My 94 Z28 a4 has been running rather sluggish off the line, but after about 2800 rpms the power kicks in (80% of the time) and runs real strong. Anything below 2800 rpms (100% of the time) is really bad, the pedal can go to the floor and its like a friggen small 6 cyl. I just noticed that the exhaust smells rich, and is much more noticeable now than ever before. Could this be my 02's? what else would cause me to run rich and lose power? Any info would help! Thanks

 

Probably not your O2's, since they're not used at full throttle. Could have bad plugs/wires/coil maybe. EGR valve may be stuck open, and choking it out in the low rpm's.

 

First of all if you are "souping" you run the risk of cylinder damage. Don't run it except to diagnose the problem. Check your oil for a fuel smell and change it immediately. You should start by looking for dead cylinders. An infrared thermometer is the easiest, a squirt bottle of water on the ex manifold is an acceptable sustitute. When you find the cool manifold tube, check spark at that cylinder and even throw in a new plug. Retest the cool manifold. If it's still out, try swapping wires from another cylinder. See if the cool manifold moves with the plug wire.

By all means, quit driving if you have a dead hole!!!!

 

Plugs and coil (MSD) are brand new, both replaced within the last 2,000 miles. The oil does have a gas smell to it. I will change as soon as next paycheck comes in, and i have no choice but to drive it. wouldnt it run rough if a cylinder was out? It doesnt run rough, and all these problems are not at WOT....the car doesnt see wot much, but lately its been close. I will check for a cool exhaust tube tomorrow, and the wires probably do need to be changed...i will do that in the next week most likely (dreading that especially after the PITA the plugs were)...how can i check EGR?

 

Well, if the probs are NOT at WOT, then it could very well be O2 sensors that are shot. Has it thrown any SES lights at all?

 

I had an SES light go on once for about 2 miles and go off...i thought it was just a fluke, and it never did happen again....also my gas mileage has dropped significantly...from about 22-26 down to about 14-16...what do ya think?

 

Plugs and coil are new, did you replace the wires?? I had this problem a few years ago. I installed new plugs, it solved the problem for a day then it happend again, turns out the wires needed changing. put your car in a pitch black place, then open your hood, see if you see a light show under there. Since you don't have the problem at WOT, you may have the same issue i had.

 

Sounds a lot like O2's the more you describe it.

GM Parts Direct has stock AC Delco replacements for like $37 dollars or so a piece. I'd be willing to bet thats your problem, but I'd get it scanned first, and see what that light was.

 

Alright well i have a buddy who knows how to test O2's...so he is gonna give me a hand wednesday...and ill replace them most llikely no matter what...and as for wires...thats my definite project ( with my headers that is) I wasunder the hood in a dark place a week or so ago, and did not see a light show....so i will replace with the headers and will most likely be doing so in the next two months....thanks for the help...if there are any more ideas please send them on, i want to take the car to the track soon and get some pre-headers/cutout times...thanks

 

if you have stock wires, and put headers on, you may see that light show soon definatly get a good high temp set of wires

 

I had a problem with my 95 Z28 A4 a low revs it would stumble when I stabbed the throttle and then rev cleanly through to the red line. this became a problem cause when you are cruising around town you are just off idle and it would get stuck it this stumble.

Like you I went the obvious route plugs, plug wires and then O2's but none of these solved the problem. ( by now it was running like a bag of s**t)

So I order a new opti and msd coil fitted those and the Z pulled like a train.

I then got my cable and scanned the car and found the MAF was bad code 48 and the car runs on speed desity when you have this code. My car had always run rich ever since I got it 8 months ago.

So I got a used Maf on Ebay for $65 delivered to the UK put that on and now my gas mielage has returned and the car goes like stink.

Hope this is of help.