I have a 1986 corvette with an l98 that I've been working on. I've been having problems with the engine sense I got it. Passenger side exhause before the cat glows red hot and it backfires on the passenger side after warming up. I've replaced the injectors, and plugs and we attempted to adjust the lifters on that side but the problem persists. I've also changed the egr valve and checked for vaccine leaks. I've also replaced the ecm And suggestions?

 

This sounds like a pretty serious problem and without a lot of technical information would be very hard to diagnose here.

I would seek local professional help on this one, there's just way too many variables that need to be checked out.

Good luck and hope you get the problem resolved, let us know what you find out.

Rick

 

Was it running good when you bought it? If it was then you must have done something to change how it performs. If it ran like this when you bought it then what did the previous owner do to it that might have changed things.
A couple of things to check: Vacuum leak somewhere in the intake system to include the sealing of the plenum and runners and the intake manifold. A plugged cat. A slipped inner ring on the crankshaft balancer that is causing you to set the timing wrong. A very worn distributor. An extremely worn cam.
If the engine has a lot of miles on it then it might be time for a rebuild or time to buy a crate engine.
Have you thought about buying a used engine? I know that Vette2Veette has them and will guarantee them.
The most expensive route would be to simply continue throwing parts at it without a proper diagnosis.
Do you own a Field Service Manual (FSM)? Sounds like you should buy one if you don't own one now. The book has diagnostic flow charts that can save you a ton of time and frustration.

 

The engine has 31k original miles. It ran much worse when I got it but as I replaced sensors and other parts it ran a little but better each time. The fuse panel was curroded so I wired a new one in and ensured all connections were good. Before I rewired the panel, the drivers side manifold maxed out at 130° and the passenger side would overload the temp sensor we were using. After replacing the panel, the drivers side will hit around 300-400 and the passenger side will hit around 800-900. I was looking into a repair manual as well. Thanks for the reply

 

Hopefully someone will step in here that has more knowledge than I as it puzzles me as to why those temps are so high on one side only.
I was thinking that the pre-cat might be plugged but I am pretty sure the 86 I used to own did not have them.
Is there a chance that the exhaust manifold is blocked or the passenger side of the front Y is plugged? That does not seem possible.
Is there a possibility that the intake manifold was removed at one time and that the gasket between it and the head was put on backward? If that happened then the water passage would be blocked. Almost sounds like the water passage(s) in the head are blocked.
Best of luck brother!
What part of the country/world do you live in? Maybe someone that lives nearby could come by and help.
Edit: I just remembered a couple of mistakes that I have made on L98s. I once purchased a ported intake manifold for my 91 along with a set of aftermarket runners. The seller of the intake manifold did not tell me that it originally came from a car that had a ninth injector. When I installed it I had a massive air leak until I plugged that injector port. I also mistakenly installed the runners on the wrong side when I first put it back together.
Might be something to check but I doubt this would cause your one-sided temp spike.

 

I live in south eastern Massachusetts. I took the manifold apart to put new gaskets and injectors in and have the manifold powder coated but when I put it back together I was incredibly careful to ensure everything went back where it was supposed to be. The car does have a ninth injector for cold start but it all went back together properly. I think its a mix of the cat being clogged and the timing and tps being off

 

Once some of the snow clears I'm getting it off the ground and taking the y pipe off. I'll update once I've made some progress. Thanks

 

Be sure to disconnect the battery when you work on the Y pipe. Otherwise sparks may fly! Don't ask how I know.

 

I'm going to say a bent/burned exhaust valve, or one being held open because of lash misadjustment. Your rocker adjustment might be too tight on an exhaust valve and not letting it fully seat. Sounds like fresh air/fuel mix is being pushed into the exhaust manifold on a compression stroke and ignited there instead of inside a cylinder on the passenger side.

 

I know that on my old Harley, exhaust pipes will turn rosey red from unburnt gas mixing with ,and then burning, with the air in the exhaust pipe. That leads me to believe , plus the backfire, that Klondike is hitting the nail pretty close to the head.

 

Agreed. I believe that the backfiring is because the fuel charge is igniting in the exhaust. Could be a stuck or bent exhaust valve.

 

Compression test will tell you very quickly.

 

I smashed out both the cats and out the y pipe back on. As well as adjusted the timing to 6° past zero (factory setting). It was waaay off, but the heat is gone on the passengers side. But the heat moved to the drivers side but not as severe. Pipes no longer glow red and no more backfiring. Now it has a struggle to idle, it will stall unless you give it a little gas the whole time. IAC is already replaced, going to try to set the timing to 9° and see if it equalizes the heat distribution between the 2 sides of the motor.

 

Engine runs well, a valve is clacking so I'm going to re-adjust them but severe engine problems have been fixed.it stl wants to almost stall when it idles down from a high rpm but that should be simple adjustment of timing and tps. Thanks for the assistance