Question about Chevrolet Corvette

3 Answers

I have a 1990 chevy corvette with the L98 engine. I have replaced the fuel injectors, all the sensors, the cap and rotor. Plugs and wires. And a new ecm. My car runs and sounds like a million bucks untill you kick it, then it just goes nuts. Its starts stumbling and blowing white smoke out the back. It continues to run this way untill I turn the engine off and restart it . Then it runs great again unless you give it full throttle. It even does this when the car is in park. If you rev the engine to high it starts running crazy. Could I possibly need to replace the ecm again? I did get it from auto zone.

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  • lazysteve73 Sep 03, 2009

    I don't have any check engine lights on and I just had all the vacuum line replaced at a corvette dealership.

  • lazysteve73 Sep 03, 2009

    In my experiance if I had a cracked head or head gasket, it would not fix itself by resetting the computer. This is only a problem when you give it full throttle.

  • lazysteve73 Sep 04, 2009

    Thank you

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3 Answers

Have you checked the timing? Your timing may be off and although the car would run, it would not run correctly if the timing was off...I would also take the ECM out and get one from a corvette salvage yard..this will insure you are getting an OEM factory GM computer and not some aftermarket special..be sure al of the spark plugs are gapped correctly and that the plug wires are seated firmly over the spark plugs..also check every sensor to be sure that they are connected. The white smoke often means that you are burning antifreeze. Sometimes when the head gasket goes or you have a cracked head it will produce a passage for the antifreeze to pass from the capillaries into the combustion chamber. It is easy to check if you have an air compressor. Remove one of the rear sparkplugs and the radiator cap. Fill the radiator and then push some air into the sparkplug hole (get a good seal in case a valve is open). Repeat with all the cylinders and watch for air bubbles coming up into the radiator. If bubbles come up or fluid is pumped out, the head gasket is blown and must be replaced. It is more likely to happen at the back of the engine because it is farthest away from the fan and therefore gets less cooling...Also check your oil for discoloration. If it is a brownish color it could mean your oil and antifreeze are mixing and has the potential to damage your bearings.

If the exhaust billows white smoke for only a few seconds when first starting the engine after it has been sitting for a while, such as overnight, and then runs normally, it could mean that the rubber valve stem seals have perished - especially if the vehicle is a few years old and has done over 60/70,000 miles.

When you reinstalled the spark plug wires, were they re-placed in the correct firing order?

Posted on Sep 03, 2009

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  • Master
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It often means that you are burning antifreeze. Also have you noticed any leaking out of the reservoir tank while you are running it? Sometimes when the head gasket goes it will produce a passage for the antifreeze to pass from the capillaries into the combustion chamber. It is easy to check if you have an air compressor. Remove one of the rear sparkplugs and the radiator cap. Fill the radiator and then push some air into the sparkplug hole (get a good seal in case a valve is open). Repeat with all the cylinders and watch for air bubbles coming up into the radiator. If bubbles come up or fluid is pumped out, the head gasket is blown and must be replaced. It is more likely to happen at the back of the engine because it is farthest away from the fan and therefore gets less cooling.
Also check your oil for discoloration. If it is a brownish color it could mean your oil and antifreeze are mixing and has the potential to damage your bearings.
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Also another reason can be ------ If the exhaust blows white smoke for a few seconds when first starting the engine after it has been sitting for a while, such as overnight, and then runs normally, it could mean that the rubber valve stem seals have perished - especially if the vehicle is a few years old and has done over 60/70,000 miles.
Another clue is: does the exhaust smoke smell like fresh, rather than burnt oil.
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to figure out sporadic tailpipe smoke , with no other negative engine symptoms, a malfunctioning PCV valve. If the ball-check isn't fully seating, allowing small amounts of oil to sneak past and into the combustion chamber. Then the white smoke occurs.
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White smoke or semi white can be produced in several ways. One way is oil this is normally a whitish blue to blue smoke and has the apparent smell of oil being burned. Next could be antifreeze when it is being burned it has a sweet type of smell and tends to dissipate in the air rather quickly. Next is automatic transmission fluid which is normally found on automatic transmissions and its normally drawn into an engine thru a vacuum line via a defective transmission modulator valve or some other defective part. Transmission fluid is very apparent and blows out so bad that you can't see anything behind you. Last but not least another type of smoke that is not white but black is the presents of to much gas/fuel being burned in the engine.
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White smoke is caused by engine coolant/Antifreeze being processed in the combustion chamber(s) of the engine.....ie burning, melting, frying, whatever....
Peirod....
I'll explain further.... This is automotive chemistry 101....
Oil of any automotive type burns blue.....
too much fuel issues burn black
not enough fuel issues burn grey
on a cold day you may see what appears to be white smoke from the exhaust that will disappear after the vehicles engine has warmed up to it's normal operating temp.. This is a normal reaction called condensation... condensation is the result of a small amount of water/dew being drawn into the exhaust usually collecting in the muffler and/or the catalytic converter and is caused by our friend mother nature..... like when you see your breath on a cold day...
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check out all the options 1 by 1.
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Posted on Sep 03, 2009

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  • Chevrolet Master
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What trouble codes do u have? the ECM is seldom if ever the cause of problems like this, do the basic tests, trouble code retrieval is 1st and foremost test you need to do, here is how you do that on this ODB 1 control system. go to link.
http://check-engine-light-codes.blogspot.com/2006/03/gm-1983-95-vehicles-obd1-codes-self.html
here is a ist of ODB 1 data trouble codes and there difinitions. go to link
http://www.gmtuners.com/OBD1_DTC.htm

Posted on Sep 03, 2009

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  • yadayada
    yadayada Sep 03, 2009

    suit yourself, have rebuilt one of these C4's from the ground up, know the whole system well, this is sound advice i assure you.

  • yadayada
    yadayada Sep 03, 2009

    very seldom is there a check engine light, I have been doing this years and know this for sure do the tests humor this old tech.

  • yadayada
    yadayada Sep 03, 2009

    U CAN ALL ME AT 925-577-7157

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350 Chevy engine in what? 1990 Corvette? Who built it, did you?

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