finsished my swap today! one problem.....

[1991 e30 bmw 318is]

today i made the exhaust and that was basically all i had left to do. so it sounds good i think, it drives great. pulls really nice I'm very happy with the performance. but after it sits at idol for a could minutes the rpms bumped and almost stalled, then i was driving it and it works great i stopped to talk to a guy for a couple minutes, then the rpms burped again. i was like humm that's odd, i drove down the road to pull in the gas station and it went to idol as i was slowing down and stalled. so after sitting at idol it acts up. but when i'm driving it seems to works great. any ideas? might have to go to the dealer monday...




also a big thanks to everone on the forum for all the help!

[hoveringuy]

Where do you have the Oxygen sensor mounted?

[e30polak]

Is your ICV clean? How's the TPS? What tune are you running? Could be the MAF...

[1991 e30 bmw 318is]

new o2 sensor in my x pipe, cleaned the icv and new hoses on it. its a 93 obd1 m50b25, its only doing it after its up to temp and is at idol.... and when it starts to do it the check engine light comes on.....

[mbonder]

Run the check engine codes...and its idle

[1991 e30 bmw 318is]

Run the check engine codes...and its idle

so i need to go to the dealer and plug it in?

[hoveringuy]

so i need to go to the dealer and plug it in?

No, do a search on "stomp test"... you can pull the codes from the Check Engine Light. stomping the gas pedal 5 times in rapid succession will trigger the ECU to flash the code through the CEL.

[matt]

I had identical symptoms on my car that were fixed by replacing the throttlebody and TPS.

[1991 e30 bmw 318is]

did the stomp test it said its the o2 witch is brand new. so maybe it just needs to be put further in the x-pipe? its on the side of it with a bing welded on it.

[hoveringuy]

I think you are suffering a common ailment. The usual symptom is the car will run great when it is warmed-up, but if you get to a redlight and idle for more than about a minute it will noticeably jerk and stumble with an associated CEL light. Sometimes it will stall completely.

Once the light turns green, the CEL will clear after around 15-20 seconds.

What is happening is that the O2 sensor is getting too cool for it to provide accurate readings and the ECU goes open-loop. Once you drive away it heats up sufficiently for accurate readings and the light goes away. The sensor needs to be above something like 400 degrees Fahrenheit for it to work, hence the heater.

Having it further downstream compounds the problem. Move it up into one of your manifolds. You will only be sampling 1/2 of your cylinders but it will stay hotter at idle. Also scheck your O2 heater wiring, although there has been much talk about a difference between e30 and e36 circuits.

The heater element WILL NOT be energized when you start the car, the ECU will not command it on until you've driven for around 1 mile. The best way to check it is with a 12v LED taped to your wiper arm. Ground goes to a bolt and the +12v side goes to your O2 relay load.

BTW, I always loved my stops in Halifax!

[1991 e30 bmw 318is]

that's interesting I'm surprised tho because my x pipe is right at the end of my headers, i thought it would be hot there. Maybe if it was pushed into the x pipe more it would help my bing is welded on the out side if i cut it i can push it in a lot more if might do the trick. i was told its not a good idea to only have it read 3cly.... but what you described is exactly what its doing.

thanks a lot for the help. might put it in one of the headers and go for a drive.

[hoveringuy]

that's interesting I'm surprised tho because my x pipe is right at the end of my headers, i thought it would be hot there. Maybe if it was pushed into the x pipe more it would help my bing is welded on the out side if i cut it i can push it in a lot more if might do the trick. i was told its not a good idea to only have it read 3cly.... but what you described is exactly what its doing.

thanks a lot for the help. might put it in one of the headers and go for a drive.

I even had it happen when it was directly on one of my manifolds, so don't expect that to fix it.

I even had my heater connected directly to power once and it still did it.

I don't think a concrete solution was ever found or even an an answer to why it does that.

There have been previous discussions about this with speculation about the O2 sensor heater sharing a circuit that it didn't with the e36 or vice versa. Do a search on "02 heater" and you'll find it.

[OrganicMechanic]

fuel and o2 relays have combined wiring for e36's. check the o2 relay. green wire should be sending 12v directly to the o2 heater. likewise, the red/white wires should be 12v. i would bet that you are not getting the 12v .......and it is causing the red/white wires to backfeed too. disconnect the green/violet wires at the c101 and pull power (via fusable link) from fuse 11 (fuel pump fuse) to green/violet (e36 harness wire) at c101. i capped off the green/violet wire on the e30 side.

car runs MUCH MUCH smoother as the o2 heater element is now working and the o2 sensor is getting the correct readings

[1991 e30 bmw 318is]

I was driving around town the other day and at the stop lights i got sick of keeping one foot on the gas and brake at the same time. To keep the idol up so it doesn't start acting up. So i turned the idol up a little about 1050rpms it idols when its up to temp and its been working great. idol is nice and smooth. going to try and get it a little lower and see if it still works good. so i can live with the idol up there that doesn't bother me at all. but it does smell rich at idol. is that still something to do with the o2 sensor??

[OrganicMechanic]

yes--