Engine stumble & pop

[cst69]

Ok, just got this 92 ext. cab shortie. 350 tbi w/ 700R4 tranny. I am trying to diagnois a problem with the engine and need some advice. Engine runs great at idle and at low RPM's. When you get it under a load or step on the gas it stumbles/almost cuts off/pops thru tbi. I have installed new plugs, rotor button, wires, dist. cap to no advail. Next, I will replace the fuel filter. It smokes also. I am afraid it is on it's last leg and will need the engine replaced. Any ideas I can try?

[FritzA]

You didn't mention how many miles are on it...is it over 200k? These engines are known for having strong shortblocks but get heavy wear on camshafts and valveguide seals. Timing chain is always a concern over 150k.

A big yes on changing the fuel filter. Also do the air filter. Make sure the timing is set correctly. I would also replace the coil (easy and not expensive). The O2 sensor is also not expensive for this year and probably due.

Next, I would look around the tbi unit itself. Make sure it is clean around the sensors like the TP (throttle position) sensor.

Look into how to retrieve codes from the ECM. It will help identify if there are unusual readings from the sensors. Do a search in this forum.

Good luck. Keep us posted on what you find.

[mountie]

ECM? It controls fuel & Ign and can drive you nuts.

When coils go bad, they usually go out completely, but some rare times they fail like your description?

[bloertcher]

before you buy ANYTHING,look over every single vacume hose.The PCV hose that runs from the TB to the valve cover should be replaced if it's the original,regaurdless of it's condition.Then,and only then,would I throw a coil at it.
Pulling codes is an old wives tale,it will only be productive if you have a check engine light.And even at that,the computer won't just "tell you" exactly what the issue is.