AS Iposted a few days ago I just put a new 5.0 in my truck.It started right up but after a few minutes of running it started loping or surging harder and harder until it finally dies.I've checked and re-checked quite a few things until I'm lost.Checked for vaccumn leak by cutting off air supply..it stalls,checked egr by unplugging it ..it stalls.unplugged throttle positioning sensor..it idles smoother until I put it in gear...it stalls.Had a throttle body spacer on it,took it off ...still the same thing.checked O2 sensor...o.k.Did'nt have any codes or at least the engine lite was'nt on until unplugging egr..have'nt erased it yet.I did switch the motor over to H.O. firing order by changing cam.I was told this would'nt affect it because an H.O. injectors fire the same as 302...Any suggestions before I take it to the shop and have it scanned?

 

I forgot to mention the truck is running real rich.I had to pull off the y-pipe and make adjustments to it to fit my shortie headers because of small exaust leak.Seen it was all carboned up.Also the thrttle body was inadvertantly cleaned wile off truck when it was'nt supposed to be.Could this be it,even though when you give it gas while running and surging it smoothes right out? I'm really perplexed.Sure it something simple that I'm overlooking.

 

13726548 is the firing order of an 302 HO is this how you wired it an HO is wired the same as an 351w not a 302

 

Yes,I wired it just like a H.O..That is the cam that I put in it.,you are right about the firing order the same as a 351

 

The sludge tollerant throttle bodies were introduced sometime in 1991 so odds are you have one. Have you adjusted the idle screw? If the butterfly is open enough to expose the canister purge port it will cause the oscilliations. But cleaning it is a no no.

Regards

Jean Marc Chartier