Brendahlz

So I purchased a 1992 Corvette LT1 Base coupe last year with 57,000 miles on it. Since I purchased the vehicle I have replaced 2 injectors, all new spark plugs and wires, new water pump. After the water pump was installed (around 61,000 miles) I started to experience a few different things. The car started to backfire through the exhaust it sounds like and the car wants to jump forward while in drive. There is a rough idle when in drive as well. The vehicle will backfire when it gets into about 3rd gear. once up to to speed it doesn't seem to do it. Took the vehicle to a repair facility and they told me that they believe it is because the Opti needed to be replaced. After replacing the Opti, they informed me that it didn't fix the issue. Car is still at the shop right now but don't really feel comfortable with them at this point. Any suggestions would be greatly appreciated. Thanks yall.

C4hillbilly

pacoW

Engine running rough, backfire always start with fuel then spark (ignition), standard procedure. 1st test fuel pressure, at idle then WOT (tape the gauge to the windshield). Why not all the injectors replaced? Only 2?

s carter

Back Firing is usually caused with a Problem in Ignition/Timing, Since the Opti has been Changed with no improvement has anything been done with Ignition Control Module or coil? I would even take a look at the TPS & O-2 values, and Knock Sensor for any Activity, While I had on a scan Tool. Which they Should Have.

RandomTask

In order of easiest/cheapest:

-Check spark; take boot off plug, take spare plug and hold against engine. Should be CONSISTENT bright spark. Failing opti will still fire, but spark will look weak and intermittent.

-Check fuel pressure. Should be around 45psi. (Will need a fuel pressure gauge, can rent for free from auto store)

-Check injectors via noid light. Look for consistent firing.

-While I severely doubt it would be the cause, do a compression check on the motor just for the hell of it.



As an aside, I’ve installed brand new opti’s that were bad right out of their packaging.



In fact, last motor build (LT4), the brand new Opti was bad and did the above things. Still getting spark and all, but just intermittent and weak. The motor actually was backfiring so badly, the motor ran in reverse for a solid 5 seconds (not exaggerating). The replacement opti died (at the track) about 13 hours later. Replaced with ANOTHER brand new unit that was AGAIN bad out of the box. Replaced w/ a 3rd used unit.



Quality control on (most) opti’s is garbage and they’re super sensitive to manufacturing defects.