Low RPM stumble/poor idle

[blaisetd]

So...i'm still troubleshooting. I OHM'ed my O2, checked my plug wires/firing order. Took off my EGR valve and cleaned it. The diaphram wasn't leaking. When rechecking my TPS voltages I found it had changed since last time. Tried to adjust, but couldn't get better than .71 ratio (4.7/3.36). I'm going to pick up a new one tomorrow. Can anyone steer me to or away from a particular brand or parts store for this part? Autozone is half the price of Napa on this part. thanks blaise

1990 4.0 AW4

 

[RickyN29]

I've had numerous defective AutoZone electrical parts, tough call. The savings in tempting, but not worth the headache.

 

[dirtyxj97]

hey i had the same problem low idle or stumbeling idle and @ almost every intersection it dies...97 jeep cherokee sport auto tranny all i did was replace my MAP sensor and cleaned out my throttle body now im @ a lil high rmp in park and in neutral but normal rpm when in gear hasn't stalled out or died on me yet....what causes high rmp people well in park and neutral only....

 

[blaisetd]

Update:
This morning I started working on it again. I pulled the valve cover to see the pushrods in action. I found that the #1 intake pushrod was not moving/no oil flow. Long story short the lifter was well worn and concave. I tried to check the cam lobe but couldn’t see it very well. Common sense tells me to pull the cam and check it out. Questions: does anyone think the cam is repairable or should I start looking for a replacement? Also what could have caused this lifter failure? The lifters were new about 20K miles ago during a rebuild. Thanks in advance blaise

or http://photos.yahoo.com/blaisetd[url]

 

[blaisetd]

Rant:
A serious engine question is asked and no replies! WTF? Nobody knows about lifters and cams??? Maybe I should have asked what color I should paint my dif cover or can I fit 44’s on a 3 inch lift and I’d get a response….
:explosion

 

[90xj06]

umm. you may have not put it in 100% correct. or it was defective to begin with. and paint the diff candy apple red. tell me about them 44's you got stuffed in there

 

[old_man]

If the lifter is not going up and down, the cam is toast. The lobe is worn down. Get a new cam. This is usually caused by a plugged oil line in the block.

You could have a shot lifter. Does it make any noise, ie ticking or clattering?

 

[blaisetd]

Notice the pic. the left lifter shows almost no wear. It was making a slight tapping intermittantly.....no movement on the pushrod when running.

 

[90xj06]

what pic?

 

[old_man]

Boy that lifter is toast and so is the cam. I can tell you that without even seeing the cam. Now you have to worry about the fact that all that metal that wore off is now floating around in your engine. Most likely the bearings are scuffed and worn as well. Its time to tear it down and see what that damage is. If you paid for the rebuild, you have a warranty issue. This should not happen. There is nothing you can do to cause this. The problem was there when the rebuild was done. It was either a plugged oil line (should have been cleaned and tested) or the lifter was bad.

 

[blaisetd]

Thanks old man....you rule! rant over.

 

[blaisetd]

The gentleman that handles the warranties at the machine shop I used is giving me a super price brake on another short block. This is totally unexpected since the engine is out of warranty. I was just calling to get another opinion on whether to rebuild or clean/new cam/lifters. Good people over @ Precision in Houston, TX
www.precisionengine.com