AEM UEGO Full Lean at Idle, Sequential COP Base Timing
 

Hello. This is the first thread I have started on this site. I have been lurking for a few years soaking up all the knowledge I can, and this is the first time I've been stumped by something that I couldn't find a solution for by searching.

Last week I completed the fab and install of my turbo setup. Something that I have been slowly researching, planning, and purchasing parts for, for the past year.

The car is a 1990 1.6L with a custom turbo setup and a Reverant built MS3/MS3x ecu with sequential fuel and spark. Right now the car starts and idles, but I'm running into a few issues.

First. My brand new AEM UEGO wideband 02 sensor reads full lean 99% of the time. Once I start the car, warm or cold, it moves to full lean and maxes out the gauge. Tunerstudio shows 18.4 AFR and stays there. Sometimes when giving it some gas it will go down to 15 or 16. Most of the time it just stays at 18.4. The strange part is, the cars seems the idle relatively well.

Things I have done to try to fix it. First was to move the wideband ground to the same place as the ECU ground, same issue. Next was swapping in a known working gauge from a friend's car. Same issue. Next was testing the 02 sensor using the brake clean in a rag test. 02 sensor tested good. I still went ahead and bought a new replacement 02 sensor. Same issue. I tried adding fuel to the area where it was idling. Same issue. I moved around the power and grounds for the AEM gauge. Same issue. Took a multimeter to the AEM output wire and it stays at 4.3v. I found an exhaust leak where a vband on the downpipe wasn't tight, fixed the leak. Same issue. I'm at a loss as to what could be causing this.

Second major issue. I haven't been able to verify my base timing. I set it to fixed timing at 10 deg and aim the timing light at the crank pulley. When I do this with the timing light inductive pick up on cylinder 1. The timing light shows it as being basically 180 deg from the TDC mark on the timing belt cover. I connected the pick up to cylinder 2 and it shows the same as cylinder 1. I connected to the 3 at it shows at 10 deg BTDC. This is pretty confusing.

So all in all I'm at a loss as to how to fix these two issue. These are holding me up from driving the car around and street tuning with VE analyze live. Any help is appreciated. I wouldn't have even made it this far without this forum.

Thanks in advance.

See if this thread doesn't help you, perhaps your maps are very very lean


https://www.miataturbo.net/megasquir...-inside-67385/

Im using the basemap that Reverant sent me. I can post it up if that would help. Im open to any suggestions.

Looks like I may have found the problem. The cop triggers for cylinder 1 and 3 were swapped. Once I moved these to the correct location, the car fired right up first try, idled much better, and best of all was right around 14.7AFR. Looks like I can verify base timing and start tuning. Thanks to Reverant for the suggestion to test coils.

Drove the car for the first time last night, looks like the problem has been solved, the car ran great, and I was able to drive around auto tuning without issue.

Excellent!