Persistant misfire issue

[nicknorth11]

Back-story: I was out doing some very easy driving when all of a sudden the car started missing. I was barely able to get it home, and it barely runs unless I give it continuous gas and keep the RPMs higher. Nothing was worked on prior to the drive. A log is posted at the bottom of this post.

Below is everything I have tried so far:

Spark:
Replaced plugs (gap is correct)
Tested wires with ohm meter: all were good
Removed all plug wires one at a time: no noticeable change
Replaced coil pack with known working one
Replaced ignitor (power transistor) with known working one
Disconnected Dynatek ignition box and tried stock setup
Tested spark by setting plugs next to screwdriver: all had great spark before and after all tests

Fuel:
Replaced injectors with stock, known working ones
Checked fuel pressure
Checked fuel filter
Checked all wiring going to the fuel pumps to ensure they weren't intermittently losing signal or power.Listened for injector "click" with screwdriver to ear: all were getting signal/working
Unhooked each injector individually to identify bad cylinder. Each one made the misfire significantly worse, and all were the same before and after.

Air:
GM MAS is reading appropriately on link
GM MAS has no debris inside

Electrical:
All settings in link are correct
Tested battery ground with ohm meter: good
Checked all relays and fuses
Replaced coolant temp sensor
ECU looks/smells good. Everything else on the car is working perfectly and link shows no issues.
Replaced cam angle sensor and crank position sensor

Engine:
Tested compression: 182, 182, 190, 186
Tested for boost leaks: held 20 (not ideal, but not bad enough to cause this problem)
Checked timing: it was dead on

What is left?

 

[nicknorth11]

If you're referring to the global setting I am using being different than the calculated, suggested setting, the suggested setting didn't work nearly as well as what is programmed in now. But, to answer your question, I am still using the 1450's. Thanks for the continued efforts.

I was working on the car this morning and tried/noticed a couple of things.

1) I removed all plug wires one at a time and I didn't notice any change (other than my heart rhythm when I was SHOCKED like a mofo)!

2) I checked all wiring going to the fuel pumps to ensure they weren't intermittently losing signal or power.

3) My crankshaft position sensing plate is rubbing against the sensor. I bought a new plate and installed it thinking the original may be slightly bent, but the new one does this too. I think this is being exacerbated when I push the clutch in, as the sound increases with clutch disengagement. I can't feel any play by pulling on it or trying to wiggle it manually, though.

 

[ChrisMgst]

Your voltage based injector DT is still in the stock setting. Does anyone think that could cause a misfire with the type of temps we've been seeing?

 

[nicknorth11]

Deadtime is/has been set for my current injectors. The issue is almost certainly not related to my link settings, as the problem started on its own while I was driving, not tuning.

 

[ChrisMgst]

I came across this http://www.dsmtuners.com/forums/newbie-forum/368833-fic-bluemax-1450cc-tuning-2.html

 

[nicknorth11]

Again, I appreciate your help, but I have been running these injectors for many miles with no problems. Also, I have swapped in stock injectors with no change or resolution to the problem.

 

[nicknorth11]

Another update, (still need help with this guys)!
A couple of buddies came over and helped me out with the car and we were able to narrow the issue down to a fuel problem. The car smells rich, so we removed the fuse to one of the fuel pumps and just ran off of the walbro, which drastically lowered the fuel pressure (to around 30psi with vacuum). This allowed the car to start up and idle pretty nicely, which it otherwise won't do. Nothing changes with the logs when doing this though.

What can cause my fuel mixture to be so rich all of a sudden?

 

[Colt4G63 also]

What can cause my fuel mixture to be so rich all of a sudden?

A torn diaphragm in the FPR.

 

[troubleshoot]

Not long ago, I put on a new exhaust that has a bad leak right before the wideband, so it's not accurate right now. The tune is fine, though. Fuel pressure was tested with the car off and at idle. I didn't check the return line for flow. The issue happens under all conditions, so checking flow under boost isn't necessary. I have two pumps, a walbro 255 in-tank and a bosch 044 inline. Both pumps are kicking on, and the filter is clean.

Im no expert by far, but if you have an exhaust leak before the wideband causing it to read lean, wouldnt the ecu add fuel making it rich?

 

[nicknorth11]

The ECU only uses the front o2 sensor for that when it's in closed loop.