'89 325i Starts Hard, has misfire

[camaroman]

Hey guys, I really need some help with knowledge and advice here. I've got a 1989 325i and the engine has a problem with starting hard all the time, hot or cold. To get it to fire up, I have to hold the gas pedal to the floor and sometimes pump it. When the car starts, it runs...tolerably, but it has a miss as it idles. Not a huge one, like disconnecting a plug wire, but it's a discernable miss, nonetheless. Horsepower is not feeling good, either. This morning when I started it, I noticed a whole bunch of fuel-rich exhaust for the first few seconds of running.

I was suspecting leaky fuel injectors, but am not sure how I test them to see if they are in fact leaking. The car is freshly tuned up with Bosch parts, so it's not an ignition problem. Any ideas??

[jase007]

Mike:

1. Temp sensor to ECU so it knows what is going on (on radiator and also cylinder head near t-stat) Replace for cheap insurance.

2. Potentiometer that is called "throttle position switch" on air flow meter. Indicates to ecu where the AFM flapper is [one of three positions - idle - open - wide open throttle].

You need a Bentley manual if you don't have one. There are myriad other tests I would check. If you suspect injectors, check the C-191[pretty sure is the #] injector harness connector under the top of the intake manifold. Is a screw in connection that gets gunked up. Usually is the culprit on misfiring injectors. Are you sure the replaced ignition parts are all correct?

Did you use plugs other than the OEM bosch copper ones? Platinum, split-fire, or whatever else all cause these M20 engines to not run right.

I have never had an ignition / misfire problem runing OEM spec'd Bosch copper plugs and cap and rotor in 20 years and 192,xxx miles.

Jase

[camaroman]

Hey,

I replaced the coolant temp sensor a year ago, although I may do it again just in case.

All of the ignition components are Bosch, except for Bremi wires (from thsi site): Bosch super plugs, Bosch cap&rotor, Bosch coil. All are definitely the correct ones.

Air flow meter potentiometer tested okay.

I've got the Bentley manual. I'll have to check out the connector for the injectors that you mentioned. If I don't get it straightened out within the next few days, then when my Camaro goes back on the road in a week or two, I'm tearing the intake off and tearing down to the timing belt and am gonna go nuts taking stuff apart. I'm conviced it's gotta be a fuel delivery problem, but I'm also curious to check the timing belt and make sure it didn't jump a tooth.

Once I have a two or three day stretch off of work/classes (for the most part), and the weather and roads are good enough for the Camaro, I'm gonna tear the BMW down until I can hash this nonsense out once and for all. I've had nothing but trouble with it since the end of last summer, and all of the troubleshooting in the world isn't helping me pinpoint the problem. Only thing I haven't tested yet on that stupid motor are the fuel injectors and the pressure regulator. That and check the timing belt.