C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

close loop stumble

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Old May 1, 2011 | 01:18 AM
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Default close loop stumble

1991 383 44lb trickflow injectors. had tune. before and after tune car would misfire after cloosed loop and then bog down at wide open throttle for a couple of seconds then come out of it. tried injectors timing, valve adjust, car made 340rwhp and 410rwtq with slipping over priced ram c4 conversion clutch
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Old May 1, 2011 | 07:20 AM
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You need to hook it up to a scanner, this should help point you in the right direction..If its doing it in closed loop only then it may involve one of your sensors since most of these don't come onto play until the car reaches closed loop.. My first guess would be an 02 sensor but it could be as simple as a coil , or Ignition control module malfuntioning after it warms up, but a scan may tell you where to look.....WW

Last edited by WW7; May 1, 2011 at 07:28 AM.
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Old May 1, 2011 | 01:28 PM
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Default close loop stumble

Originally Posted by WW7
You need to hook it up to a scanner, this should help point you in the right direction..If its doing it in closed loop only then it may involve one of your sensors since most of these don't come onto play until the car reaches closed loop.. My first guess would be an 02 sensor but it could be as simple as a coil , or Ignition control module malfuntioning after it warms up, but a scan may tell you where to look.....WW
hooked up solus and watched data all seems normal, o2 says the same in or out of closed loop
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Old May 2, 2011 | 12:11 AM
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Clean your MAF
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Old May 2, 2011 | 03:23 AM
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Let me know if you ever find that MAF. lol.

Whats the deal on the exhaust? Stock, headers?
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Old May 2, 2011 | 11:13 PM
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sorry no maf. I also noticed when temp reads 185 the car has big flat spot. any ideas? has headman headers, no cats, (live in north dakota) magnoflow mufflers real duals.
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Old May 2, 2011 | 11:36 PM
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Originally Posted by getnakd
sorry no maf. I also noticed when temp reads 185 the car has big flat spot. any ideas? has headman headers, no cats, (live in north dakota) magnoflow mufflers real duals.
something with the tune is way wrong...sounds like starving for fuel...or too much air, same thing in many ways.

Go pull some plugs and see what they can tell you. if its been lean, or rich you'll see it on the insulator.
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Old May 3, 2011 | 01:11 AM
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Originally Posted by bill mcdonald
Let me know if you ever find that MAF. lol.

Whats the deal on the exhaust? Stock, headers?
Argh yeah didn't notice it was a 91 the first time!

Something is probably off in the VE table in your tune
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Old May 3, 2011 | 01:42 AM
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Originally Posted by getnakd
1991 383 44lb trickflow injectors. had tune. before and after tune car would misfire after cloosed loop and then bog down at wide open throttle for a couple of seconds then come out of it. tried injectors timing, valve adjust, car made 340rwhp and 410rwtq with slipping over priced ram c4 conversion clutch
Was it bone stock before the tune? No exhaust mods? Too little detail.
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Old May 3, 2011 | 10:47 AM
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Also that is way more injector than you actually need - I assume the tune has been adjusted for that?
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Old May 3, 2011 | 11:52 AM
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If you can, get a hold of a wideband. It'll tell you in a second what your problem is if it's afr related.
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Old May 3, 2011 | 11:47 PM
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I notice my fuel line is about 1 inch away from my headers. do you think that it might be causing vapor lock symtom.
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Old May 3, 2011 | 11:52 PM
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forgot to tell the whole story 383 comp heads cam 556-566 lift 344 354 duration 44 injectors holly stealth ram bbk 58mm throttle all roller. 12.1 keith black pistons with long stroke stroker kit.
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