Well, I have been having the same problems that many of us on here are having with an iradic idle, hesitation under load, and sputtering up to like 3000 rpm. My idle was so bad it started dieing on its own. I took my car to the shop, and this is what was done.
1. Changed both o2 sensors ( I had a check engine light)
2. replaced fuel pump
3. replaced fuel filter
4. replaced spark plugs and boots
This solved all of my engine woes! So, if you are having this problem, I would suggest you check your spark plugs and boots, fuel filter, and get your fuel pump pressure tested. I changed the o2 sensors as well, I dont know if this was the cause or not, but if you dont have a cel code, then I wouldnt worry about them fixing your problem. I dont guarantee this will work, but I hope it will be helpfull to those with the same problem that I had.


98z24, lowered 2", aem intake, cat-back striaght pipes!, cop ligths in the front and rear, 18" liquid metal's, primer black, tint, full audio and video.

I have done it all except the boots, looks like my next option.

i'll ive been having the same problems,

so far ive changed

plugs, wires, injectors, fuel pump, fuel filter

sorry forgot to say it hasnt fixed anything yet.

but yes im having the same problems. it happened after i got fuel pump/filter changed.

well, I did change my boots as well... And I went back to a stock delco plug, I was running bosh +2 plugs. It still does it ever so slightly, but cant be noticed unless you are staring at the rpm guege. It only jerks in idle between 1000 and 950. Not even noticable. The only thing I can think of to cure that would be my idle sensor thing (forgot what it was called) or my fuel pressure regulator. I had a shop do all my work as well. I also threw a bottle of injector cleaner in there as well. I have an ld9, and this cured my problem, dont know what engine you have, but you cant possibly have an ld9 with plug wires, ld9's have plug boots.


98z24, lowered 2", aem intake, cat-back striaght pipes!, cop ligths in the front and rear, 18" liquid metal's, primer black, tint, full audio and video.

@$#%!!!!!!!!!!! I thought it was solved! Well, my idle is fine, but it randomly wants to sputter under load?!?! DOnt know why? It seems after it is running for 10 sec. or so, I go to give it gas and sput-kuput? It stays running I just give a couple of revs and its good.I am going to check the tps and iac. If that doesnt help, I heard someone on here say something about coolant leakage into the cylinder? If that were so, I believe it would happen as soon as I fired it up? I dont know. I will post my results. I can see alot of us on here are having the smae problem...


98z24, lowered 2", aem intake, cat-back striaght pipes!, cop ligths in the front and rear, 18" liquid metal's, primer black, tint, full audio and video.

today i changed the coils it got better for about 3 mins. grr i want an ecotec

me too!!!!! I unhooked the tps and it just revfved to no end! So, I know this is not my problem... Does anyone know where the iac is and how I would go about checking it for malfunctions??? What about the map sensor? Where is it and how would I check it? Would the iac or map throw cel codes?


98z24, lowered 2", aem intake, cat-back striaght pipes!, cop ligths in the front and rear, 18" liquid metal's, primer black, tint, full audio and video.

-I am having the same phantom problem man. I have no C.E.L. and cannot figure out why it is hesitating so bad before 3k RPM . Here is where I am going to start. It is a article regarding No Trouble Code Problems. Pretty good info from what I have seen so far.
http://autorepair.about.com/cs/faqs/l/aa042603a_1.htm

-I also thought it was fuel related and had my buddies shop hook up a mechanical fuel pressure guage and it is reading good pressure at idle and up high is 60psi. I thought maybe it was that Sock thing clogged thats attached to the pump causing a problem in a specific operation range.

-I should note that the car is running extremely lean regardless of the pressure of fuel going in according to my wideband. It is reading 18-20 AFR at idle . Should be 14.7 like it was before, I haven't changed any tuning with HP Tuners and I know that my injector constant is correct.

-Now my idle started going crazy so my first assumption is a faulty Throttle Position Sensor, but why no PO122 or PO123 Code ???TPS Low Voltage & or TPS High Voltage... I hate to buy the damn sensor only to find out thats not the problem.



Windy City TurboZ

I have the same issues as well... conspiracy?


When you start the car from a cold start it'll idle in the low 800-900 rpms, rev up a few times into 1100-1200 then idle fine at 1000rpms.
or just die out. After that it runs perfectly fine.

If you start it up and drive, it chugs, sputters, backfires, you can push the gas pedal to the floor and it does no good.
All of a sudden it moves. and after that its fine.

I've changed plugs(actually went over to the dodge neon coilpack, so I do have plug wires), Change out the TB(and all sensors), EGR, Fuel rail, injectors and regulator.

Only thing I got left to try is fuel filter(can't get old one off.. damn quick release tabs!), cat and o2 sensors....

Someone said the timing might be off a tooth or so and after running for a few minutes the pcm adjusts the motor to run..
and when the car is turned off long enough, it has to relearn it again...
anyone heard of that?


<img src="http://www.majhost.com/gallery/HCAJosh/crap/shooshined.jpg">
- putting the pieces back together -

No Trouble Code Problem Hesitation / Stalling / RPM Drop Off / Bogging / Sputtering Symptoms lol : Thats a mouth full

- No C.E.L.
- Hesitation @ low RPM Throttling / RPM's drop off car almost stalls/ afr goes into 20s
- Stalling at idle on occasion
- Floored it takes the fuel but is running too lean for safe operation.
- Running extremely lean at idle and w.o.t.

Methods Performed :

- Changed Fuel Filter
- Had Fuel Pressure Test Performed , no apparent problem with psi at idle and acceleration.
- Fuel Pressure Regulator Leak Test, Vacuum jumped 10psi from disconnecting vac line.
- VCM Scanner , no stored history codes pertaining to mechanical or sensory issues, a few brake codes iirc .
- MAP changed
- IAC Removed and Cleaned
- Checked for vacuum leaks.
- Checked for fuel leaks
- Compression Test Good

- Fuel pressure tests can sometimes be inconclusive. I have heard of people saying they took their car to a shop and
had the pressure test only to be told that its not the pump. Low and behold it finally craps out soon after and they replaced the pump and strainer & voila ,
there problems miraculously disappear. Numerous cases of this on the internet.

Here's what Im doing next.
1. Pull fuel rail
2. Safely check injector spray mist .
3. Replace fuel pressure regulator , I have an extra new one.
4 Replace injector o rings
5. Reinstall fuel Rail and fire engine.

If that doesn't work the tank is getting dropped and inspection commences.
1. Drop Tank
2. Look for sediment
3. Inspect Fuel Sock / Strainer
4. Repair or Replace any needed in tank components.

NOTE: GM Supecharged 01 Z24 Auto / Mods in Registry.



Windy City TurboZ

Try changing your coil pack housing. My car took a dump on me earlier this year. Actually let me sit on the side of the road. The house crapped out on me and was causing all kinds of misfires. The dealer replaced it and then it started with the mis at low RPM when I would give it some gas. Once the RPM's got higher, it went away. I think the dealer put 3 of those things in my car before the found a "good" one. It's started doing it again, although not as bad so back to the dealer she goes for warranty. Apparently a bad batch of them went out. Autozone sells them for $43 bucks.

what brand o2 sensors did you get and from parts store or dealer?


~1996 Cavalier LS 2.4L (auto)

I forgot to mention that I did change the complete idi cover and coil pack assembly from a stock Z24 running properly and still no dice.

Dragracemyz24 wrote:No Trouble Code Problem Hesitation / Stalling / RPM Drop Off / Bogging / Sputtering Symptoms lol : Thats a mouth full

- No C.E.L.
- Hesitation @ low RPM Throttling / RPM's drop off car almost stalls/ afr goes into 20s
- Stalling at idle on occasion
- Floored it takes the fuel but is running too lean for safe operation.
- Running extremely lean at idle and w.o.t.

Methods Performed :

- Changed Fuel Filter
- Had Fuel Pressure Test Performed , no apparent problem with psi at idle and acceleration.
- Fuel Pressure Regulator Leak Test, Vacuum jumped 10psi from disconnecting vac line.
- VCM Scanner , no stored history codes pertaining to mechanical or sensory issues, a few brake codes iirc .
- MAP changed
- IAC Removed and Cleaned
- Checked for vacuum leaks.
- Checked for fuel leaks
- Compression Test Good

- Fuel pressure tests can sometimes be inconclusive. I have heard of people saying they took their car to a shop and
had the pressure test only to be told that its not the pump. Low and behold it finally craps out soon after and they replaced the pump and strainer & voila ,
there problems miraculously disappear. Numerous cases of this on the internet.

Here's what Im doing next.
1. Pull fuel rail
2. Safely check injector spray mist .
3. Replace fuel pressure regulator , I have an extra new one.
4 Replace injector o rings
5. Reinstall fuel Rail and fire engine.

If that doesn't work the tank is getting dropped and inspection commences.
1. Drop Tank
2. Look for sediment
3. Inspect Fuel Sock / Strainer
4. Repair or Replace any needed in tank components.

NOTE: GM Supecharged 01 Z24 Auto / Mods in Registry.

Windy City TurboZ

I think I have my issue solved.
checked around the intake for a vacuum leak and found one on the manifold.

Got a new gasket gonna change it out and see what it does.


<img src="http://www.majhost.com/gallery/HCAJosh/crap/shooshined.jpg">
- putting the pieces back together -

Let me know if that solved the problem Josh Watson.


Windy City TurboZ

I'm going now to get the gasket, I'm hoping to get it put on tonight or tomorrow. we'll see.


<img src="http://www.majhost.com/gallery/HCAJosh/crap/shooshined.jpg">
- putting the pieces back together -

i'm also very interested on what fixes this problem. i know my first thought was gunk on the tb..



maybe not today, maybe not tomorrow....... but some day

mines been doing the same lately, i recently got a CEL that the fuel system was running lean, couldn't find out why. changed my plugs and wires, mechanic couldn't find anything wrong then he changed the wire to the o2 sensor in my downpipe, which solved the CEL problem.

still bogged and almost stalled on my way to class just now at a stop. rpms dropped to 250 and came back up. still can't find out what it is. my dad had a 00 s-10 with the 2200ohv like my car has and he had the same problem around 90k said it ended up being the catalytic converter. i don't see how but i'm not changing it until i do my full exhaust sometime in the summer.

Similar problems.. fuel filter helped some but still had the erratic idle etc..

Turned out to be a vacuum line from the MAP sensor to the intake manifold... it wasnt leaking, it was collapsing once it got warm enough.. never noticed it because my car was always off when i checked, or i just started it so the line was cold and not crushed in on itself... lol

So really i spent 2 months and about $1000 in parts trying to get this car running A1.. granted it all needed to be done anyways... but ended up being a $4 hose and 30min of my time.. lol.. go figure

Mine 98 Z was doing the SAME sh*t for a long time....changed injectors, spark plugs, boots, coils and still did it....so i changed the fuel pressure regulator and found the timing to be off by a tooth and since i did booth of those its been running AMAZING!!! i ran this problem for almost 4months till we dug dirty and found it!!! good luck!!

Any update on this. Mine is doing the same thing. idles a bit erratic, when I go to pull out it bogs down, sputters, rpms drop until I mash the gas. After that its fine. Ive also noticed that if i let the car warm up, it doesnt do it. Runs great.

I had a similar problem, i had a vacuum leak on the EVAP solenoid. There is a inch long vacuum hose that connects a plastic hose to the EVAP solenoid, it was so dry rotted it wouldn't hold vacuum. The other vacuum leak was where the 90 degree fitting on the brake booster tube connects to the throttlebody. The problem i had was because of my header, I have an rksport 4-2-1 header & i had an exhaust leak where the 4 meet the 2. The o2 sensor was after that, so It screwed up what o2 sensor read and the car ran really rich. Hope this helps.

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My car started doing the same thing when the RPMS dropped below 2K, I have to down shift just to bring the idle back up, only does it whne the car is hot and ruuning after a while so I took a video of it to see if this is the same thing that is happening to you guys, I check the Hanyes and everything points to a Vaccum leak.

I want to make sure its the same issue before I start checking all the lines and manifold!

Let me know whats going on



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