My DSM starts and runs like crap.

[Fatpig363]

Okay I have a 90 eclipse gst with 0 mods on it. its 100 stock, my issue is that when I start it cold it cranks over and runs just fine. while driving after the initial cold start the check engine light comes on and reads codes for the barometric pressure sensor and the coolant temperature sensor fault. after I turn it off, I try to start it again and it will run really rough and quite erratic for about 5-7 seconds and then dies. while it runs very erratic you can just smell that it is running extremely rich. now I,ve figured out for some odd reason if I advance the timing by unbolting the cam positioning sensor and turning it clockwise it will start and run just fine? ive done an ohm test on the coolant temp sensor and it was just fine, I replaced it anyway with a new one. and I got a used mass airflow sensor and put that in. it worked just fine after changing those two things for a short while (maybe a week at most) and then it starting kicking the same two codes and continued to become very hard to start. Im hoping maybe someone has had this issue too and has resolved it.

much appreciated

p.s. sometimes when I would start it and it would run erratically I could put the peddle on the floor and it would hit about 7000 rpm, backfire and run just fine until the next startup when it was hot. if anyone has any other question, im happy to answer them.

 

[DSM1G90]

ECU checked out okey ?

You might have bad drivers that control those two sensors from inside the ECU, which means ECU could be getting tired as well.

Been there and done that with my '90 Laser where I had to replace my ECU.

 

[Fatpig363]

was hoping that wouldnt be the issue. will hooking up to a full blown computer tell me anything?

 

[Greedy Pimp]

Just pull the Ecu out and take a look, it's very simple, its behind the radio, just half to take off the two center consul panels and 3 bolts for the Ecu. Pull it apart and look for Anny f up stuff, or leaks from the caps (acid) that will eat stuff up. Here's a site to help u what to look for.

ecurepairhome [ECMTuning - wiki]

 

[deylag]

If my Evo was doing this I would think it would be a boost leak.

 

[Fatpig363]

ive tested the whole system, charge pipe and all, and it checked out 100%.
but definitely a good idea.

 

[Rs AWD]

there are 2 wires going to the CTS one of them is a ground, if there is a short anywhere in that wire the car will not start after its hot. also causing to throw those two codes do to it adding more fuel because its not reading the CTS correctly and then its throwing off the barometric pressure readings. i just fixed a vr4 with the same issue.

 

[steve]

Since you have changes both the Engine Coolant Temp sensor and the Barometric Pressure sensor (in the MAF) you would have seen the typical broken off connectors for the ECT. The most likely cause to begin with would have been the ECU capacitors leaking and still is.

Pop it out, open the top cover and take good pictures of the circuit board so we can see what shape it's in.

 

[Rs AWD]

Steve just FYI the connectors at the sensor were in perfect condition, i had to unwrap the wiring harness and follow it back about 3 or so feet before i found the broke line.

ECU is a good point as well. i was just thinking a little deeper.

 

[DSM1G90]

Even those two connection blades coming out of the ECT can just work loose and lose connection within the unit.

With this happening, one experiences bad hot starts and occasional Code 21 CEL readings.

 

[Fatpig363]

Great! Thankyou for all the help, I will go ahead and pull my computer and take some pictures and post them.

 

[Fatpig363]

One other Quick question, can anyone send me a link or photo of a full wiring diagram of my engine harness to my ecu, including wire color and all junctions of the wires and where they lead.

its the 90 mitsubishi eclipse gst, vin u, turbocharged 2.0 liter

 

[Fatpig363]

these are pictures of my ecu, and to my untrained eye, looks just fine? lets see what you guys have to say.

 

[steve]

A nice replacement 90 Federal AWD EPROM ECU. Get the caps replaced and the EPROM socketed and it should serve you well.

How are you reading the codes? If you have a datalogger like MMCd what do the ECT and BARO sensors read normally when cold and again after the car is warmed up?

 

[Fatpig363]

i read my codes manually with a test light. unfortunately i dont have a computer at hand