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m42 mysteriously low on power

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    m42 mysteriously low on power

    I just drove my car back on a 250 mile road trip. the car did great. I parked it and drove it earlier this week.

    Friday night I was going to drive it to Denver and as I hit the first uphill the car felt low on power. I went full throttle and it seemed to be struggling getting up to 60 mpg up the hill, usually no a problem.

    So this problem started out of nowhere. The car idles great and doesn't seem to have an issue until you are moving about about 20 mph when it is noticably slower. I noticed there was a bit of a hissing noise that i haven't heard before so I thought maybe there was a vacuum leak.

    Here is what i checked:

    -oil still clean, no milkshake texture at all
    - spark plugs look good, they have a few thousand miles on them but are like a light brown color, no issue there
    - I removed vacuum lines and one line to the ICv had a small crack. I wrapped electrical tape around as a temporary fix to see if that was issue

    I drove it around again and it was still low on power.

    - Stomp test, code 1221- 02 sensor. The sensor looks ok, but shouldn't cause this big of an issue, should it?
    - remove intake manifold to check other vacuum lines. I don't see any issues with the lines, fpr line was replaced last year.

    What could cause this out of the blue? Here are a few ideas I had, any input?

    - fuel filter (I haven't replaced it)
    - Fuel Pump (never had one fail before, but it buzzes when i turn on the key)
    - FPR - could this cause this issue?
    - Coolant temp sensor - I can't find this, i guess is under the lower intake manifold
    - oxygen sensor - I couldn't think this would have that big effect on the engine performance
    - spark/ ignition?

    maybe I will put it back together to see if I can get better symptoms
    318iS Track Rat :nice: www.drive4corners.com
    '86 325iX 3.1 Stroker Turbo '86 S38B36 325

    No one makes this car anymore. The government won't allow them, normal people won't buy them. So it's up to us: the freaks, the weirdos, the informed. To buy them, to appreciate them, and most importantly, to drive them.

    #2
    So I messed with it tonight and i may have fixed the issue.

    After removing the lower intake manifold, I realized my previous attempt at cleaning the mess under the intake did not remove the coolant line to the throttle body heater. so tonight I cut one of the hoses to fit to remove it. It turned out there was a tons of grease in that lower manifold so I cleaned it out with a few rags. I checked the vacuum and fuel lines under there and all looked good.

    So I put it back together and pulled out my spare fuel filter to swap. The lines into it have slight cracks so eventually those will need to be replaced. I pulled the old filter out and it drained clean looking fuel out both sides. I'm not sure if it was flowing through the filter or just on both side of the filter element. Either way I swapped it and went for a test run. At first it didnt feel right but after a few minutes of romping on it, its back to normal.

    Hopefully I have actually fixed the issue and it didn't just disappear temporarily. I'll drive it some more to find out. I'm still getting a 1221 stomp test code, but moral of the story: If you don't know when the fuel filter was changed, its probably best to do it before it fails on you.
    318iS Track Rat :nice: www.drive4corners.com
    '86 325iX 3.1 Stroker Turbo '86 S38B36 325

    No one makes this car anymore. The government won't allow them, normal people won't buy them. So it's up to us: the freaks, the weirdos, the informed. To buy them, to appreciate them, and most importantly, to drive them.

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      #3
      Any update on the issue?

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