white smoke from exhaust ecu? help

[1990 300zx]

okay, so today i was driving when the check engine light came on. To be cautious i went straight home to check the ecu codes.
As this is my first time checking it, i discovered there was no wood from the last owner. i tried to turn the ecu screw to check the ecu, and i found out it wasnt even there . it was like a half of it, and the other half was gone, nothing to catch with.
i managed to turn it, but no codes were coming up. i tried to start the car, but it wouldnt start.

The ecu now makes a loud sound when i turn the key to on, not actually turning the car on. i managed to turn the screw with tweezers, and the car will start, but the sound is still there, and white smoke comes from the exhausts. i know this is a bad description, but any help will be great, thanks!

[t.mcginley.jr]

I'm gonna go ahead and say you should probably pick up another ECU. Someone obviously played around with it and messed some stuff up. You can usually get a good used one for $100 or less. Just make sure if you have an auto that you get an auto ecu, and obviously get an NA one.

White smoke out the exhaust almost always means coolant is being burned, which implies bad head gaskets. Check your oil to see if it looks milky and also take the radiator cap off to see if the coolant appears oily (like an oily film).

[1990 300zx]

the oil seems fine, i just got it changed a few weeks ago. The coolant also seems fine to me, here's a picture from underneath the radiator cap. http://i974.photobucket.com/albums/ae22 ... d49080.jpg
As for the ecu, here/s what it looks like from the side view. this is why i was have so much trouble trying to get the codes.
http://i974.photobucket.com/albums/ae22 ... ecab79.jpg

[t.mcginley.jr]

That ecu looks pretty trashed, I don't know what they heck someone tried sticking in there to turn the screw but they obviously messed it up. I would really look into getting a good used NA ecu from someone, there are plenty floating around.

[1990 300zx]

i just purchased one off of ebay for 110, its supposed to get here anywhere from tomorrow to friday. once i get it i can find out what code turned my engine light on. i'll keep you updated, thanks.

[nexus08]

My coolant temperature sensor has acted up a couple of times on me, and it blows "white ish" looking smoke like crazy and runs like sheet until I monkey with it.

Also, I have the same problem with my ECU (screw is broken on one side) so I bought one of those USB OBDI readers on Ebay for about $100. Came with software and everything. Not a bad thing to have.

[t.mcginley.jr]

Yeah bad coolant temp sensors cause all kinds of problems on our cars. When mine went bad, it would throw off the timing and wouldn't let me start the car, almost like it was flooded. Eventually I could start it again but it ran rich as hell. It wouldn't be a bad thing to replace, they are only $20 from Z1:

http://www.z1motorsports.com/product_in ... ts_id=1723

[1990 300zx]

I wonder if that could have anything to do with my problem, because every time I do start my car the temperature gauge shakes and doesn't get a reading. It takes a couple of minutes of driving for it to get an accurate reading. Could the bad coolant temp sensor have anything to do with that?
I would agree, that really would not be a bad thing to have.

[t.mcginley.jr]

Well there are 2 temperature sensors both located on the front water pipe. If you're looking at the front of the engine, the sensor on the left (slightly larger) is the temp. sensor for the ecu, it tells it what the temp is so it can adjust fuel and timing. The smaller sensor to the right just sends a temp. reading to the gauge. It sounds like you need both of them.

Here's the gauge one, its only slightly more:

http://www.z1motorsports.com/product_in ... ts_id=1724

[1990 300zx]

i should probably add that my car hesitates quite a bit. whenever i hit 20 mph, the cars rpms go quite high, while the car goes the same speed. once it finally speeds up i get thrown to the back of my seat. I also experience bad mpg.

[1990 300zx]

i think im going to purchase those next week when i get my check, thanks for giving me the links. its very helpful.

[1990 300zx]

Update: I still haven't received my ecu, but I have tried something else for the mean time. I used two bottles of fuel injector cleaner, and my car doesn't hesitate as bad now. However my mpg is horrible!
I had 3/4s of a tank yesterday, and it's at 1/4 of a tank today. I didn't leave town, or drive too much. Any ideas for that?

[1990 300zx]

i got some good news, i finally switched the ecu out. the rpms are not as high when idle now,no smell of gas inside car, no white smoke and no hesitation! The check engine light has went off too, and for the temperature reads as soon as i start the car.
i also noticed there is no buzzing sound when i have the key to the on position. I am very glad i decided to get a new ecu.

[t.mcginley.jr]

i got some good news, i finally switched the ecu out. the rpms are not as high when idle now,no smell of gas inside car, no white smoke and no hesitation! The check engine light has went off too, and for the temperature reads as soon as i start the car.
i also noticed there is no buzzing sound when i have the key to the on position. I am very glad i decided to get a new ecu.

Awesome! Glad it all worked out. The old ECU obviously had something wrong with it which was preventing it from running right. If the idle is till high it might need to be adjusted.

Check this out: How to set your idle

[1990 300zx]

The idle is perfect when in drive, but in park and neutral its at about 1200 rpm or so. any way to even them out?
will the link you gave me work for that?

[t.mcginley.jr]

The idle will go up in neutral/park but it shouldn't be 1200, more like 900 or so. How is your mpg with the new ecu? still crappy?

It sounds like your still running rich, or your IACV is gummed up/stuck.

[1990 300zx]

its a whole lot better, but still not the greatest. i get around 70 miles to a half tank.
the other day, i was in park, and my rpms shot up to 2500 and went back down. it hasnt happened since.