I just bought myself a 1992 525i for $800, it was advertised as having bad compression when i bought it but my own test yeilded 220 (!) psi per cylinder. the figures were pretty close from cylinder to cylinder, so i doubt compression is an issue, but while driving if a little bit of throttle is applied the engine cuts out and runs very rough. The self-diagnostic fault code is 1221 which i beleive is an oxygen sensor. What do you guys think could cause this? Thanks for any input
E34 525 running rough
- Thread starter Cody318
- Start date
oxygen sensors, catalytic convertors, or a vacuum leak. As cheaply as you got in this vehicle, I'd give it new oxygen sensors and have someone do a smoke test under the hood looking for vacuum leaks. That would be a good idea anyway, and if the error code comes back up, it's probably time for a new cat. Do all that before changing plugs or oil, because it's probably running way too rich which will ruin new plugs and may dump some gas in your oil. Congrats on your steal. Keep us posted.
I just got a brand new oxygen sensor in, and replaced the air filter. I found that the intake bellows is shot, with a lot of cracks in it. I patched these up with tape for a quick test drive, and I had the same problem. I started to notice a backfiring "pop" under load which led me to beleive it was a coil. I switched coils over from another 525i and now it runs great. Just one of the coils is bad so I got very lucky in this sale. I appreciate the replies
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Okay, maybe I was a bit too optimistic here. After the first 30 miles or so, my problem seems to have come back slowly in a less severe form. Now it wants to cut out, once again, at low engine speeds with any "excessive" throttle, but if I am very, very easy and gentle on the gas pedal it drives smooth. A popping sound is still present under load at very low revs, but past 2,000 only roughness and hesitation. I found that the problem is worst when the engine is warming up, and is much subdued, but still noticeable, at operating temp. I've had suggestions that the timing chain has hopped a link, but I personally experienced the engine running smooth as an M50 should so doubt mechanical failure. I have tested so far the TPS, mass air sensor, power to coils and coil resistance, and replaced the oxygen sensor. I am awaiting shipment on a new intake boot, and if that doesn't solve my issues I could try testing fuel injectors, possibly running a good quality fuel system cleaning solution through, replacing all 6 coils with a high performance set (on sale from Bavarian Autosport). Is there a method for testing catalytic convertors? I hope to get this sorted out soon. Thanks again
