Hello guru's a question about the EGR System on my '93.

Since I bought my '93 the 2nd gear syncro was bad. This past week I finally swapped out the 6 speed with another unit. Unfortunately while removing the exhaust the studs on the manifolds snapped off so I had to remove the exhaust manifolds to extract the studs. While trying to remove the EGR pipe the pipe cracked so, as a temporary fix I cut the EGR pipes flush with their retaining nuts and welded the nuts solid. I then made a block off plate for the port in the back of the intake manifold (where the pipe that connects to the right side exhaust manifold connects to the back of the intake).

So I got the car finished up tonight and took it down the street. It started and ran great, no check engine light at all.

It now seems to have a backfire at higher RPM's, and sometimes when blipping the throttle sharply.

The engine was pretty cold, I went no further than a mile at the most.

I did not have a chance to look the car over tonight as I had to get going but I want a solid plan of attack for tomorrow.

My first thought is that a plug wire is crossed/not installed all the way. If this is not the case could removing the EGR pipes cause this backfiring? I didn't think so as others remove their stock manifolds in place of headers etc.

Any thoughts or ideas would be appreciated thank you.

I don't see a cause/effect. Unless your welds are not perfectly sealed, that is.

I had to replace my EGR pipe, once, too... good luck getting one! I think they are seriously hard to come by these days.

In general, EGR won't effect drive. What it will do is effect emissions and cause potential detonation. The EGR adds a touch of exahaust gases to the intake charge. This will then in turn allow the combustion temps to drop, lowering the chances of detonation and lowering NOx emissions.

I would reach out to Vette2Vette for a newer EGR tube. Also, you might be able to fix with the welding equipment you have - just weld the sucker on there!

The threads on the manifold go really bad after a while. Mine were chewed up so bad, I had to grind half the threads off my new on! I used antisieze on the remaining threads.

I am a fan of EGR, for both jobs it does. Removing it makes no performance advantage, and if anything, it creates a performance disadvantage. Many complain about the dark colour inside their intake... eh... minor annoyance, really. The inside of the throttle body is the biggest problem, but an occasional cleaning will resolve that.

I don't think you have a crossed plug wire... if that was the case, it would do it at all the time and be really down on power. Oh, one last thing, 1992 LT1s were prone to popping out the exhaust. Considering how simular 1992/93 Vette's are, that might be a consideration. I will admit, tho, the problem was atributed to early 1992 Vettes...

Thanks Andy. I would not have removed it if the damn pipe would not have cracked/broke. That, plus it's been on my friends lift all week so I really wanted to get it out of there tonight. Other than this now and a claw intake the former owner put it the car is 100% stock under the hood.

My car does have popping out the exhaust when decelerating, especially from higher RPM's. It actually sounds good and does not bother me. I know it's normal and not an issue. This is not that sound.

Guess I'll dig deeper tomorrow.
Welds on the manifold caps are very solid.

I forgot to mention - from what I could tell the miss seemed to be coming from the rear right area of the engine.

I am wondering if the egr is trying to activate and is just sucking in air?

Did you disconnect the EGR valve?

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Nope - and I was thinking about this last night. I've removed the EGR pipes but, have done nothing with the EGR valve itself. Perhaps this is my issue?

comes back to my question about the EGR trying to activate and just sucking air.

Could I get away with disconnecting the vacuum line to the EGR valve and blocking it off at the EGR valve and at the manifold or, should I remove the EGR valve entirely and install a blockoff plate?

I'm afraid I'm going to need to remove the manifolds again to get the plugs out to re install the EGR pipes. They are really seized in there. As I have plenty of other projects lined up that take precedence I will probably be running without EGR for a few months. This sucks as the LT1 is a pretty high compression engine and I'm sure benefits from EGR in the form or reduced detonation.

the knock sensor will save the engine, but at a cost... about 20hp is my guess.

I would start with just disconnecting the EGR and capping the line. See what that does.

Well thanks for the tips - I tried disconnecting/plugging the EGR and associated lines but, no dice. Still skips/pops.

Tomorrow I'll pull the plugs. That should tell the tale.

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Check for a shorted plug wire before you do.

Yep thought about that too - could be a wire got shorted when I pulled the manifolds/laid the wires back. I believe they may well be original wires w/100K on them.

I've been back/fourth over changing out my opti, or installing the delteq unit I bought. I had the delteq installed on the car this weekend and it tested as working fine but, I bought the wrong plug wire ends for the delteq coil packs! (my plan was to make my own plug wires) so, it's running off the original opti again for the time being.