1999 Tahoe 5.7 Vortec, 258,000 miles, 4WD. Engine swap about 2000 miles ago. Original transmission.

Best truck I've had, ever. Trying to keep the old girl alive....can't afford anything else.

Engine swap went smoothly, truck has been running perfect, but SES light has been on constantly since engine change. Code P1345, which I see is very common when the distributor is removed and replaced. Truck was running so well, and time was a problem, that I have not addressed the SES issue.

It now has developed an intermittent, but increasing in occurrence, engine miss. It normally happens when under a load....going up hills...and can be quite severe. Tends to lessen or disappear if I jump on the throttle and get it to down-shift, but not always. And, also intermittently, it now will sometimes run very rough at idle and low speeds, after start-up. (Starting has never been an issue...cranks and runs always)

Mechanic who did the engine put his basic scanner on it today. P1345 code remains, and after erasing and starting over a few times, we also got a P301 (#1 cylinder misfire), but did not get that code every time we tried. He claimed all other parameters looked OK, but I have doubts as to his knowledge of that scanner. At times the miss is so severe that it would have to be more than 1 cylinder.

We threw an ignition coil at it with no improvement. Plugs, wires, distributor cap (I think) were all new at engine change.

Would there be any chance that the transmission or torque converter could be starting to fail and making it feel like an engine miss?

I will follow up on any and all leads anyone can give on possible causes to check. Just don't have the money to turn someone loose on it.

Thanks in advance for any and all help.

 

Don't be so sure that one cylinder missing can't be the problem. A V8 w/o one cylinder can be a dog.

 

Is the distributor new? I'd check it for any play...

 

It would not be the first time i got a bad cap or faulty plug wire. Don't eleminate the simple things just cause you replaced them at install. Small price to pay for new cap, rotor. Pull the plug and see what they look like. #8 cyl seems to be my usual culprit. If you feel a wire is potential swap between cylinders and see if you get e same response.