Engine Loping.

Here goes! I've checked most of the postings, some might help. After a G.M. tuneup ($432, spark plugs, wires, pvc, air filter, fuel filter) I took my 95 for a 500 km trip. After one 5 minute stop half way, I drove the rest, this was on highway averaging speed of 110 kph. When I slowed down into city traffic, the engine started loping a few times and stalled. It started right up, kept it going by short revs, the went when light turned green. The van smoothed out, then no more problem while there. On return trip, no problem (about a 5 hour drive) til a block from home at a corner, check engine light on and loping again. Left it off for half an hour, started it back up, check light off, but still idling rough. Reved a few times, smoothed out a bit, Idle low, I just turned it off, didn't want to push it. 255,00 miles, but was running great, is it just the EGR? Thanks in advance, Johnny Fargo.

A loping engine is usually the sign of a vacuum leak. Since it the loping happen shortly after a tune up, my guess is the Mechanic either knock something loose or didn't put a hose back on correctly. Since your check engine light came on, have your codes read, that might give you a good starting point. Things I would check first is pull off the dog house and take a good look around and see if you see any hoses off, then since the pvc valve was changed make sure the rubber boot that holds into the rocker cover is in good order and won't allow a vacuum leak, and also check if the valve is the proper one. Finally take it back to where the tune up was done and complain like hell and see if they will fix it for free. Good luck

Will do, thanks for the tips!

bite the bullet and replace the injection spider under the main cover....i did everything else outside with the same symptoms you described. This is a expensive part, but is a bad design that was changed in later years.

Thanks red2001, The problem turned out to be pieces of carbon plugging open the egr valve, in essense causing a vacuum leak. It kept happening, so I made a steel gasket and punch smaller holes in it to stop the big chunks from entering. The only down side so far is a code read for low egr flow, but the van runs like a top!

There is a special gasket that you can buy that has a metal screen in place. If will get rid of that SES code and will keep the big pieces of carbon from clogging up the egr valve.