Rough idle! Think its dumping too much fuel I need help

97ebaygst · Oct 9, 2009

I just recently purchased a 97 gst with 125,000 miles on it. When I bought it the guy that sold it to me said it ran real rough and that u could smell unburnt gas coming from the motor. When I got it home and pulled out the plugs they where black as could be. So to see what it would do I bought a new set of plugs and those blacked out after letting it warm up a little.
When I start the motor it has trouble starting. It'll turn, chug and repeat once or twice before it'll turn on. Once it's on it'll idle real low, like it's barely above 0 on the tach. When i try and rev it it'll jump like 500 rpm up then act like its gonna cut off before i take my foot off the gas. If I do this to or three times then press the gas slowly it'll crawl to between 4 and 6 grand before it sounds like it's backfiring and then bog down again.
I have done a compression test and it read between 170-180 across the board. I hope I did it right cause It was my first time doing it. Things I checked are the coil pack and the tps. The coil primary resistence read .3 on both leads. Where I read it said the norm is .75 anything else to replace, but it still runs, so I was wondering if the sence of extra fuel could be from the coil not firing hard enough to burn it all.
Thats all for now but if anybody could help me out i would be very grateful. This is my first turbo car so im a little lost on working on it compared to a n/a motor

forcdndukshun · Oct 9, 2009

Sounds like it is gas fouling the plugs. Is the car throwing any cels? I had the same problem on my 98 and it turned out being that the cam angle sensor was going out. Check the cam angle sensor if you haven't.

aferraro21 · Oct 9, 2009

Sounds like you have a fuel injector that is stuck open, issues with your FPR, or problems with your Mass Airflow Sensor. If your car is in fact running too rich, it would probably come down to one of those three problems. I can not post in classifieds, but if you in fact find out you have bad injectors, PM me I have an extra set of stock 450cc I'm never going to use off of a 99 GST (I don't want to get banned from the forums, I'm just trying to help out).

It def sounds like you're running rich though. Have those things tested.

aferraro21 · Oct 9, 2009

forcdndukshun said:
Sounds like it is gas fouling the plugs. Is the car throwing any cels? I had the same problem on my 98 and it turned out being that the cam angle sensor was going out. Check the cam angle sensor if you haven't.

Great point too, keep in mind if you're getting any spark, chances are it is firing hard enough. Timing and CAS could cause the symptoms you are having too.

93_GSX · Oct 9, 2009

Um, first, what has all been done to the car?

Have you done a boost leak test? That could be a problem. http://vfaq.com/mods/ICtester.html
That will help you with the leak tester.

It could also be a fuel pressure regulator issue, or the coolant temp sensor.

It could also be as simple as huge injectors and no engine management.

97ebaygst · Oct 9, 2009

I'll make sure to check that out. Also i was just snooping around under the hood checking wires and stuff and i noticed that the coolant temp sensor pig tail is broken could that have anything to do with it even though its throwing fuel even when its cold?
It's pulling air intake temp sensor circuit malfunction and coolant temp sensor circuit malfunction.

forcdndukshun · Oct 9, 2009

I know that coolant temp sensor will cause it to run in open loop and rich if it is out.

93_GSX · Oct 9, 2009

Yes, that could be your problem. Fix that, then report back.

97ebaygst · Oct 9, 2009

I thought it was the injectors too but they r all black. But I'll still check it out and get back to u. Any body know where I could get a pig tail for that?

93_GSX · Oct 9, 2009

Heh, I got mine from a buddie who pulled it out of a box of wires. Literally a 25" cube box of random DSM wires. It was funny.

97ebaygst · Oct 9, 2009

93_GSX said:
Heh, I got mine from a buddie who pulled it out of a box of wires. Literally a 25" cube box of random DSM wires. It was funny.

if only I were that lucky. lol

93_GSX · Oct 9, 2009

Try a junk yard in the area?

Trelo203 · Oct 10, 2009

I had the same issue wit my car could be the temp sensor....but for the blackening spark plugs I am clueless. It can also be the cam angle as stated befor. Maybe even your ecu.... I myself had that happen when my ecu was on its way out. Was the car in running order when you bought it?

97ebaygst · Oct 10, 2009

Ok guys I found a pig tail for the temp sensor and fixed that. I also changed out the cam sensor but it stills runs rough. It's better where it doesn't back fire or chug anymore but still low rough idle. I haven't taking it out on the road yet but now the gauge isn't showing any boost, I hear the bov opening but it's just not reading. I've heard that it doesn't build boost while sitting still but when i got it the gauge still read some boost. Did I disconnect something on accident?

After looking more into it I notice that he disconnected the wastegate actuator and the flap moves freely. I had my wife sit in the car and look at the gauge and rev the engine while i held the flap shut thinking that could part of the problem, but still no sign of boost on the gauge but bov still pops off.

So looks like i just added to my problems. I think i fixed part of the problem but still something there that i cant fix. Could the IAT code that pops up have anything to do with it? Well I'm gonna take it out for a test drive any see if it builds boost.
any help would be appreciated. thanks

97ebaygst · Oct 10, 2009

Could a bad knock sensor cause my problems?

97ebaygst · Oct 11, 2009

i worked on it all day today and I'm more confused then ever!!! Everytime I start it it acts different. I got the coolant temp sensor pigtail on like I said earlier and it ran a little better, like i could rev straight to redline without a hiccup but it reved slow. Now when I crank it (no stereo) it makes a clicking nosie from the stereo area and lights start to dim while the car dies then comes back on then dies again. It's really hard to type what its doing. It's more a u got see to know kinda problem.

MustangBill347 · Oct 12, 2009

(I am new to DSMs BTW) but I think it could make boost when revving if it were running rich so it not making boost now may not be a problem but a sign that you did fix it, somewhat.

but i am also having a similar sounding problem in my 93 talon, where it does not start right away i have to crank it a bit and wait and crank again... till it fires some, than fires enough to run. but it revs up and down for a little while than finally calms down and runs well. it will also start up fine as long as it is still warmed up.

BUT.... I did find 4-5 little holes in the pipe coming off the stock intercooler i didn't think that the little holes could cause it to run sooo bad but i dont know...

forcdndukshun · Oct 12, 2009

97ebaygst said:
i worked on it all day today and I'm more confused then ever!!! Everytime I start it it acts different. I got the coolant temp sensor pigtail on like I said earlier and it ran a little better, like i could rev straight to redline without a hiccup but it reved slow. Now when I crank it (no stereo) it makes a clicking nosie from the stereo area and lights start to dim while the car dies then comes back on then dies again. It's really hard to type what its doing. It's more a u got see to know kinda problem.

How is your charging system and battery. The car is running better which is an indication that you have fixed a couple of things. I know from experience if the charging system is going out it will cause the car to idle poorly. This could also explain why the stereo is shutting off and the lights dimming. Check the battery and the alternator.

97ebaygst · Oct 12, 2009

Well i just replaced the battery and the charging seems good. I figured out that the relay that I hear is either the fuel pump relay or the mif relay. What could be making either one of these things go off and cut the car off? I've heard that the mif is called the auto shutoff so I think thats the one thats clicking but I'm not sure. I dont know if I fixed the problem because I can't keep it running long enough to tell. It's still pushing out black smoke. It did runn better for like five minutes but started acting up again so I think that the good revs was a fluke.
So I guess my question for now is what could cause either the fuel pump relay or the mif relay to click and could that clicking be why the car shutoff?

97ebaygst · Oct 13, 2009

forcdndukshun said:
How is your charging system and battery. The car is running better which is an indication that you have fixed a couple of things. I know from experience if the charging system is going out it will cause the car to idle poorly. This could also explain why the stereo is shutting off and the lights dimming. Check the battery and the alternator.

I went out and checked the alternator with my digital meter and the battery read 12v and when the car started it read 13v plus. So its not the charging systems even though the car starts idles for a few seconds the jumps to 1000 rpms (it'll do this once or twice) dim and brighten the lights then finally the motor will cut off.

Any advice anybody? I really want to get my car on the road, so show me what this forum is made of!!!

Rough idle! Think its dumping too much fuel I need help

97ebaygst

forcdndukshun

aferraro21

aferraro21

93_GSX

97ebaygst

forcdndukshun

93_GSX

97ebaygst

93_GSX

97ebaygst

93_GSX

Trelo203

97ebaygst

97ebaygst

97ebaygst

MustangBill347

forcdndukshun

97ebaygst

97ebaygst

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