weird engine bog?

[darkfox]

My 2.4 has been having an intermident problem on start up... it only happens occasionaly. it idles fine, but just after start up sometimes when i start moving the car under moderate acceleration down the street, the engine will accelerate normally for a few seconds, bog and sometimes (as the case was tonight) act like its about to SHUT OFF... regardless of my foot being down on the peddle. Then the computer seems to "recover" and the engine starts to act normal again, and this doesn't happen again for a while. This only happens just after start up, typically when the engine is lower than the normal operating temperature.

I am running a brand new TPS and IAC sensor... i've replaced the two several times, because i thought they were the problem (i was messing with my LD2 TB, and right around the time i started that this problem appeared...)

I'm now thinking ignition problem, but its only on start up... ECM problem? Help me out...

[BobGAGT]

My girlfriends sunfire does the EXACT same thing. I didn't know how to describe it, so thanks for doing it for me. It almost feels like its gonna die, then the throttle surges (if you will). I was thinking IAC, but it also has a SLIGHT miss on idle, so I'm gonna change the plugs... but yea... what is going on? Anyone know?

-Bob

[urweak]

My car has the same problem. When i start it up and start to go it will bog like that (it doesnt bog everytime i start the car up, just when it wants to) But i just rev it to like 4 grand and is all good. But im thinking it might be my EGR valve. Do you have a check engine light on? I was also thinking it might be something with the fuel system, or maybe even bad plugs or something. I have no idea.

[darkfox]

i mean... i turn the car on, let it warm up for a few minutes. then i pull outta driveway, its fine doing that. I hit the gas, VROOOOOOO-oooooo-ooo-poodpoo-OOOOOOM-VOOOOOOOOOOOM. It seems like its fine, then like 3 seconds after i hit the gas it just jerks, rpms go down, then its normal again. Then, for the rest of the whole day, IT NEVER DOES IT AGAIN. Only happens on cold startup... Tonight, it did that, and then it was like IM GONNA DIE NOW, no power, and the rpms go WAAY down like to idle, and my foot's halfway down on the gas... and then its fine. I was like WHAT?

I'm going to try just letting it warm all the way up and seeing if it still does it.

Mine's got a slight miss at idle too... and i just changed the plugs. :rolleyes:


EDIT: I think i found the problem! I'mma go get this part tomorrow at crapozone...

http://www.j-body.org/forums/read.ph...42#reply_49183

[darkfox]

oil pressure makes for stalls at startup, and will make the car run rich. My car definately isn't running rich, its probably running slightly lean from the condition my plugs were in when i pulled them.

Other possibilities...

Coolant sensor. This makes the most sense to me, because the car NEVER does this when its warm.

Ignition Module. I doubt this is it... if it where, it would be happening more frequently, and not just at the initial acceleration after startup. Same goes for coil packs and other stuff.

EVAP line leak - guess what... i have a code thrown for this! I think its my gas cap, because i got a cheap autozone cap. I will go to the dealer and get a good cap in a few days.

O2 sensor - a couple of guys on jbod have complained about the bosch o2 sensor... and this problem did manifest itself shortly after i changed my o2 sensor with a bosch sensor. I'll see how much the AC delco unit costs.

[BobGAGT]

Hmm.... I am wondering what I should do now. I read all that at J-Body, but we haven't done anything to her car (as far as repairs like replacing the o2 sensor, etc) since we got her car. The problem just came up when the temps outside dropped, and it will only do it once (MAYBE twice) upon cold start. This would be my first time workin on the 2.4... anyone have a pic of where the coolant temp sensor is??

-Bob

[SL04P0PR]

my 2.3 does this too. it will also do it on a cold start if i'm letting the car warm up in the morning for a few minutes. it will be idling fine (high idle) and then it will start bogging by itself, barely chugging, then it blasts right back up and idles fine the rest of the time. and if i don't let it warm up, i'll pull out of the parking lot or something and all of a sudden it jerks and sorta cuts itself off for a second, no matter how far down the throttle is... then it jerks back to life. i can't figure out what is causing it for the life of me. i used to think it was the tps, but that pretty much got ruled out when i changed it a year ago and cleaned it this year.

[darkfox]

it might be the ignition module... hmmn. Ur computer is totally different form mine... and the sensors are different from the LD9, so its nothing pcm or sensor related i think. The ignition module is basically the same for just about every quad 4 ever made, tho...

[BobGAGT]

JP, did you fix yours now?

Have you checked/changed your fuel filter?

[BobGAGT]

Its not that... read the above.

[SL04P0PR]

my fuel filter was changed ~ 10k miles ago so i doubt thats the problem.

[BobGAGT]

That would be an all the time problem too, not just during cold starts.

[Prozac]

There is a sensor on the coolant lines that likes to screw up. They have a huge post on it on Jbody.org. I gives the computer the wrong parameters and causes this. I have been having the same prob and have to go and purchase this sensor. One of the guys on the site said that after he changed out the sensor, no more probs. I would give you the link to the page, but I am at work and for some reason the stupid lan system will not let go to that site. It is like a 18 page write up on that exact prob and shouldn't be hard to find. It is in the maintainence forum. Hope it helps you out.