1G Coolant temp sensor

[SrKegler]

Guys, I'm completely stumped. Car is running pig rich, replaced coolant temp sensor twice, ran extra ground wires, replaced maf 4 times, replaced throttle position sensor and adjusted it in.

Replaced 3 capacitors in the ECU. Replaced plugs and plug wires (BPR6ES gapped to .28. Wiring checks out OK as far as I can tell. Still have a CEL, car will run but stutters/bucks if you try and give it too much gas. Hard to start in the mornings but starts OK after that first time. Feathering the throttle lets you build speed up, mainly in 3rd gear once the RPMs get over 3000.

Will be doing a BLT tomorrow. Just wondering what to try next. No logger and it costs me $50-$60 to get it checked at the shop.

 

[JayRolla]

Go to any local parts store. Advanced autoparts, Autozone, Checkers all checks CELs for free.

First thing I think of is the motor is not getting a maf signal. Usually from faulty wiring at ECU when installing an SAFC. But I see your car is stock other than 255lph and AFPR. What FP do you have it set at when you unplug the vacuum line? Also what FP does it hit once its installed?

Second thing I think of is your stuck in open loop but car should still run without bucking. That would happen if the O2 sensor is bad which you have not replaced.

 

[dsmfa9nutter]

Get a logger.


Are you running a bigger fuel pump? How's your fpr look?

 

[Bluesideup]

Similar problem on my 2G except that it ran so rich it could only drive 3 miles before it quit due to the plugs loading up. I did the BLT and it held up to 30psi, changed the MAFS, replaced the coolant sensor, replaced the ECU, checked all of the grounds, and tested the o2 sensors. I also don't have a logger so I just systematically tested everything until I found the problem. It turned out to be the incorrect TPS installed by the previous owner. I don't know what Mitsubishi uses it but there is a tps that fits our throttle bodies that is wired completely backwards from ours. It may have been telling the ecu the engine was at full throttle when it was at idle causing the injectors to go 100% duty cycle.

A shorted sensor can also cause the ecu to be totally scrambled and cause weird problems. Try the blt and if that doesn't turn anything up start testing sensors with a multi meter per the service manual.

This is the thread with my pics about 3/4 of the way down

http://www.dsmtuners.com/forums/newbie-forum/285251-running-pig-rich-stuttering-not-driveable.html#post151902379

 

[SrKegler]

Ran a BLT today, no leaks. Checked the TPS, reading is .48 with throttle closed, 4.83 with throttle wide open.

Tomorrow I'll run seperate lines from the coolant temp sensor to the ECU and see if that helps any.

I've been searching, can't find any way to check the maf though. Does anyone have a link that will help.

 

[Bluesideup]

Did you check for continuity between the engine compartment connector and the ecu connector for the coolant sensor? You might do that before running a new wire.

 

[SrKegler]

Get a logger.


Are you running a bigger fuel pump? How's your fpr look?

Fuel pressure is set at 37#, running a 255LPH. That was the only pump available when my OEM pump went bad.

 

[dsmfa9nutter]

Are you running an afpr with the 255 pump? They flow a lot more than a stock pump and can cause the exact symptom you're having. Base pressure isn't an indicator of overflowing the fpr. That causes an extreme rich condition (the hole in the fpr is too small to let all the excess fuel through, higher rpms=alternator putting out constant max voltage=fuel pump gets more power=fuel pump has higher flow). Pull your plugs and see if they're black.

 

[SrKegler]

Car has a AFPR, can't remember the name, it's the red & silver one. Oil filled pressure guage, fuel pressure set at 37, vacuum line off & plugged.