Bought myself a cheap Z24 to drive back and fourth to work. Car has 160k on it, and needed a head gasket. I replaced the head gasket, water pump and did the typical check over of everything. When I brought the car into the shop, a code had tripped but I didn't check it at the time. Once the gasket replacement was done, I went ahead and timed in the cams with the 8mm bolts and crank at TDC. After we got the tensioner back in place we spun the motor over a few times and everything was good. When we spun the motor over as it would be running, it seemed like we had some slack in the chain at the tensioner. I figured this was just because the tensioner didn't have any oil pressure on it. We fired the car up and it ran alright. Nothing major, let it build heat to assure head gasket was sealed. I noticed that after I started driving it, the car would surge at idle and at stop lights. It sounds almost as it has a misfire so I checked the codes. It pulled a MAP Sensor High Voltage and High Idle code. Replaced the MAP and it still ran the same. I went ahead and replaced all the plugs/boots with new as well as cleaned the IAC Valve and checked for vacuum leaks. The car runs great on the highway, or as long as you are on the throttle. It has been getting poor fuel mileage though.

Just wanted to see if anyone else thinks that the tensioner has gone bad and is allowing the timing to move off throttle. It shakes pretty good at low RPM but no knocking, or rattles. Just like a misfire or something slightly off. I've thrown quite a few parts at it and no other codes have came up. I'm out of ideas. I'm a SBC Guy, this DOHC Stuff is a little new to me. Have a vast background in dirt race cars and such.

Thanks for your input! If it is the timing tensioner I am going to go ahead and replace that and the guides.

How about instead of shotgunning parts at it you diagnose the code? Probably a damaged wire or hose/fitting.

As I said, the MAP was replaced and the code has since disappeared. The wires were all traced and were completely fine. I didn't ask for a moronic response.

While idling, unplug your tps sensor and see if anything changes... if so... don't replace... I would go and inspect the intake gasket and the injector o-rings. Normally there is a leak around these areas and they run like crap during idle. Pull battery after these inspections and hopefully your fixed.

I will go ahead and do that right now. I was wondering about the injector O Rings, but the motor doesn't gain RPM or lose RPM when I spray the area down with starting fluid in a search for leaks. I failed to mention that I did replace the Intake gasket with a new one during the head gasket replacement. If unplugging the TPS does change things, I'll go back thru and take the intake off and check that as well as pull the injectors and replace the O-Rings for insurance.

Thank's for the post and I will let you know what I find out!

Pulled the TPS while at idle and nothing really changed. Of course when you try to open the TBI up some it'll choke out after that. I'm lost. It runs great off idle. I do think I will replace the injector O-Rings tomorrow morning though just for insurance. I didn't even think to change them while I was doing the head gasket.

Brett Ladehoff wrote:As I said, the MAP was replaced and the code has since disappeared. The wires were all traced and were completely fine. I didn't ask for a moronic response.

Just because there is no stored code does not mean there isnt a problem with a part/control circuit. I have heard the "wires are fine" line to many times to still just find a broker or damaged wire or terminal, but I guess I just dont know what the @!#$ im talking about. Have fun throwing parts at your car.

BTW your car does not have a TBI on it, but im sure you would figure that out soon enough on your own.

I will withhold any further 2.4L info I might have.

An ASE Mechanic diagnosed the MAP Being bad. Withold information, I'm sure you're a wizz!! WHOOOOOOOOOO That's why your a Union electrical worker and not a mechanic.

And no, you don't know what you are talking about.

Just so you know, I was a GM mechanic for 7 years as an ASE Master mechanic. Also, I worked around a lot of mechanics that didnt know how to correctly diagnose a problem. I do know what I am talking about.

eeek, lets stop this before it gets nasty...

Clyde knows what he's talking about... end of story...

moving on... I probably would have replaced the timing chain, they are prone to stretch... i had 40k miles on my last chain, and it stretched almost a whole link... Generally now if i have to pull the chain off, i just replace it with the tensioner...

Put a scan tool on it and make sure you TPS reads 0% with the gas pedal released and 100% with the pedal at the floor. Also check your IAC wiring, make sure the pins are intact and there are no flaws near the connector...

If i read this right, you said you replaced the map sensor and the codes went away... i assume you have put three ignition cycles on since then (MAP sensor codes take three ignition cycles to set a hard DTC from pending status)... check your pending DTCS

EDIT: Oh and most manufacturers don't hold ASE in as high of a regard is they used to... My dealer says our manufacturer says "We don't care about ASEs at all... You go to the manufacturer's school"


Edited 1 time(s). Last edited Monday, November 07, 2011 5:16 PM

The car has gone through at least 50 ignition cycles since I replaced the MAP.

In the same breath as you say the dealer says... I wouldn't trust our dealer here to fix a lawn mower engine. It's all where your at.

I need to go thru with the scan tool as you said to check the TPS. I am also going to check the timing as it runs. It's just an odd problem. It seems so much like a vacuum leak.

Yes, I should have replaced that timing chain. First time I've done any work on a 2.4. I don't think if it IS the timing chain tensioner that it's skipped any teeth, but it's not keeping tension on the chain when you let off the throttle. It would be like watching the timing mark on a SBC move around with a loose timing chain. In this case, a computer is trying to keep up with it.

hahaha brett jackoff, shut the @!#$ up. clyde could run circles around you with the amount of mechanical ability he has.

maybe if you'd stop being a tard and open ur mind instead of coming up with ur own conclusions on whats wrong left and right we could actually help you.



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