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My 308GTS Nightmare

Discussion in '308/328' started by Archer911, May 13, 2018.

  1. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Two Time F1 World Champ
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    May 4, 2001
    27,377
    Birmingham, AL
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    Tommy
    Back in about 2006 I decided I wanted to "do it right" so we went through everything, hoses, new caps, rotors, plug extenders, plugs, wires, careful CO adjustments - everything.

    And it would still surge with the new O2 sensor. I hated it, it was like I was VERY slightly tapping the brake pedal as I drove. I stopped on the side of the road on the way to work one morning and unplugged it. I made it about a week. Back to smooth as silk again instantly and still is 12 years later.

    Interestingly it was disconnected when I bought it. Everyone told me to just leave it unplugged, even mechanics that charge to "fix" it said don't bother.
     
  2. spicedriver

    spicedriver Formula 3

    Feb 1, 2011
    1,235
    A dozen cars with no problems ? I guess you have the magic touch !
     
  3. Archer911

    Archer911 Formula Junior
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    Sep 26, 2016
    859
    New England
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    Tim
    Where to begin?

    I spent the afternoon in the garage and my back is killing me. The wiring harness that lays across the engine that goes to the throttle position switch, warm up regulator, cold start valve, AC compressor, oil pressure sender (I think), time thermal switch, and a sensor I have yet to identify, has always bothered me. The AMP connector boots are ripped on those components that have them, and the 9 pin connector next to the oil cooler stinks of resistance issues. So I replaced all AMP connectors, cleaned contacts (again) and got a better feel for the car. I also replaced the Cold Start Valve which I suspect was leaking (the old O ring was shot and the gasket was ugly. I checked continuity on all 9 pins to the destination contacts and all was well.

    But there was one surprise. One holy **** moment. The braided hose #11 (I replaced last year) that connects between the cut off valve #1 and the air cleaner intake (this is in the Air Injection System diagram) was disconnected. So this to me means that the cut off valve has a supply of air without the restriction of the air cleaner. Maybe this won't make a difference but maybe it will. I'll put everything back together tomorrow and give it a test.

    One way or another I will stay the course and get a rebuilt WUR installed and replace the injectors.

    NOTE. The car worked fine the first two times I drove it this year. It even passed the state inspection. Then it went to ****. In my mind it was an event like a component failure or the aforementioned hose coming undone. Wondering how you guys read this. I know, more info coming...

    So thankful that there is a forum like this or I would have given up a year ago and sold the dream car.



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  4. johnk...

    johnk... F1 Veteran
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    Jun 11, 2004
    6,114
    Yes, I have incredible luck with cars since I graduated from college (1969). Before that, the $75 junkers I was driving, not so, much. God, you could actually by a car for $75 in 1964.
     
  5. spicedriver

    spicedriver Formula 3

    Feb 1, 2011
    1,235
    More importantly, it means the engine has a supply of air which is not going past the air vane in the FD. I.E. vacuum leak. Big one.

    This would explain the buzzing FV, backfiring, and loss of power. All symptoms of a lean mixture. Perhaps you should not ship that WUR out just yet.
     
  6. Archer911

    Archer911 Formula Junior
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    Sep 26, 2016
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    Tim
    I hope you are right (but shouldn't the FV always buzz?). But pipe 11 on diagram 9 is not a vacuum line, is it? I read it as open to atmosphere albeit restricted by the air filter. Pipe 14 would be under vacuum, or am I missing something?
    The number on my WUR indicates it's apparently the wrong model for my car. I found a correct rebuilt one today and I'll have it on Thursday. In the meantime, tomorrow after I put everything back together and triple check everything I will fire it up. Fingers crossed.
    Thanks
     
  7. thorn

    thorn Formula 3
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    Aug 7, 2012
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    Tallahassee, FL
    I have a Euro 308, which has several differences from yours - but, unmetered air can do things that lead to other undesired things. I wouldn't be surprised if you hook that line back up and find a few problems disappear.
     
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  8. Brian A

    Brian A Formula 3

    Dec 21, 2012
    1,731
    SanFrancisco BayArea
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    1983 US 308 GTS QV
    It looks to me like you are referring to part 10 on Tav 17 (Blow-by System) which is the hose that returns vapors from the "oil vapour separator" (Part #1 on Tav 17) to the air inlet (part #23 on Tav 13).

    Although the connection point for this hose on the air inlet is after the air filter, it is before the CIS unit. Other than sucking some unfiltered air into the CIS Unit, I speculate that there is no consequence to engine performance.
     
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  9. GordonC

    GordonC F1 Rookie
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    Aug 28, 2005
    3,418
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    Would you mind sharing the name of the vendor who you're getting the rebuilt WUR from?

    Thanks,
    Gordon
     
  10. johnk...

    johnk... F1 Veteran
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    Jun 11, 2004
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  11. Archer911

    Archer911 Formula Junior
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    Tim
    Post # 30

    CIS FlowTech can rebuild the 132 WUR to 083 specs. So my WUR will be rebuilt properly.
    The cost for rebuild would be $325 plus $25 for shipping and handling and take 3-5 weeks.
    Nice people to talk to and highly recommended by several here.
     
  12. johnk...

    johnk... F1 Veteran
    Silver Subscribed Owner

    Jun 11, 2004
    6,114
    Tim, when you get this all back together, assuming the problem is resolved, I would suggest that you disconnect that hose and see how the car runs so you can verify whether it was the problem or not.
     
  13. kcabpilot

    kcabpilot Formula Junior

    Apr 17, 2014
    540
    California SF area
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    Paul
    I think the only real consequence of that is that you have a source of unfiltered air to the engine. This would not cause an unmetered air leak as it is upstream of the fuel distributor and metering sensor.
     
  14. Archer911

    Archer911 Formula Junior
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    Sep 26, 2016
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    Connecting that pipe back made a BIG difference. If you look in the air cleaner housing there is a built in restriction (in addition to the resistance of the pipe itself and the air filter. I think that is significant. So now the engine runs "reliably" —in that I mean it doesn't sound like it's going to stall, the idle is steady, and starts instantly. I had a similar problem with a Honda generator. The air intake is in the battery compartment which has a gasketed access door. If you leave the door off the generator runs POORLY.

    Now, I still have a problem with getting the right mixture numbers. Upon restart, after several days of sitting, the AFR read 11.2. So I turned the mixture adjusting screw CCW approx 5 degrees. The AFR fluctuated between 14.7 (good) and 16 (too lean). I backed the mixture adjusting screw CW a couple of degrees and the AFR read higher 14.8-16.5. It should have gone lower (richer). At that point I decided to call it quits for the day.

    Tomorrow I will install a rebuilt WUR. I hope it's the WUR and not the FD that needs rebuilding.
    I also need to research the importance of the "Air Bypass Screw" in this equation.
     
  15. thorn

    thorn Formula 3
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    Aug 7, 2012
    1,359
    Tallahassee, FL
    The bypass screw (big nut right beneath the plenum intake) is pretty key is getting a good idle - definitely do your research on that.

    Glad to hear about the hose reconnection success. :)
     
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  16. spicedriver

    spicedriver Formula 3

    Feb 1, 2011
    1,235
    In the older carbed systems you would adjust the actual position of the throttle plate in order to change the idle speed. In this system, the throttle plate remains closed, and the "air bypass screw" allows additional air/fuel around the the throttle plate, increasing the idle speed. It's an idle speed adjustment.

    Make sure the engine is completely warmed up before you check/adjust the air/fuel mixture. Also, if you're tuning for best power (12.9), it's better to delete the cat.
     
  17. Archer911

    Archer911 Formula Junior
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    My Cat is gone. So is 12.9 the target for warm Idle?
    I'm concerned about allowing the engine to run on a lean mixture until it reaches normal operating temp.
    My 87 911, with electronic fuel injection, is at 14.8 on cold start. Shouldn't the 308 behave like that too? Or are we comparing apples to oranges here?
    Also, does the "air bypass screw" change the AFR?

    Thanks
     
  18. spicedriver

    spicedriver Formula 3

    Feb 1, 2011
    1,235
    Air bypass screw does not affect mixture, but the frequency valve does. I would disconnect the connector to the frequency valve. Check the mixture at different RPMs. But most important is when the engine is fully warmed up. These cars are adjusted lean at the factory to around 16-1 for low emissions. Also, make sure the mixture plug hole is capped, or that will affect the mixture.

    Sometimes you can get a vacuum leak when the engine is cold, but it goes away when the engine is warmed up. I've seen this with the boot that goes from the FD to the throttle body. Make sure that is tight, and not leaking air.
     
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  19. Archer911

    Archer911 Formula Junior
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    Thanks...back at it on the morn.
     
  20. thorn

    thorn Formula 3
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    Aug 7, 2012
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    Tallahassee, FL
    Tim, has your throttle cable stop screw (I can't recall the official name) been messed with? I'm referring to the small, perhaps capped, vertical screw that adjusts the stop-point of the throttle cable.
     
  21. Archer911

    Archer911 Formula Junior
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    Oh yeah. The monkeys, including me, have messed with that. Now, however, I believe it is in the right place and the TPS is engaging properly.
     
  22. thorn

    thorn Formula 3
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    Aug 7, 2012
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    Sending you a pm.
     
  23. Archer911

    Archer911 Formula Junior
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    Sep 26, 2016
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    The rebuilt WUR went in without a hitch. The old one (wrong part #) had a little crud on the intake screen, maybe 1 percent restriction.
    The car started fine and parked at about 1100rpm, then ran a little rough with the AFR fluctuating between lean and rich but behaving a little better than with the old WUR and hovering around 14.7 for a short time. As the car started to warm, 10 minutes, the idle dropped to 900rpm, sputtered a bit then backfired. I shut down, gave it a rest, and started again. After a few minutes and more sputtering at 900rpm and lower it backfired again and died.

    So the engine got warm after running 10 minutes but not warm enough to run the fan. Ambient was 62 deg.

    If I knew what cold start idle rpm at 62 deg should be that would be my target to set with the air adjusting screw. I believe the drop in rpm was due to increased operating temperature and a responding sensor(s).

    From what I have read in the service manual proper idle needs to be set BEFORE the mixture can be adjusted. I haven't yet achieved that goal.

    At this point I wish there were a Bentley manual for the 308 that showed how to balance this system out—assuming I don't have any other component failures like the ECU, temp sensors, bad fuel distributor, etc., maybe it's just the turn of a few screws? The puzzle continues.

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  24. kiwiokie

    kiwiokie Formula Junior

    Aug 19, 2013
    532
    Tulsa, OK
    Have you read the CIS primer? The term Warm Up Regulator is a misnomer as this component continues to influence mixture even after warm up is complete. It provides the back pressure against the plunger in the fuel distributor which affects fuel delivery across all operating temperatures and throttle positions. The circular insert with the inlet and outlets is an interference fit in the housing. Moving it in and out affects the control pressure. I dont think this can be set accurately when rebuilt without adjusting it on your car.
     
  25. Archer911

    Archer911 Formula Junior
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    Sep 26, 2016
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    To kiwiokie:

    I haven't seen any posts where people have made an adjustment to the WUR after replacing it. My assumption was that if this is the right model for the car there was nothing left to do except install it. I'll check again. Thanks
     

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