16v Engine miss-fire / snatching on overrun

  1. #1
    Easiest way to do this is probably to list the symptoms I've got and go from there.

    • Engine miss-fire at idle when cold
    • Very easy to stall the engine when putting under load when cold, say reversing etc
    • Car pulls and drives absolutely fine under power
    • After a good drive when it's hot, the miss-fire returns at idle, slightly worsened
    • when coasting or maintaining a speed, say 30, it feels like the engine is snatching every now and again

    However, like I said, it pulls and drives fine, if you've got the throttle on, there's no hint of a miss-fire or anything, it really is spot on.

    The only modifications from standard are a cone filter the previous owner fitted, which I'm removing next week for a standard airbox, and the car has a powerflex lower gearbox mount fitted.

    I'm going along the usual lines of checking the throttle body out, I can't see any issues with the coil pack, it's just been serviced etc, however I also noticed the other day that after I'd left it for 2/3 days it cranked over more than normal before it started, as if it was low on compression.

    I bought the car knowing it had a top end rebuild last year after the timing belt snapped, there's a receipt for all the work including 2 valves. I guess what I'm thinking now is that from the symptoms I've got, its sounding to me like there's potential for piston / bore damage to the block on one cylinder resulting in lower compression? Easiest way to check will be to do a compression test, so I'll try and get hold of a tester, but it's not using any oil, and I'd have thought it would do if there was bore / piston damage?

    Argh etc? It drives fine, but the idle is starting to hack me off.

    Suggestions before I take the engine out and kick it a bit?
  2. #2
    Compression test 1st if thats okay then try another coil pack mate.
  3. #3
    Try all the usual idle related problems techniques.

    Sounds very similar to mine. I found bodged wiring to the map sensor, sorted that and it was fine. So maybe clean the map sensor?
  4. #4
    I have a spare coilpack, in the boot of the BM!
  5. #5
    Quote:
    Originally Posted by MuZiZZle View Post
    I have a spare coilpack, in the boot of the BM!
    Do you indeed mongflaps?

    I have an 18mm deep socket and a torque wrench for tightening your rear beam! Do you know if your spare coil pack works?
  6. #6
    Muz in "items stored in boot" shocker!

  7. #7
    Update to this, I haven't had a chance to compression test it yet, but I have just about sorted it.

    Last night I stripped the throttle body down (easiest thing in the world to remove?!) and removed all the sensors. It was fairly mucky with a good bit of carbon build up, so I cleaned everything up and re-assembled it, and it made no difference at all.

    After that I fitted Muz' spare coil pack, and it's totally transformed the car. I think I might fit an ICV valve and a new coolant temperature sensor anyway, as it occasionally still misses on idle, but it's a completely different animal to what it was. Even under load now it feels stronger, and I didn't think there was an issue with it under load.

    Happy chappy!
  8. #8
    Another update - it still wasn't a happy bunny, although it was far better, while trying to hold a constant speed, it was "snatching" still and hesitating. I removed the map sensor and cleaned it with a cotton bud and some WD40, and it's like a new car, idle is spot on, no miss-fire, it's brand new.

    Happy days.
  9. #9
    Quote:
    Originally Posted by D4MJT View Post
    Another update - it still wasn't a happy bunny, although it was far better, while trying to hold a constant speed, it was "snatching" still and hesitating. I removed the map sensor and cleaned it with a cotton bud and some WD40, and it's like a new car, idle is spot on, no miss-fire, it's brand new.

    Happy days.
  10. #10
    Quote:
    Originally Posted by MuZiZZle View Post
    Hahaa!


    But my car sounds and seems the same i'll give that a shot might sort it. apart from the fact its a 1.1 not a 1.6 16v lol