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Thread: Ungrateful Car - Acceleration Hesitation

  1. #1
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    Ungrateful Car - Acceleration Hesitation

    Having treated the car to a new front suspension (bad rear thrust arms and struts for sure), reservoir brake line and windshield washer pump last weekend, it rewarded me with a front end clunk (found that), the other brake line leaking (at the reservoir) and real issue... big hesitation accelerating from a stop. In fairness, I had noticed it recently but for some reason it got much worse on the post-suspension test ride. (I'm all tuned in for a suspension or brake issues and I get an engine issue, WTF.)

    1995 M60 (OBD1) 141K.
    These are all minor and haven't really affected driveability (or I've gotten use to them)

    • At a very low idle the CEL sometimes come on for a second or two but goes out, particularly if the idle goes up a bit (i.e. +50-100 RPM).
    • Sometimes on starting, hot or cold, I need to rev it a once or twice to get it running smoothly.
    • Once, started, it idles smoothly (in or out of gear).
    • Once at speed (street or highway speed) the engine/transmission are perfectly smooth.
    • Everything else "sounds and looks" normal, except
    • There is a faint fuel in the car when it has been closed up for a couple of hours. Use to be just when the tank was above say 3/4 full, now more common. (Next project.)


    The problem is getting rolling from a standing or near standing stop. The engine acts like it has a over-fueling problem, tries to rev but bogs then catches. It take a second or 3 but then seems to catch and do better, but not great. It ranges from very annoying to almost alarming.

    • Transmission seem to be working OK and it doesn't feel like it slipping although I guess it could be trying to start in high gear.
    • The engine feels like it has no power.
    • Maybe a vacuum leak? I sprayed started fluid around the front of the engine (didn't pull the plastic cover off though) but didn't get any change of RPMs.
    • Not sure how old the fuel filter is, but the car was well loved before I got it.


    Any thoughts on were to start looking? Thanks. Grady

  2. #2
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    Start simple, fuel filter

    if not, look at MAF or fuel pump.

    02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)

  3. #3
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    There's lots of 'could be's' in there! But it's worth saying that vacuum leaks don't cause acceleration issues unless they are massive - and then the car will not idle.

    First, make sure the transmission is actually changing gear by using the shifter to select the gears (2+Sport mode = 1st, 2+ E Mode = 2nd, 3, 4 and D to go through the gears. If changing gear with the shifter makes no difference then you are in TRAN FAIL-SAFE mode and stuck in 4th.

    But, lack of raw acceleration is usually one of two things - a tired MAF or failing catalytic converters. And the first thing I would try is a replacement MAF
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  4. #4
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    Thanks -
    We can cross off a vacuum leak, then.
    The transmission seems to manually shift up and down OK. And some years ago it went into transmission limp mode once and that was quite a different level of driveability - also no warning light.
    I'll order a filter and play with the MAF
    Grady

  5. #5
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    Not sure how this thread got split in two but thanks, filter ordered, MAF next.

  6. #6
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    Merged threads.

  7. #7
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    I played with the car today. It drove better and I'm eliminating the transmission for now. Fuel filter on order. Drives OK on the highway but doesn't have a whole lot of passing power, but does kick down, etc.

    I disconnected the MAF (electrically). The first time, I did it with car running, it almost died but caught, then when I tried to increase the RPMs in steps (1500, 2000, 2500) I couldn't hold an even value. Turned off the engine, plugged it back in and the car ran normally, easy to increase the RPMs.

    Then I found Timm's instructions and started with the car off (I only have a code reader/re-setter and I don't think it will clear the Adaptations). It started, idled lower but developed a notable miss when trying to hold higher RPMs. Turned off the engine, plugged it back in and the car ran normally but there was a strong smell of gas in the engine bay for a few seconds.

    I have a couple of MAF questions:
    1. If the car runs worse with the MAF disconnected, what does that say about the MAF?
    2. Can the car be test driven with the MAF disconnected (and based on the above, would I want to)?
    3. Any reason not to pull the actual sensor out and give it a good spray of MAF cleaner?


    Thanks. Grady

  8. #8
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    DME uses the MAF, and other sensors, to regulate air/fuel mix. That it almost died when you unplugged it tells me it's doing it's job. So unless it's an aftermarket (non Bosch), I'd say it's good. If DME is not getting a reading from the MAF, car would be in default mode and there would be no change when you unplugged it.

  9. #9
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    In addition to what the Mayor said, you can drive the car with the MAF disconnected but mixture will be way off and in some instances may quit on you. Pulling it and using a spray cleaner is a cheap first step.

    02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)

  10. #10
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    If pulling the MAF connector makes it run a lot worse - that indicates that the engine has a problem - and adaptations are keeping the engine running near to properly. Disconnecting the MAF means the DME has to use other sensors to keep the engine running - and those sensors cannot use the adaptations, hence the poor running.

    From this point you need INPA diagnostics, that will reveal where the problem is. I recently did an article on how to use INPA to find running problems, and a video - as you have the same engine as me you can compare your values against mine - and there you go!

    http://www.meeknet.co.uk/E38/Diagnostics.htm

    Have a look at the video at the end of the article, it shows the three most important pages. INPA is easy to use these days with a 1-click install, and cheap as muck!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  11. #11
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    INPA Update

    I got INPA 5.0.6 running on my WIN7 machine - sort of. It's buggy with lots of script errors and missing things like the smoothness (F6) screen/function. I guess I need to go back to a XP machine with a serial port and buy another 20 pin connector with an ADS adapter. (I'm a 1995 m60 OBD1 car).

    I was able to clear the engine codes and immediately got the same error messages for 201 (bank1) and 203 (bank2). Thanks to Google translate:
    201 Lambdaintegrator Bank 1
    Error frequency: 50
    Engine speed 560.00 1/min
    load signal 2.50 ms

    Short circuit to ground
    Exhaust-reluctant fault
    Error stored after debouncing
    Error currently present
    static error

    Would that be indicating oil in the spark plug wells? I've had to clean them out before but I may have developed a bigger oil leak, causing a mis, resulting in too rich a mixture going to the exhaust??? No CEL and, other than accelerating, the car runs smoothly (much better than when I first posted).

    This is the Analog 2 screen 65 degrees ambient, car warmed up, a/c off:
    Analog value 2a.PNG

    Thanks Timm for the diagnostic video!!! I would not have had a clue what to look for. Grady

    ETA: Of course the CEL light was on this morning and has stayed on.
    Last edited by Grady in Texas; 03-03-2018 at 10:18 AM.

  12. #12
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    Wow Timm! That is one heck of a illustration, great work.

  13. #13
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    Thanks Chris!

    Cor blimey - look at the additive adaptation values >128 - they are so positive they have popped off the end of the scale! That means that the mixture is way too lean before adaptations start doing their thing. The worst I've ever seen on my cars is +20 or so, and that was with a number of vacuum leaks.

    You could have a massive vacuum leak, and the only massive leak I can think of is when the vent pipe that runs between the OSV and PCV is not fitted correctly (the one shown where it says 'clear gasses....':



    I've re-assembled an M60 manifold in the past and failed to fit the vent pipe at the front end:



    ....and it failed to idle properly with the revs all over the place. I can't think of any other possibilities that would leak air in those quantities except perhaps the PCV itself may have a huge tear in it, but you would probably hear a sucking sound from the back of the engine.

    Of course, the MAF itself might just be absolutely miles out - can you borrow one to check? If you can you will need to delete the adaptations first - you can just disconnect the battery on the M60 - or go to the error memory page and press F7, that will clear them.

    But, unless the MAF is the problem you will have a massive vacuum leak somewhere.

    After re-reading your first post - this caught my eye:

    "The engine acts like it has a over-fueling problem, tries to rev but bogs then catches"

    That is classic 'Chinese MAF' behaviour - have you changed it recently? Or just a dead one....
    Last edited by Timm; 03-03-2018 at 12:36 PM.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  14. #14
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    I pulled the coil packs. The left side was sloshing in oil, all 4 plugs a wash. The right side was better but all 4 plugs were in oil. The leak must be on the lower side on the left side (closer to the exhaust manifold) as the ridge was holding oil. On the right side, the leak must be from above the coils as they were soaked in oil. No O rings fitted and no "pop" when removed. I didn't pull the plugs this time as I need to go back in and change gaskets and I didn't want to dump more hydrocarbons in to the cats.

    Car runs MUCH better cleaned up. Still has a miss and hesitation on low-end acceleration but nothing like before.

    ETA: I cleared the two error codes noted above and they didn't come back immediately (like before).

    Tim - The MAF came with the car and I've never touched it. I'll get to it next. I'll look for a vacuum leak but the idle is very steady and I don't 'hear' anything. I'll report back.
    Last edited by Grady in Texas; 03-03-2018 at 03:23 PM.

  15. #15
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    Update - I cleaned the MAF (it's a Bosch, at least 10 years old). The barrel was pretty oily. I also unplugged the battery and killed the adaptations while I cleaned the MAF. The first time I restarted it, the car did want to idle, rpms dropped unless I kept a foot on in it but then it settled out. Plugged it in to INPA and all the codes and adaptations were gone.

    I went for a 3 mile run. OMG - Very sooth, hesitation gone (or almost gone) and so much quicker. I guess the power has been slowly going away.

    But I noticed that if I took my foot off the gas and coasted, sometime the CEL would come on. (I can't run INPA live b/c the 20 pin connector is too tall to close the hood.) At the end of my run, I plugged it in again and:
    • Codes 201 and 203 were back.
    • There were 61 adaptations on both banks.
    • I noticed that the lambda voltage stayed between 86-91 at idle (engine hot); if I revved it, the voltage would drop to the bottom of the scale. This is a change from before when the voltage would drop at a hot idle.

    analog 2c.PNG
    I sprayed starter fluid all over (generously) and got no reaction.
    Last edited by Grady in Texas; 03-03-2018 at 04:44 PM.

  16. #16
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    The mixture at idle is much too rich now - the huge change from positive to negative adaptations after just cleaning the MAF makes me think that your MAF is a goner!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  17. #17
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    Just to (hopefully) wrap this up, Timm called it.

    Timm - many thanks - although you may have started me on the lost art of OBD1 engine computers - I'm firing up the XP laptop and have ordered a special cable/chip set.

    Changed the fuel filter as suggested (but since the old one had a 2011 manufacture date, s/o (me?) had changed it during my ownership) New filter helped a little maybe.

    Received my new Bosch MAF and that nailed it (so far, so good, anyway!). Engine seems to run like a locomotive (that's a good thing).

    Thanks all. Grady

  18. #18
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    Glad to hear it - the give-away is the 'doesn't run well on a warm start' - either a dead or Chinese MAF!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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