b4 to clean it) and to hook it to a 9v battery and see if it opens and closes quickly if its slow or stuck it may be the problem. The only thing I see wrong with this is I thought an IAC problem wouldnt matter whilst cruising though I could be wrong. Other than this anyone have any other ideas. I am determined to eventually get to the bottom of this.

[mercurygm88]

Ok so maybe I did manage to fix every other problem that this car has had but this one is really really pissing me off and leaving me feeling helpless. I have replace every thing on this damn car except the tps and IAC. This is a very slight miss barely at all only at 65 and above equal with or w/o cruise set and I have no vacuum leaks anywhere. Sometimes it is slight and once and a while sometimes it is sudden and happens several times very quickly. I've talked to several ppl today who all have told me it has to be some or another solenoid or sensor that tell the torque converter when to lock and that its not doing so. But as far as I can find there is no such thing on the AOD just the TV cable and that is all. If I am wrong plz correct me but regardless of what it is going to cost me I wanna get this fixed. One very important thing I forgot is it will not do it in drive only in overdrive

[1990LTD]

A/C will cycle on and off even if you don't have it engaged.

[mercurygm88]

Even with the heat and air completely off? If so I guess thats still possible but it just doenst seem right

[sly]

A/C will cycle on and off even if you don't have it engaged.

false. It will cycle in AC, Hi/Lo, Defrost, MIX. Floor, Vent, and OFF it will not cycle.