This needs to be done folks!
I see so many posts (including my own) on Z24's with high,rough,or bouncing idle issues. I basically gave up on my 2002 Z24 5-speed because no matter what I have tried it hasn't worked. This thread is designed for people to talk about the issues they've had with their Z24 and if/how they fixed it or haven't gotten it fixed yet. The idle issue is brought up so much here that I think this thread can help alot of people including myself!
I'll go first:
Right now my car is at a shop down the street because I can't stand the high bouncing idle anymore. I start the car and everything seems fine (starts at about 1500rpm and slowly goes down to near 1100rpm. BUT, 5 seconds later it shoots back up to 1600rpm and bounces from 1300-1700rpm from there on out. If I hit the brakes at all the idle shoots way up... I'm thinking vacuum line? They replaced the IAC motor, I changed the spark plugs, IAT sensor, cleaned the TB thurougly, and am basically givingi up on it. The shop can't figure out the problem and I have a feeling they are going to charge me up the wazzooo for it. Tomorrow they are putting in another Throttle Body from a Z24 so we'll see if it makes any difference. I'm also going to tell them to check if the cat is clogged or to try replacing the Throttle Position Sensor. If anyone has any ideas on what to do please post, or post your problem so others can help. Lets just keep this thread going so that when people search they will find this and hopefully get the answers they need!
Same problem with mine right now when I got my 2.4L 59mm bored RSM throttlebody installed.
Its annoying, I want to fix it!! i dont see any way of adjusting it? maybe adjust the cable on a gas pedal?
I know you said "they" replaced the IAC motor. Well, I would make sure they used a Delco IAC sensor #12482707. I would check the Vacuum lines to see if there is a leak, especially around the rubber elbow on TB. Then I would check the TPS, oxygen sensor and MAP--sensor since that checks pressure/vacuum downstream from the throttle plate inside the intake manifold. But basically inspect all your emission sensors.
But since I can not see the car to tell you better and seeing you are using a Pacesetter header, I am going to blame the header triggering a faulty signal from the oxygen sensor to the PCM. Since the 02 port is measuring just one cylinder causing it not to heat up well enough and causing it to run at a high idle. Again, it is hard to diagnose as I'm not able to see it.
Good luck.
>>>For Sale? Clicky!<<<
-----The orginal Mr.Goodwrench on the JBO since 11/99-----
map sensor, coil packs, intake manifold gasket?
My car was doing that for awhile. It was because the power prake assist hose was leaking (the cruis control didn't even work). There's this small rubber elbo that comes off the throttlebody and hooks to a pipe that goes to the vaccume boost on the master cylyinder, if it cracks, it will cause those problems. I've got a Pacesetter exaut on my car and the O2 sensor is below the collector on the headder, so it should be reading all the cylinders. Although I have some seriouse idle/running problems until the car gets the O2 sensor reading correctly (I've posted a question on how to remedy this in the 3rd gen forum).
Here are my problems. 2000 Sunfire 2.4L
1.)Start car, Starts up just fine with RPM at about 1500rpm on initial startup only.
2.)RPM slowly drops to about 1200RPM after a min or two
3.)Let car warm up for a couple min and RPM still at about 1200RPM. (which seems to run a bit fast for it being 20 degrees celcius outside in the morning)
4.)Go to drive away and RPM still the same.
5.)Drive down the street and say stop at stop lights and RPM still about the same 1100-1200RPM even though the car has started to warm up a little maybe 1/4 temp on the guage.
6.)Car runs and drives fine in stop/go traffic but my RPM doesnt seem to drop to normal idle until the car is at 1/2 temp
7.)When car is at 1/2 temp and hot the RPM at stop is probably in the range of 900-950 where even normal idle is.
To try and cure this problem I went out and bought a new IAT & IAC sensor from the dealer and installed it them other day. I unhooked the battery, Pulled the IAT sensor out of my AEM intake tube and replaced the IAC on the throttle body. Put the new one in and plugged the connector back in. Also cleaned out the hole where the IAC plugs in real good.
Is this idle thing normal b/c the motor just isn't warm enough? I mean at the end of the day it's like 30 degrees outside and the idle is still fast until warm-up(A/C is turned off). Should I change the throttle Position sensor?
Any help would be appriciated. I'm thinking it could be a vacuum leak b/c it's fine when it warms up. Can someone point me in the right direction or provide pictures of what to check for the vacuum leak or to replace?
Regards,
I talked to the guy fixing my car yesterday and he told me that my TPS is showing 5% when idling and it should be showing 0%. They went and put in a new TPS (throttle position senser) but it didn't do anything. He is thinking this is the problem and I don't have a vaccuum leak. Anyone ever heard of this before?
If the TPS is showing any throttle opening while the throttle is closed it will cause a high idle. The 2.4 is know for a very odd idle. My 98 bounces around by about 300 RPM and has since day one. My 02 has had the same issue along with the ever famous 2.4 stall when coming to a stop. My 00 when I had it did the same things. There is no deffinate fix for the crappy idle as long as all your sensors are reading correctly and all parts are in decent shape. There is a fault in the programing that is to blame for a lot of the idle issues. (per GM program engineer for the 2.4L program). The Eco had the same issue until GM developed a software update to correct it. (Yes I do know what I am talking about as I have talked with the engineer and have had to call GM technical assistance numerous times for this very issue while working at the Pontiac-Buick-GMC dealer I work at.)
^By any chance do you have the TSB info so others can see on the re-programing?
NeoJuice wrote:Here are my problems. 2000 Sunfire 2.4L
1.)Start car, Starts up just fine with RPM at about 1500rpm on initial startup only.
2.)RPM slowly drops to about 1200RPM after a min or two
3.)Let car warm up for a couple min and RPM still at about 1200RPM. (which seems to run a bit fast for it being 20 degrees celcius outside in the morning)
4.)Go to drive away and RPM still the same.
5.)Drive down the street and say stop at stop lights and RPM still about the same 1100-1200RPM even though the car has started to warm up a little maybe 1/4 temp on the guage.
6.)Car runs and drives fine in stop/go traffic but my RPM doesnt seem to drop to normal idle until the car is at 1/2 temp
7.)When car is at 1/2 temp and hot the RPM at stop is probably in the range of 900-950 where even normal idle is.
To try and cure this problem I went out and bought a new IAT & IAC sensor from the dealer and installed it them other day. I unhooked the battery, Pulled the IAT sensor out of my AEM intake tube and replaced the IAC on the throttle body. Put the new one in and plugged the connector back in. Also cleaned out the hole where the IAC plugs in real good.
Is this idle thing normal b/c the motor just isn't warm enough? I mean at the end of the day it's like 30 degrees outside and the idle is still fast until warm-up(A/C is turned off). Should I change the throttle Position sensor?
Any help would be appriciated. I'm thinking it could be a vacuum leak b/c it's fine when it warms up. Can someone point me in the right direction or provide pictures of what to check for the vacuum leak or to replace?
Regards,
Everything seems to be normal. 20C is 68F and that is cool climate. So the engine will try to warm up the engine in order to run in normal operating temperature.
>>>For Sale? Clicky!<<<
-----The orginal Mr.Goodwrench on the JBO since 11/99-----
Weird. I have never heard of a high idle issues with the 2.4. Never seen a issue (that was not caused by a faulty aftermarket part). I have seen aftermarket TB's cause high idles. Usually a good fix is to lightly sand the inside of the TB so the TB plate can closed completely.
markaj04- you might want to pull your TB off and open and close it in your hand. See if the TB plate sticks. I have seen this (mainly on aftermarket TB's).
Phewes- I'm beating your issues for sure is the TB, could also have too much gap alowing too much air to suck in.
As for the cold start issues that is a known thing. More so with aftermarket headers (Pacesetter headers) have the O2 sensor in a bad spot (in my opinion). I also feel GM should have given the 2.4 a heated O2 sensor. I just added a heated O2 sensor and my cold start issues are gone.
I have never had a O2 sensor cause a high idle. Usually TB's and vacuum hoses. Check the hose on the map sensor they like to crack over time (but usually cause a rough idle and sputtering.
FU Tuning
There is no specific TSB for this issue. For the Eco GM developed a new software program for the PCM, but the 2.4 was left out.
I was reading on another thread that it might be a vacuum line problem. There is that little line that comes off the TB that is for the break booster line or something. I was going to check it's condition and shape. Dealer wont have a new one in until next week b/c it has to come from the US. For $4 bucks I'll replace it but today Ill check it's condition for cracks. What other hoses should I be looking at for cracks/wear?
Where is the MAP sensor on the TB? can someone post up a picture?. I'm going to pick up some TB cleaner today. When i installed the IAC I took my intake off and looked down inside the TB and everything looked nice and clean. I always put in fuel injector cleaner at every oil change as well. Maybe Ill unhook the battery today for a while and see if things clear up.
Regards,
The map sensor is bolted to one of the bolts that hold the TB on the intake manifold. If you are looking at your motor from the front of the car it is on the right front bolt. It has a small hose about 2 inches, maybe 3 inches long that goes into the intake manifold. Check all the hoses that connect to the TB as well. Another thing you can do is take TB cleaner while the car is running and spray it around the hoses, intake manifold gasket etc... If the car's idle changes while doing that you have found the area your leak is at.
FU Tuning
John, Ill definately give that a try today. I found the map sensor on the side of the TB. I checked the hose that attachs to the bottom of it and goes to the intake. It looks in OK condition but is a little cracked but doesnt seem to be leaking. I had the car running and was giving it a squeeze to see if it made a difference and so forth but it didnt. What Ill do today is like you mentioned, ill buy some TB cleaner and spray it around all those hoses and see if the idle changes any. Then I'll know if I have a leak which might be affecting the idle.
About the MAP sensor, mine seemed fine also (just a few cracks like you said) but then I started to notice that sometimes the hose itself would collapse
. I'd do a few test to make sure that isn't whats going on. At least it fixed my problem.
I didnt have a chance to pickup some TB cleaner on the weekend. I was to busy. But I'll pickup some tonight and give it a test by spraying all around the TB area. I found out the part number of that little hose. So If it may be leaking ill order a new one and replace it. If I dont find a problem with it I may replace it just because it looks to getting in rough shape.
if you didn't read my thread, also spray around the intake and injectors.
I'm pretty sure my high idle problem was due to a vacuum leak around one of my injectors.
Desert Tuners
“When you come across a big kettle of crazy, it’s best not to stir it.”
FReQ Z Ill definately give that a try. Thanks for the tip.
If the hose on the map is collapsing then you need to replace it. It shold not collapse. Those little cracks can cause a bigger problem than you think. YOu can just go to the parts store and get some vacuum hose for that. Also as FReQZ stated spray the TB cleaner around the intake manifold at the head and injectors.
FU Tuning
It's not collapsing. I was just squeezing it between my fingers to see if it was making a difference in the way the car idles.
So I can just pickup some vaccum hose to replace it? Dealer part is $18 bucks. When I go to the parts store tonight Ill pickup some vacuum hose and some TB cleaner. But I'll do the TB cleaner part first to test for air leaks.
When I put my RSM 62mm TB on, I had to loosen the throttle cable a turn or two on the plastic adjuster knob... then the idle was fine.
I placed a order for the map sensor hose to the intake. GM Part # 24574715. Im going to replace it anyway just b/c it looks to be in rough shape. I will replace it tonight and also pickup some TB cleaner to do the test like mentioned above.
im about to sell the car because of a similar problem. Its driving me crazy, ive had a lot of people look @ it, i dont know sh!t about mechanical stuff so im clueless. I start the car .... and it sounds like I have a big cam it misses bad, i have to give the car gas and hit the brake at the same time so it doesnt stall. When the gas hits 1,000 rpms it runs perfect and evens out. All obvious problems have been either looked at or fixed. Its driving me crazy.
Yeah this is really frustrating. My Throttle Position Senser is still reading 5%, yet I already replaced it. So why would it be reading 5% and im guessing thats whats giving me the high idle...
