I have a 1997 Chevy Cavalier Z24 with a 2.4L motor. Just as the weather turned cold, it now starts up rough and idles rough for the first 20 seconds or so until warm. It also stalled a few times on me at red lights.

There was no check engine light for me to get any info off of and I am waiting on a shop buddy to get back his car scanner to see if his can pull any real data from the computer.

I have changed out the Fuel filter, added Injection cleaner, and cleaned out the throttle body thinking it was a fuel related problem. I have also changed out the Spark plugs (Bosch Platinum 4) plugs, Plug Boots, Both Coil Packs and Coil Valley that holds everything together thinking it maybe spark related.

Although these items helped performance on my now 12 year old car and it no longer stalls out at low idle anymore. It is still takes a 2-4 second crank before it turns over, idles rough for about the first 20 seconds and then runs fine.

Anyone have this problem before? Any ideas? Map Sensor, Throttle Position Sensor, Fuel Pump, Vacuum Leak?

Any information would be appreciated.

Seen this happen several times.

A possible head gasket leak, or your valve cover gasket seals around the spark plug holes are leaking.

The reason being, the fluid, either oil or coolant drains down a little bit overnight. So when first started when it is running rough, it i burning off the oil or coolant, and once it is burned it, it runs normal.

A way to check it, let it sit overnight, before starting it up, remove the spark plugs, take a flash light and look down into the cylinders, seen any coolant on top of the cylinders, are your plugs full of oil.

If yes to either you have located your problem


- 2004 Cavalier - 124k, owned since new

My plugs looked good and there were no signs of fluid leaks or and loss of fluid. Any other ideas?

How old is the battery? My car will do the same thing. Run a bit rough at first start when cold. All my electrical stuff (radio, interior light) will be dim as well. Then the idle smooths out and everything comes on at the regular brightness. Get the battery and even the alternator tested. Autozone and I think advanced auto does it for free.

Alternator is about 2 years old, the battery is about 3 years old (highest cranking amps I could find at the time (more than factory). Cranks fine. Power is spot on from 0-90. Just hard starting and seems like I have to give it a little gas to start it. Where in the past, before this happened, I just turned the key and didn't have to touch the gas.

Do you think the fuel pump would cause this? However, I still hear it give a humm when I half crank the key and it runs fine at highway speeds.

Oil pump?

Seriously, change the spark plugs. We solve a lot of similar issues with cars that have Bosch plugs in them. We normally use Autolites at our shop, but from what I've read here the AC plugs seem to work the best in these cars. Either one would be better than Bosch.

stay away from bosch!.

i dont think it is head gasket related. These 2.4s arnt known for head gasket issues. the older 2.3's yes, but not these motors.

could be a fuel pressure regulator.
give this a try- turn the key to the on position let it sit for a while then start it. It isnt the easiest to check the fuel pressure on these cars. I used to have a Jegs 100psi fuel guage tapped into my fuel rail.


are your battery terminals clean? air filter new?

did you clean your IAC (idle air controller) motor nipple thingy in the throttle body?

also a coolant temp sensor you think doesnt mean much, but i put a new one in my cav one time and it ran better.


fuel filter leaking?

maybe run some ISO HEET (red bottle stuff) through it.

could be alot of things. good luck and keep us updated.

but first thing first, get them damn bosch plugs out of there! put in some delcos and i bet your problem goes away!!!!! seriously. dont post back till you have them plugs removed and ac delco's back in.... haha

Jake wrote:stay away from bosch!.

i dont think it is head gasket related. These 2.4s arnt known for head gasket issues. the older 2.3's yes, but not these motors.

could be a fuel pressure regulator.
give this a try- turn the key to the on position let it sit for a while then start it. It isnt the easiest to check the fuel pressure on these cars. I used to have a Jegs 100psi fuel guage tapped into my fuel rail.


are your battery terminals clean? air filter new?

did you clean your IAC (idle air controller) motor nipple thingy in the throttle body?

also a coolant temp sensor you think doesnt mean much, but i put a new one in my cav one time and it ran better.


fuel filter leaking?

maybe run some ISO HEET (red bottle stuff) through it.

could be alot of things. good luck and keep us updated.

but first thing first, get them damn bosch plugs out of there! put in some delcos and i bet your problem goes away!!!!! seriously. dont post back till you have them plugs removed and ac delco's back in.... haha

Like he said, ditch the Bosch and stick with stock AC-Delco. I'd still test your battery just for the heck of it. Simple install and reinstall plus free testing. Can't hurt.

Rough starts are a drag in more ways than one, mine is coming back it was fine for the longest time no problems at all, but the other day it started doing it a little bit. No rough idle or backfire with mine, but i am overdue for a fuel system cleaning and i only notice that because along with the occasional hard starts when cold my gas mileage is also starting to take a major dive.

Ok, so I have found one problem. There appears to have been a vacuum tube coming off the throttle body that was cracked on the back side of the tube. I have taped it up for the time being and it appears to have helped a little. (Yes, I will purchase a new vacuum line). However hard starts are still there.

I will be reviewing all lines to see if there are any other cracks once some of this cold weather leaves.

I have checked the battery and the alternator. Alternator is charging strong and voltage on the battery are solid. Connections are clean.

As for the spark plugs. swapping the Bosch with ACs did nothing. Maybe even a little harder of a start with the AC plugs. The Bosch +4 Platinums plugs are back in.

No fuel leaks.

Anyone else have any ideas?

Solution FINALLY.

Here is the summary:

Items that helped with power but didn't resolve the issue:
Spark plugs <-(Bosch or AC, either didn't help the starting issue. Old plugs seemed clean enough, I will keep them as a backup set)
Coil Packs <-( Didn't seem to help the starting issue, maybe the stalling issue when this problem was occuring. Totaly keeping the old ones as a back set)
Coil Tray/Valley <- (Although a little dis-colored, this didn't seem to help)
Fuel Filter <- (Didn't seem to help the starting issue but did seem to improve the over all running performance)

Items that did seem to improve idle but not fix the problem:
Idle Air Control <- ( IAC did seem to make a minor improvement on roughness. Don't forget to spray your Throttle body clean with Throttle Body cleaner)
Fuel Pressure Regulator <- (This was the core of the problem.)

Fuel Pressure Regulator was the deal that fixed this 100%.
I recommend everyone replace this item if you ever have any of the following: rough starting, hesitation while driving or a P300 code. That as well as your fuel filter if your ride has never had them replaced. Those two items have made this car purr again. Can't tell you how much of a difference on not just start up but the over all car sounds quieter.

No more hard starts or having to put my foot to the floor to get this beast started. No more clouds on start ups. Just turn the key, listen for the fuel pump to spin up and it cranks right over.

I hope this follow up post helps future people with the same problem.

-Jim

Almost for got to add to check for vacumm leaks around the throttle body as I did find some dry rot there (spray some Throttle Body cleaner around the suspect area, if the idle changes look there.). Replacing cracked tubes did help the computer (ECU) control my stalling issues but not the hard starting.

I have 1997 Chevy Cavalier Z24 with a 2.4L motor In morning starts fine then it starts hard time going after I drive for about 1 hour then I try to to start turn over no fire? for about 15-20 mins! these things I have change on the car spark plugs oem, ignition coils oem, ignition module, ignition coil housing, idle control valve, fuel filter, fuel pump. Any help will do thank you.

thanks Jim, and good to hear you fixed it and what all you did.
Paul, check the gaps, plug wires, get the battery and alternator checked for free. That's the lowest cost regular maintenance first.

My opinion is becoming that if you replace the fuel pump, get a new pressure regulator too they depend on each other a lot, and consider new injectors every 80 to 100 thousand miles. After the 20 minutes, do you still hear the pump priming as usual when you turn the key to the ON position?
Also check the vacuum lines like Jim did.

I've check gap ok, battery 2 years old, alternater in new holding charge, vacuum lines seam ok to, new fuel pump a year ago. I will look into getting new pressre regulator and look at new injectors thank you.

but don't you have to have an engine light first?
Can a pressure regualtor not work good enough with no CEL?

There's no engine light, no codes, just change crankshaft sensor there seams to be lot of Cavaliers with this problem, the one way you can test your fuel pressure regulator is to put a hose on the top of it and suck if you taste gas then you have to change it.

Having the same issues on my '00 Z-24 with the 2.4L. Where are the coils physically located? Changed out he Throttle Position Sensor, no change.


'00 Z-24, 2.4L, Automatic, Stock

On top of engine there are four bolts it removes the cover the coils and the ICM are inside, you might want to change spark plugs and boots DO NOT USE AFTER MARKET PLUGS OR BOOTS OEM ONLY It took me a bit to fix my problem it end up being ignition control module, when it gets to hot shuts down the car, you will have to test it with volt meter or back probe it with a scope it will show you what's happening with the spark plugs. I hope this will help you.