So, my buddy has an '84 Corvette with Crossfire Injection.

It runs fine, except for surging at idle. My car used to do that. Replacing the throttle shaft bushings in the TB solved it. I told him that.

He showed it to an old guy who loves CFI Corvettes, and knows a whole lot about them. He pulled the hose of the EGR, stuck his thumb over it, and the surging stopped. He told my budding using a block-off plate, or even simpler, putting a ball bearing in the hose would solve the problem. My buddy put a ball bearing in the hose, and it's running great.

In our cars, you can't just block the EGR, you also have to turn it off in the ECM, don't you? I thought CFI was the same?

 

You have to tune it out or you get a CEL.

 

Were you talking about on my TBI, or his CFI? His car is running great.

Also, what is a CEL?

 

On your TBI not sure about CFI.

Cel is check engine light. EGR being unplugged or blocked off won't affect performance.

 

Or fix the EGR valve so it stops passing exhaust gas at idle.

Likely has carbon deposits on the pintle so it won't seal to the seat.

 

In this case it sounds like a solenoid issue, not an EGR valve.

 

OK< so what I'm curious about is, if you do away with EGR on a 3rd gen, you have to tuen EGR off in the ECM, don't you?

What happens if you don't turn it off in the ECM?

 

You get a CEL. Nothing more.

 

Actual it runs lean and pings!

 

Well there you go then haha.

 

Yes, you're correct. My mistake.

 

So, the CFI Vette with the disabled EGR is not throwing a code.

He said it was running fine; I'll ask about the pinging.

If he does away with EGR, doe he need to disable it in the ECM, as well?

 

Yes. EGR is activated by the ECM during cruising and some light load driving conditions, then the ECM commands a leaner mixture with additional SA to take advantage of the cooler combustion, provided by the EGR (effect of the Recycled Exhaust Gasses), to improve MPG.
If no Exhaust Gas is Recycled, the combustion will maintain its temperature and the commanded highway mode will cause early lean combustion with the result of engine knock.

 

The egr is activated by a solenoid so by blocking off the port I do not think you will get a cel as the computer is just activating the solenoid, not getting an improper reading from a sensor.

 

I do not think he will get an error code from unhooking the EGR solenoid. But the ECM will still lean the fuel mixture and add additional SA during highway mode, to take advantage of the additional exhaust gas the EGR is supposed recycle during that condition.