Long thread but it explains the problem, I've read many idle problem threads but still not one like this yet. Thanks for taking the time and your help (reply) is greatly appreciated.


OK I bought a 97 Sunfire GT w/ a Autotragic. Ever since I bought it, it's had a rough idle and a rubbing noise coming from the front engine so I figured the cause was a loose timing chain.So I bought a timing set and the chain was crazy loose. After I installed it no rubbing noise but the idle is still rough and it still drinks gas like a V8. So I have change many sensors and clean the throttle body. the sensors changed are the MAP,TPS,IAC, Crank and Cam pos. Sensors, O2 sensors. Did a full tune up right after I got it, like Plugs,Air filter,oil & filter change,fuel filter. BTW there are no codes being thrown except Fuel mixture is rich then lean (P0171 and P072 I think).
I have been using a Snap On scanner to monitor the Data stream and best I can tell it the idle problem starts at close loop or shortly after that. Here's the problem, I start up the car and idles good but after about 40 seconds the idle goes crazy like"da da da da (then idle goes crazy) dida dida dida(for about 10 sec. then back to normal) da da da da" dad so on. It's wierweirde idle goes back in forth good 20 sec then crazy for 10 sec. then 20 good. BTW the time frame is a rough estimate. When driving there are no problems, as far as power loss I have no Idea since I got the car like this. But it has constant power tho. It does not die out too. Oh yeah I did change out the Ignition (IDI)cover with a spare engine that I bought and the it's still there. My next attempt is to clean the injectors and replace the fuel regulator. I did a injector test with the scanner and it passed. Is there a Technical Service Bulletin or a recall I don't know about. One last thing, the previous owner said she had a new (used)engine put in cause the last one threw a bearing, It was put in at 74k and the car is at 82 k now.

Thanks in advance.

maybe your fuel pressure regulator is leaking....just a thought

Since its a GT its a 2.4, check the vacum hose that goes from the intake manifold to the MAP sensor, its notorious for cracks, mines a 2001 and it was filled with little cracks now my car is more responsive.

Well I changed the hose already and the Reg. was not leaking.

I did Change the Regulator a installed new O-rings for the injectors and still the engine Idle is Bad. I did notice that the idle seems to go crazy longer as the vehicle warms up, to a point where the idle proble does not go away after a fully warm.
This car is pissing me off now.


Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS

i hate to tell ya man, i just had that exact same problem on my 3.1, its your ignition module...and its quite expensive to fix, i know on my 3.1 its a 300$ part, its behind your front coil packs. hope that helps man, i know how it feels i changed EVERYTHING b4 i tried that...and finally after 1500$ down the road and a engine rebuild it was the damn module. anyways let me know if that was it

Thanks for the heads up. I'll give it a try and hope it is that. When I have the vehicle in drive while iding the car rocks back in forth very noticably. Embarssing when your in traffic


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Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS

I have a 97 that has the same idle problem, but mine's a stick. I've replaced the same sensers you did, plus a knock senser and both coil packs and the ignition module. Still does the same thing. I read on one post that a plugged cat converter would make it idle rough, so I put a test pipe in for one of the mufflers to blow out anything in the exhaust. Still no difference.

So I'm in the same place as you. Mine runs great when you mash the gas pedal down and drive hard, but stumbles at idle. btw, mine is the original motor,80,000 miles.

If you figure out what's causing this, please email me. I'm out of cash for "maybe this one" parts!




John Wilken
2002 Cavalier
2.2 Vin code 4
Auto

I just changed the whole IDI cover with me cousins Z24(who's is running fine) and still doing the same thing. I'm also out of money to try anything else. Funny thing is that a Co-worker of mine has a 2000 Grand Am with a 2.4 and she has the same exact problem( I mean exact same problem) If I get it solved I'll post it up on here, if you (J Wilkens) find out whats wrong please post it up here. DId you by any chance pressure test your fuel lines? That was my next step in this, maybe the fuel pump is starting to GO.


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Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS

I haven't tested the fuel pressure because it runs too good when you hit the gas hard, and it doesn't sound right that the pump can make enough pressure to run at wot but not at idle. Maybe the regulator isn't cutting the pressure down enough and causing the injectors to squirt too much fuel.

Hmmm... Ok, I've got to call Autozone and get a regulator. If that does the trick it'll be posted here.




John Wilken
2002 Cavalier
2.2 Vin code 4
Auto

Or the FPR is not working up to the specs and it gradually starts to build up pressure and when builds up enough presure, it releases the pressure then the idle then returns to normal. After a few seconds the FPR then does it again.

I did change out my FPR but I did it with a used one. Maybe I needed to throw a new one on there. You gotta take the whole fuel rail off to get the FPR off there so get a Oring set (if you haven't already) so you can put those on the injectors while your in there. Its only like 5 dallors so it's well worth it. When your putting the O-rings back on, on the injectors and FPR put some WD40 on to ease them in easier. Also when your intsalling them on the block too.

Another tip is when your putting the assembly back together, Install the FPR on the fuel rail 1st then connect the fuel line on the oppisite end.

The reason I was implying that the fuel pump might be going is I know the problem has to be electrical cause if it was mechanical then the problem would be present throughout the powerband. And the idle problem becomes more constent as the vehicle warms up. Let me know how it goes with the new FPR.


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Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS

do a compression test on each cylinder???

in the days of the "V" motors, there were twin head gaskets, one for each side...any break to the outside in the head was VERY noticeable, it made a heck of an erratic lope 'cos of the pressure difference....but when i had a slant 6 that drank gas, I was amazed to later learn an inline will often times start and run very well with the blown head gasket, no pressure differential to make it "lope"

the old "tech 4" 's ont he used car lots were notorious for having a partial head gasket blown, and the trick was to listen for the idle always going fast, going slow, going fast, going slow, several seconds or more each shift in idle speed.

a simple compression test would rule this out. a tiny head gasket leak can easily be missed til lit gets worse, on an inline engine.


Is an '82 Olds Firenza a "Flash Ride" ?

I'll be doing that as soon as I go to town. Thanks for the info.

Anyone Else?


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Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS

ok. i am having the same problems. i posted another topic because i searched but not with the right words. mine is doing the same thing. the tech 2 is telling me that it is 25 points over. i am heading back to the dealership in a little bit. i have to change both the injector and sparkplug on number three and swap them with number one. to see if number one is running rich. mine is doing the same in the closed loop. it has to be a sensor or a wire though is my thought. if i find anything out i will post it. and i also did a compression test and all tested out around 130-140 psi.

ok. i just got back from the dealership. we have it narrowed down to a couple of things.

1. the inner seal on one of the injectors is bad and making it leak into other cylinders which i have to pull out the spark plugs tomarrow and check if they are wet. and bring down the injectors next week on my day off.

2. there is a massive amount of pressure in the fuel rail. we took off the fpr and fuel shot back pretty hard. then scott. (the tech) put another one on to see if that was the problem and was just holding it in place after we blew out the return lines. it ran fine for about a minute then all of the sudden it shot out from his hand and fuel was shooting everywhere so there was too much pressure becuase he was using a lot of force to hold it in.
so in that case it might be either one of the lines, the fuel filter or the biggest thought would be the regulator on the fuel pump which is what i think that it is. the reason being is that the pump sounds pretty loud when i am sitting at idle.

i will let you know what i find.

Thanks for the input, You should get a fuel pressure test done. I wanted to but my motor mount adapter went out (striped) so I have to replace that before I go to a shop to get that done. Let us know what happens.

I never knew there was a FPR on the fule pump assembly itself....mmmmm...you learn something new everyday. : )


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Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS

There's a fpr on the fuel pump? Then what's on the fuel rail with the vacuum line? Are there 2 fprs?

I miss carbs... So simple. A float, a few gaskets and idle mixture screws. I know fuel injection is better when it's working right, but when it's not, it sucks. My winter project is going to be making an adapter plate for a 2 barrel holley.

Yea, I'm an old dude venting. But I'm an old dude with tools, so I'll post photos when it's done this spring!




John Wilken
2002 Cavalier
2.2 Vin code 4
Auto

What will cause a rich run or bad idle?

FPR diaphragm leakage into manifold
Leaky injectors
Pinched return line (dead headed pump)
Skewed O2 signal
Skewed MAP signal
skewed ECT signal

IAC this is an out put and is not likely to cause a rich run. But could cause a poor Idle.

Also don't forget to check all of the high and low reference voltages to the sensors.


<img src="http://geocities.com/jimmythekid1/gecat2.gif">

Thanks for the input, I'll be doing that for sure. If the reference signals are not what they should be than the PCM would be trash right?


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Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS

Possibly, but I have found the main power wire broken to the PCM, so heck your power and ground before you condemn your PCM. Also most of the high reference voltage to your sensors should be 5vs.


<img src="http://geocities.com/jimmythekid1/gecat2.gif">

all voltages were testing out ok on the tech 2. the last two days it hasn't been as bad. it is a little quirky but not as bad.

yes there is a regulator on the fuel pump and at the rail.
i need to borrow a pressure test kit from my buddy and i will do a fuel pressure test on thursday or friday. i am also going to trace all fuel lines to make sure there are no kinks anywhere. i just hope it has nothing to do with the fuel pump. i don't want to have to drop the tank and spend $$$$$$$$$$$ on a new fuel pump.

OK, so I took my car to a reputable repair shop and this is what they've found...
Fuel pressure is 43 pounds at idle, they said 41 to 47 is normal.
Compression is 210-ish for all 4, which they said was good too.
Passed a leakdown test, so the head gasket most likely isn't toast.
On their machine, all systems appear to be running normal, no weird voltages/signals.
They took it for a test drive, they said it ran great at speed, but still couldn't get a smooth idle.

They suggested taking it to the dealer, because the dealer has all the spare parts to play "guess which sensor", and could swap in/out test parts. So my ride is still a mystery.

:rolleyes...


John Wilken
2002 Cavalier
2.2 Vin code 4
Auto

know what i think?? i think there is a secret program in our ecm's that @!#$ with our idle every so often just so we HAVE to take it to the dealer and they can hit a bbutton or two and charge us some dough....thats my thoughts on it



"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)

if it is a sensor problem you could unplug one at a time, when the problem goes away that is your skewed sensor. This works because when the PCM sees an open circuit it will make up a correct value so the car can continue to run.


<img src="http://geocities.com/jimmythekid1/gecat2.gif">

thats a VERY good idea..BUT..what if the problem ISNT constant..for instance..my car idle fouls up about 30 seconds into startup and straightens its self out a few minutes later..i never have time to try that



"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)

Man that sucks.....I was hoping that we found the problem, The Saga continues...........

My friend that has a 99 Grand AM with a 2.4 also told me that his car was running fine before his engine threw a rod. After that he got a used engine swaped in and thats when his car started to do this also. So I am convinced that that the problem is comong from the engine. Just thought this would help too.


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Red 1997 Sunfire GT bonestock
White 2003 Nissan Spec-V I/H/E/P/MMI/GW/SS