Odd Miss

[johnd]

Just thought I'd toss this out to see if anybody has any ideas. I have an LT1 Camaro 350, 1997. A few weeks ago it set a code for an EGR valve and a new EGR valve fixed the problem. I don't think the two events were related but now I have a slight miss under light acceleration. Amazingly the thing does not miss under heavy acceleration but only light and this problem does not occur when it is cold but only after it is warmed up and goes into closed loop. I replaced the plugs and wires earlier this year (75K mi.-The plugs didn't need it but the wires made a difference). I can't find any vacuum leaks and I have sprayed water on the ign. wires while running to see if anything showed up and nothing did. I'm stumped. I cleaned the ICS port and throttle plate last weekend just because it had been a while but it didn't make any difference. Anybody got any ideas? The fact that it is at partial throttle has me stumped.

 

[mechtech]

The EGR is bypassed when under hard acceleration.
On cruise or light acceleration, it is engaged to various degrees, and makes the engine ingest exhaust gas swith the incoming mixture.
That's why it feels cruddy then.
That's why people have been trying to bypass them for years, also.
So, this is normal but unfortunate.
Maybe a good tune up will attenuate the miss, however.

 

[kc8adu]

if you get a one fits all egr with the port washers you have to be sure to install the right washer.
had a chevy truck here that had bucking and stumbling just off idle.seen the shiny new egr and unplugged it.
problem gone.
p.o installed the valve and left 2 bags of washers and the instuctions in the glovebox unopened.
neighbor got it cheap due to this.dealer tried and failed to fix it.no check engine light or codes stored.neghbor bought this 94 truck for $500 due to the stupidity of the owner who installed the new egr.

 

[johnd]

The theory that the new egr is causing this holds water. When the car is absolutley cold-where the egr would not be functioning-there is no miss. I'm going to put a light on the egr vacuum valve actuator wire and see if it lights up when the miss occurs. That would be a pretty strong indicator of where the problem is.

 

[mechtech]

Sometiomes a plugged, inoperative EGR system makes the car run better, because it ins't recirculating exshaust into the cyls.
Repairing the system often makes the car run poorly.