Need help with this engine problem...lol

[Zack]

That sucks. Are the heads and block flat?

Yeah I did a straight edge test.

 

[Flyn]

If this was the old days, I'd guess your distributor loosened up and moved screwing up the timing. any chance your timing chain could have jumped a notch?

 

[Zack]

Gonna swap injectors next. The car runs ok at idle or 4500+ rpm.
I wonder if one is hanging open.

 

[Jon01]

EZ fix:

 

[Zack]

Trust me Ive thought about the LS1.

I have too much broken stuff right now and its bothering the shit out of me.
I have to fix my woman's Escape, then a timing chain on my 59, then fix the Cobra, then start on the Blue.

 

[Jon01]

I would've done it to mine were it not a low mileage pristine car.
You simply can't deny the hp/$ factor they bring to the table.

 

[Zack]

Well the pig isn't fixed. Kinda ironic I took the engine out of one car running fine then swap it in another and one cylinder loses a lot of compression.
Fail...there goes another summer day to pull it out and replace a piston.

 

[guspech750]

Geesh dude. Hope you fix it soon.

 

[Flyn]

Trust me Ive thought about the LS1.

I have too much broken stuff right now and its bothering the shit out of me.
I have to fix my woman's Escape, then a timing chain on my 59, then fix the Cobra, then start on the Blue.

One at a time. Fix one. Feel a little good. Fix two. Feel more good...

 

[Zack]

Let me ask this:
Would a cylinder producing only 150psi compression even cause the symptoms ive described?

If go WOT from a stop to 100mph the engine runs STRONG. Makes no sense right?
Im gonna swap PCM's.

 

[Burt Ragio]

By no means do I have the level of mechanical knowledge you and some other members have so this is just for thought. Does it continue to run good through the entire RPM range after it reaches optimum operating temp ? Is there any sign of cracked piston or piston wall in cylender #6 or #7 ? You did say you had two different readings from same cylender. Check cylender pressure before & after a warm up. If thats not it it may be computor related.

 

[Zack]

Ok I may be onto something after an extensive and exhaustive search.

While datalogging this morning, I happened to notice something very peculiar.
During normal driving, the pcm is showing its in WOT TP Mode. Interesting!

So, I floored it and it read that it was in P/T Mode (Part Throttle)

I will swap TPS sensors later today and report back.

 

[Zack]

Just drove the car with the TPS disconnected and it still breaks up.
Funny, it still reads WOT TP Mode when I take off.

 

[Zack]

Just did some research to find that the WOT TP Mode and P/T TP Mode are reversed on the older Diablo Hendheld Devices.
Back to the drawing board.

 

[bugsyc]

Who indeed

Who does a master mechanic and expert on Marauders go to when he has a problem that he can't fix??

 

[Zack]

Who does a master mechanic and expert on Marauders go to when he has a problem that he can't fix??

My friend at Ford with an IDS machine.

 

[Flyn]

I keep checking this thread hoping you found the answer. I know it's frustrating to be chasing a hidden problem and this one is a toughie.

 

[Burt Ragio]

I am confident you will find a solution to this problem. This head scratcher would keep me awake staring at the ceiling.

 

[Zack]

Still racking my brain.

Funny. The pcm did not recognize when I had the knock sensor removed, or the TPS connector unplugged.

I have to swap pcm's to rule it out.

 

[Zack]

Swapped pcm's.
Same shit.
Im now getting upset.

 

[MMBLUE]

I know this sounds silly, but go back to stock on the tune and give that a try. When I had the never ending could find out WTF was going on with the rough idle in my car. I put it back to the stock tune and WOWSER, the problem reared it's ugly head and it was easier to detect the faults as the tune masks them. That's when I could explain the problem better to you because it gave out more symptoms to detect. If I remember correctly, you were the one who told me to do that.

 

[Burt Ragio]

CLASSIC LARRY......GIT-R-DONE!! - YouTube

 

[Zack]

I did load the stock tune and it made no difference.

The only thing I have not done is swap O2 sensors.
As I watch the datalog, they are varying voltage as they should...but I suppose the real test is with an osciliscope.

I guess ill try that next.

 

[Jon01]

Have you swapped injectors?

 

[Zack]

Have you swapped injectors?

Yep.
Just bought a leakdown tester....ill use it tomorrow.