I need your help guys

So... I have had an intermitten problem with my idle for about 4-5 months now. I idle problem start around october or november when my front o2 sensor went bad. I was having a really bad chuging during idle and when I went to take off I had to baby the gas to get any power at all, if I pressed the gas too much it would just sit there and not do anything. I replaced the o2 sensor and this problme cleared up, but I was left with another problem. My car seems to want to die every 10-15 seconds maybe. It idles around 800rpms consitantly but every so often the idles will drop down to about 500 or 600 for a second and almost die, and then jump back up to about 1200 or 1300. It's never actually died and when I take off of drive its fine. I have been throwing a code lately, I believe its the P0700 that might not be the right code but the code description in auto tap says fuel system too lean. I am pretty sure that I dont have a vacuum leak, one because my vacuum gauge is exactly as it has been for the past 3 years, and two because I have sprayed all over the vacuum lines with carb cleaner and havnt gotten any idle surge at all. I've tried the ground wire upgrade, the extra + from the alt to the fuse box, replaced the fuel filter used injector cleaner several times and I just cant seem to figure out what the deal is. When the code comes on its only on for a little bit, maybe two separate drive sessions and then it goes off again, thats why it frustrates me so much. Any ideas would be much appreciated. I had a friend suggest the fuel pump relay and the fuel pump spd cont relat in the engine fuse box as possible problem causers and am replacing both of those tonight. Let me know what you think guys, I am at a loss

P0700-Transmission Control System Malfunction

Is that the code you're throwing???

no, that must not be the code number then, I will scan it when I leave work and get back on when I get to class and repost the exact code that it is throwing, but the description is correct, I remember it said fuel system too lean

Clogged injectors?

ok, the code is P0171 Fuel system too lean, I changed the relays tonight, didnt help at all, I dont believe its the injectors because I havnt noticed any other syptoms durint regular driving, no bogging during starts or anything like that

If anyone is handy with a autotap I can give you scans to look at?

Maybe the IAC motor? Or maybe the O2 sensor you replaced is defective and is giving the computer inaccurate info and thus the PCM isn't delivering enough fuel.

IAC motor? I havnt ever heard of this... where is it located, also, I dont think it is the o2 sensor, but I will try replacing it, its only like $12

You can test the O2 sensor with a multi meter and a propane torch. Do a google for O2 sensor testing.

I'm still leaning on dirty injectors.

LOL, I knew you wouldnt let me get outta this without pulling those out, I'm gonna take a look at testing the o2 sensor and if that turns out ok I guesssssss I will pull the injectors and take a look at them :rolleyes:

Edit: I think I might try this first

Causes= code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled
There could be a vacuum leak downstream of the MAF sensor.


Possible SolutionsPossible solutions include:

In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure

anyone have any tips for cleaning the maf and wanna tell me exactly where its located to make sure I thinking of the right thing?

Check out this thread..... I'd also suspect your EGR valve.

http://www.grandprix.net/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=004585;p=1&r=nfx

Follow clint's link to that thread, and go down to his post with the diagram and find MAF.


Can you post or email a scan?
(with O2's, long and short term fuel trims (ltft & stft), injector pulse width, and the rpm stuff.. more the better)

The MAF idea sounds good. I would also think of fuel pump resistor or the pump itself.

$12 O2 sensor ?!?!!

Ok, I think I may try and replace the PCV valve and clean the EGR valve tonight, along with the MAF sensor. What exactly do I clean on the EGR, I'm assuming I need to unscrew it and pull it out to be cleaned?

Also, I will post scans tonight

Ok, got scans sooner than I thought I would...

During Idle

RPM 830
STFT O2 bank one sensor 1 10.9%
STFT O2 bank one sensor 2 99.2%
LTFT bank 1 16.4%
STFT bank 1 10.9%
Throttle Position Angle 0.4%
Ignition Timing Advance 27deg
IAC Motor Position 55counts
Injector Pulse Width #1 2.12ms
Linear EGR closed position 1 volts
Mass Air Flow Rate 0.61 lb/min


During Surge at idle


RPM 1022
STFT O2 bank one sensor 1 9.4%
STFT O2 bank one sensor 2 99.2%
LTFT bank 1 16.4%
STFT bank 1 9.4%
Throttle Position Angle 0.4%
Ignition Timing Advance 27deg
IAC Motor Position 68counts
Injector Pulse Width #1 2.48ms
Linear EGR closed position 1 volts
Mass Air Flow Rate 0.585 lb/min


During Cruising


RPM 3964
STFT O2 bank one sensor 1 0.0%
STFT O2 bank one sensor 2 99.2%
LTFT bank 1 -2.3%
STFT bank 1 0.0%
Throttle Position Angle 61.2%
Ignition Timing Advance 15deg
IAC Motor Position 141counts
Injector Pulse Width #1 18.01ms
Linear EGR closed position 1 volts
Mass Air Flow Rate 25.635 lb/min

Do you guys want to see more of the scans or want to see something else?

That ain't cruising, that's floored!

61.2% Throttle to be precise.......

I'm wondering if the lower MAF signal during the higher RPM surge would indicate a dirty MAF sensor, or a faulty MAF sensor..... I may be off, so if anyone can correct me, please do so.

If you want to clean your MAF sensor, you may be successful by shooting some carb cleaner into it while the car is running. You will have to work the throttle to keep the car running, but this is a simple way to clean it. If cleaning it doesn't work, you may want to contact someone with a similar car and swap sensors. If this cures the problem, you need a new sensor. If the problem persists, you can rule out the Maf sensor, but don't forget about the wiring.... Wiggling wires is another troubleshooting method.

That is regular cruising

GP OWNERS PLEASE dont use carb cleaner to clean your MAF. It may work well once or twice but eventually its going to ruin your MAF. You must use plastic safe electric cleaner... anyways on with the story

Last night I picked up some electric cleaner from the auto parts store and came home and went to work on the maf. I pulled it out and took a look at it, didnt look that dirty but I sprayed it anyways. Sprayed it once really good then let that dry, then sprayed it again just to make sure, put the maf back in hooked everything up and started it up and immediately I could see a difference on my A/F gauge. Lately its always been running on the lean side of ideal, not the way it used to, used to run rich for the most part, I thought this may have been because of the different O2, I put a bosch in and have heard they make some cars run lean. Anyhow, fired it up and right away, I'm seeing green and blue (rich) lights on my a/f gauge. I took it for a drive and it felt 100% better than it has lately, and my a/f gauge was pegging solid blue when I floored it like it used to. I returned home and let it sit and idle for a little bit. Its running a lot better bet I still get some idle suddering and then surging but not as often and not as harsh. I was thinking maybe a sticky pcv valve, or something in the egr valve, but no one ever answered my question on how to clean that... does anyone know how, or what exactly you need to clean? So anyhow, its running much MUCH better, and I suppose if I never quite get it to idle perfect I wont get too dissapointed, after all she is getting to be a pretty old lady I'll keep you updated as I replace more stuff

Well, How about shooting some Carb Cleaner into it....

Really, Unbolt the EGR valve and underneath is a pin that should move around freely. Flush out the port with cleaner several times to remove carbon build up.

I didn't think about the Carb Cleaner being detrimental to the plastic MAF sensor. When I use it the car is running and it evaporates instantaneously.

yeah, I didnt mean to come off impolite, I have just read about a lot of people messing thier MAF up with carb cleaner and they can be pretty expensive to replace, just dont want anyone to have to go through that trouble.

Anyways... when I'm looking at the EGR "unit" from the driver side I see a black cylinder on top then underneath there is some sort of plate with one nut on it. Which piece exactly comes out?

There are 2 13mm nuts that are on studs looking straight up. Those are the nuts you want to remove to clean the EGR.

so... I bought a new pcv valve last night and replaced that... I made my way over to the EGR valve, unbolted it from the houseing that connects to the exhaust and took it off. I didnt take anything else appart, but all I could see were two holes, I didnt see any pins hanging down or anything to that effect. I just sprayed some cleaner into the holes on the portion that I took off and let it dry for a little bit. Put it back on fired it up and my SES light went off about 15 seconds into idle, still has a little stutter but its much less, only jumps around 1-200 rpm's which I guess is not that bad for the amount of miles, I'll let you guys know if the SES light comes back on

sitting in my car smoking a cigarette... ses light comes on again its not really that big of a deal I dont think, its just driving me insane not knowing what it is back to the drawing board, I think I may have the injectors cleaned, and I was also thinking about getting a case learn just incase, I never got one when I installed my pcm, just a thought, opinions anyone?

Have you inspected all of your vacuum lines?

I've seen the tee at the base of the SC snout crumble on 3 cars now. Be sure to check all other connections.

reinstall your TB screen!! that could make your car idel rough

yeah, I've gone through all the vacuum lines and also gone over them with carb cleaner a couple times and havnt ever found anything. Plus, I also highly doubt a vacuum leak because I have been keeping a really close eye on my boost gauge and its steady as ever, in fact I was hitting almost 14lbs of boost at the top of first yesterday, but see, the light also went off yesterday afternoon on my way home from work. I didnt clear the code or anything

As far as the TB screen, I took it out roughly 2 years ago almost to the day and it has never given me problems before, I find it hightly unlikely that it would all of a sudden start

Good news from all this mess, heard from one of my buddys whos step dad words for GM, I'll be getting the GMPP suspension kit with a hefty discount on it

Have you got a FP gauge you can hook up?

If you're having problems at idle, you can hook one directly to the schrader valve on the fuel rail and watch it while idling. IIRC mine runs around 48-49psi at idle.... If that number doesn't sound right, I can start it up and make sure.

I'm assuming you don't have any exhaust leaks?

I'm surprised carb cleaner was considered for a MAF sensor. It's an electronic device after all.
Also, I found that electric cleaner works good for most applications of getting rid of grime effectively.

Actually, I was thinking about that today, I do have a small exhaust leak where my downpipe bolts up to my headers, its not major but its a definate exhaust leak, I was thinking that this could possibly be the cause for the inconsistant idling, do you think this could also cause the ses light?

Sheese, You got any more salt for this wound?

I've been told that the O2 would read lean with a collector outlet leak, doesn't make sense to me since the collector should have a positive pressure on it at all times, but who am I to argue?

well, its been 3 days now and I think my idle problems is completely fixed, and you guys will never guess what it is...

My air filter. I have it halfway through my fender wall, and I took a gender at it when I cleaned my MAF, and it didnt look too dirty, but on friday while I was swapping t-stats I decided to clean it anyways, OHHHHH MAN! when I pulled it out, I could tap it on the ground and like sand just started falling off, it was all caked to the outside where it was in the fenderwall. So, I cleaned it up, reinstalled and it idles purrrrrrrrfect. I'm glad that it was something simple, to bad I kept overlooking it though

What a shocker.

Hey, it's least she's running sweet.

wow! well atleast now you have all the hard matance done for the next year! haha

Resurrecting an old post. I've been having this same problem since my top swap, at idle car almost dies then recovers, but is idling higher than normal and I can hear the engine sucking in air to try and compensate. So far, I've replaced the O2 sensor, IAC motor, and PCV valve. No dice.

Thinking maybe I'll try replacing/cleaning the air filter? You guys think that might help?

Definatly sounds like a vacuum problem.Chico.

I've checked all the vac lines, they are all new and they look good, I used 7/64" rubber hose for vac lines after my top swap, what vac should I be seeing at idle. right now i see 13-15 in. vac and after it kind of chokes and recovers I will get about 10 in. Hg, is that too low?

Also I've noticed when the motor is cold it will not act up. Once the temp gets above 140ish, it starts to idle like crap.

10 is very low. i get 2x that. And your symptoms sound like a vacuum leak

Here is something i did. On the TB there is a vacuum port that the EVAP canister is connected to. My vac. line was split so i completely cut the evap canister off of it and used a vacuum cap over the top of it. I figure it is one less thing to worry about. It will set an SES light, but it can be deleted with a Powrtuner. Also, check all of the rubber "adaptors?" Mine were all very brittle when i did my swap, so i replaced all of them.

Ordonez, could you maybe snap some pics of how your vacs lines are setup? Maybe mine are hooked up wrong. I replaced my TB screen today, and that didnt help.

sure, i can take some pics tomorrow

thanks man. so you aren't having idle problems at all? also what RPM does your car idle at?

I'd enjoy a series of vacuum pics as well. I'll need it before long.

I have a High Idle issue too after my TB port. I can't find it out. Checked vac lines 10x. Changed out my IAC to a new one, no fix. Another new gasket on TB with RTV on both sides. I also have this issue now when I begin to slow down to approach my house, I shut the A/C off and the car begins to accelerate on its own till about 2500-3000 rpms, kinda scarey. Has happened 5 times now.

I'm not sure if mine is a tuning issue or not. Guy said my O2 sensor was crapped out and wasn't switching like it should, so i swapped it out, now it still does it but only when the motor is warm. I bought a Bosch O2, anyone know anything about those?

Drummer here is what you will need to have proper operation on a top swapped 97,first off the trans. vacuumline will need to run from the nipple under the front of the SC ,T this line and run to the FPR ,the reason you run the line fom trans. to sc is it will need to see boost to shift properly,now the line that normally runs to the FPR will run to the MAP sensor (are you useing the L-36 map sensor?) all other vacuumlines will run as they were before swap except the line that went in beside the brake booster hose this line will now go to the tree on the top of the SC ,hope this helps .Chico.

I have mine setup like that except for my L36 MAP sensor is tied into the line that sees boost because it was giving a high input code when tapped into the line coming off the TB. After I switched it, the MAP kPa readings were normal.

My setup is like this:

Boost/Vac line goes from the LIM -> FPR -> MAP sensor -> Transmission

There is a vacuum only line that comes off the TB and is setup just like it was before the swap.