Check engine light ON, J30t idles rough and stalls

[josephv909]

So about 6 months ago, my J30 started to idle a bit rough. Well it slowly progressed and then the check engine light turned on and it started to stall out when I was stopped at red lights or when I was going from reverse to drive. I went to the local Pepboys and they told me the code was telling them it was the IAC valve. So I had that replaced and it was fine for about a week. The check engine light turned on once again and this time I took it to the local Infiniti Dealership and they told me it was the wiring harness that connected to the IAC valve so after another 180, I picked up the car and it drove fine for a week and now the check again light is back on. Has anyone else had similar problems? Any suggestions??

[driverdriver]

Have you pulled codes recently? It could be any one of several things, from 02 sensors, MAF, fuel pump/sending unit to a fuel injector. A code will narrow it down. What year is your J? You can use the instructions in one of the "stuck" items on this forum and pull the code yourself.

[josephv909]

I'll see if I can get the exact code tomorrow. All I know is it says it's the IAC motor, but I'll get the specific code. It's a 1997 j30

[josephv909]

I still haven't retrieved the code but I did take it to the dealer since i've been having this problem for the last 4 months and at first they told me it was the harness connected to the IAC valve motor, so I payed 180 for the diagnostic and replacement of the harness. The check engine light turned on again and now they are telling me that it's the IAC valve motor, which I just had replaced 2 months ago! They are telling me its going to cost over 800 dollars. I am going to take it back to the mechanic who replaced the IAC valve motor and see what he tells me. This is turning into a hassle.

[GerryO]

Read this, clean and ohm test the solenoids. One may need replacing.

http://home.swipnet.se/e-solutions/IdleTech.html

I once had a terrible experience at the local Frontier Ford dealership with an engine that sputtered at its' automatic transmission shift points and bucked violently at freeway speeds, in and out of OD lock-up. The dealership replaced the O2 sensor, then the plugs and wires, and also flushed the transmission.
Turned out to be simply a dirty MAF and the service contact flat-out lied about it, saying that one of the new plugs they'd installed was broken. I read about the MAF cleaning in the service technician's report.

[josephv909]

so the code is P0505.

[swimshark]

idk how much dealership charges exactly for the diagnosis but get one of these guys so you can do it more yourself and not spend all the money and make sure it is the exact code they have been telling you.

http://www.amazon.com/OBDII-Engine-Scan ... B000LEPT5G

also just curious to see if you are relatively car savvy as in like to do stuff yourself?

i know a lot of things on these cars can be extremely pricey if you take it to a general mechanic or dealership.

on page 298 of the FSM http://www.nicoclub.com/FSM/J30/1997_J30/ec.pdf it will tell you how to test the connections of the IACV. i highly doubt that the unit has gone already in 2 months time unless it was installed completely wrong. do a quick visual inspection and make sure they have the connections properly hooked up. there will be a yellow and blue plug on the iacv unit on the back of the motor on the drivers side.

[josephv909]

ok so check it, I've had problems with my ECU before, somehow water gets to it whenever it rains and I drive thru puddles. Well this time around I think when it rained last (I live in Southern Cali) is when my J started giving me problems. So I asked my mechanic to take it out and he told me that it looks like it has water damage. HOPEFULLY this will fix my problem and if it does, now I have to figure out how water is leaking into my car. Fix one problem, find another.

[driverdriver]

If water is leaking into the passenger footwell, its likely

(a.) the sunroof drains are clogged and the weatherstripping around the sunroof doesn't seal.
(b.) improperly fitted replcement windshield.

[GerryO]

j30-ecm-engine-light-error-code-51-t66003.html

[josephv909]

Okay, so ECU replaced, ran great for two days aaaaaaand now the SES light is back on! WTF! I'm seriously stumped. and kind of frustrated. more stumped than anything though.

[swimshark]

is it still running rough? what codes is it throwing now?

[josephv909]

Same code P0505. my mechanic thinks it might be the wiring harness, the same wiring harness that the Infiniti dealership said they replaced. I looked at both of the wiring harnesses that hook to the iac valve and they both look worn. So now It seems as if the dealership lied to me about the work they said they did.

[GerryO]

P0505 IACV/AAC Valve

Just to confirm that you have checked all resistances and cleaned things per these instructions.

http://home.swipnet.se/e-solutions/IdleTech.html

Disconnect the battery. You should be able to disconnect the FICD, AIC and Air Regulator, and the ECM connector to test harness wire continuity. Cleaning/some dielectric grease on the contacts, before you reconnect them, would also be a good idea. If there was moisture in/on the ECM, there may also be corrosion on the connector. Make sure ground connections are good too.

Obviously the wiring harness is just wires bound together and only one or two of them is probably the source of your problem, in the form of an open or shorted connection (permanent or intermittent).

[swimshark]

how much did they charge for the harness? only thing they could change is splice in new connectors. im not sure this would work but here is what the wiring harness looks like for the 300zx which has the same motor.

[yodawill2000]

Too little Too late advice but, on the rare occasion I have work done on a car I always demand they return the part that they replaced.

Although there's always a chance they could give you something from a scrapper they at least know you are serious about whatever job they do.

If the harness/connector looks worn I would be all over them like white on rice !!!

[josephv909]

Does anyone know where I can get a reliable replacement ECU??

[swimshark]

i can see if i can get one from a pull a part here. less than $40. can you give me the letters on the side of the ecu?

[josephv909]

i can see if i can get one from a pull a part here. less than $40. can you give me the letters on the side of the ecu?

yea i'll do that tomorrow. I know its a replacement ECU because I have a leak in the windshield that I just recently fixed.