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Thread: No Power

  1. #1
    Join Date
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    Default No Power

    Advice sought from all.

    US 49 Noble M12R GTO, original owner. Original build was by Gregg Robb and since, it has spent time with Hoover. The car has ECU tuned by Hoover, Turbohoses Hard Pipes and BOV with Turbohoses exhaust. It has around 30K miles, around 10K miles on engine 2 as first engine developed piston slap and was replaced. It has been used as a good weather daily driver and HPDE track car. At the track, it was running great, typical Noble when it started to develop a miss and then black flagged for fluids. Pulled over and opened up the clamshell and fluids turned out to be antifreeze. Car was allowed to cool off and put back into the hauler. Turned out there was a small hole in the hose between the engine and radiator where a cable was rubbing (Drop the bottom pan and make sure the hoses are aligned appropriately) and the loss of fluid caused overheat and the fluids were antifreeze.

    The hose was replaced and everything seemed fine. Oil was changed and no evidence of antifreeze in the oil. Car runs fine in 1 and 2 but as soons as a load is put on the car, 3rd gear, the engine starts to sputter and miss with no power around 3000 RPM. There is no boost in 3rd gear and boost in first 2 gears is low although the car feels strong. When the engine is cold, you can get it up to 70 mph on the highway in 6th gear as long as you don't come on boost and stay below 3000 RPM but as the engine gets warmer, it starts to sputter.

    1 Fuel pressure was falling at higher RPM. Fuel pump was replaced and filters were changed (Pump is no longer so loud). Coarse filter between tank and pump with fine filter between pump and engine. Apparently the Bosch 044 pump doesn't like to suck but blows against pressure well
    2 Injectors pulled and sent to RC Engineering, 2 injectors were clogged with poor spray patterns
    3 Igniters were replaced with Accel injectors
    4 Exhaust was pulled to make sure there was no obstruction, all of the packing in the catalytic converters was gone so no obstruction
    5. ECU was checked, no codes and the adaptive maps were reset using Version 1.3 of the diagnostic software
    6. Compression and leak down performed with cold engine - Normal
    7. No vacuum leaks

    Results: Car idles smoothly, no intermittent miss as was present in the past. Still no power. What to do? ? Warped head or valve issue which can't handle boost / load and gets worse as the engine warms up? Any ideas about potential issue would be appreciated.

    Options: 1 Get the current engine fixed
    2 Replace the engine with another AER engine
    3 Replace the engine with a long block built motor
    4 K24 Swap
    5 V8 Swap
    6 Sell the car as a rolling chassis? Value?

    Open to all of the above and would appreciate input. Obviously trying to contain costs.

  2. #2
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    Jan 2016
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    Find out what is causing the loss of power. If you don't have a leakdown problem I highly doubt it is a valve sealing issue. If the car is not building boost correctly the first thing I would check is for boost hose leaks. Check the turbos for free rotation and play. If you take the output hose off of the rear turbo can you feel the turbo blowing a small amount of air at idle? Is the wastegate hose hooked up properly and not leaking? I don't think this sounds like a catastrophic problem to me.
    --Calvin

  3. #3
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    No boost hose issues. Exhaust removed and the turbos move freely. Front turbo was loose but no change. Wastegate hose was fine. Boost builds fine in first 2 gears when there is minimal load on the car and the engine is cold. Gets worse as the engine warms up. Similar report by others but no outcome reported except by someone who reset the adaptive maps.

  4. #4
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    A few quick thoughts:
    - Regarding boost, what does "fine" mean? What kind of boost were you running? Are you seeing that exact same amount of boost now? I often notice that when a new problem pops up, people become hyper-focused on monitoring that problem, when in the past they usually neglected it entirely, meaning you might have a skewed perspective...What are your boost numbers in 1 and 2? And what are they in 3? When are you hitting full boost? And what does easimap say that your target boost levels should be at WOT?
    - Ive experienced all kinds of strange issues on turbocharged cars with spark plugs that were off. Might replace the spark plugs with factory suggested plugs and make sure they are gapped properly for your boost levels.
    - Other items I can think of that would cause problems with increased load, how long ago did you replace your clutch? May it doesnt have a good contact surface anymore.

    Im with Calvin, this does not seem catastrophic to me...

  5. #5
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    Check electrical connections... sometimes the heat will cause them to expand just enough to create enough resistance for the connector to not function properly.

  6. #6
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    Replace your spark plugs? I had similar issues, was the spark plugs.

  7. #7
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    Quote Originally Posted by Driven View Post
    Check electrical connections... sometimes the heat will cause them to expand just enough to create enough resistance for the connector to not function properly.

    Agreed above.

    Previously after part of track day, blew hose. Car idle and drive fine without any load. As soon as try to boost nothing and stutter.

    Check all hoses, vacuum, waste gate, vacuum, boost controller, spark plug gaps, change spark plugs, etc. End up connector to crank sensor was loose! Replaced the connector completely. A while later, drove whole day at another track and the car was fantastic. Temperature didn't change much at all and great boost.

    Good luck.

  8. #8
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    I'm tracking my car as well and one of the issues that cropped up was a burnt waste gate actuator due to the extra heat from the exhausts. It was only discovered by the vacuum smoke test.
    I also popped out one of the vacuum line elbows connecting directly to the intake plenum. All I had to do is to pop it back on and I was ready to be chased by Miatas for the rest of the day!

  9. #9
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    Put a hand vacuum pump on the waste gate line, should open around 13 inches, also make sure the are closed completely​ after vacuum is removed

  10. #10
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    Sounds similar to a problem I had that was a faulty ignition coil.
    Over 3000lbs=boring. 0-60 over 4 seconds=boring. Under 1g=boring. Noble, not boring.

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