98 5.7 rough idle and stalls

[Schurkey]

#2- 109, #4- 131, #6- 0, #8- 138,
#1- 145, #3- 150, #5- 140, #7- 132.
does that sound like head gasket?

No. That is, I suppose it COULD be a head gasket...but "zero" compression in ONE cylinder is more likely to be a valve that doesn't seal. Zero compression in two adjoining cylinders could be a head gasket bleeding compression from one hole to another.

"Zero" compression is not likely to be ring seal. Could be a hole in the piston or other genuinely significant carnage, but typically it's a valve that's held open by carbon, or a valve head/valve seat that's burnt.

 

[beedubleyew]

Waste of time. I lost faith in "oiled" compression testing about thirty years ago.

Leakdown test would be useful.

Here's what I think happened, and tell me if I'm wrong. Head gasket is blowing slowly from age, startin at cylinder 6 and moving it's break around. because bank 1 side is pretty good compression except the back 7 headed to the other side.

just read the last response and I believe it makes sense that my valves are fouled with extreem carbon build up. time to sell. hey it's clean otherwise

 

[beedubleyew]

I have no idea what an "OL fault" is.


Because the tool won't report it, or because the computer has failed?


P0300 because the tool won't report the correct code, or is the misfire REALLY random? Crappy scan tools LIE about P0300. The real code might be P0301--P0308, but the cheap tools report P0300 instead of the true cylinder-specific code.

What are the misfire COUNTS for each individual cylinder?


I'm starting to suspect you have a faulty scan tool. Perhaps a faulty computer.

You'll need to trace the wire harness to those two sensors to see if this is a harness problem.


WHEN is the fuel pressure "55"? If it's during the prime cycle, you may need more than one prime cycle to get to max pressure, and that pressure better be higher than "55".

Of course, that assumes that your fuel pressure gauge is accurate.


That's gotta get fixed.


A faulty oil pressure switch--or the wire harness connected to it--could cause the engine to stall when you pull the fuel pump relay. However, a faulty oil pressure switch/harness is not going to kill the signal from two O2 sensors, and cause the scan tool to fail to report fuel trims.


Better. Still not there, yet.


HOW do you know it was "super rich"?


If this thing is burning oil, all bets are off. May be time for serious engine work.


I expect the pressure regulator has a vacuum port, but being sealed inside the intake manifold, there's nothing connected to that port--no hose. It's just open to the manifold vacuum inside the manifold.


The timing isn't off. Turning the distributor DOES NOT change the timing. The cam sensor signal is not aligned/synchronized with the crank sensor signal; and the rotor tip won't be positioned optimally in relation to the terminals on the distributor cap.

yes if i had the tooth alignment off by around by like 20%, it would throw a cmp code not aligning with crank shaft position sensor. I believe the harmonic balancer shifts over time and you have to use the pencil in the #1 spark plug hole trick to get true TDC. This problem turns out to be bad engine cylinders.

 

[Schurkey]

Here's what I think happened, and tell me if I'm wrong. Head gasket is blowing slowly from age, startin at cylinder 6 and moving it's break around.

Head gasket breaks don't "move around".

because bank 1 side is pretty good compression except the back 7 headed to the other side.

I don't know what this means.

I believe it makes sense that my valves are fouled with extreem carbon build up. time to sell.

Remove the valve cover, tappety-tap-tap the #6 intake and exhaust valves with a small plastic-tipped hammer. Hit the valve tip, or the valve end of the rocker arm, not the retainer. Re-test cranking compression pressure. While you're in there, make sure the valve springs aren't broken.

The valve spring snapping the valve back closed after you tap it open will crush any carbon deposits, the valve should seal again IF IT'S NOT BURNT.

 

[2drXmobb]

Your doing a good job at narrowing down the problem just keep at it.

No, haven't tried squirting oil in. Does that make a difference? thanks i'll try it

Well if you add oil and the compression goes up it's the valves or rings that's bad

 

[2drXmobb]

The oil creates a better seal , if compression goes up it's the rings if it doesn't change it might be the valves.

 

[beedubleyew]

took off the bank 2 valve cover, #6 push rod was bent and off the hat. took a rubber mallet to straighten and put it back in. I had to tighten around 3 turns for it to seat but still have a little play. doesn't die at stop lights anymore. about to replace the new downstream o2's with the old ones, oil change with "engine restore" from O'Rielly.

 

[Schurkey]

Get that pushrod out of there IMMEDIATELY. You need new pushrod(s).

 

[alpinecrick]

Straightened the pushrod with a rubber mallet? Seriiously?

Problem is there's a thousand L31 pushrods probably laying on the ground or in the corner of garage's all over this continent, and are a dime a dozen--until a guy actually needs one.......

 

[beedubleyew]

No. That is, I suppose it COULD be a head gasket...but "zero" compression in ONE cylinder is more likely to be a valve that doesn't seal. Zero compression in two adjoining cylinders could be a head gasket bleeding compression from one hole to another.

"Zero" compression is not likely to be ring seal. Could be a hole in the piston or other genuinely significant carnage, but typically it's a valve that's held open by carbon, or a valve head/valve seat that's burnt.

Get that pushrod out of there IMMEDIATELY. You need new pushrod(s).

I just put it in to make it to work a few miles away, I have new ones coming tomorrow