This is bizzare...and its causing damage.

The last month while driving on the highway i've notice a surge and rpm jump at a sustained 2200RPM. Then, on Saturday it happened again. This time I had back fires and tonnes of black and brown smoke out the tale pipe. I couldint get past 2000 rpm. If I stopped or kept below 2000 it was ok. This only seems to happen on the highway. I have no codes at all. I tried to duplicate the problem by warming up the engine from bombing around the local streets. Different RPM in the gears. (350, 700 R4) but nothing.

So last night I went for about a 30km drive to a friends at around 120 kph no problem. We left his place. I follwed is 4th gen back onto the highway. As we got on we both hammered them all the way up to 170 kph. Then all hell broke loose. My backfire and bogging along with huge smoke reappeared. Couldint get passed 2200 rpm. I pulled over and idled with no problem. This time it backfired so hard the exhaust gaskets blew. So i limped it home at 80 kph no problem. Tried getting it to a 100 kph at around 2000RPM. and it started to backfire again. Put it in idle. Reved it to about 3500 and let off. It backfired hard again. Got it home left it till now started it, and nows theres no problems. It revs perfect. But I know if it hits the highway for any length of time ill be exploding again.

What the hell is going on here?


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1987 T/A GTA 5.7L, Bored .020 and ported for .202 valves, edelbrock headers, flowmaster exhaust, JET STAGE II chip, Comp CAM, Adjustable fuel pressure, Airfoil, K&N filter, B&M stage 2 shift kit, and a home depot ram air(Hey it looks good and it works)

 

Sounds like ignition trouble. The pickup coil in the distributor can cause this problem. sort of a pain to change, distributor has to be removed. The shaft goes through the coil. a lot of work for a cheap part. problem happens when the engine heats up. thats why it is ok when cold. If it is the coil, eventually it will die, leaving you stranded.