Rough idle when hot

[rob101]

hello everyone,

Firstly i'd like to say that i have searched but i can't find the exact symptoms the car has, I have a rough idle after the car warms up, however the needle on the tacho is dead steady so there is no surging or the like. I suspect it could be the oxygen sensor because the exhaust smells like its rich. also there seems to be a slight ping or valvetrain noise (only noticeable when the windows are down and am travelling near a wall or such) when cruising, and oh yeah i have a 2/92 525i with the m50 non-vanos. also what does an m50 sound like above 4000 rpm cos mine certainly doesn't sound like an m30 does...

Thanks in advance, this board rocks

[permit]

Probably your O2 sensor, but your check engine light would go on if it were blown. The O2 sensor only goes into effect when the engine is warmed up, so it makes sense.

As for the pinging and such, I'd say its normal and just the sounds of everything moving.

M30 will sound much deeper than an M50 when revving because of the liter difference in displacement. M50 should sound more "race-like" though, tough to explain, just sounds happier.

[rob101]

thanks, Australian E34's don't have a check engine light as far as i know... i will have to buy one of those peake tools

[Jose]

Damm Mr.Permit!!!! That's one f...ing nice white E30 you got in the sig. picture. Is it yours ? What two piece wheels are those ?

[permit]

Why thank you.

Believe it or not, they're American Racing 2-piece. M52 engine and Ground Control suspension.

[632 Regal]

Jeremy, reboot the computer and see if that smoothes things out.

[permit]

Jeremy, reboot the computer and see if that smoothes things out.

I'm not the one with the problem at hand...

[rob101]

yeah i took it in for a major service lately which included resetting the computer, the problem was still around afterwards its strange they didn't mention anything about it in the inspection, as they did pick up a few other things i wasn't aware of

[rob101]

anyway so is it likely that my idle problem could be caused by the oxygen sensor? i will have to test it but it is an annoying job when you don't have a H-lift so i don't want to do it if there is a more likey reason, it also seems to burble on the overrun which would suggest it is rich wouldn't it?

[permit]

Well, a messed up oxygen sensor would distort the amount of air that is getting into the chambers, and so would the AFM (MAF, HFM, whatever). I would go with the O2 sensor first since its only a $30 part.

OT: I'm trying to stay on topic, but you can go here and comment/PM anything you'd like. http://www.cardomain.com/ride/2201333