Bad ECU?

[gorbilax]

I haven't had a chance to to check the EGR harness or any of the others because it's been pouring down rain all day. Tried driving in the rain to see if something would ground out and I can't repeat the problem.

I did decide to pull codes to see if there were any stored in memory, though. It had 22, 24, and 41... (coolant temp, IAT, TPS). They're all sensors on that same 16 pin connector. I pulled the fuse and cleared them. I think I may drive it as my commuter this week (if the gas prices don't kill me!), see if any codes come back or it decides to shut down on the road again, and hope for better weather next weekend so I can start checking the harnesses.

Thanks again for all the advice.

 

[gorbilax]

Checked the EGR harness today. Sure enough, one of the two wires going to the EGR gas temp sensor was melted. I'm waiting for the engine to cool down a bit more before I fix it, but hopefully this will cure the issue. I've been driving it for two weeks though, and it hasn't shut down on me again, so perhaps we'll never know.

As far as the rough idle goes, turns out my roommate accidentally removed the MAF element from the housing when he was trying to unbolt the whole assembly earlier in the project and never thought to tell me. He must have damaged it because the new MAF from arcteryx seems to have cured that issue.

Once again, thank you all for your advice while my stubborn ass kept insisting it was the ECU. Case closed (I hope!)

 

[elhombre]

Well done, time for that

 

[gorbilax]

sorry to bring this one back from the dead, but the symptoms have returned.

I've now traced it to pin 16 (brown/black) of the 16 pin ECM connector, which is labeled E11. Both the factory wiring diagrams and Mitchell 1 have this pin unlabeled. FSM seems to indicate it's a ground, but putting a meter on it reveals +5v. Whenever I reconnect the pin, the ecm goes out, but with the pin disconnected, the ecm works, but car runs rough and dies. Yesterday it ran fine!

Anyone have any insight on what this pin is connected to? it seems to be shorted to ECM ref voltage somewhere.

 

[TrickyT]

Try this: with the E11 connector installed, verify that pin 16 is still reading too low. Now disconnect the VAF/MAF connector in the engine compartment and re-check pin 16. If it's now reading +5v then the problem is the VAF or VAF wiring. (Yes, I know you replaced this part.) If instead it's still reading low, disconnect the throttle position sensor in the engine compartment and re-check pin 16. The VAF/MAF and TPS are the only sensors that use +5v.

 

[gorbilax]

i was reading the connector backwards, the pin is actually pin 9. (E2). Disconnecting the TPS doesn't stop the problem, but disconnecting the VAF sensor does. Thanks for the tip. Since the problem predates the used VAF I installed, I'm guessing wiring. I'll diagnose more tomorrow.

 

[gorbilax]

Well... turns out my original VAF (contacts ripped loose by roommate) and the used VAF I bought were both shorting the system. Ripping the covers off revealed that the tabs were torn loose from the board and touching just enough to short out the ECM. A quick solder job and an idle relearn test drive, and I'm back in business. Once again, thanks for the advice. Still gotta deal with one melted EGR temp sensor wire, but it's disconnected and insulated for now...