92 Grand Am idle issues??

This 92 Grand Am was given to me but has idle issues. Once it starts it runs fine but after a few minutes the idle will jump up and down and eventually die. I ran a scan and they were a bad MAF sensor which was replaced with a used one, Neutral Saftey Switch sensor and a Vehicle speed sensor. Nothing came up about a TPS but was told to check it anyway. I put a meter on it and on one side the ohms were very high, 6000 and dropping to around 150 with WOT. One the other side it was open. Is this my problem?? I was also told the the NSS could be the problem because the computer is getting confused weather it's in P or D???? Please help.

Thanks

NSS is possible also, but you should get a code for that, I suggest you replace pcv valve.. I had similar problem and pcv valve solved it. Pcv was ok when cold but when it gets hot it sticks in open position making large vacuum leak. Then IAC is unable to compensate fo such large vacuum leak thus making your rpms jump from 300 to close to 1200 rpm (up and down constantly). If this happens only when engine is warm replace pcv.

NSS is possible also, but you should get a code for that, I suggest you replace pcv valve.. I had similar problem and pcv valve solved it. Pcv was ok when cold but when it gets hot it sticks in open position making large vacuum leak. Then IAC is unable to compensate fo such large vacuum leak thus making your rpms jump from 300 to close to 1200 rpm (up and down constantly). If this happens only when engine is warm replace pcv.
Yes I did get a code for the NSS. I didn't think of the PVC, I'd feel so stupid if it was that...:icon16:

Well I just replaced the TPS and WOW I can't believe how nice this car runs.. It does idle around 1500 RPM but my next question is how do I set the TPS and what should the #s be? I thought I read somewhere that while it's running you're suppose to loosen the two screws and slightly rotate the sensor, is this right?? And does GM make a special scredriver for this, I mean you can't even get anything to loosen the screws with.

tps is not adjustable on this engines (2.3 or 3.1 or 3.3 3.4) there are only two screws star shape, If you just replaced the tps you should know how to loosen them :icon16:


IAC is the one that adjusts the idle speed however, you will notice that when you open and close throttle by hand that throttle pivoting part is leaning against a small screw. If someone tightened that screw too much the pivoting part will lean as far as the screw will allow it. But I don't think it is the problem. Tps at idle should give about .59-.64 volts (engine warm)

did you try pcv? If you don't have new pcv disconnect it and plug the vacuum line with your finger see if idle improves.

tps is not adjustable on this engines (2.3 or 3.1 or 3.3 3.4) there are only two screws star shape, If you just replaced the tps you should know how to loosen them :icon16:


IAC is the one that adjusts the idle speed however, you will notice that when you open and close throttle by hand that throttle pivoting part is leaning against a small screw. If someone tightened that screw too much the pivoting part will lean as far as the screw will allow it. But I don't think it is the problem. Tps at idle should give about .59-.64 volts (engine warm)

did you try pcv? If you don't have new pcv disconnect it and plug the vacuum line with your finger see if idle improves.
Yes I did just replace the TPS and my screws were phillips and I removed the throttle body to do so just because of that reason. The TPS is adjustable that's why it has pivot points. No I didn't get a PVC yet, I'll get one tomorrow and will also back probe the TPS to see where it's at.

again TPS is not adjustable, 100%, the screw that I was talking about is something similar to the one used on old carburetors where you had to tighten the screw (plate inside opens) or loosen screw (plate inside closes) to adjust the idle. But chances are small that someone was playing with that on your car.

or just take a picture and show us what two screws you are trying to loosen

All I want to do is set the TPS, I know it doesn't adjust the idle. I just want to get it to the spec it's suppose to be. I think I remember seeing a small screw by the IAC valve so that must be what you're talking about setting the idle with.

Well I went out to set the TPS to .39V and now it runs like crap again. Idle is surging up and down, I checked the codes and had three. Two for low TPS voltage and one for the NSS. I cleared the codes but do you think the NSS could be causing my problem? When the car was running good the voltage on the TPS was .06 but the idle was a little high. I don't know where to go from here.

definitely nss will cause that pcm will not know if trans is in p or d and thus confusing all other sensors..

tell me the codes that you got?

also is your scanner capable of reading live engine data if yes give me the following:

for idle:

map:
Maf:
IAC:
TPS angle
TPS voltage
Engine Load

is idle any different when you shift it into N?
did you try blocking pcv valve line with your finger tip?

Yes my scanner is capable of live data. No I never did the PVC yet but I'll have the wife pick one up for me. It will be late tonight before I get to that, leaving for work but the data will be jumping around so much because of the idle issue. In a eariler thread you mention the voltage for the TPS, should I try setting it to that but with the engine off? And what I did was that right?

you probably noticed that your tps looks like a pacifier (metal part is about one inch long and looks like half circle stud that fits exactly into its opening so there is no adjustment involved here. The only think you can adjust is the screw which when you tighten will push on the throttle plate lever this you can do with engine off ignition on and watch the reading for tps voltage bring it to .6 V.

Is your prndl reading showing wrong gear when you shift into D dos it show D or it shows something else like N or 1 ?

Welcome to AF alconk !!

Your engine size would help here.

But idle issues most of the time are vacuum leaks or the IAC is clogged.

But from the description you explained about how it runs warm, sounds like a bad MAF sensor, or bad wires(short). lightly taping it, if the idle fluctuates check for bad/loose wires.
The used one could have been worse off then the original.

I'd also try cleaning the MAF sensor with MAF cleaner, and cleaning the IAC and its port(the TB).

And your scan tool should see if/whether the TPS is working correctly.

To add on the TPS, with engine running, using jumper wires, the TPS should read aprox .45 -1.25 vlts , wide open throtle should be about 5vlts.
Also it is NOT adjustable unless you have a 3 or 3.3 L engine. Since you said you have a MAF, that means you have a V6.
Here are the instruction for that.

- You'll need jumper wires for the TP sensor harness connector, or using your scan tool and check throttle position.
- With ignition in the "ON" position, using a voltmeter connect it between A and B terminals on the plug.
- Now adjust the position of the throtle sensor to get a reading of 0.50-0.59 vlts for the 3.0L, and 0.38-0.42 vlts for the 3.3L.
- Torq the screws to 18 in lbs, then recheck the readings to make sure the adjustment has not moved.
Then remove the jumper wires with the key OFF.
Should be good to go, hope that helps!

Welcome to AF alconk !!

Your engine size would help here.

But idle issues most of the time are vacuum leaks or the IAC is clogged.

But from the description you explained about how it runs warm, sounds like a bad MAF sensor, or bad wires(short). lightly taping it, if the idle fluctuates check for bad/loose wires.
The used one could have been worse off then the original.

I'd also try cleaning the MAF sensor with MAF cleaner, and cleaning the IAC and its port(the TB).

And your scan tool should see if/whether the TPS is working correctly.

To add on the TPS, with engine running, using jumper wires, the TPS should read aprox .45 -1.25 vlts , wide open throtle should be about 5vlts.
Also it is NOT adjustable unless you have a 3 or 3.3 L engine. Since you said you have a MAF, that means you have a V6.
Here are the instruction for that.

- You'll need jumper wires for the TP sensor harness connector, or using your scan tool and check throttle position.
- With ignition in the "ON" position, using a voltmeter connect it between A and B terminals on the plug.
- Now adjust the position of the throtle sensor to get a reading of 0.50-0.59 vlts for the 3.0L, and 0.38-0.42 vlts for the 3.3L.
- Torq the screws to 18 in lbs, then recheck the readings to make sure the adjustment has not moved.
Then remove the jumper wires with the key OFF.
Should be good to go, hope that helps!
Thank you for welcoming me to the forum. The engine is a 3.3 V6. I adjusted the TPS to 0.39vlts with the scan tool and no jumper wires since the scan tool tells me what it's doing. This was with the car off but the key in the on position. That's when it started to idle up and down again. I already cleaned the MAF and the IAC along with the throttle body itself. My wife picked up a NSS since that was in the codes as well plus sometimes it didn't start in P but did in N. From what I remember from the scanner the O2 was lean but had 4 bad Quad drivers (whatever that means). I will write down some info and get back. Does this make any sense?

nss is not adjusted properly then

loosen up nss bolt pull e brake while engine is idling play left and right with nss see what happens with idle

Could just be a bad wire on the NSS, or it could be out of adjustment.

Does this model have a brake/ shift interupt solenoid ?

You mean BTSI yes, powered by gauges fuse 10A, but I guess it is working since he can shift gears right?

You mean BTSI yes, powered by gauges fuse 10A, but I guess it is working since he can shift gears right?
Boy, this keeps getting deeper. I can't tell you if it shifts ok??? No brakes, bad wheel cylinder in the rear. I'll be replacing the rear brakes this weekend. I don't know what a BTSI stands for and since you mentioned gauges when I first got it and would rev it up the speedo gauge would slowly rise. But I also had a vehicle speed sensor fault which I think is causing this?? I's so sorry guys... please bear with me. I'm trying to make this a decent car to drive but does have a few issues. Oh, no blown fuses.

Never mind on that BTSI (brake/ shift interupt solenoid)

Are either the throttle/cruse cables adjusted a bit too tight? Are you sure there are no vac leaks?

Are either the throttle/cruse cables adjusted a bit too tight? Are you sure there are no vac leaks?
I think the cables are fine and I don't believe there are no leaks. This car was my Neices and she owned it for about 7 years. When she got it it was very nice but she don't take care of her stuff. Over time this happened then that and when the brakes went out that's when she parked it. So actually when she owned it nobody messed with it so all adjustments should be exactly how it was when it was running good.

Ok, I was finally to get some data and this was after I changed out the NSS and the idle calmed down a bit.
A/F Ratio 59
RPM 650-700
IAC Pos. 24-29
INJ PW (ms) 2.9
MAF (gr/s)1200
O2S (mv) 350
O2S Crosscounts 41
TPS sen 0.41 vlts

Also I mentioned I had 4 bad quad drivers and now I only have 2 so the NSS must have been part of that so if I change the VSS I bet the two will go away as well.

AS far as the PVC I'm a little confused. I don't see anything that resembles one, the only thing I see is a tube that exits the throttle body and goes into the valve cover. No PVC though??

A/F Ratio 59 -------------you did not copy this right
RPM 650-700 ok well not ok but ok. because you have idle problem
IAC Pos. 24-29 ok
INJ PW (ms) 2.9 ok
MAF (gr/s)1200 this is not in gr/s because this is way 2 much, it should be 3-5gr/s or about 2000 - 2500 HZ
O2S (mv) 350
O2S Crosscounts 41- also too much
TPS sen 0.41 vlts


disconnect MAF sensor and O2 sensor see how it behaves.

please take a picture of your engine, we had similar problem last time someone else could not find the pcv. You have one trust me take several pictures and post them here so we can use the for the future reference.

to find your pcv go here -

http://www.automotiveforums.com/vbulletin/showthread.php?t=959198

then scroll to post #7 and open the picture

Ok here goes again,

AF ratio 59, that is how it is displayed
IAC at first is was around 37-42 but then dropped to 16-18
Inj pw 2.7
MAF at first 1400-1500 then down to 1060-1150
O2S in the 300s
O2 Cross 41 dropping to single digits and back up to around 28 or so
TPS 0.41

I unplugged the MAF while it was running and did nothing but killed the engine when I plugged it back in.

I'm new to these forums and not for sure how to post pictures, I can either email you one or email me and I'll reply back. [email protected]

to find your pcv go here -

http://www.automotiveforums.com/vbulletin/showthread.php?t=959198

then scroll to post #7 and open the picture
Picture didn't open??

thanks for the live data,

please check you e-mail regarding the pictures

If you can take pictures mostly concentrating on the lower intake manifold corner by the cylinder #1 so take pictures from the passenger's side.

back to live data:
you have a strange reading for AF ratio usually it should show something like 1 : 13.5-15:3) 1:14.7 is ideal so I don't know what 59 represents.

also maf reading in g/s you say is 1200 that is to much normal for idle is between 3g/s-6g/s when engine is cold in the morning it will be close to 6 and warm close to 3 or 4g/s. Large cross count tells me that you have vacuum leak somewhere. Let me try to find one post where I said that for o2 and it ended up being pcv valve.

Also you never told me MAP reading or if you have vacuum pump connect it to one of the manifold ports and read the vacuum it should be steady between 19-21 inches of Hg

Found the PVC, holy crap... it's in the intake pretty much under the alternator. That's going to be fun to replace.

Now that you found it, you can disconnect the pcv and plug the vacuum line with finger so it does not suck outside air, start the engine and tell me how is your idle.

Now that you found it, you can disconnect the pcv and plug the vacuum line with finger so it does not suck outside air, start the engine and tell me how is your idle.
Ok back at work, will let you know tomorrow.

Well, for a update it's not a pretty one. To start off with I had to pull the alternator to remove the PVC valve and it was the original one and came apart in my hand. The grommet in the intake was extremely brittle which also came apart. then when installing a new grommet I pushed it into the intake and couldn't get it out so I ended up pulling the intake. And in doing so I found a vacuum line broke in half so that could have also been part of the idle problem. Once the intake was pulled I was happy to see how clean it was along with the coolant and I emptied it from the rad. But here's another thing while waiting for parts I decided to replace the serpentine belt BUT you have to remove the motor mount to get if off and put the new one on. What kind of crap is that?? This is the hardest car I've ever worked on so far and I've had many. There is no space, I also had to replace the VSS and that alone took two hours to remove. Still have to put a new one but I broke one of the bolts but can't get to it??? So there it is, my update.

Well I finally get this back together and start it up and no different. Idle bounces around until closed loop then finally settles back down. Here is some info after warmed up and idling somewhat ok.
A/F ratio 59
CCP Duty 15%
CCP solenoid ON
RPM 675-725
IAC direction FWD
IAC position 17
MAF (gr/s)924
02S (mv) 337
02S crosscounts 35
Quad Driver 1 BAD
Quad Driver 2 Bad
Quad Driver 3 OK
Quad Driver 4 OK
TPS 0.41

Anybody have an idea what's going on?

Well, it's finally running great. Ended up taking it to a local shop and one of the coil packs was dead. He had a extra one laying around and so for $30 I'm taken care of.