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Discussion Starter #1
Drove 300 miles to NJMP on Fri. Sat, I ran a session and after appox 15 minutes it began to stumble. I came in with motor shutting down several times. Now the car will run poorly for a while but once it's hot the stumbling and backfiring comes back. I've tried cleaning connectors and at first that seemed to modify, but not fix the behavior. When I do get it running the idle hunts around a lot and tach needle fluctuates, more than the actual rpm changes I think.

TVS blower on GReddy manifold
EFI 1.2
2bular header
Nearly new injectors

Any ideas? Any chance iI can fix this on the road?
Must get to work (200 miles) by 5pm tomorrow. I'm probably going to see if Princeton Lotus can pick it up tomorrow, but if I can get a semi-fix on it and limp up to Princeton, all the better.

Your advice appreciated.
 

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Throwing any codes? Any dash lights flickering? Mine did a similar thing when the alternator was going out. It would intermittently die, stumble, etc. but I was also getting CEL, ABS, tach/dash weirdness. Check your alternator output. Should be about 14.1 volts I believe.

What connectors did you clean that seemed to help? That might help someone else trouble-shoot it.
 

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Discussion Starter #3
No codes at all.
With the EFI system, the stock ECU is only driving the throttle body and gauges.

I'll try checking voltage.

Forgot to mention, the laptop I use to monitor the EFI crapped out on the trip down. Oy.

Been fiddling with connectors:
Throttle body
Cam position
MAP
MAF
VVT
 

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Have you checked all the engine bay fuses? Most specifically R6 (7.5 amp) this powers VVT,evap solenoid and cam phasing as well as the ignition signal to the alternator to charge, it also provides reference voltage to the IAC which will screw up your idle.
Just had similar fail on a TVS charged car,...the two wire harness (wrapped in factory friction tape) that crosses over to the evap canister had rubbed through on the snout of the SC and shorted taking out this circuit and causing the running issues you described.

Long shot but worth checking... Good Luck!
 

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Does the EFI use the stock cam position sensor, or does it have it's own crank trigger? If it does, I'd check that ( along with the other sensors you've already checked). Also check the battery and ground connectors, and reseat the EFI connectors. The way you describe it, my first guess would be that it's an electrical/sensor issue. Can you easily swap back to the stock ECU, and see if it idles and cruises OK? Maybe you could limp home that way.

Good luck,


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Drove 300 miles to NJMP on Fri. Sat, I ran a session and after appox 15 minutes it began to stumble. I came in with motor shutting down several times. Now the car will run poorly for a while but once it's hot the stumbling and backfiring comes back. I've tried cleaning connectors and at first that seemed to modify, but not fix the behavior. When I do get it running the idle hunts around a lot and tach needle fluctuates, more than the actual rpm changes I think.

TVS blower on GReddy manifold
EFI 1.2
2bular header
Nearly new injectors

Any ideas? Any chance iI can fix this on the road?
Must get to work (200 miles) by 5pm tomorrow. I'm probably going to see if Princeton Lotus can pick it up tomorrow, but if I can get a semi-fix on it and limp up to Princeton, all the better.

Your advice appreciated.
I was there yesterday!. Were you on Lightning? I know a local Race car mechanic by NJMP that works on my car sometimes. PM me if you want me to get him call you.

I will PM you his number...
 

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Discussion Starter #7
Mike, Austin, RBH, thanks for the input.
I'd need to put in stock injectors to switch to stock ECU control. Don't have any on hand.
Engine bay fuses were all ok.
I'll look for abraded wires in the morning.
 

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Discussion Starter #9
The mechanic recommended by RBH came to the car this morning. We fooled around with it some and came up with a working theory that it's the crank sensor or associated wiring/connector. He loaded up the car and my little tire trailer and gave me a lift to a car rental agency. A very hectic day but I made it to work on time. I'll update in a few days.
 

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Sorry for your bad experience.

It's clear to all here, probs especially you, but this shows how risky it is to drive off to track in a car with a modded engine.
And I promise, your lap time goes down two seconds knowing that you have a trailer :)

I know, everyone can't do that especially when we are just beginning to dabble with it.
 

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Discussion Starter #11 (Edited)
Loong day yesterday, but Quicksilver and I are back home. (Redeye flight, 4:30 am arrival, car rental, 2 hour drive to shop, settle up, lunch, 7 hour drive home in heavy traffic and no a/c).

It was the crank sensor, as Austin had guessed. I was thinking that was a possibility from the get-go, but not able to test in the paddock environment. Maybe Bob is right, and I should have recognized the increased monetary/logistical risk of going to a distant track without all the proper tools - such as a laptop to look at EFI data. I think I would have settled on the problem quickly if I had taken the time to buy or borrow another laptop.

Of course, I still would have had to wait for the part and to find a shop to do the work while I was away at work; no difference there.

I wanted to say, thanks to RBH, I found a great one. (Forum to the rescue!) TJ and Ian at TKAutosport were very on the ball, and bent over backwards to get me out of a jam and on my way. They even washed my filthy car! I was pretty surprised by the bill... it was only about 60% of what I was rough guessing. Great service, very reasonable rates. They manage many high end exotics and race cars.

So if you are in the Millville/Vineland, NJ area, it's TKAutosport. Highly recommended.
 

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Loong day yesterday, but Quicksilver and I are back home. (Redeye flight, 4:30 am arrival, car rental, 2 hour drive to shop, settle up, lunch, 7 hour drive home in heavy traffic and no a/c).

It was the crank sensor, as Austin had guessed. I was thinking that was a possibility from the get-go, but not able to test in the paddock environment. Maybe Bob is right, and I should have recognized the increased monetary/logistical risk of going to a distant track without all the proper tools - such as a laptop to look at EFI data. I think I would have settled on the problem quickly if I had taken the time to buy or borrow another laptop.

Of course, I still would have had to wait for the part and to find a shop to do the work while I was away at work; no difference there.

I wanted to say, thanks to RBH, I found a great one. TJ and Ian at TKAutosport were very on the ball, and bent over backwards to get me out of a jam and on my way. They even washed my filthy car! I was pretty surprised by the bill... it was only about 60% of what I was rough guessing. Great service, very reasonable rates. They manage many high end exotics and race cars.

So if you are in the Millville/Vineland, NJ area, it's TKAutosport. Highly recommended.
From the pics RBH posted, I would go by that place even if I did not need work on my car, just to check out the cars.:crazyeyes
 

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Interesting read. I agree about trailer on Heavily modded (esp engine) cars. They seem to be 90% of cars that fail at track in all honesty. Thus reason I stick with the level 1 mods--> CAI Exhaust and tune.

Glad I still remember my Elise symptoms as Crank sensor and intake tube were at top of my list. My car dropped its intake off edge (on bottom of course) of manifold years back and damn near wouldn't run at all.

Good to know a guy is in the area to help us!
 
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