That problem that I fixed? It's back.

[J.DeFeo]

After sitting for a while (at least several hours), my car, a 1992 535iM with 128,000 miles when starting would have several issues:

1.) The engine would vibrate hard.
2.) It sounds and feels like one cylinder wasn't firing correctly.
3.) If throttle wasn't added, the engine would almost immediately stall.
4.) If the throttle is held, eventually (about 10 seconds) the engine would smooth out and idle normally.
5.) A faint odor of fuel in the passenger compartment.

There are no codes, no CEL, no warning lights of any kind. I just replaced the fuel injectors (albeit with used ones, but what are the chances that two sets of fuel injectors both leak?). The sparks plugs are basically new (<1000 miles on them). When I replaced the spark plugs, there did not appear to be any oil on them.

After replacing the fuel injectors, the problem completely disappeared for a couple days. That is, until this morning, when the exact same problem resurfaced.

I'm thinking now it's time to crack out the ohm meter and start checking sensors. Likely candidates I can think of are: TPS (not signalling idle correctly), ICV, Coolant Temp. Any others? How do I check these sensors? What values should I get when I check them?

Is there a way to tell definitively if there is a fuel injector leaking?

Occam's Razor says my "new" injectors are probably also leaking. But the more I think about it, I think zebra is actually the correct answer here. The injectors were part of the problem, but now another has come to the forefront.

I'm getting fairly desperate here. Any suggestions and advice at all would be greatly appreciated. If I can't figure this out, I'm just going to... ...take it to a mechanic. Any other information needed I can supply, I have a full maintenance history for the car.

[Ross]

Sounds like an injector leaking down after shut off flooding that particular cylinder(s).
Check for fuel pressure remaining in the rail before a cold start. You'll need to disconnect something as BM thoughtfully provided no port.

[J.DeFeo]

Sounds like an injector leaking down after shut off flooding that particular cylinder(s).
Check for fuel pressure remaining in the rail before a cold start. You'll need to disconnect something as BM thoughtfully provided no port.

How do I do this? What tools do I need? What reading should I get on said tool?

If indeed this is what's happening, what is the fix?

Thanks in advance.

[Ross]

On the M30 you can unclamp the fuel line just beneath the intake. There are two lines just aft of center, the rearmost one is pressure I recall.
There ought to be residual pressure in the line, not just a dribble.
All you need is a screwdriver.

[J.DeFeo]

On the M30 you can unclamp the fuel line just beneath the intake. There are two lines just aft of center, the rearmost one is pressure I recall.
There ought to be residual pressure in the line, not just a dribble.
All you need is a screwdriver.

When I replaced the fuel injectors, there was a sharp "hiss" of releasing pressure and then fuel came out at an alarming rate when I pried the rail off of the first injector. Is this what I should have seen?

[Ross]

If it was under presure, yes.

[shogun]

you need:
fuel system pressure: 2.94-3.06 Bar
coolant temperature sensor: 300-360 Ohm at 80 degree Celsius
speed sensor: 486-594 Ohm
fuel injectors: 15-17.5 Ohm

Resistance idle control valve:
Bosch DME connector 1 and 3= 40 Ohm
connection 2 and 1/2 and 3 =20 Ohm

Siemens MS40 : connector 1 and 2= 20 Ohm

and for testing the fuel pressure you need a simple kit, not as professional like this one
http://www.midwayautosupply.com/ps-6...it-cp7838.aspx
maybe like this
http://www.justoffbase.co.uk/Pressur...l-Sealey-CT952

[J.DeFeo]

you need:
fuel system pressure: 2.94-3.06 Bar
coolant temperature sensor: 300-360 Ohm at 80 degree Celsius
speed sensor: 486-594 Ohm
fuel injectors: 15-17.5 Ohm

Resistance idle control valve:
Bosch DME connector 1 and 3= 40 Ohm
connection 2 and 1/2 and 3 =20 Ohm

Siemens MS40 : connector 1 and 2= 20 Ohm

and for testing the fuel pressure you need a simple kit, not as professional like this one
http://www.midwayautosupply.com/ps-6...it-cp7838.aspx
maybe like this
http://www.justoffbase.co.uk/Pressur...l-Sealey-CT952

Do I just disconnect the sensors and shove the multimeter probes into the connector?

[Tiger]

How about crank position sensor? If injector are leaking, one of your plug would have fouled out.

[J.DeFeo]

What about the fuel check valve? This morning, before I started my car I turned the key to position 2 and left it there until I couldn't hear the fuel pump anymore. I turned it off, then did it again to make sure the pump was done. It then started up fine, no hiccup/stall/non-firing cylinder. Could be a fluke, I'll try it throughout the day and tomorrrow to make sure.