I'm at my wits end with this problem....

It's a 96 cavalier Z24 with 156,000 miles. If I attempt to drive the car without letting it warm up, it will quite often hesitate badly right when I attempt to takeoff in 1st gear. It usually happens after I'm already moving, and just want to accelerate. If I don't push in the clutch and baby it, but instead leave the clutch out and push on the gas harder, it will jerk a few times then kick in and be fine. If I push in the clutch, the idle will sometimes drop very low, and even stall.

It will also very rarely do this when the engine is warm if I attempt to drive it right away after starting.

I suspect that it will only do it when the engine is running open-loop (before the oxygen sensor is warm enough). I suspected a vacuum leak, so I checked the vacuum lines and found some very questionable ones, which I have replaced. The problem didn't go away, so I changed the fuel filter, spark plugs, oxygen sensor, and air filter. It seemed like it was fixed, then it hesitated again yesterday.

I was thinking about taking it to the dealer to get the PCM flashed to the latest software.

Anybody have any ideas??

thanks

I'm experiencing a very similar problem, but it doesn't sound quite as severe. Mine's a 2000 2.4 with a 5 speed. I'm wondering if it's a temperature sensor, but haven't done any research on it yet. If I do get a chance & find something, I'll post it here. Is yours okay once it warms up? Mine just does it for a short time, then seems fine.

Anyone else have this hesitation?

mine has pretty much always done it i usually let my car warm up for a couple minutes before i drive but sometimes i notice the same thing.

Yeah, it's fine after it warms up. And even if I don't let it warm up, it will only do it once. It's just that it's sometimes unexpected, and leaves me sputtering in the middle of the road for a few seconds... which is embarassing.

I do know that a slight vacuum leak can cause the same thing. At one time, the problem got much worse all of a sudden after I changed the head gasket. It turned out that the egr tube was bumping against the hard plastic vacuum line that feeds to the HVAC controls, and melted a small hole in the side of the tube. I fixed that, hoping that was the problem the whole time, but it just went back to how it was.

I'm thinking about getting one of those hand vacuum pumps and checking each vacuum line to make sure it holds vacuum. I'm also wondering if the EVAP solenoid might be sticking open a little.

Well I believe it normal, Cause while the my cavalier is cold its does the same thing. Its usually caused from when then car is cold their is not much vacuum beening produced, In which causes these issues. Every fuel injected car Ive had has the same issue. Even GM tehc says it was normal, Unless you got check engine light on, Or youre car is got or issues.

rich weeks wrote:Well I believe it normal, Cause while the my cavalier is cold its does the same thing. Its usually caused from when then car is cold their is not much vacuum beening produced, In which causes these issues. Every fuel injected car Ive had has the same issue. Even GM tehc says it was normal, Unless you got check engine light on, Or youre car is got or issues.

That is the biggest load of bull@!#$ I've heard in a while.

I dont believe you one bit a GM tech said it was normal.

As for the solution of running @!#$ty.

It could be lots of things. Ifirst thing I'd do is check your ECT sensor if it was saying the car was hotter than it was , then the A/F mixture would be around 14.7:1, instead of 12.5 :1 that would cause a serious lack of power when cold.





- 2004 Cavalier - 124k, owned since new

mine does the same thing, if i just take off it will go away within the first 5 seconds of driving.. so i usually let it run for 3-5 minutes and all is well... im not worried, i like warming my car up my exhaust sounds better warm...


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ayo 8 Iz Enuff

I know chrysler publishes factory service manuals. Does GM do the same thing? And, does someone have a copy of this manual?

I'm looking for one myself on EBay. Here's a link for a 99 service manual. Stay with the OEM ones though, they're much better than the Haynes,etc, IMHO


1999 Cav & Sunfire Manual


Here's a DVD version that covers a lot of models & I have no idea how good these are. I'd like to see this cuz it'd be nice to have it on the laptop.

Service manual on DVD

They're big bucks at the dealer & I don't know if you can get them for past years or I should say how far back they go. I checked with a friend of mine who is a parts mgr at a dealer for my Blazer ZR2 & the full set was around $150 (3 volumes) but that was a few years ago.

try replacing your spark plugs... i have a 96 z24 i had an issue with accleration i had to downshift whenever i wanted to acclerate depending on my rpms. it runs much nicer now..

Yeah, I tried picking up a set last night. You guys recommend the AC's?

I have a set of Bosch in it now, but I didn't like them in my ZR2. It runs much better with AC plugs, so that's what I was looking for with the Z24. The place I stopped at last night on the way home didn't stock the AC's. I figure it can't hurt. I pulled all 4 & they did look like they were in there for awhile.

I just replaced my AC's with Bosch platinums... It didn't seem to make any difference.

Thanks, maybe I'll try another set of the Bosch then. I know they're 2 completely different engines, so who knows. I also just bought the car & these plugs have been in it awhile. I'll post up anything I find out

Yep both my 2000 and my 98 do the sputter and run like garbage for the first couple of minutes. It get s real annoying, and noone seems to have a fix for it.

I got a 2000 sunfire gt and it also sputter's at every cold start,I got the cold start reflash last year,and it worked a little for a couple of months but a year later,it does it all the time again.


Friends Don't Let Friends Drive Stock!!!!!

Rob S wrote:

rich weeks wrote:Well I believe it normal, Cause while the my cavalier is cold its does the same thing. Its usually caused from when then car is cold their is not much vacuum beening produced, In which causes these issues. Every fuel injected car Ive had has the same issue. Even GM tehc says it was normal, Unless you got check engine light on, Or youre car is got or issues.

That is the biggest load of bull@!#$ I've heard in a while.

I dont believe you one bit a GM tech said it was normal.

As for the solution of running @!#$ty.

It could be lots of things. Ifirst thing I'd do is check your ECT sensor if it was saying the car was hotter than it was , then the A/F mixture would be around 14.7:1, instead of 12.5 :1 that would cause a serious lack of power when cold.

Whoah man calm a bit down.

I had the same problem for a while, and just attributed it to a cold engine start ( the oil not well enough distributed because of a night of no flow) which would be totally natural. Think about it. If you cold start from a dead stop over night, doesn't it make sense that it might take a second for your oil to warm and get flowing? If I cold started the engine and started driving, I could definately feel a lull in the engine like it was about to stall. The only thing I changed (and it hasn't happened since) was a change to Mobil 1 as well as started to use K&N's gold oil filter, the one with the flowback valve to keep oil from back flowing back into the engine when the oil is cooling.

That was my problem and solution, but if your problem was getting worse than that, maybe it is the vacuum leak. Just trying to add some feedback.

ShiftyCav wrote:thats probably the dumbest thing i have ever heard. you should take that serpentine belt and wrap it around your neck.

ZealR24 wrote:Yeah, I tried picking up a set last night. You guys recommend the AC's?

I have a set of Bosch in it now, but I didn't like them in my ZR2. It runs much better with AC plugs, so that's what I was looking for with the Z24. The place I stopped at last night on the way home didn't stock the AC's. I figure it can't hurt. I pulled all 4 & they did look like they were in there for awhile.

For giggles, try the AC Delco Platinum Plugs, it may fix the issue..

I also have the same problem with 98 2.4 cavalier Z24 Its idles like @!#$ until it is warm. I changed my spark plugs, boots, Air Fliter, Fuel Fliter, Map, TPS, IAT, and ECT sensors... still idles like poop. My check engine light does not come on either. If anyone figures out why it does this... PLEASE Let Me Know.. ITs Embarassing!!

I've got the same problem with my 97 2.4, and I'm about $2000 in parts into trying to fix it. I'm on my 3rd set of plugs, all gapped at .060 just like the sticker under the hood says, (NGK, AC Platinums, Champion Platinums), 3rd oxygen sensor (bosch, some werid brand, AC), IAC, Coolant sensor, EGR, TPS, MAP, coil packs, ign module, ign cover, boots, Seafoam in the tank, had a shop check compression, leak-down, cam chain, fuel pressure, hooked it up to the "big machine", all signals within range, and it STILL IDLES LIKE A MISLOADED WASHING MACHINE!!! It's always done the "attempted suicide" when I first start it, I've just gotten used to looking like a chump if I try to drive it right away. I checked vacuum likes, and just recently replaced the intake gasket ($35) and throttle body gasket. Nothing I've done has improved or even made worse this problem.

No cel, no codes, no hope.

Next attempt at fixing this will be to unplug sensors one at a time until the idle gets better.

Has anyone tried gapping the plugs at .050 or .040?



John Wilken
2002 Cavalier
2.2 Vin code 4
Auto

Wow, I searched and didnt find this thread. Just started my own. Woops.
Anyways, I too have the same damn problem. Really Pisses me off. I will fix this problem.
My cars started fine until recently.

Nathan Nighbert wrote:Wow, I searched and didnt find this thread. Just started my own. Woops.
Anyways, I too have the same damn problem. Really Pisses me off. I will fix this problem.
My cars started fine until recently.

I wouldn't worry too much about starting another "rough idle" thread. This has been a common problem since I've been posting here, and I can't remember anyone ever posting that they've actually fixed their rough idle after starting a thread.

The 2.4 is cursed.


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John Wilken
2002 Cavalier
2.2 Vin code 4
Auto

John Wilken wrote:
Has anyone tried gapping the plugs at .050 or .040?

My '98's plugs are .050, but thats what my owner's manual says as well as my Hayne's manual (btw 98 was the first at .050, with 41-942 plugs)

OK, this may not be the right way to fix this, but it helped mine out. Here's what I did...

1. Engine off, had my son hold the pedal to the floor while I wiped the inside of the throttle body (by the butterfly) with a rag sprayed with carb cleaner.

2. Removed IAC valve, cleaned it too.

3. Gently pulled out the stopper on the IAC until it just touched bottom when reinstalled.

4. Leave the IAC unplugged - start the car. If it won't stay running, get someone in the drivers seat to keep their foot on the gas. There's a torx adjusting screw by the throttle cable that points straight down. This is the adjustment for the butterfly to stay open at idle. Tighten it a quarter turn and "goose" the throttle. Keep doing that until it idles at 1000 rpm's on a warm engine and no AC running.

5. Shut the car off, disconnect the battery for a half hour to clear the CEL for the IAC being unplugged, reconnect the IAC.

This almost completely cleared up the bogging on a cold start. I did it this morning and let the car sit all day. Tonight at midnight it fired right up and didn't bog when I tried to drive. Maybe it has something to do with the tps, or just makes the car gods smile. Whatever it is, I don't have to wait for the "bog cycle" before I can drive now.

I'll check tomorrow morning if it's still idling at 1000 after sitting all night and post back here. It still has a rough idle, but at least now it doesn't stall.


John Wilken
2002 Cavalier
2.2 Vin code 4
Auto

i posted a while ago about having the same problem over the winter. a lot of ppl said it just had to warm up cuz of the oil distributing or whatever like Jace Evo2 said. makes sense to me. just let it warm up. might not be a cure...

*groan* It still did the "bog cycle" after adjusting the butterfly and sitting overnight. But while I was banging my head on the cement, I thought to disconnect the vacuum line going to the fuel pressure regulator, and it didn't change the idle. It was kind of rusty so I popped the $70 for a new one and $12 for new fuel injector o-rings. And guess what? I'm out another $82 and it still idles like total crap.

I can't put much faith in the "oil warming up" theory, I've had other cars that had 4 cyl's and 5W30 that ran fine right from start up, and I know Sunfire's didn't do that when new, so it can't be oil.

What's really annoying to me is I also have a 97 Mercury Sable (wife's car) with 159,000 miles and it runs incredible, and all I've ever had to do is change the oil, spark plugs and air filter. I've had it for 2 years and only paid $1600 bux for it. The AC even blows frosty cold, and all the power options work too.

I hate cars. Anyone have a moped for sale cheap?


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John Wilken
2002 Cavalier
2.2 Vin code 4
Auto