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89 C4 sputters and rough idle while accelerating

 
Old 03-10-2019, 07:40 PM
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nathan johnson
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Default 89 C4 sputters and rough idle while accelerating

Good evening fellow Corvette enthusiast! I am new to the forum and almost at my wits end! I purchased a 1989 one owner Chevrolet Corvette C-4 with 76,000 miles in December from my boss. He took meticulous care of this vehicle and has sat in a garage at work covered for the past 15 years. In December I installed a brand new top-of-the-line battery with a higher CCA as well as A new alternator dura last gold. It ran fine for a month but then started to stall out as soon as I give it gas it sputters and then cuts off. Today I hired a mechanic and we tested the fuel pump and it was dead so we replaced it. Also replaced the fuel filter. Brand new ignition coil. Brand new air filter. Brand new full set of eight Bosch spark plugs. Brand new mass airflow sensor. Brand new fuel pump relay switch. After doing all of this it still sounds completely the same. If anyone has had this issue before please help before I dump any more money into this beautiful blue car prematurely!! Edit Quote
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Old 03-10-2019, 09:23 PM
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aklim
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Originally Posted by nathan johnson View Post
Good evening fellow Corvette enthusiast! I am new to the forum and almost at my wits end! I purchased a 1989 one owner Chevrolet Corvette C-4 with 76,000 miles in December from my boss. He took meticulous care of this vehicle and has sat in a garage at work covered for the past 15 years. In December I installed a brand new top-of-the-line battery with a higher CCA as well as A new alternator dura last gold. It ran fine for a month but then started to stall out as soon as I give it gas it sputters and then cuts off. Today I hired a mechanic and we tested the fuel pump and it was dead so we replaced it. Also replaced the fuel filter. Brand new ignition coil. Brand new air filter. Brand new full set of eight Bosch spark plugs. Brand new mass airflow sensor. Brand new fuel pump relay switch. After doing all of this it still sounds completely the same. If anyone has had this issue before please help before I dump any more money into this beautiful blue car prematurely!! Edit Quote
What did he do to test the fuel pump? Did he check that it was priming? What is the Key On Engine Off fuel pressure? Did he test it for holding pressure when the key is turned off? Did he check for spark? Why is he changing the MAF for this? How did he determine it was bad?
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Old 03-11-2019, 02:21 PM
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Y-bodluvr
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I had a sputtering issue I couldn’t figure out in an L98 GTA I had with pretty much new everything EXCEPT IGNITION MODULE and I don’t see that on your list it was an INSTANT cure they’re cheap enough not to worry about the “dumping” money part..

Last edited by Y-bodluvr; 03-11-2019 at 02:22 PM.
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Old 03-11-2019, 02:57 PM
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aklim
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Originally Posted by Y-bodluvr View Post
I had a sputtering issue I couldn’t figure out in an L98 GTA I had with pretty much new everything EXCEPT IGNITION MODULE and I don’t see that on your list it was an INSTANT cure they’re cheap enough not to worry about the “dumping” money part..
I'd test it first.
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Old 03-11-2019, 03:21 PM
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vette196
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BAD "brand new" MAF.....someone a few months ago had a terrible problem getting a "new" MAF to work (multiple units)
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Old 03-11-2019, 05:15 PM
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leadfoot33
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i had a similar issue, stall/stumble when parking lit speed in my 87 l98, turned out to be the EGR, i unplugged it from the passenger side and the issue went away. something to try
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Old 03-12-2019, 01:16 AM
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Pull the codes to see if the ECM gives any clues.

Check fuel pressure and manifold vacuum.

Did you check spark plug wires?
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