Help!! High and Rough Idle!!
Thread Starter
TECH Fanatic
Joined: Aug 2008
Posts: 1,740
Likes: 2
From: Nebraska
Help!! High and Rough Idle!! I need help, I bought a 93 Formula M6 LT1 T-Tops with 87,000 miles for $3000 about 8 months ago, It sat for a year and a half without ever being ran before I bought it!( nothing wrong with the car, the guy just didnt drive it)
Now for the question, The car runs flawlessly except when I race someone or rod on it a little, I would get home and shut it off, and when I go to start it again, it starts and then suddenly revs up to 1,500 rpms and then starts spuddering and popping as if it is flooded and hardly runs. Then It comes out of it after about 3 minutes. I tried a new OPTI, coil, plugs, and wires but that didn't help. Then I thought maybe it could be my open 3" exaust ( no cat, no muffler) because it has no back pressure? not sure please help, I'm new to 4th gens.
Now for the question, The car runs flawlessly except when I race someone or rod on it a little, I would get home and shut it off, and when I go to start it again, it starts and then suddenly revs up to 1,500 rpms and then starts spuddering and popping as if it is flooded and hardly runs. Then It comes out of it after about 3 minutes. I tried a new OPTI, coil, plugs, and wires but that didn't help. Then I thought maybe it could be my open 3" exaust ( no cat, no muffler) because it has no back pressure? not sure please help, I'm new to 4th gens.
What kind of opti did you use when replacing? You will find that people have lots of problems with anything other than AC Delco/MSD/Dynaspark ect...
But if your setup is stock, I would highly reccomend getting a stock AC Delco piece (If you havent already).
But if your setup is stock, I would highly reccomend getting a stock AC Delco piece (If you havent already).
Thread Starter
TECH Fanatic
Joined: Aug 2008
Posts: 1,740
Likes: 2
From: Nebraska
Yeah I paid $470.00 for a new Delco Opti, The old opti worked just fine, my car fired right up every time, I just figured it was getting weak and wasn't making enough spark to burn all the fuel thus making it spudder after rodding around. But the new opti didn't do anything, it still ran exactly the same, so then I was stumped knowing that wasn't the problem.
Ok, good stuff then. The delco opti was the right choice anyways. How much have you driven it since it was stored (you mentioned you bought it 8 months ago)? Bad gas could be a possibility, but I think you would have driven it enough (and filled it enough) to flush out anything like that.
How about fuel pressure, been checked recently that you know of?
How about fuel pressure, been checked recently that you know of?
Thread Starter
TECH Fanatic
Joined: Aug 2008
Posts: 1,740
Likes: 2
From: Nebraska
Yeah I bought it with 87,759 miles on it in April, It now has 91, 495 so I do drive it very often, its my daily driver, kinda feel bad racking up those miles. But I changed all fluids, filters, plugs,wires,opti,coil right away and started driving it 2 weeks after purchase so it's been broken in.
It does rumble and kinda shake very slightly while idleing normaly but performs well during a race and doesn't cut out or lose power until afterwards when its shut off and started again. It also backfires and pops like a mother when I downshift during normal driving.
Could it also be sticky or plugged injectors from sitting so long?
Also I have never checked fuel pressure.
It does rumble and kinda shake very slightly while idleing normaly but performs well during a race and doesn't cut out or lose power until afterwards when its shut off and started again. It also backfires and pops like a mother when I downshift during normal driving.
Could it also be sticky or plugged injectors from sitting so long?
Also I have never checked fuel pressure.
Anything is possible really, could be fuel or spark at this point but I am leaning torwards fuel (considering your ignition system is almost entirely new).
Checking the fuel pressure would be a good place to start, a new fuel filter would also be wise if the car sat for awhile and then your using it again. If that doesnt help you at all, then you could take a look at the injectors but stick with the simple and cheap stuff first. Last thing you want to do is a fuel pump/injectors and have it not be it.
Checking the fuel pressure would be a good place to start, a new fuel filter would also be wise if the car sat for awhile and then your using it again. If that doesnt help you at all, then you could take a look at the injectors but stick with the simple and cheap stuff first. Last thing you want to do is a fuel pump/injectors and have it not be it.
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Thread Starter
TECH Fanatic
Joined: Aug 2008
Posts: 1,740
Likes: 2
From: Nebraska
No Ive never checked those things, but the problem is, my car runs great while driving or racing, never cuts out or anything it's just after a hard run or race, I shut it off then start it again, and it start spuddering and acting like its flooded, and if I hit the gas while its doing this it will almost die but about a min later its fine, it doesnt make sense.
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