Sputtering under light acceleration.

[Coup D E'Tat]

Profile is up-to-date. Denso 720's, 2G MAS, and DSMLink NOT installed. Stock 450's and 1G MAS at the moment.

Other relevant info not in profile - Accel 8mm wires, NGK BPR7ES', fuel pressure set to 37 PSI (vac. hose off,) BOV is recirculated. No boost leaks.

The car has idle surge. On a cold start, the motor will float up to ~2,000 RPM's, hold for a bit, drop down to ~500, hold for a bit, raise back up, yadda yadda.

When it does it, the car hesitates upon acceleration. Once it catches, it will begin to accelerate. If I hold it at a steady RPM, the car will begin to buck fairly hard. It does not do this every time. Only sometimes, and more when cold. If I give it a little more throttle, it will generally go away and drive normally. I have not gone WOT yet, nor built any real boost (maybe 1-2 PSI) or even past 4K RPM's because of the injectors/MAS.

I had the idle set to about 850-900, and pulled ~14 in. hg. Recently, the car has been idling at 600-650, and only pulling 5-8 in. hg. It has been this way since I picked it up from the dealership after they diagnosed a drivetrain rumble that I thought might be associated with my recently replaced transfer case. When I picked it up, the guy said it was stalling on him, and I could not get it to stay running unless I kept a bit on the gas. After I searched around the motor, I noticed the BISS was missing. I replaced it with another I had laying around (which came from another 1G throttle body, not sure if 2.0 NT or 1.8 NT, but the diameter goes from 2.5" to 2" I believe. Haven't measure it in a while,) and it will remain running, but the idle is jacked. Adjusting the BISS does nothing (idle won't move,) and I had the ECU and the plug on the firewall grounded.

Compression is 125 across the board (was 150 before the cams) Both of those numbers were on a cold motor.

TPS is fine. Meant to check the ISC, didn't get time. Tried another set of plug wires I had, didn't help. Haven't gotten the chance to try anything else yet.

Any suggestions?

Thanks a lot, and sorry for the long post.

Jesse

 

[Coup D E'Tat]

Tried another ECU, and tried a set of BPR6ES plugs, didn't help.

 

[Coup D E'Tat]

Did another boost leak test post-turbo. Found two very tiny leaks at the throttle body, neither of which are significant enough to cause these problems.

Swapped in another MAS, car seemed to idle cleaner, and run smoother. I think the MAS, and most likely the ISC are both to blame. I'm going to test the ISC tomorrow.