Engine runs very rich out of the blue

progman · Post by **progman** » Mon Aug 30, 2010 7:29 am

Hi all,

I'm having a very frustrating time with the Megasquirt right now. I'm new to Megasquirt and I'm trying to finish my first project. Everything is working great and I'm very impressed with it but one out of every three or so dyno pulls the engine just runs pig rich and seems to ignore the entire fuel table. It seems to do it when the engine is hot (around 190). If I leave it sit for 10-15 minutes with fans on it then do another run it will run fine and my fuel ratio is at ~11.6(+/-) across the board right where I set it. When the system misbehaves my o2 sensor runs flat 10.8 which is the minimum it reads. This dyno/o2 setup is used everyday and the problem is only on my car. I checked the car for intake leaks checked all wiring (which is all sodered btw) and can't seem to find anything after hours of double checking! I'm searching the forum and internet now because I'm almost positive this is something with my settings or the Megasquirt. Please let me know if you have any theories or know what might be going on! Also let me know if you need more information.

MSII 2.89 B&G firmware on 3.0 board
Megatune 2.25p3
I'm using the EDIS 4 system with a trigger wheel on my crank pully
I have low impedance injectors (PWM Threshold 1.0ms, PWM current limit 30%)

Thank you!!
-Ben

Matt Cramer · Post by **Matt Cramer** » Mon Aug 30, 2010 1:25 pm

Could you post data logs of both the engine running and when it's misbehaving, along with your MSQ file?

progman · Post by **progman** » Mon Aug 30, 2010 8:01 pm

I'm trying to get the datalogs for you but I'm having a problem getting my O2 sensor working (This is a different controller/sensor than at the dyno shop). While trying to get the car to do it's thing I notaced that my IAT just sits there and barely changes. start at like 82 degrees and fluctuates by 10 +/- very slowly. This is a turbo engine running 210Kpa. Shouldn't the IAT shoot way up when the turbo is compressing the air? In my log there was no correlation.

Is that normal?

http://www.prog-x.com/datalog201008302116.xls

As soon as I get my lc-1 working again I'll post up logs of it running good and bad.

Thanks.

progman · Post by **progman** » Mon Aug 30, 2010 10:59 pm

http://www.prog-x.com/datalog201008310221.xls

O2 running but the car ran normally while I was logging. I need to find a place i can run this thing without being on the road... I probably won't be able to get this until the weekend.

Matt Cramer · Post by **Matt Cramer** » Tue Aug 31, 2010 4:25 am

I take it these are "running correctly" logs?

Where is the IAT sensor located?

progman · Post by **progman** » Tue Aug 31, 2010 1:36 pm

Matt,

Yes those logs are of it running correctly. The IAT is right before the throttle body. AFTER the turbo and AFTER the intercooler

I'm going to have to find a large open area to get the datalog. I might go back to the dyno to get it. I don't know why it never occurred to me to datalog the problems!! But the car runs 11.5 +/- .2 while at WOT about 2/3 runs. Then that "bad" run it goes 10.8 (O2 sensor min) and runs richer than 10.8 the entire WOT for unknown reasons.

But is my IAT working?? do I have a bad sensor or have it plugged in backwards or something?

Matt Cramer · Post by **Matt Cramer** » Wed Sep 01, 2010 4:41 am

The IAT looks like it is working, but it may be picking up heat from the engine compartment.

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Engine runs very rich out of the blue

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