1990 Camaro V8 issue.

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CWPottenger

G-Body Guru
Oct 9, 2012
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I'm going to put this out here to see if any one familiar w/ the GM TBI system has some ideas.

I have a bone stock 1990 Camaro RS V8 305 TBI. I am having an issue that "feels" like ignition dropout, but at this point I do not know.

The issue I have is extreme backfire, loss power on acceleration, but only between about 18-2600rpm below that and above that range it is just an occasional stumble(dropout).

The engine has a new Dist, coil, plugs, wires, cap, rotor, ign module. No engine codes stored. manifold vac is a steady 18 @idle Base timing is a stable 2degrees @ idle w/ advance wire disconnected, both injectors have a nice even cone spray pattern. The issue is also very minimal when in open loop just an occasional stumble no matter RPM , but as soon as it warms up and goes closed loop it gets bad between 1800-2600rpm

In neutral it will rev just fine without the backfire, just the occasional stumble.

Any thoughts,ideas would be very helpful.
 
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HAFROD

Royal Smart Person
Jul 15, 2013
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Claremore, OKLAHOMA
I'd start by checking connectors and grounds since you've already put on some parts that usually cause the issue. Check your main wiring harness so that its not on the exhaust. I had this happen to a 95 Impala SS I had. I'd clean the IAC pintle valve with carb cleaner. If its really bad carboned up, I'd remove the TB and clean that passage. I have seen them clogged.
 

Pontiac455

Master Mechanic
Jun 8, 2010
470
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Check the vac. line going to the map sensor, the throttle body is known to carbon up restricting vac.
 
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