Noob w/ semi-interesting 1989 ga16i EGR +ECU questions

jdfromla · Feb 7th, 2005, 11:55 PM

Hello Everyone,

I just bought an '89 (Feb '89) Sentra 4sp GA16i with 171k miles at an LA police auction for 300 bucks. The car is ratty looking but the engine runs really well. I'm getting the car ready for the killer CA smog check. I replaced the dead O2 sensor, and am working with the EGR system. My problem: The EGR works only with the vacuum switching solenoid disconnected. All vacuum operated functions of the EGR system are fine. The passages are not blocked. I have alternator voltage at the VS solenoid connector. The solenoid resistance is 41 ohms, which I understand to be in spec, so I have continuity.

Is this normal? My understanding is the presence of voltage opens the valve, not closes it. Am I wrong? Is the coolant temp sensor the determinant of EGR VS solenoid operation? The coolant gauge reads low but the fans do come on. No, I haven't checked for the presence of a thermostat yet.

Also, I would like to pull any trouble codes off the ECU. The <irony>fabulous</irony> Haynes manual shows the procedure but they neglected to reveal the ECU's location. So where is it?

Any help with these queries would be greatly appreciated. I have about a week to get this car smog tested. It would probably pass now, but the motor pings at certain throttle openings so I'd like the EGR to work as designed.

Thank you in advance,
JD

Mervic · Feb 8th, 2005, 12:58 AM

The ECU is located below the passenger seat. As for your EGR problem, getting the codes from ECU diagnostics might shed some light to your problem. Post back with the result.

Crazy-Mart · Feb 8th, 2005, 02:00 AM

to my knowledge, the Egr valve works with the throttle position sensor... as it was told already, it only work on cruising, idling... hard accelleration/low vacuum should get it to open.

jdfromla · Feb 8th, 2005, 03:43 PM

Mr. Mart,

I followed the procedure from the Haynes book to make the valve open. When the solenoid power supply is disconnected, it works as the manual says it should. However, when the power is applied to the solenoid......that is the mystery. If I have time to pull the front seat out today, I will pull codes from the ECU and see what it says.

BTW, I've tried using the search function before asking my questions. there does not seem to be a lot written on the subject of the electrical side of the EGR system. Perhaps if I search all forums instead of just this particular one....

Thanks for responding,

JD

Crazy-Mart · Feb 9th, 2005, 01:42 AM

Actually i dont think anyone as ever provided such info about the EGR system... you might find something else on the forum but i wouldnt be surprised that it wont be much of help to you... different engine/different system... basic should be the same but when you get down to facts/application... it all change. The selenoid valve is probably used to block/acces vacuum to it (that you probably did know) ... As for why and when it is energized... im in the dark !! best way would be to plug a lightprobe on it and drive the car on different load, see for yourself where it let vacuum be applied to the EGR...