91 3.0 just put new engine in 20miles ago all the sudden fires and shuts off fires and shuts off . If I press the gas pedal it will start but super low idle sounds like valves rattle. If I keep the pedal down enough to keep it running it straighten it’s self out and will idle at around 800 stays running at that idle for ever shut the truck down and ten minutes later fires but huts off fires but shuts off and so on and so on??? Any help would be appreciated!!!
Fires up shuts off fires up shuts off????
- Thread starter Montero91
- Start date
Swift_45a
Observer
This is my guess, too. I had a 6g72 LS Gen 2 that had this issue after I bought a new re-manufactured ECU when it fried; the timing jumped (I'd never dealt with timing belts, only chains up to this point) and it had similar symptoms as it would shut off I didn't have the throttle at WOT.
Sadly that rig died of a crank seal leak soon later and went off to the junkyard.
Get a timing light and dl the FSM and start there.
Timing checked out okay. Listening to each injector sounds fine. Almost sounds like it’s not advancing the timing smell lots of raw fuel valve rattle & if you accelerate to around 1000 rpm 2 or 3 minutes it’s like you flipped a switch the rpms go up and it clears up and no valve chatter & idles just fine . But if you shut the truck off and instantly try to start. your back to low idle and rough running and the smell of raw fuel at the tail pipe?????
MonteroWhisperer
New member
Long time lurker, but this is my first post on here.
As always with starting issues, make sure that you have the following...
-Spark
-Fuel
-Compression
I'm not clear on how this issue started. From your first post it seems that you drove 20 miles with no issues, and then began having issues; is that correct?
If it were mine I'd check all of the obvious stuff first. Plug wires at both ends, battery connections, crankshaft and camshaft position sensor connections and the rest of the harness connections, fuel supply, etc. I'm assuming that you have decent compression since this is a new engine, but I wouldn't entirely rule that out. The fact that you can get it to run makes me think that it's either an intermittent electrical issue/bad connection, timing or possibly bad fuel.
I once had a 6G72 that wouldn't start. Checked everything and narrowed it down to a timing issue. Stripped the engine down to the timing belt, and it was all correct. I was really confused. Turned out to be that the roll pins that hold the reluctor disk in place behind the crankshaft sprocket had sheared off and the disk had moved. $2 worth of parts and about 5 hours of labor. Truck started on first key after that.
Does a '91 even have a CPS? I only have experience with the OBDII versions of this engine.
Hope you get it figured out.
As always with starting issues, make sure that you have the following...
-Spark
-Fuel
-Compression
I'm not clear on how this issue started. From your first post it seems that you drove 20 miles with no issues, and then began having issues; is that correct?
If it were mine I'd check all of the obvious stuff first. Plug wires at both ends, battery connections, crankshaft and camshaft position sensor connections and the rest of the harness connections, fuel supply, etc. I'm assuming that you have decent compression since this is a new engine, but I wouldn't entirely rule that out. The fact that you can get it to run makes me think that it's either an intermittent electrical issue/bad connection, timing or possibly bad fuel.
I once had a 6G72 that wouldn't start. Checked everything and narrowed it down to a timing issue. Stripped the engine down to the timing belt, and it was all correct. I was really confused. Turned out to be that the roll pins that hold the reluctor disk in place behind the crankshaft sprocket had sheared off and the disk had moved. $2 worth of parts and about 5 hours of labor. Truck started on first key after that.
Does a '91 even have a CPS? I only have experience with the OBDII versions of this engine.
Hope you get it figured out.
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