I've checked everything... vacuum lines, I've replaced the PCV valve, EGR tube, spark plugs, removed chip, etc. Are there any sensors prone to failing? I've not gotten a CE light, and it goes away if I give it some gas for a second. I'm guessing it's the TPS, as the truck will rev up when I give it gas in neutral, then drop back to about 1500 rpms and stay there for a second before it drops back to the 500-750 range. Then it'll drop back down to about 500 or lower and just be shaking a rumbling. It sounds like a hot cam and the whole truck shakes from it. Could it possibly be a dirty or bad fuel injector?

Help!!

-Flea

 

This sounds a lot like a problem I had with my truck. Ended up the A/C was dripping on the oxygen sensor and shorting it out. Extended the drain past the O2 sensor, put in new sensor and the problem was solved. My truck would idle very rough and even stall it only happened occasionally so it was hard to track down the problem. At least it's an idea for you to consider. Good luck.

 

I think I'm going to go ahead and replace my upstream O2 sensor for the passenger side (driver's side took a dump already) and see if that gets rid of it. I've heard that O2 sensors can kind of half way fail without triggering a code. Was your truck fine at highway speeds and most of the time while idling? Mine does fine when I'm moving, but idling it's rough only some of the time. Then tonight, it just died. Started back up no problem, but it just cut off. Could it be a charging problem? I've cleaned my MAF element, checked the EGR system, and was working on my IAC today, but ran out of time. ERG! I'm getting ready to pull my hair out as I'm moving in a week and a half!!!!

-Flea

 

With all the dealer techs floating around in here, you'd think that someone might have a clue....

 

How many miles?

How many miles on the new plugs? and was the problem there before you changed them out?

What was the condition of the plug boots when you changed the plugs...they are known to crack and short to the well.

Just a couple of additional things to check:
Fuel filter (good for 15000 miles)
Plugged or inoperable Gas tank vent system (may create a vacuum in tank and subsequently low fuel delivery at idle)

 

Got 60K on the truck, 3K on the new plugs, and I just changed the fuel filter not 2 weeks ago. I know my IAC wasn't working right, and it finally broke altogether tonight. Truck now idles in the 1000-1500 range. I'll have to check that vent line on the tank.

Thanks

-Flea

 

bad coil pack giving you a misfire?????????? thats what happened to me anyway...did you reset the computer before all this happened...

 

Twice... once with the chip and once without... I've narrowed it down to the fuel/ignition systems, as it's now happening while I'm driving. Today while on my way home, I was going up a hill and lost like 50 HP! The truck was in first gear turning 5200 rpms trying to climp a hill I usually climp in OD! Wasn't there something about a heater line leaking onto the #4 coil pack?

-Flea

 

yup if your heater lines going to the heater core are leaking they drip on the #4 pack and kill it...i figured the computer was relearning the idle point with your previous posts ..Mike T was telling me when you reset the computer it sends out full spark to your packs untill it learns where to set them..so if your packs are old and weak it can hurt them also.....

 

Plugged or inoperable Gas tank vent system (may create a vacuum in tank and subsequently low fuel delivery at idle)

I've noticed at times when I remove my fuel cap there is indeed a vacuum in the tank. Mine idles rough sometimes too, and I often thought the tank vacuum might be the culpurt.

Anyone know how the fuel tank venting is plumbed on the new series trucks, and a good check to see if we're venting properly?

TIA
R...

 

After remembering the #4 coil pack can be damaged by a leaky heater hose, I peeked my head under there today to have a looksee and low-and-behold... my problem! I noticed the green residue on top. Looks like a new coil pack is in order. Thanks everyone for your help.

-Flea