OK, I am having a problem and have been having issues diagnosing. 1996 Z24 with 173,000 miles, 4 speed auto.

The problem occurs at 50% throttle or greater. It seems as if the engine bogs down, and doesn't want to increase RPMs. It feels almost as if a traction control system or something of that nature is limiting throttle, but no lights appear, and traction is not an issue. Eventually, it breaks free, only to do it again further up in the RPM range. It most occurs between 2500 - 4000 RPM, and always with significant throttle input.

I received a suggestion that it could be a dirty MAF sensor, since I run a K&N filter (has been installed almost 90,000 miles now). I bought MAF sensor cleaner, cleaned it, and it did not seem to make a difference. Cleaned air filter, changed oil, newer fuel filter (less than 10,000 miles).

Basically, am out of ideas, and don't have the time to take the vehicle to the garage right now, as its a daily driver. Any suggestions would be appreciated. I am pretty handy at working on it, as long as I have guidance on where to look for things. Thanks in advance.

John

are you sure you cleaned the MAF sensor properly? I mean, being that there isn't one on the 2.4 and all?

Have you done a tune up? I would start with the basics, air, oil, plugs. Do the regular basics. When did this start? Was it after you did anything to it?

To answer your questions:

A tune-up was last done about 15,000 miles ago (158,000 miles), with no problems until about 2,000 miles ago (171,000 on the odometer).

Oil has been changed regularly ever 3,000 miles. Plugs last replaced at 150,000 miles, and replaced before that at 75,000 miles.

Air filter cleaned (K&N type) every 20,000 miles, last done at 172,000 miles. Fuel filter replaced at 162,000 miles.

Nothing mechanically changed.

As for the MAF sensor, there is a sensor in the tube from the air filter to the intake manifold. According to a diagram for the engine, this is listed as the MAF.

Also, the problem does not always or consistently occur. There are times when the engine has no problems at all, and other days, it will do it all the time while accelerating. Temperature seems to play into this a little, as it will occur more often on a warm engine (than a cold one), and also more often when the air temperature is warmer. Moisture in the air does not seem to play into it, but if the A/C or defroster are on, it seems to be more pronounced.

Thanks again for any help.

John

That sensor would be your IAT intake air temp sensor. The MAF sensor is a very large sensor and is installed in-line with teh intake tube. You can't mistake the MAF for an IAT, thats like mistaking tits for bawls, and let me tell you, my hands will be on the tits, not the bawls. I won't make that mistake, so why make the MAF/IAT mistake? lol

thanks sweetness for the analogy.

A/C and defroster turn on your A/C compressor pump which bogs the engine all on its own, so its accentuating the issue.

Seems like your tune up is on schedule.... hmmmm.....

its a high mileage motor? maybe the cams are wearing? Is it making any noises?

I've had the same problem for over a year.

Installed new:
Plugs
Wires
Coils
IAT
Crank position sensor
Cam posistion sensor
Throttle position sensor
Full tune ups
Seafoam

Even put in a different ICM and relocated ICM with a heat sink to keep it cool, but still, no dice.

However I do have a bad A/C compressor that had leaked all the coolant out, but I thought that there was a sensor to tell the electric clutch not to engage if there was no coolant pressure?



Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.

No other noises, and doesn't need a tune up, as it was just done not that long ago, and it is not consistent. If all it needed was a tune-up, I would think the problem would be consistent.

I am guessing that you didn't figure out the problem, Transporter7220?

I am starting to think that it is the coil housing, as another thread here said they had the same problem and that was the cause.

pull the plugs...that's a lot of miles on stock internals which wear over time. If the plugs are covered in oil, it could be worn piston rings or valve guides/seals. Check the spark plug boots for cracks. Coils are common to be bad after awhile as well.

Still trying to figure it out, just changed the crankshaft position sensor last weekend, which was a pain. But it didn't help.

Almost everything I've changed could have been the problem, but it didn't help.

I'm going to try the MAP sensor and start replacing all my vacuum lines next.

Also, I know another guy with the same problem, and we've both changed the same things, he was a couple weeks ahead of me on the crank position sensor, but it didn't help him either.

Mine only does it once, right after you start it from cold. After it gets over it's little fit it runs great. I'm starting to wonder if my computer is having problems.



Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.

Well, pulled the plugs last night. They look fine. I'm hesitant to start throwing parts at it, due to its age. Any other suggestions?

Also, yours seems to be different in that yours does it only when cold. Mine does it only when the engine is warm. While the engine is not up to operating temp, it doesn't seem to do it at all.

The other issue I have, though, is that when first started, it starts, but doesn't run up the revs right away when cold. For example, previously, start the car, engine revs to about 1500 rpm and settles down. Now, it starts, turns about 800 rpm, then about 3-5 seconds late, goes up to about 2000 rpm and then settles down. Also, about 1 in every 8 or so starts, if the engine is let to idle, it starts revving and almost dying, cycling back and forth until you either play with the gas or put it in gear.

They may or may not be related, as the starting issue has been occurring for over 20,000 miles now, but they could be.

I would try the throttle posision sensor. If you don't want to buy a new one you could always get one from a junkyard, but that has the possiblity of being bad also.



Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.

Check your ignition housing. It's the white housing that the plug boots connect to. If you have a buddy with a 2.4L that runs fine, swap it out and see what happens. Sound very familiar to what happened on my car.

check your main o2 sensor, the one in the header. it fixed my problem for a little while. but i need a heated one. its a problem with it not getting hot enough. then after the car warms up it will be just fine.





click sig for my car audio videos

I'll have to give that a try, thanks for the idea.



Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.

Well, after reading up some more, I am thinking that whatever is bad is causing my Cat to go bad. Starting the car first thing (while cold) creates a foul odor. I am guessing that during the hesitation, gas is getting passed through the exhaust system, and settling in the cat. The cat was new less than 2 years ago, so I really dont want to have to replace it. This would also explain the hard cold starting.

I hope to get to replacing the TPS this week, although I am no longer sure this will help the issue, as it could also be the coil housing. However, being that the coil housing has been replaced in the past, I am wanting to do the TPS first. I will keep you informed, as I hope something will correct the problem.

If gas is getting into the Cat, and the new TPS fixes the problem, do you think that the Cat would eventually clean itself out? Thanks.

Also, forgot to mention, that with the windows open, and the engine bogs, it almost sounds as if the car wants to backfire, or has a bubble in the exhaust. I am guessing this is the unignited gas passing through. Any additional thoughts?

Do you have a code for the cat yet? If not, maybe you'll get lucky. I wouldn't drive it. FYI, the dealer went through 3 coil housings on my car before they found a good one.

No codes registered, no check engine light, nothing.

Don't have the option of not driving it, as it is my only vehicle.