What's up everyone,

I've been dealing with an idle issue that is now starting to drive me insane. I've searched to no end and I've found several threads with similar issues, but nothing exact as of yet.

The car first started having issues when I left a friends house where it struggled to start, but once started it idled and drove perfectly so I didn't worry about it. The next day I went to the gas station and after filling up, the car wouldn't start at all. It finally started after 8-10 minutes of letting it sit and it idled/drove fine once again. On my way home, I made a WOT pull (AFR's were good) and then depressed the clutch and it died immediately. Took me a while to get it started but this time, it wouldn't idle on it's own. This is pretty much where I am now.

I can start the car with throttle input but it will struggle and die if not assisted. AFR's are going lean when it's struggling FYI. I am able to get the car to idle on its own if I keep a steady throttle for a few minutes and very slowly lift off of the pedal, but it idles 100rpm below it's target of 950rpm. Any added load such as depressing the clutch while it's idling on its own will cause it to struggle and die. At this point, the car will idle for as long as I let it but once shut off, it will not restart unless it sits for a while. No CEL's through Evoscan or my strap-on (snap-on) scanner.

Here is a list of the most recent things done to the car (all less than 300 miles on them):
- Skunk2 intake
- Skunk2 TB
- FIC 1200cc
- AEM 340 pump
- Fuel lab FPR
- JDC COP kit
- EVAP/EGR delete
- OEM FPR solenoid delete
- Head work with S2 cams

What I've done and checked so far:
- swapped the IACV
- swapped the cam position sensor
- swapped the TPS sensor
- swapped coil packs back to stock
- swapped plugs
- swapped back to stock TB
- boost leak tested
- compression tested
- MAP is showing readings and responding
- O2 sensor is showing readings and responding

My tuner suggested switching back to the stock intake manifold but I'm not accepting that as a potential solution

Thoughts?
- failing fuel pump?
- failing MAP?
- vapor lock issue within the fuel system?
- signal issue of some sort to one of the sensors? (No CEL tho?)
- failing crank sensor? Would it even start if that was the case?
- EVAP/EGR delete issue?

Any help would be greatly appreciated!

Thank you

 

Sounds like an IACV problem. Since you already tried swapping out the motor I would suggest checking the wiring harness. Inspect the harness/connector for corrosion or damage and use a DMM to test resistance between the connector at the motor and ECU. Also just check over everything electrical, paying special attention to chassis grounds. Make sure the ground from the intake to the chassis is good and from the battery to the engine is good. If you have corroded terminals clean them up etc.

 

Just redid the ground for the intake manifold but no change. I haven't tested the restistance from the IACV to the ECU. Any tips on that?

I did just remove the vacuum line to the FPR and it idled better. Any ideas there? Still struggled to start when warm with it unplugged

 

Long test leads help. If messing with the FPR had an effect then that would suggest its fueling related. Any chance you can do some logging? Knowing what your fuel and IACV trims are doing would probably help you troubleshoot.

 

Here is a log that I made a few minutes ago. This is with the FPR vacuum line removed. During this log, I depressed the clutch and plugged the vacuum source. Lmk if you're able to see this and if you have any questions

 

a couple things stand out right away and thats ISC steps are very high, and your voltage is not very stable. Check your alternator connection to the battery and your battery to fuse box connections. Also double check your ECU grounding behind the passenger kick panel. As for ISC try loosening your BISS screw out. I'm not sure how your ISC is tuned but stock is closer to ~20 steps at idle.