Help - Engine Running Rich at Start

[Dave_ET]

Hello Everyone,

I own a ’90 turbo e30 and want to see if you guys can help me with a problem I’m having. I’ve taken it to two mechanics and they can’t seem to find a solution. Let me lay out some of the basics for you first:

--the car has 24lb injectors for the turbo

--the car (luckily) has an air/fuel ratio gauge right above the steering wheel. A proper ratio is 14.8.

--I have replaced the spark plugs with new ones.

Now for the story. I left an inside light in the car one night, and the next day my car battery was dead. After reviving the car I noticed that the car was running extremely rich when the car started. I share a theory with the previous owner that the car’s ECU was reset when the battery died (the trip computer was reset as well), but as I let the car idle the Air/Fuel will get back to 14.8 after 3-4 minutes. I then drive the car once it hits 14.8. A few things to note about waiting for 14.8:

--When I start the car, it’s almost like the battery is dead. Almost no sound is made, there’s a delay and a couple of little cranks come from the engine like it absolutely doesn’t want to move. Then after those 2 or 3 small cranks the engine bursts on and everything is golden.

--The car starts at 7.4 A/F. It jumps to ~11.8 after 30 seconds. It sits there for 3-4 minutes, and then once it hits a threshold of maybe 12.5 it jumps to 14.8.

--The car takes a good minute longer to 14.8 when it’s cold out. If I drop by a quick errand such as the cleaners, once I start the car 5 minutes after I turned it off it takes 1-2 minutes to hit 14.8.

Diagnostics on the car say it’s fine. The battery voltage is fine. I believe it has something to do with the cold start/ignition system. Does anybody have any suggestions? Much thanks in advance.

[jlevie]

I'm going to guess that the car has a stock DME (hopefully tuned correctly for the turbo & injectors). If that is the case the rich start is probably from when the DME is running in open loop mode off default cold start maps. Once the engine warms up enough it switches to closed loop mode and the A/F ration improves.

I can think of two ways to fix this. One would be to find a tuner that can modify the open loop maps. The other would be to use a standalone engine management (like a MegaSquirt) that can be tuned properly for the car's configuration.

[89 e30]

Check the cold start injector maybe its not closing right after you started it

[jlevie]

Check the cold start injector maybe its not closing right after you started it

Unless the engine and management system has been swapped to an ETA engine, which makes no sense with a turbo, this car won't have a cold start valve.

[Dave_ET]

Could it be a weak O2 sensor that is slow to warm up?

[BavBeater85]

I'm going to guess that the car has a stock DME (hopefully tuned correctly for the turbo & injectors). If that is the case the rich start is probably from when the DME is running in open loop mode off default cold start maps. Once the engine warms up enough it switches to closed loop mode and the A/F ration improves.

I can think of two ways to fix this. One would be to find a tuner that can modify the open loop maps. The other would be to use a standalone engine management (like a MegaSquirt) that can be tuned properly for the car's configuration.

good thread...may have finally got the amswer needed for why mine is runs rich...its fine after about ten or fifteen minutes of driving, and I think the period is so long because my thermostat is out. So Im guessing that the chip doesnt kick in til the closed loop mode begins?