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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 01-13-2020, 12:13 PM
BeeRich BeeRich is offline
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Bad Gas? Need Insight

Hi folks.

My E36 318i Convertible has gone through three catalytic converters. Been replaced with a good aftermarket brand, but I just went through another one in about 5 months and it's apparently not from any physical abuse. I had knocked the first replacement version as it was hanging low for some reason. Turns out it's going bad from the inside.

So I'm using 89 Octane from up the road, and I'm definitely going to change that station for a better one.

Is there anything else I should be watching for? From time to time the "Check Engine" light goes on, which arrives only when idling at a red light. Revving slightly higher makes the light go away. Other than that I'm completely blind as to what could be going wrong.

Relatively new O2 sensors, and again, no error messages.

I don't have my own garage and can't be buying testing equipment. The unit has low efficiency as I get maybe 400 km out of a 55 litre gas tank, city driving.

Any ideas? Any insight? Love to hear your take.

Cheers
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  #2  
Old 01-13-2020, 12:56 PM
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hornhospital hornhospital is offline
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Have you had the codes read?

It's running WAY rich. Fuel pressure regulator failure is the likely suspect. Check the vacuum line to the regulator. If it's leaking the regulator defaults to full pressure. That's why you're getting a CEL at idle. It's literally choking the cat converter to death.
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  #3  
Old 01-13-2020, 01:03 PM
BeeRich BeeRich is offline
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Just got back from the shop. Codes read just fine.

They're sending me to an exhaust shop and I'll have them read the pressure regulator. If it's flooded wouldn't the exhaust show that?

Ya the issue here is that the codes read fine. The CEL comes on only low revs, then disappears when I move away from the red light. So sporadic that I can't turn it off and check right there/then with the dash codes.

Would this sort of error of a leak happen all the time though?
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  #4  
Old 01-13-2020, 01:28 PM
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hornhospital hornhospital is offline
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I'd get someone else to read the codes again, this time with a BMW-specific reader. If you see a CEL there is a code stored, whether their reader can find it or not. It's probably an "out of range" code for the fuel regulation. The O2 sensors are reading a rich condition that the ECU can't correct.

The fuel pressure regulator should be tested with a fuel pressure gauge between the injectors and regulator. I doubt the exhaust shop will have the facilities to do so. A 1999 model E36 should have a Schrader fitting on the fuel rail. Connect the gauge to that, crank the engine, read the pressure (should be ~40psi). Then remove the vacuum line from the regulator (plug it while it's off) and read the pressure. It should rise substantially. If it (1) is over 40ish psi at idle with the vacuum line connected, or (2) doesn't rise with the vacuum line disconnected, the regulator is bad.
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Quotes to live by:
guessing gets expensive...drivinfaster
nothing is more expensive than a cheap BMW...c4harpe13
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito) 7pilot
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BMW-CCA #441426

1993 325is M3 clone"Ashlyn"; 1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette";1995 318is"Bebe "; 1985 325e "Hazel Ann"

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  #5  
Old 01-13-2020, 01:33 PM
BeeRich BeeRich is offline
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Oh believe me, they have done this for decades with specific BMW readers. Fully compliant, and great service. Initially I thought it was knocking because the Walker replacement part was hanging low.

https://centralimport.ca/

Anyway, the place I'm going to, is inserting a new cat as the Walker part isn't being made anymore apparently. They diagnose engine chemistry so this should tell me what's going on.

https://noyzboyz.com/

But now I have an idea of what can be the issue.
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  #6  
Old 01-13-2020, 01:36 PM
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hornhospital hornhospital is offline
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I cannot understand how there's no code stored, but okay!
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Quotes to live by:
guessing gets expensive...drivinfaster
nothing is more expensive than a cheap BMW...c4harpe13
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito) 7pilot
Ken Kanne, Silverhill, AL, Bimmerfest Site Moderator
BMW-CCA #441426

1993 325is M3 clone"Ashlyn"; 1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette";1995 318is"Bebe "; 1985 325e "Hazel Ann"

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  #7  
Old 01-13-2020, 01:37 PM
BeeRich BeeRich is offline
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Would it show up as a dash code?
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  #8  
Old 01-13-2020, 01:42 PM
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hornhospital hornhospital is offline
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ANY time you get a CEL, even momentary, it means a code was stored. There should be something there when read with a BMW compatible code reader.

Please keep us posted on your outcome. This is something I've never seen before. Good luck.
__________________
Quotes to live by:
guessing gets expensive...drivinfaster
nothing is more expensive than a cheap BMW...c4harpe13
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito) 7pilot
Ken Kanne, Silverhill, AL, Bimmerfest Site Moderator
BMW-CCA #441426

1993 325is M3 clone"Ashlyn"; 1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette";1995 318is"Bebe "; 1985 325e "Hazel Ann"

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  #9  
Old 01-13-2020, 01:50 PM
BeeRich BeeRich is offline
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OK, but I'm asking if I use the brake method, if it will show up. I just tried the brake method and nothing showed up. No I do not have a BMW reader. My garage does and they used it. I'm not saying the brake method is the same, which I'm assuming it is not. I'm asking if it should show up using the brake method.

Last edited by BeeRich; 01-13-2020 at 01:54 PM.
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  #10  
Old 01-13-2020, 03:09 PM
spyderg0d spyderg0d is offline
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Obdll e36 do not have the stomp test available.
If your killing cats and not getting codes, then obviously either your lieing, or the sensors or ecu is faulty. Theres only 1 thing that kills cats beaides physical damage and thats extreme lean or extreme rich running conditions. When a proper mixture is burnt a converter can literally regenerate its lost composition from previous faults to a certain extent. To suggest anything else is at your fault, is suggesting magic amd complete ilogical and mechanical incompetence.
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  #11  
Old 01-13-2020, 03:11 PM
spyderg0d spyderg0d is offline
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Also.. The stomp test is with the gas pedal. Not the brake.
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  #12  
Old 01-13-2020, 04:24 PM
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hornhospital hornhospital is offline
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Quote:
Originally Posted by spyderg0d View Post
Also.. The stomp test is with the gas pedal. Not the brake.
That ^^^^^

The last year the stomp test worked in BMWs was 1995. Just for reference the stomp test goes like this:

Engine off, turn the key to the run position but not to start

press the gas pedal all the way to the floor 5 times in 5 seconds

the CEL will do one long flash, then a long pause, then one flash, followed by three more sets of flashes, then repeats. ALL OBD1 codes start with a 1. To read the next code you repeat the 5 in 5 presses after the last flash(es).

When you've read through all codes the CEL will make one long flash, then nothing. To clear all codes hold the pedal down after getting the long flash. Retest, and you should get 1-4-4-4, meaning no codes stored.
__________________
Quotes to live by:
guessing gets expensive...drivinfaster
nothing is more expensive than a cheap BMW...c4harpe13
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito) 7pilot
Ken Kanne, Silverhill, AL, Bimmerfest Site Moderator
BMW-CCA #441426

1993 325is M3 clone"Ashlyn"; 1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette";1995 318is"Bebe "; 1985 325e "Hazel Ann"


Last edited by hornhospital; 01-13-2020 at 04:32 PM.
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  #13  
Old 01-15-2020, 12:55 PM
BeeRich BeeRich is offline
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Uh, why would I lie? I'm an adult looking for answers.

I'll post an update in another post.

Quote:
Originally Posted by spyderg0d View Post
Obdll e36 do not have the stomp test available.
If your killing cats and not getting codes, then obviously either your lieing, or the sensors or ecu is faulty. Theres only 1 thing that kills cats beaides physical damage and thats extreme lean or extreme rich running conditions. When a proper mixture is burnt a converter can literally regenerate its lost composition from previous faults to a certain extent. To suggest anything else is at your fault, is suggesting magic amd complete ilogical and mechanical incompetence.
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  #14  
Old 01-15-2020, 01:00 PM
BeeRich BeeRich is offline
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OK, an update:

Cat replaced with what I'm thinking is a Magnaflow 51305. It was not burned out. It was rattling. Two in a row Walkers that were both labelled bad parts, by two different places. I did use the gas pedal. I'm still tired after having a 3-week cold, so I might have said brake. As for competence, I have three science degrees. I'm not a grease monkey, because I've chosen better things. That's why I'm in here asking. So your two suggestions how a cat can break, are both not what happened. It was a faulty part. Might want to read up on that one.
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  #15  
Old 01-16-2020, 08:59 AM
spyderg0d spyderg0d is offline
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Obviously buying faulty parts isn't your incompetance. Although there isan obvious difference between a converter going bad than from coming inoperable. Being said, getting a bad converter from the box is very rare as converters are mandated warranty by law within a large use limit.
Also, degrees in science mean nothing if you are not doing "science" things in which your degree applies. Likewise, we have all had a highly degreed doctor that fail at diagnosing a common cold, or a teacher that is unable to do anything but hand out packets.
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