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2G Rough, Lean Idle; Rich, Weak WOT - Injector Clogged?

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randman2011

10+ Year Contributor
552
282
Feb 26, 2012
Indianapolis, Indiana
I recently resurrected my GSX after months of being disassembled only to find that it doesn't run properly. The assembly was pretty standard with the only changes from the previous configuration being 9:1 compression and 1000cc Deatschwerks injectors. The E3 16G is running wastegate pressure. I was expecting the car to start and idle without issue and I could jump into tuning, but that has not been the case.

Compression is 165-170 across all four cylinders. Spark has been verified on all four cylinders. The tune is unchanged from a known good state with the exception of injector scaling and voltage compensation values taken from Deatschwerks.

The wideband registers 35-100:1 at idle and this is accompanied by a rough idle with poor throttle response. Above around 2000 RPM the engine smooths out and throttle response is actually really good. At WOT the AFR drops all the way to 7.0:1 and the engine fails to make significant power. I unplugged each injector in succession and found that disabling cylinder 3's injector had no effect on the idle. That is where I left the investigation last night.

Does anyone know what might cause these symptoms? I am wondering if that injector is clogged in some way, preventing cylinder 3 from igniting or getting any fuel at all, but that wouldn't explain how it manages to drop to 7.0:1 AFR at WOT.

I intend to swap injectors between the cylinders when I get home today to see if the problem follows the injector, but that's as much as I have come up with to troubleshoot. Is there a way to clean injectors myself just in case this brand new injector is somehow clogged?
 
Swapping the #3 and #4 injectors had no effect. Cylinder 3 still isn't firing. I also swapped the injector connectors between the two cylinders to see if the harness itself is causing the issue and that also had no effect. I redid the compression test and got a strong 168 psi, which is within 3 psi of each of the other three cylinders. If the fiancé will ever get off the phone I will visually check spark since I already have the plug out of the engine. Any other thoughts? I'm rather baffled.

Update: it's cylinders 2 AND 3. That makes more sense as those two cylinders share the same coil and are on the same injector channel, but since I have been doing injector testing between 3 and 4, I feel pretty confident that it is not fueling. Is it possible for just that coil to be off on timing so far that neither cylinder ignites?
 
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I checked the PTU according to this thread and both transistors illuminated the light in the same manner. I have been searching ever since for a way to test the 2gb Cam Angle Sensor and have found nothing of value yet. I did try unplugging the connector and found that it had no effect on idle when unplugged but the engine ould bog down when I plugged it back in, which is weird.

At some point in all of this the car threw a P0202 code. I don't know when that was triggered, but since it now might be relevant, the injector resistor pack has been deleted because the car is running high impedence injectors. I have installed a FIC Resistor Delete connector because I was too lazy to make my own.
 
Cylinders 2 and 3 just started working abruptly. I undid all of my testing changes and it continues to run on all four cylinders now. I replaced my valve cover since it was cracked and I found a boost leak in the charge pipe that I corrected. The car now hits a solid 9.5:1 AFR at WOT but at idle the O2 trim is still around 25%. It sounds to me like the latency data from Deatschwerks is way off and I'll see tonight if I can characterize these injectors better.
 
Oh, I am far from a solution. I was trying to make adjustments elsewhere in the tune to accomodate this bizarre behavior from the injectors and actually maxed out several different values and tables in the ECU and still couldn't get the short term fuel trim to drop below 12.5%. I thought I was onto something when my ExtremePSI order gave the part number 22S-03-1000-4 for the injectors and the calibration sheet that I have lists 18U-08-1000-4, but the 18U number has superceded the 22S number and ExtremePSI just hasn't changed their website yet. Oddly the characterization data for these injectors seems much less suited for the DSM than the old 22S part number because my car idles between 1.8 and 2.0ms duration. The 18U injectors begin their nonlinear region at 2.3ms but the older 22S injectors continue being linear down past 1.7ms.

This is where it stands: at idle, the calibration from DW in conjunction with a known good tune is more than 37.5% off (as high as the ECU can read). I ordered a replacement set of OE injector seals and I'm just going to go back to the stock 450cc injectors until this gets sorted out. I don't have time to deal with this while being down a car. The guy from ExtremePSI said that they had never had a defective DW part but he'd be happy to initiate a warranty claim if there was an issue with one of the injectors.

The replacement cam angle sensor should be in Thursday. I'm hoping that was what was causing the original issue.
 
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