M52 b28 into an 87 325is. I smoke tested it thoroughly and there's no vacuum leaks even confirmed with a can of carb cleaner. Tried new plugs, coil packs to no avail. Swapped a spare TPS in to see if that would change anything but no go. I'm using a 413 red label ECU and I've even tried burning a tune where I bumped up the idle timing to see if that would make anything better but no go. I cleaned the icv a number of times and just ordered a new one just in case. Sometimes if I rev her she settles back to a steady idle however most times she surges. Fuel pressure is 48 PSI at idle which might be a little low but I wouldn't expect that to cause the surging. I'm at a loss and stuck please let me know if you have any ideas. Maf unplugged or plugged the surging persists. New o2 sensor and I placed it 6 inches after merging into my 3 inch exhaust which is about where the heat shield begins underneath. I can't even stomp test it because my check light is no longer working after the swap. Please help thank you in advance.
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Wild, I've had the same issue for years and also gave up. It's not that bad on mine, seems to only happen when it's hot, or like after I get off the freeway. I don't know what it is. Are you saying yours surges all the time at idle, no matter the temp? I'm running OBD2, so at least we can say it's not an ECU thing.
(I'm also running an M52 in an 87) -
Exactly. Only after she is warm she starts up with the surging. I was thinking maybe warm up enrichment compensating. I wish I installed my wideband when I was welding in the o2 bung. The new iacv comes in today I'll post back if that gets it but I don't think so.Comment
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