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Old 05-10-2007, 03:21 PM   #1
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Default Timing problem?

Car is running again. Yay! And it idles decently and fueling is tuned, BUT I have a weird hesitation above 10-12psi where the rpm drops then rises rapidly and the car stutters. Car runs absolutely fine during off boost and up to about 8-9psi of boost. Unfortunately, I can't upload a datalog from work, but here's what I do know:

1) Double checked timing w/ timing light and all is well
2) New plug wires, new plugs (one step colder, gapped to 32), old plugs looked fine
3) AFRs are steady around 11 so it is not a fueling issue. No lean/rich spikes during the stutter. Injectors just cleaned. Fresh tank of 93 octane gas.
4) Boost stays steady so it is not a boost leak as the gauge and MAP sensor stay around the same psi of boost
5) Car is not knocking (no pinging, no oil pressure gauge wiggle)
6) Ms Extra 029v using Al Hounos's timing map

It actually feels like a cylinder is completely missing above 10psi and causing the stutter. I'm thinking too little timing in higher boost as too much timing should make me ping/knock? Thoughts?
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Old 05-10-2007, 03:26 PM   #2
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over-boost setting too low? well i guess not, since no lean spikes.
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Old 05-10-2007, 03:28 PM   #3
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Quote:
Originally Posted by Braineack View Post
over-boost setting too low?
At 18psi, no.
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Old 05-10-2007, 03:31 PM   #4
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triple check the timing was set to fixed 10° before you adjusted it. I did that, was acutally at 4° when i triple checked it again; felt a weird hestitation in high boost, but no signs of knock, AFR was good, etc.
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Old 05-10-2007, 04:07 PM   #5
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any datalogs?
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Old 05-10-2007, 08:35 PM   #6
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a break up under load typically points to ignition. Plugs & wires typically. However, sometimes coils.
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Old 05-11-2007, 12:43 AM   #7
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Could be blowing out your spark at higher boost-- I'm not sure what the other guys are running into here but this is pretty typical when boosting an NA car, or raising the boost a bunch on a stock FI car. Make sure your wires and plugs are in good shape, and check your plugs gaps, go a few thou smaller on the gap than stock. I think IIRC the stock gap for the 1.6l cars is .042 - .044.

Try something like .035 - .036
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Old 05-11-2007, 09:18 AM   #8
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yeah bryan downs told me he ran down to .032 at 20 +psi it should help us to have a smaller gap. I am just waiting for the GM hei conversion to be marketed with no soldering for us lazy non electronicy types then we can run what eve gap we like and still get fire.
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Old 05-11-2007, 09:43 AM   #9
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you guys read as bad as i do:

2) New plug wires, new plugs (one step colder, gapped to 32), old plugs looked fine
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Old 05-11-2007, 09:59 AM   #10
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I'm pretty sure it's my timing now that I think about it. I think I mismarked my pulley when I set it as I couldn't find the notch and had to use a long screwdriver to find TDC on cylinder one, but I think I marked it at the ten degree mark instead of the TDC mark so I'm 10 degrees too retarded. I'll check later this afternoon.
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Old 05-11-2007, 10:26 AM   #11
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Quote:
Originally Posted by Braineack View Post
you guys read as bad as i do:

2) New plug wires, new plugs (one step colder, gapped to 32), old plugs looked fine

Doh!
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Old 05-11-2007, 10:35 AM   #12
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Quote:
Originally Posted by brgracer View Post
I'm pretty sure it's my timing now that I think about it. I think I mismarked my pulley when I set it as I couldn't find the notch and had to use a long screwdriver to find TDC on cylinder one, but I think I marked it at the ten degree mark instead of the TDC mark so I'm 10 degrees too retarded. I'll check later this afternoon.

welcome to the club!
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Old 05-11-2007, 05:51 PM   #13
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Okay looked at some of my logs and Braineack was right about what was causing my problem, BUT it was not the timing (even though I did fix that as well.)

I guess my damn boost gauge is off more than I thought since I finally had time to log some runs and discovered that it was the overrun settings b/c where I thought I was at 12psi, I was really bouncing off 19psi based on the MAP sensor so my overrun was cutting the engine out at 18psi.
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Old 05-11-2007, 07:15 PM   #14
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wow that sounds like a harry experience.
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Old 05-11-2007, 07:20 PM   #15
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happened to me a few times....pissed me off.

the timing thing sucked too, the car just didn't feel peppy like it did, but i was making boost....i also got **** poor gas mileage (read 170 miles to a tank), since fixed I've gone over 70miles on a 1/4 tank like normal....
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Old 05-11-2007, 08:13 PM   #16
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Quote:
Originally Posted by magnamx-5 View Post
wow that sounds like a harry experience.
Yeah, stupid Autometer gauge with it's f-ed up reading almost killed my engine. The whole time, looking at my gauge I figured that I was around 12psi but based on the MAP sensor, obviously not. Funny thing is that the gauge used to read higher than actual and now it reads lower. On the plus side, it hits 19psi in the blink of an eye.
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Old 05-12-2007, 08:54 AM   #17
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hmm maybe i need to check mine i was always spot on before.
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