NickD
Reader
9/23/15 4:42 p.m.
A cor-worker (fellow GM mechanic) of mine has a 238,000 mile '98 T-100 with a 3.4L V6 and a 5-speed. He's been beating his head against the wall with an issue and I figured I would come here and consult the great hivemind for him.
The issue: It idles fine and runs fine below 3000RPM. You hit 3000RPM and it falls right on it's face, starts popping and banging like it's hit a rev-limiter and will not accelerate any harder. Seems to get worse as it gets hot. The Check Engine Light never comes on either.
Attempted fixes/diagnoses: New fuel filter (plenty of fuel pressure). New plugs, coils and wires. Catalytic converter is not plugged (Removed it and issue still occurred). Right now we are considering the MAF as the culprit.
Anyone encountered this issue?
Got a scan tool with live data available? Test drive and watch O2 voltage and fuel trims.
has to be a sensor of some sort
Is that one of the cars that had the nuetral rev limiter that was lower then actual rev limiter? I know they had them on automatics and have seen a few issues from that.
NickD
Reader
9/23/15 9:08 p.m.
In reply to Streetwiseguy:
Unfortunately no. We only have access to GM Tech IIs and MDIs.
In reply to mad_machine:
That's what I was leaning toward. Do these have a crank position sensor for the ignition trigger?
the sensor makes a lot more sense actually.. because if it goes bad, it's not going to tell the computer to turn on the CEL either
NickD
Reader
9/23/15 9:14 p.m.
That's what perplexes me, is the fact that it runs like straight garbage and will actually have all the cylinders cut-out completely at the same time, and the CEL never lights up or even blinks.
Is the igniter in the coil pack? Also check ignition coil grounds.
Got an old fashioned timing light? You can connect one to the ignition lines going across the engine from the right bank of coil overs, and watch the timing against the pulley as you rev the engine.
This will let you know if indeed it is ignition, and if it is all cylinders or just a few, and if it's cutting out or moving around.
Something worth suspect on that particular engine is spark plugs. Run the correct plugs, not just plugs described as fitting. I think the right NGK plug is a BKR5EKB-11. If there is something like Champion or Bosch or tritium tipped plugs, things can go wrong, especially under load, and especially up near 3,000 rpm.
