Runs bad, surges and stalls?

JOHN VACCARO

MEMBER
1992 BMW 318I
1.9L
4 CYL
2WD
MANUAL
170,000 MILES

The problem came up suddenly. Won't hold an idle, bogs down when throttle is open. Stalls. Strong fuel smell and black smoke from exhaust. Starts quickly. Passed the smoke test. Cleaned EAC valve and tested it with battery power. Cleaned throttle body. No codes except one knock sensor out of 4, which has existed for years.

5 Replies

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

Hi,

If you smell fuel and there is black smoke, the engine is getting too much fuel. The first thing I suggest is to check the fuel pressure. If it is excessive due to a faulty pressure regulator, it can cause this.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

In addition to testing the pressure, when you turn the key off, pay attention to see how quickly the pressure drops off, and let me know what you see.

If you look below, I attached the manufacturer's fuel pressure specifications.

Also, pic 2 below shows the location of the fuel pressure regulator. There will be a vacuum hose attached to it. Inspect the vacuum hose and make sure it is in good condition, not leaking, and is attached at both ends.

Let me know what you find.

Joe

See pics below.

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Thursday, March 16th, 2023 AT 8:49 PM

JOHN VACCARO

MEMBER
3 POSTS

Thanks for the quick reply. Replaced the hose to the regulator. There is no fuel inside and no smell. I can't suck anything through the hose, all of which tells me the diaphragm is good. I don't know where to connect a pressure gauge, but do you think, given this information, that the regulator could be at fault?

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Thursday, March 16th, 2023 AT 11:35 PM

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

Hi John, it could still be faulty. With the engine running, do you have a vacuum supply to the regulator?

If you look below, I attached the directions for testing fuel pressure specific to this vehicle. Take a look through them and let me know if you have questions.

Because of the model year, there isn't a Schrader valve to connect to. Instead, you will place a T connector in the supply hose and the gauge will connect to that.

Let me know.

Joe

See pics below.

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Friday, March 17th, 2023 AT 7:44 PM

JOHN VACCARO

MEMBER
3 POSTS

It was the air flow meter. A year and a half ago I replaced the original with a Chinese-made one in order to correct an intermittent, temperature-related stalling problem. It worked, but there were some trade-offs. So, I put the original one back on, and it's running flawlessly again with the exception of the stalling problem. So apparently the Chinese one had a sudden catastrophic failure. I've been examining it to try to see what went wrong with inconclusive results so far. Strangely, the potentiometer in the Chinese one ranges from 250-600 Ohms, when I move the vane, while the original Bosch one stays on 8500 Ohms regardless of the vane position. It's a puzzle. Thanks for your help.

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Monday, March 27th, 2023 AT 1:47 PM

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

Hi,

You are very welcome, but you did all the work.

John, if you got that much time out of the replacement, you did well. LOL I can't tell you how many aftermarket online parts are bad when first installed.

Regardless, I'm glad to know you got it going again, and I appreciate the update.

Take good care of yourself and feel free to come back anytime in the future.

Joe