Hey Mark Has anyone checked the IAC Had one go bad
on me once and it was similar to what you got Something else to check.I drove it that way for 6 Mos thought it would be pricey but 54.00 later I wondered why I waited so long. God Speed and Good Luck with your Diag.

 

coil pack could very well be the cause

 

Weak coil packs show up when you're under a load - such as cruising along at 65 and suddenly floor it and it stumbles. But if it is a bad coil pack(s) it wont get any better and continue to miss.

I had my 01L I bought new just shut down once this summer for a few seconds. I was slowly accelerating from a stop light and suddenly the engine just flattened out and I checked my fuel pressure guage and my fuel pressure was falling from around 40 psi down to about 25 psi. I got off the throttle and the fuel pressue slowly increased back up to about 28 psi. Normally at idle I had about 30 psi. As fuel pressure dropped when the engine cut out, I suspected a fuel system problem so I changed the fuel filter (had about 2500 miles on it) checked all relays, voltage at relays, engine compartment grounds, etc but it made no difference. I could get fuel pressure reading of 40 psi at 0 vacuum, but it would not increase with boost. Also I found no codes displayed. I also reloaded my tune onto the PCM from my SCT II but nothing seemed to make a difference, but the truck started and drove fine. However, when pinching off the fuel return line and disconnecting my electric fuel pressure sensor and with a mechanical guage installed, I read 85 psi. I bought another fuel pressure sensor - and after installing it, everything reads as before on my fuel pressure guage. Engine and truck seem fine - runs as strong as always.

Unfortunately I have no explanation as to why it initially cut out and what, if anything the failed fuel pressure sensor had to do with it. It has not happened since, and I now suspect that for some reason I had a momentary electrical failure, possibly a PCM failure.

 

sounds like the IAC get some seafoam and clean that thing out

 

Just received my clunk washers yesterday and hopefully get them installed next week some time. Also got a lens for my left running light as it is moisture filled and will have that installed too. If the clunk washer does not work, and the body mount does not work, it is to the body shop, which is where I should have gone in the first place. The stumbling(other problem) is really kind of weird. It alway seems to happen when my foot is not completely on the go pedal, and is resting on the lower quarter of the pedal. I go for days with no stumbling and then it happens, whether going 15 mph or 65 mph and usually my foot is not completely on the pedal. Not sure what the cause is. I am going to have the coil checked also.
Mark.

 

Do you mean they removed all of those sensors permanently?
Without these sensors, it's a wonder your truck even starts and drives.

 

Well guys and gals. Hiccup solved at the tune of $500. + out of pocket as not covered by 6 months warranty. MAF and EGR valve plus install. Clunk washers did not work and had a body shop owner look at truck today and he will look at in seriously next week with sensors etc. Could possibly be right rear spring perch on front side. Question: should brake calipers move at all when grasped by the hand?
Thanks Mark.

 

I guess my last post was a false alarm as the hiccup is still happening. It happened twice today under 15 mph both times. Just took off from a stop sign both times and it is like you are taking the foot off the gas pedal for a split second and then continues on normally like nothing happened. I have gotten on the gas briskly, and it pulls like a race horse, with absolutely no hesitation what soever. It just has never happened under heavy throttle. No more check engine light though. Hey whitebolt04, the sensors are still hooked up and the only one that taken out of play is when the exhaust systems was put in(ox sensor right bank)as welding was being done and was reconnected afterwards. Right now it is anybody's guess as to the problem. Will let everybody know when the problem is solved.
Mark.

 

I am not a mechanic nor do I know abreviations but what is IAC. If I cannot get this fixed soon, it becomes a money deal with me. Can't keep putting money into something and getting nothing fixed. Can't afford it for sure. Truck will go on the market if my problem is not solved soon.
Mark.

 

IAC = Idle air control

 

JollyGreen,
Thanks for the info and will have it checked. Hesitated twice today, again under light throttle and also started up a little harder than normal. I remember when I used to have my old performance cars, as you kind of revved them before you turned the engine off to get excess fuel cleaned out. This thing feels like it is loading up to a certain extent.
Mark