First off hello everyone.

I have a 2001 DGC sport 3.3 flex that has me ready to pull my hair out. I will try to explain in detail what diagnostics I have done to pinpoint the problem.

At a cold start cyl 6 is dead. I smell fuel up front and the exhaust smells strong. when I start moving it skips and backfires through the intake as i drive until what I assume is operating temp (about 2.5 miles of freeway driving) then it stops skipping altogether and runs correctly. I can almost set my watch by it. After the demon inside the engine calms, it runs as good as it always has. If I stop and idle for an extended period of time, for example setting in a drive thru, the misfire comes back and as I pull away from the drive thru it quickly clears back up and runs on all cylinders. It does occasionally stumble when pulling away from a red light though.

Here is the reason I am stumped... the tests I've done and things I have changed.

Checked the fuel pressure, 60 at key on and 58 at idle. At key off I lose about 1psi every 1-2 minutes but pressure instantly jumps back to 60 at key on.

New plug wires, Plugs and coilpack. no change.

Pulled the fuel rail, flipped it over and cycled the key to build fuel pressure and verified none of the injectors were leaking.

Changed the #6 fuel injector with a used one from ebay and added new plenum gaskets with no change.

Removed plenum again, swapped #6 injector with #4 replaced all 6 o-rings and swapped plenum gasket #6 with #2. No change

Swapped #6 plug with #4 no change

Did a compression check on the front head with #2 125 psi #4 124 psi and #6 125 psi.

Pulled the injector wiring harness and inspected outside for oil soaking and melting, looked good. Hooked everything back up and pulled #6 connector checked it with a test light with the engine running and verified that the computer was pulsing ground to the injector correctly. the blink rate was steady at idle and increased with a little throttle as I believe it should.

The only code i get with a scanner is P0306 AND P1494. 1494 was there almost a year before this started so I assume that its a separate issue.

The only way I know to go now (besides calling in a priest for an exorcism) is to pull the head. Im just hesitant to do so because of the way it clears up after a short drive. Its like a switch is flipped to that cylinder and it starts firing correctly after a few miles.

I feel I have tested everything i can without actually tearing into the engine.

Can anyone else lend a suggestion or any advice to me?

Thanks for reading

 

Check compression on #6 with it hot. ASAP after you notice it missing. It may stare you in the face.

 

I will try that later today. Thanks

 

Well I believe i have found the problem.

Checked the compression on #6 3 different times got 90psi then 120psi and then 99psi. All with engine warm.

Did a wet test and got 175psi.

Hooked compressed air to the cylinder while at tdc and could hear a hiss out of the crank case.

My guess would be a cracked ring.

Thanks you Cougar41 for steering me back to the compression check.

 

Hate to revive an old thread but Im still stumped.
I have had the van parked for awhile and purchased another car just to stay mobile. Sweet 1992 Caddy btw.

I have finally gotten around to working on the van the last week or so. I had my neighbor help me as he's been by my side throughout all of this and now we are both stumped.

To begin with I have rented several different compression testers from AZ and Oreilly with all of them giving me different results if I could even get them to work correctly. I have lost all faith in the loan a tool program at this point.

Anyway we pulled the head and my neighbor who works in a machine shop checked it. The head was perfectly straight which was surprisingly a good thing. He vacuum tested the valves and the gauge maxed out on every port. I asked him to remove the valves from the cylinder in question to have a better look at the seats which were good. He checked the spring tension which was passable. The valves were straight and the faces were good. Aside from #6 being black with soot, everything looked fine as #2 and #4 were burning normal but #6 looked like the inside of a chimney. The black soot points to #6 getting so much fuel that it is flooding and cant fire although this stops happening as soon as the engine reaches operating temperature.

We looked over the old head gasket and mating surfaces and there were no signs of leaking anywhere. At this point I pulled the #6 piston and inspected the rings and found them to be perfectly fine. At this point I am trying to leave no stone unturned.

Now I have started back tracking external engine issues! I have torn the injector harness open again and found no crossed/shorted wires I checked continuity between every connector in the harness and the pins on the connectors to the pcm and found no shorts.
Before the teardown I had him hold the key down and tested for pulsing ground to the coil pack with good results and also back probed the #6 injector while at idle (skipping) the light blinked as you would expect and the blink rate increased when i throttled it up a bit. Everything appeared to be working as it should except it was skipping!

We even did a redneck/poor mans balance test on the injectors where I jumped the fuel pump with the fuel rail removed and flipped upside down. I manually applied voltage to each injector to check for leaks and verify spray pattern. Each one sprayed a cone shaped mist, the same across all 6 of them They all looked to be spraying the same volume of fuel and no leaks when voltage was removed.

As of now Im in the middle of reassembly and to a point where I should have the motor completely together by tomorrow. Unless there was something that was completely overlooked by two sets of eyes I dont expect the problem to be fixed.

I guess the positive note here is I know that the front bank is good internally and I now have new gaskets installed. Cause we all know these things go through head gaskets all the time. (sarcasm) The thing may skip like crazy but at least the valve cover and oil pan leak is fixed LOL...... SIGH.

My question is kind of obvious. Should I start looking at the PCM to be the culprit? Is there something else that would cause only 1 injector to spray too much fuel and settle down after its up to running temp? Keep in mind that we have swapped injectors with this cylinder already. I haven't replaced any sensors at this time due it being isolated to 1 cylinder and I dont see a sensor causing the PCM to only richen up 1 cylinder.

Sorry about the long post. I just want to put out as much info as I can.