Bad Fuel reg. Syptoms

**300kplus** · 06-21-2018, 08:36 PM

What are the symptoms of a bad fuel regulator? Or a bed throttle body. The car is a 98 E39 m62 this car does not have vanos... my cars symptoms are:
After driving her for a while shutting her off she sits a little bit, it takes me 3 or 4 times to start her. Another thing happening is I'll be cruising along and it's like somebody pulled all the power for a split second and then gave it back immediately. It's very very strange I can't put my finger on it. I pulled codes and as most of you know when something misses and it creates a barrage of misses In other areas...
Fuel regulator, fuel injector and a coil are suspect in the printout cross-referencing the codes...
TIA!

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**Grim Reaper** · 06-21-2018, 10:15 PM

Another possibility could be intake or exhaust cam sensor starting to go out. Long time ago had an E46 325 that had unusual idle and then die behavior intermittently at stop lights. It ended up being exhaust cam sensor that was going south. Never threw a code BTW.

**edjack** · 06-21-2018, 10:16 PM

Possible fuel pump failure. You don't report the miles on the car.

The only way to know is to connect a fuel pressure gauge and monitor it while the symptom appears.

There have been a couple of reports of loose power connectors on the fuel pump motor. You must remove the access cover on the right side of the rear seat cushion.

**300kplus** · 07-03-2018, 08:05 AM

Originally Posted by edjack

Possible fuel pump failure. You don't report the miles on the car.

The only way to know is to connect a fuel pressure gauge and monitor it while the symptom appears.

There have been a couple of reports of loose power connectors on the fuel pump motor. You must remove the access cover on the right side of the rear seat cushion.

Update:
Ok so very high mile car 300k (+) in continuing with the above post relative to symptoms while driving, I took about an hour trip and she misses terribly losing all power, and at one point she completely shut off [stalled]
I limped to my destination, shut her off, and the next morning drove her back and she ran like a champ. I tried turning the AC on to see if there would be any notice of loss of power or would put enough strain on the engine to make it miss again.
No trouble at all, ran like a freaking bat out of hell. Man I am super super perplexed. These are intermittent symptoms and they come and go. As I shared above in a previous post, sometimes it takes 3 or 4 times to start her. Sometimes she starts out missing terribly and will continue to do so and get slightly better as I keep driving her. Other times, once I let her sit for more than a few hours, it's like nothing ever happened before she runs like a clock. The CCV hasn't been changed in quite some time but no smoke when I start her up. I replaced some fuel injectors when I did the valve covers. The last time the fuel pump went out she left me on the side of the road one and done so I'm thinking not the fuel pump. I did the plugs when I did the valve cover gaskets less than 2 years ago and only drive her on the weekends for about the last year. It's very weird but when she sits for a while she seems to "fix" herself- until the cycle starts all over again... I'm thinking coil/ coils and or fuel injector/ injectors?

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**geargrinder** · 07-03-2018, 10:26 AM

codes codes codes codes.

codes.

start with codes. preferably in BMW reader, not just generic PeePee codes.

beyond that sounds perhaps heat related, and injectors and coils can manifest heat-dependent failure modes for sure.

the FPR is super uncommon failure. Its integrated into the fuel filter under the car. Typically that wouldn't be this kind of total on/off/on unpredictable thing though.

**300kplus** · 07-03-2018, 10:44 AM

Originally Posted by geargrinder

codes codes codes codes.

codes.

start with codes. preferably in BMW reader, not just generic PeePee codes.

beyond that sounds perhaps heat related, and injectors and coils can manifest heat-dependent failure modes for sure.

the FPR is super uncommon failure. Its integrated into the fuel filter under the car. Typically that wouldn't be this kind of total on/off/on unpredictable thing though.

Yeah, I replaced the fuel filter 3 or 4 months ago. BMW reader? Please advise. Thanks

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**topaz540i** · 07-03-2018, 02:50 PM

One time I had a bad gas cap that would allow too much pressure to build up in the tank in the sun and the car wouldn’t start. I had to get out open the gas cap to release the pressure and then it would run fine

**300kplus** · 07-03-2018, 02:57 PM

Originally Posted by topaz540i

One time I had a bad gas cap that would allow too much pressure to build up in the tank in the sun and the car wouldn’t start. I had to get out open the gas cap to release the pressure and then it would run fine

Holy cow are you kidding me? Gas caps go bad? Urrrrrrgh
Yeah I don't think it's the gas cap but good to know...

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**geargrinder** · 07-04-2018, 09:02 AM

Hmmmm. The evap system should handle any vapor pressure in the tank actually - the gas cap is SUPPOSED to seal it completely and in fact if the gas cap leaks, the EVAP system is supposed to scream at you (hence the "I got a check engine light but it was just a loose gas cap" famous scenario).

BMW code readers: Go to 'diagnostic software' forum here and and bimmerfest. Options are wide ranging but a 'proper' BMW reader will show more info and codes than generic-readers. You can do it with a laptop and software, that software can be INPA which is old obsolete and semi-clunky but still works great BMW software, or "PA Soft" which you can get from a range of online auctiony sites, or, you can use a BMW-smart hardware code reader like a Creator 310+ or a Foxwell NT510. "Real BMW Scanners" will talk to ALL the modules in the car, including climate control, body electric module, lighting module, etc. and you can within limits do some custom re-coding of those modules to tweak features (like auto-lock settings, lighting settings, etc.)

**300kplus** · 07-04-2018, 09:06 AM

Originally Posted by geargrinder

Hmmmm. The evap system should handle any vapor pressure in the tank actually - the gas cap is SUPPOSED to seal it completely and in fact if the gas cap leaks, the EVAP system is supposed to scream at you (hence the "I got a check engine light but it was just a loose gas cap" famous scenario).

BMW code readers: Go to 'diagnostic software' forum here and and bimmerfest. Options are wide ranging but a 'proper' BMW reader will show more info and codes than generic-readers. You can do it with a laptop and software, that software can be INPA which is old obsolete and semi-clunky but still works great BMW software, or "PA Soft" which you can get from a range of online auctiony sites, or, you can use a BMW-smart hardware code reader like a Creator 310+ or a Foxwell NT510. "Real BMW Scanners" will talk to ALL the modules in the car, including climate control, body electric module, lighting module, etc. and you can within limits do some custom re-coding of those modules to tweak features (like auto-lock settings, lighting settings, etc.)

Wow. Excellent information.
Thanks!

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