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Thread: weird, tricky intermittent problem

  1. #1
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    weird, tricky intermittent problem

    Ok I may have posted on this before but its still not resolved.

    It only happens with colder outside temperatures, and I think only if the van has been in the cold for a number of days w/out being driven (I don't drive it on a daily basis).

    Cold start with 40F or below outside temperatures and it starts and idles fine, and initially drives fine. But then sometime during warmup (2-10 minutes after starting to drive) the problem occurs, then goes away after warmup.

    The problem is losing power when letting out the clutch either starting from 1st gear or shifting between 1st and 2nd or 2nd and 3rd. It is as if I am trying to pull a very heavy load and have to give it 5X more gas than normal to keep it from stalling between gears. Still runs fine at idle at any rpm not under load, during this period. I think it also tries to stall out at a higher RPM than normal during driving in any particular gear (i.e need to keep it above 2500 RPM).

    I grounded the temperature sensor to help with hot soak restart, a year and a half ago, but I think I have had this problem for two winters going on three. I guess I could put this back to stock since I have since really fixed the hot soak problem with an aux. fan

    Initially I thought it might be some mechanical drag on the engine when its cold, such as a sticky pwr steering pulley or such (mine was making some noise but I loosened up the belt and its better). But since it doesn't happen until after having driven for a few minutes it seems more likely to be something with the way the engine is running at a certain point in warm up?

    Its due for a tune-up pretty soon, guess I should probably see if that helps.

    Any other ideas? Fuel pump? not getting enough gas?

  2. #2
    Administrator timsrv's Avatar
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    Re: weird, tricky intermittent problem

    Have you checked trouble codes yet?

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    Re: weird, tricky intermittent problem

    Quote Originally Posted by timsrv View Post
    Have you checked trouble codes yet?
    heh, guess I should figure out how to do that

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    Administrator llamavan's Avatar
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    Re: weird, tricky intermittent problem

    Quote Originally Posted by ARP View Post
    heh, guess I should figure out how to do that
    From our Library:

    Finding and using the Engine Service Connector to access diagnostic codes; troubleshooting the ESC circuit

    and ...

    Diagnostic Codes for Toyota Vanwagons, all years

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: weird, tricky intermittent problem

    Thanks Gwen, that write-up implies that you should do the diagnosis with the engine running, but my 1987 repair manual says to do it with the ignition on but engine off.

    Also my check engine light is not on, can you have a code even w/out the light on?

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    Administrator llamavan's Avatar
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    Re: weird, tricky intermittent problem

    No, the engine should not be running; ignition should be on, just as you say. Let me know exactly what part was misleading and I'll fix it!

    Yes, you can have stored codes even if the CEL is not on. In fact, the only times I've ever seen the CEL come on during operation ware as a result of flaky O2 sensors (and with one van, it would not stay on long taking my foot off the accelerator would make it go out like clockwork). But I've gotten a number of other codes without having ever seen the CEL illuminate.

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: weird, tricky intermittent problem

    In the first link talking about finding the connector-

    If nothing happens when you jump those wires (no check engine light and no change in idle), and the connector is in good shape, then this indicates a problem with the ECU or the Check Engine circuit somewhere in the harness.

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    Administrator timsrv's Avatar
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    Re: weird, tricky intermittent problem

    I believe that article was my response to somebody's question and was originally posted in the forum (I think regarding a TPS problem). I'm not sure how it made it into a stand alone article, but in this format, and linked to the CEL codes, it's slightly out of context and a bit confusing. The pictures are useful but I should change the text. I will try to make the time to re-write it in the near future. Sorry for any confusion. Tim

    As Gwen said (and the FSM) the engine should be off but the key in the "run" position while checking codes. Tim

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    Re: weird, tricky intermittent problem

    It just shows code 1, a single blink every 4 seconds, so that's no help-

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    Re: weird, tricky intermittent problem

    Well, like you said, intermittent problems can be weird and tricky. Since it seems to be triggered by lower temps, I would turn my focus away from the fuel system and look closer at the electronics. The usual suspects are the ignition coil (inside the distributor), the igniter, and the ECU. There's also a chance the MAF sensor could be sticking. Since I'm lucky enough to have lots of spare parts around, if it were me, I'd probably troubleshoot by swapping things out. I'd probably do the igniter or the MAF 1st because they are easy. If swapping this stuff didn't help I'd then swap the distributor, reset the timing, and I think 90 times out of 100 that would solve the problem. If none of that worked I'd then swap the ECU.

    Of course I don't expect you have these kind of spares just laying around or you'd probably already have done that. I wish I could be more help but that's all I got. Maybe NEC or one of the other members will have some other ideas to help narrow things down. Tim

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    Re: weird, tricky intermittent problem

    Thanks for the ideas Tim, glad to see I'm not the only one stumped by this one. Really not that big a deal as far as I'm concerned, but if my wife happens to want to drive it on a snowy winter morning then it becomes one. I suppose one possible solution is to let it warm up for 10-15 minutes before taking off.

    I happen to have a spare igniter pulled from a junkyard dog, it was crudely wired into the vehicle by an amateur (even more so than me) since the wire was cut and shielding was twisted together as if it needed to carry a current also, then very poorly taped. Thus I doubt that it was a new replacement part. Needless to say I have a low level of confidence in it, but maybe I'll give it a try.

    Al

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    Re: weird, tricky intermittent problem

    I have had this problem happen occassionally on my 2WD automatic LE, however, I think it is NOT something electronic although a bad O2 sensor might be another thing I have not checked out thoroughly. I once had this happen on an old Plymouth with the slant 6 engine. That turned out to be a problem with the torque converter and trans fluid. This summer I had a new trans filter put in and cleaned out the accumulated crud inside the trans and now waiting to see if that problem shows up again as the weather here gets colder. I know you have a 4WD so I admit I am out of my league there, but I would check the trans fluid for clues. I did replace my fuel filter in case that was clogged. It did not fix the problem, but I could swear the van is peppier after getting a new fuel filter.

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    Re: weird, tricky intermittent problem

    hi arp you mentioned that this problem raises its head as the season gets colder and it made me think of my first van that had a simular but different problem that would show when it got cold too. there wasnt any van sites to go n check out back then and i had to pay a shop to do this repair. here is my 2 cents worth alot of the motor opperation is run by water temp and if you have a temp sensor that is bad or not working properly it will make it run silly. on the front top near the water fill is a water temp sensor i believe that is the offender. i think if you find more info on its location. it was a long time ago and i dont recall how much it cost( i dont think it was alot). i,m sure you,ll find out the problem and be back on your way. persistance and tenacity will do it for ya. best of luck to ya .! as i said its just my 2 cents worth

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    Re: weird, tricky intermittent problem

    Thanks for the comments. I changed out the O2 sensor about a year ago, and its a manual transmission, changed the transmission oil about two years ago. And yes temperature sensor, I mentioned in the first post that I had grounded it to try to address another problem (hot soak restart) that has since been fixed much better, so yes I need to put that back the way it was! Will take all of ten minutes, just need to do it. Its on my list along with the eight other things I need to do to the van.

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