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Thread: Car running poorly

  1. #1
    Senior Member
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    Car running poorly

    Ok, I'm looking for freash ideas. First, let's talk about parts.

    New fuel pump and filter (tank and lines cleaned out)
    New fuel lines (every line under the hood replaced with braided stainless)
    New coil, plugs, wires, cap and rotor (timing is bang on)
    New air cleaner
    New battery

    All injectors spray (but I haven't done a balance test)
    I rebuilt the warmup regulator (don't assume I did it right)

    I previously had issue with power to the fuel pump. Ran a new power line. Today I ran a new ground line. Some people have suggested a plugged cat/muffler. I have confirmed the cat is clear and the muffler has been replaced with a short pipe.

    Symptoms

    Today I took it for a ride. Since I have been having trouble after warmup, I decided to unplug the WUR. Started right up. A little hunting for idle. (Not bad) I drove it around my yard for five minutes. It ran fine, even great. My yard is only 700 ft, so I can only get to second gear.

    Pulled out on the road. Drove about 2 miles to get to a good road. Drove fine, even great. Out on the paved road, Went through the gears to fifth gear and 65mph. Drove fine, even great. There was some cracking up when revs got above 5,000, but I assume you don't go there much. Cruised at 65 for about three miles and it started running rough.

    Turned around and cruised back to the dirt road in forth gear at 2500 rpm. Gradually it is losing power and missing. I went down the dirt road for about a mile and stopped and removed the gas cap. (Maybe drawing a vacuum?) Back in, no change. Stopped again and plugged in the WUR. Back in, no change. At this point, can't get out of second gear because of power.

    Get back to the house and check water temp (both gauge and handheld lazor temp show about 150 degrees.) It idles perfect with no hunting. I shut it off and dump five gallons in because it's down to quarter tank. Start it back up and drive it around the yard and it drives fine, even great. So the short time it took to dump some more fuel in cooled something down that it runs great? The water temp is still the same. I don't have that much hair to pull out.

    Ideas?

    I'm leaning towards the WUP not working right. The problem with that is why does it run good for a while? Doesn't seem like it could cool down on the hot valve cover in five minutes. This was the longest drive I've made so far. Is that because I unplugged the WUR? Do you suppose I should try to insulate the WUR? If I insulate it, I'm defeating the purpose of having it.

  2. #2
    Senior Member Bitsyncmaster's Avatar
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    When you unplug the WUR connector it takes a long time for it to go into normal mode. When cold your mixture is very rich.

    So it looks like your engine is running better with the rich mixture caused by the cold WUR.

    Sounds like your mixture is adjusted to lean. You can not adjust the mixture by tweaking it for best idle. That sets it wrong. You have to adjust the dwell of the working frequency valve to the book values if you want good performance cold to hot.
    Dave M vin 03572
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  3. #3
    Administrator Ron's Avatar
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    +1, Dave

    After that trip, I would think the engine should be up to temp and suspect that the thermostat is stuck open or missing. Even so, it would have been warm enough that the WUR/CPR should have been maxed out and make it run rich and probably not idle. BUT, when you plugged it back in and ran it a short while, it should of cleared up.
    I would check the thermostat and the WUR/CPR pressures as it warmed up after sitting all night, as discussed in the other thread. Then the CO last.

  4. #4
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    Quote Originally Posted by Bitsyncmaster View Post
    When you unplug the WUR connector it takes a long time for it to go into normal mode. When cold your mixture is very rich.

    So it looks like your engine is running better with the rich mixture caused by the cold WUR.

    Sounds like your mixture is adjusted to lean. You can not adjust the mixture by tweaking it for best idle. That sets it wrong. You have to adjust the dwell of the working frequency valve to the book values if you want good performance cold to hot.
    That's kind of what I'm thinking. I may unbolt the WUR and wrap it in a ball of bubble wrap. If the car will drive good for a long time, I think that would confirm it as the source. So far everytime I got the car to drive further, it was electrical. On today's drive I did two things. New ground on the fuel pump and unplug the WUR. I really should only do one thing at a time.

    Even if the WUR is the problem, it could be that it is raising the control pressure too high.

    Quote Originally Posted by Ron View Post
    +1, Dave

    After that trip, I would think the engine should be up to temp and suspect that the thermostat is stuck open or missing. Even so, it would have been warm enough that the WUR/CPR should have been maxed out and make it run rich and probably not idle. BUT, when you plugged it back in and ran it a short while, it should of cleared up.
    I would check the thermostat and the WUR/CPR pressures as it warmed up after sitting all night, as discussed in the other thread. Then the CO last.
    I think the WUR got warmth through the valve cover. So when I plugged it in, it was allready hot and nothing changed. The WUR gets hot and leans the engine. (I knew that's what you meant) That's why Dave is saying it is allready lean and gets leaner after warmup.

    I also thought the car should be warmer than that after that drive. Im not complaining about it though. (I live in FL)

    At this point, I don't trust my fuel pressure gauge. (China junk) So for the time being ill plod along without it.


    On a good note, I'm not disappointed in the power of the PRV when it's running good. Also, I had my first puplic encounter with a guy that flagged me down and asked if that was the BTTF car. Lol.

  5. #5
    Guru butcher Michael's Avatar
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    Until you can verify your mixture is properly set, you should not do anything else. You may just be wasting time and money. You should know that a dwell meter or at least a multi meter with dwell function is a very very wise investment.
    http://dmctalk.org/image.php?type=sigpic&userid=90&dateline=161808992  9

  6. #6
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    To properly adjust the mixture you must make sure everything else is perfect. The injectors must all have good patterns and spray evenly, the combustion chamber pressures should all be high and close, the valves all adjusted etc. All of the vacuum and advance systems, cold start, and warm-up systems working correctly. The throttle plates set, the idle system working, basically everything working as it should BEFORE you even think about touching that screw. No vacuum leaks too. That adjustment is so twitchy just a minor tweak has a big effect. Til you KNOW everything is perfect, it is probably best not to touch it. I would start by looking at all of the auxiliary systems that are affected by heat like the CPR and the vacuum advance. 1 leaky hose or one that fell off or isn't hooked up right can certainly kill performance. Even stale gas will have a noticeable effect. Another thing to look at is the electrical system If the voltage starts to drop the car will run badly. Verify the alternator is OK and the battery is good and all of the "big" connections are clean and shiny.
    David Teitelbaum

  7. #7
    '82 T3 FABombjoy's Avatar
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    You can adjust the WUR and CO by feel, by sensor, or by dyno (I've done all 3), but it really won't run optimally until the WUR is adjusted per workshop spec. Then adjust the CO. You can set CO by tweaking control pressure but transient fueling will be all goofy.

    Insulating the WUR won't do anything from a diagnostic perspective.

    How did you rebuild the WUR exactly?
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

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  8. #8
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    Quote Originally Posted by FABombjoy View Post
    You can adjust the WUR and CO by feel, by sensor, or by dyno (I've done all 3), but it really won't run optimally until the WUR is adjusted per workshop spec. Then adjust the CO. You can set CO by tweaking control pressure but transient fueling will be all goofy.

    Insulating the WUR won't do anything from a diagnostic perspective.

    How did you rebuild the WUR exactly?
    If I insulate the unplugged WUR and it drives good and then plug it in and it drives bad, I would say that narrows it down to a couple things.

    I just bought a rebuild kit. The instructions were in German, but it's pretty straight forward. The big issue is no way to test it after I was done.

    To all, I've adjusted points with a dwell meter, never fuel mixture. I guess I need to do some reading. It would seem to me that if the car runs good sometimes, it can't be far off.

  9. #9
    '82 T3 FABombjoy's Avatar
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    There is a pressure chart in the service manual. With a functioning gauge set you can verify/set WUR warm pressure via the hex screw under the cap on the bottom. Disable the vac enrichment system as indicated, and ensure the screw turns freely and isn't binding on the diaphragm. If it's all new parts this should be OK.

    Cold will be harder to verify, but provided that you didn't alter the topside adjustment will hopefully be OK. This might be harder to perform in Florida and you want to stick the WUR in the freezer overnight once you're ready to test & adjust. I set the bottom end range on mine years ago on a February Michigan day.
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

    Console5.com - Game console parts, kits, games and more. [shop] [wiki] [RSS] [f] [t]

  10. #10
    Guru butcher Michael's Avatar
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    Quote Originally Posted by David T View Post
    ....firm grasp on the obvious book
    Problem is if I understand right, he has already done the basics and he had already messed with the mixture screw and tried to set it at idle. I could have read an old post wrong but if he has already cranked on it, he needs to get it at least close before buying any more parts so he can get a handle on what the car is doing with a close mixture instead of one that may be miles off.
    Last edited by Michael; 04-20-2021 at 11:09 PM.
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