I put it in this section because I've noticed the problem ever since I added some performance items. So I am running out of ideas as to what it can be.
Year: 2002
Engine: 2.4L lD9 S/C
Tranny: Manual
Mods I did then I started noticing the problem:
-60mm TB
-RKS header
-2.25in full exhaust with Magnaflow cat
Problem:
The car generally run excellent, but the problem lies at idle at regular operating temperature. It idles at 900-950 (Normal) but once I do a quick blip on the throttle in neutral the car sometimes goes down to 800, 700, 600, and even to 500 RPMs and then it catches itself (not normal). If I am backing in to a spot (2-5 mph) sometimes it drops to 800-700 rpms as I engage/disengage the clutch (Not normal). Then if i am coming to a complete stop and I disengage the clutch the RPMs will drop to 800 (not normal) then go back up 1100 rpms until I come to a complete stop 900 RPMS (normal).
When I turn on the car and the engine is cold and in neutral, I blip the throttle and the acceleration hesitates (Not normal). As the engine gets warmer, the accelerator does not hesitates and I blip the throttle the car does never goes under 1000 and never tries to catch itself and idles normally. When it is in normal operating temp, that's when the problem arise like mentioned before.
I have changed with new genuine GM parts.
-IAC sensor
-Fuel filter
-Primary oxygen sensor (on header)
-IAT sensor
-TPS
After I did the sensor changes, it has helped some what (60
, because before it used to shut off easily now it doesn't but at times it comes close.
So what could be the issue, I'm running out of ideas?
Thank-you
>>>For Sale? Clicky!<<<
-----The orginal Mr.Goodwrench on the JBO since 11/99-----
maybe a small intake leak.
I do not think there is a issue. Well let me say it a different way. I think it is normal for the most part. I think some tuning of the eCU would take care of it. I have noticed that with mods the ECU at times has problems catching the RPMs as they fall after letting off the gas. The drops to 500-800 then comes up to normal RPMS is normal. I have had a dealer say that it is just the ECU not being fast enough.
Quote:
When I turn on the car and the engine is cold and in neutral, I blip the throttle and the acceleration hesitates (Not normal).
I think what is happening here is when you hit the gas the car tries to go into closed loop, but O2 sensor is not ready. A heated O2 sensor would help that. When I installed a heated O2 sensor it made my car soo much better.
FU Tuning
This is normal, well for a 2.4. Mine has done it since it was all stock with only 24,000 miles. If you get on and of the throttle real quick you kind of throw it off and it does not react quick enough to keep from dying. BTW my other 2001 z24 did this with and it had less than 6,000 miles on it. As far as I can tell the problem is the IAC moter can't react fast enough fast enough which would explain why a new one did not fix the problem. I can stall or almost stall any 2.4 with a manual trans just by blipping the throtle. I have tried to reproduce this effect in many other cars and have never been able to get another car to do it. I have been looking for a fix for this ever since I the second day I had my cavalier.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
It's normal. Mines done this since day 1 also....
2000 Camaro V6.
| SLP Loudmouth | CAI Intake | HID's |
2.4's are really pickey. When you start to mod them, it gets worse. My car has done that since it was stock. Now that I have a full exauts on it..EVERYTHING has to be working perfectly for the car to even be drivable below 2 grand. If the fuel pressure is off even a little, an injector is dirty, or if the plugs start getting old, I notice imediatley, because they car starts hesitating. To be honest, I'de be glad if the only problem is a rough idle like your talking about. The hesitation your talking about is probably your O2 sensor not heating up fast enough like Higgens said. That's somewaht normal and I have the same problem, installing a heated O2 sensor usually helps a lot. You generally can't get any performance out of a car without sacraficing some daily drivability anyway. If you really can't stand it, put the stock exaust manifold on your car and all the problems in mention will probably get a lot better. Or live with the idle, and get a heated O2 sensor, thats really all you can do.
Hmmm odd.
I am reading that this is normal. Really?
I have had these parts mentioned for about 10 months but from what i can remember I never had these issues.
One thing i did not want to to do is put that heated sensor, I am afraid that it may trigger some code and the engine may not work properly with mixtures.
I tell you this is dangerous, because one time a few months back before I changed the sensors, I was making a turn while coming to a stop, I stepped on the clutch my engine shut-off, my steering got firm and I was heading straight for a curb with a tree, I was lucky to slam the brakes totally.
Would HPT help this out?
Anyone else?
>>>For Sale? Clicky!<<<
-----The orginal Mr.Goodwrench on the JBO since 11/99-----
I would say that your IAC table needs to be adjusted in the computer since you installed the larger TB, what TB is it? The IAC table is also dependant on engine coolant temp which explains some of the issues you have noticed while the engine is cold and up to temp. I had the same issue a few weeks back when I fired mine up with the NS TB, different engine and TB configuration but same principle. Do you have an HPTuner or know anyone with one? If you have access to a wideband put that in and see if it is rich (which sounds like the problem) and if so then you should bump your IAC table up a bit, with mine I had to bump it up to 1005 pretty much across the board for it to idle and rev properly, too low and it was just flooding itself out. Hope that helps.
Quoth the Raven 'Nevermore
raven@accesswave.ca
Raven Autosports
55 McQuade Lake Cres,
Halifax, Nova Scotia, Canada
(902) 850-3330
10.82@132
Weebel wrote:2.4's are really pickey. When you start to mod them, it gets worse. My car has done that since it was stock. Now that I have a full exauts on it..EVERYTHING has to be working perfectly for the car to even be drivable below 2 grand. If the fuel pressure is off even a little, an injector is dirty, or if the plugs start getting old, I notice imediatley, because they car starts hesitating. To be honest, I'de be glad if the only problem is a rough idle like your talking about. The hesitation your talking about is probably your O2 sensor not heating up fast enough like Higgens said. That's somewaht normal and I have the same problem, installing a heated O2 sensor usually helps a lot. You generally can't get any performance out of a car without sacraficing some daily drivability anyway. If you really can't stand it, put the stock exaust manifold on your car and all the problems in mention will probably get a lot better. Or live with the idle, and get a heated O2 sensor, thats really all you can do.
I'm not too sure that would be the problem, the PCM is told to stay in open loop till a few things happen like engine temp coming up and time after start. In open loop when the car is warming up input from the O2 sensor is ignored. This also allows the O2 sensor time to heat up. If it was just an issue with the O2 sensor it should go away when the sensor has heated up and is working properly.
Quoth the Raven 'Nevermore
raven@accesswave.ca
Raven Autosports
55 McQuade Lake Cres,
Halifax, Nova Scotia, Canada
(902) 850-3330
10.82@132
John Higgins wrote:I do not think there is a issue. Well let me say it a different way. I think it is normal for the most part. I think some tuning of the eCU would take care of it. I have noticed that with mods the ECU at times has problems catching the RPMs as they fall after letting off the gas. The drops to 500-800 then comes up to normal RPMS is normal. I have had a dealer say that it is just the ECU not being fast enough.
Quote:
When I turn on the car and the engine is cold and in neutral, I blip the throttle and the acceleration hesitates (Not normal).
I think what is happening here is when you hit the gas the car tries to go into closed loop, but O2 sensor is not ready. A heated O2 sensor would help that. When I installed a heated O2 sensor it made my car soo much better.
Same issue, when the buteryfly plate closes the IAC is not open enough, or open too much which will cause these symptoms. Your PCM can correct it if it is not way out of wack but with some tuning of the IAC table you should be able to get rid of that. Two weeks ago when I posted the first startup vids of my car it had a very irractic idle and someone said "have fun tuning that idle in" It took about an hour and now it idles just as smooth as it did when the factory 2.4 was in there, just a matter of tweaking things. The IAC is also very very sensitive in how it allows the engine to run, I could change my idle in the table by only 10rpm and see a change +/- of .3 - .5 AFR on my wideband depending on if I richen it up or lean it out. It really is rather picky.
Quoth the Raven 'Nevermore
raven@accesswave.ca
Raven Autosports
55 McQuade Lake Cres,
Halifax, Nova Scotia, Canada
(902) 850-3330
10.82@132
Well my 99Z does / did the same thing till I took it in and had a new updated calibration done on the computer. If I remeber correctly it is $90 at your local dealership......but after a few months mine always came back. Hell it even loops sometimes when it cold like a big cammed car.
Click Me Enter your vin and you will get any updated list of thing done since release of you ECM.
PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO
since you changed your throttle body your map sensor is freaking out cuz the conditions it sees arent what its supposed to so get the ecu tuned and youll be fine
I just cant drive 55
Robert Bennett wrote:since you changed your throttle body your map sensor is freaking out cuz the conditions it sees arent what its supposed to so get the ecu tuned and youll be fine
MAP sensor measures vacuum (or boost depending on the sensor) in the system and the only thing that is going to cause a difference in vacuum at idle is either a vacuum leak or the IAC motor not open enough or open too much (there are other things too but those two will do for this example). Changing values in the MAP sensor table is not the proper way to correct this if at all because it will throw part throtle and WOT numbers off. If your engine is not maintaining enough vacuum at idle a lot of strange stuff can happen including excess pressure in the crank case which will lead to a blown seal somewhere. Like I said above, if you correct the IAC table your engine will produce the proper amount of vacuum to keep everything happy as well as provide the proper amount of air to the system to allow it to idle and rev properly. I could be way off in left field here but this is how I understand it to work and I have had success with my own when it comes to your symptoms.
Quoth the Raven 'Nevermore
raven@accesswave.ca
Raven Autosports
55 McQuade Lake Cres,
Halifax, Nova Scotia, Canada
(902) 850-3330
10.82@132
when you increas the size of the throttle body you decrease the venturi effect which creats the vaccume which in turn throws off the map
just adjust for the decrease in vaccume
I just cant drive 55
Yes you are correct there but it is caused because the inlet for the IAC motor has changed, or the IAC motor itself is different and most likely the table in the PCM is not going to match the new physical setup. The proper way to tune that is to change the IAC values so that it makes the proper vacuum. If the engine is not able to make enough vacuum it will put a lot of stress on the seals in the bottom end which will cause problems in the future. For example when I fired mine up last week I was only making 5 inch pounds of vacuum at idle and steam was just pouring out of my valve cover breather (way too much crank case pressure). I played with the IAC table and I now make 16 inch pounds of vacuum at idle, no more steam from valve cover breather, no serging or stumbling issues with idle or part throtle and absoutly no hesitation when reved. Before I made those changes I had every symptom mentioned above except mine were more extreme, black smoke out the downpipe as it flooded itself out because the IAC motor was not opening enough to allow the proper amount of air in and causing it to run extremely rich. I didn't have to make one change to my MAP sensor, IMO the MAP table should be a static table and only changed if you replace it with a 3 bar or something like that (now my train of thought on that is a little different as I have a MAF sensor that is much more important to my PCM than the MAP). Yes you can probably accomplish the same thing by changing MAP values but then you are going to be changing the actual metering of fuel which over time will effect your VE table which in effect will alter every fuel table you have since most are calculated from the VE table. I maybe getting a little too technical here now so I will just leave it at that, play with the IAC table if you can and see what happens.
Edited 3 time(s). Last edited Thursday, July 19, 2007 1:26 PM
Quoth the Raven 'Nevermore
raven@accesswave.ca
Raven Autosports
55 McQuade Lake Cres,
Halifax, Nova Scotia, Canada
(902) 850-3330
10.82@132
Robert Bennett wrote:when you increas the size of the throttle body you decrease the venturi effect which creats the vaccume which in turn throws off the map
just adjust for the decrease in vaccume
really? gee i went from a 52 mm TB to a 58 mm TB and did not have any problems with the map sensor. or anything else
Im a Xbox 360 fanboy...and damn proud of it!!
99redz24 wrote:Robert Bennett wrote:when you increas the size of the throttle body you decrease the venturi effect which creats the vaccume which in turn throws off the map
just adjust for the decrease in vaccume
really? gee i went from a 52 mm TB to a 58 mm TB and did not have any problems with the map sensor. or anything else
Did you happen to use a ported stock TB? If so that would explain it perfectly since the IAC passage and motor would be exactly the same as stock and would match everything in the PCM.
Quoth the Raven 'Nevermore
raven@accesswave.ca
Raven Autosports
55 McQuade Lake Cres,
Halifax, Nova Scotia, Canada
(902) 850-3330
10.82@132
I'm running a RSM 57m TB. It is a stock ported out. I agree and did say in my post that some eCU tuning could probably fix this.
Quote:
One thing i did not want to to do is put that heated sensor, I am afraid that it may trigger some code and the engine may not work properly with mixtures.
How would this happen?? The only difference with a heated O2 sensor is just that. It is heated. This means it get to tempature quickly. The only thing I have noticed is it causes my car to go into closed loop quicker. Not really a bad thing.
FU Tuning
^^^
Yeah,
First thing I thought of too was the TB.
I remember the idle screw had to be tweaked a little.
Not sure what vac port it goes to, but the little rectangular hole on the inside ends up being a larger circle.
So its like the tb plate is closed, but just not quite enough, so the car will plib to adjust itself, then things are ok.
So if you could get us a pic or two of the ins and outs of your tb.
Or let is know who made it up for ya.
-M
Remember....syringes go in the RED waste basket.
ya,crank up your idle screwa a little. i did with my rsm 62mm t/b.
Messing with the idle srew is a bad idea it will cause the car to run at a higher idle all the time. How about we just fix the problem at the source like Raven was talking about.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
Wade Jarvis wrote:Messing with the idle srew is a bad idea it will cause the car to run at a higher idle all the time.
On the 2.2 motors, the IAC valve will re-adjust to bring the idle where it is supposed to be even after playing with the screw. I would imagine the 2.4's are the same way.
mmmm...where would this idle screw be on the 2.4 throttle body that you speak of. (not sarcasm, actually wan't to know).
^^
On the 2.4.
If you look around the edges on the tb, you should see a star shaped screw with like a little nub in the middle.
Take a specialized bit to mess with it.
Or you can just punch it out and put in a diff screw.
I'd have to get a pic up to better explain what I was meaning with the screw.
All I remember with mine was the screw had to be adjusted maybe a half turn to get the tb plate to sit below one of the vac holes on the inside of the tb itself.
And that fixed things for me.
Still,
Even cranking on the screw, the computer likes to try to compensate, and eventually does to a point. like ^^ (Zach) was saying.
-M
Remember....syringes go in the RED waste basket.
VanquisherOfTheVariance (Zach) wrote:Wade Jarvis wrote:Messing with the idle srew is a bad idea it will cause the car to run at a higher idle all the time.
On the 2.2 motors, the IAC valve will re-adjust to bring the idle where it is supposed to be even after playing with the screw. I would imagine the 2.4's are the same way.
The reason I say that is because the throttle plate should be fully closed at idle and the screw pushes the plate open slightly to adjust the idle.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
