My car has been at a dyno shop for over six weeks now and we've been through a plethora of problems. With or without knock retard showing ....the power curve goes to hell above 5000 RPM....there is an SES code for the knock sensor as well. The tuner has checked the ohms of damn near every wire on the car, replaced the knock sensor and module, removed tons of timing to insure it's not real knock (it's on a wideband too). He says his scanning software shows that real timing isn't truely being removed even though there is false knock retard showing on the scanner...but the power curve gets screwed up anyway ....but the jiggly power curve happens whether any false knock appears or not. He said he even programmed it back to stock and it acts exactly the same way....suggesting the computer isn't really processing the LT1 Edit commands. He says he can merely start the engine and let it idle and it shows some false knock retard even while idling...this couldn't be real knock at idle with no load so it has to be false......but no matter what it will not go away, no matter what he does....and it is not bad gas. Is the computer just goofing up or what? He is going to swap in an extra computer that a friend of his has and see if it acts the same way on the dyno with the same program he has tuned in my computer....that should narrow it down I guess. Any better ideas? Also, could it be that my HPP just fried the computer? I believe he downloaded my HPP program to a flash file, then I removed it from the computer so it was all stock in order to be able to sell the HPP, then he put a modified version back in with the first tune for the first dyno pull. This is what he has done many times before without a problem...any ideas? How do you troubleshoot a messed up computer? Is swapping the only way to see?

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94-Z28 M6-Supercharged Powerdyne 6 PSI w/solid intake/lg filter conversion, Hooker LT's, Mufflex 4-inch Y-Pipe, Borla Cat-back, TB bypass, GM 3.73's, Nitto 555R Drag Radials, Eibach Pro Kit, Lakewood boxed relocated LCA's, BMR SFC's, LT1 Scanmaster, full instrumentation, stock from throttle body to exhaust ports, way too many bolt on's and interior/exterior mods to mention. ....Upcoming mods to be completed VERY soon: TurboXS BOV, Borla "E-Valve", oversized crank-blower pulley, 42# SVO's, !FMU, Wideband dyno-tune

8.49 @ 87.52 w/2.09 60-ft "spin/bog" previous to solid intake. I can and will hit high 7's at low 90's

"What's the brown bag taped to the glove box for?" LIC="ZYOUL8ER"

 

I would guess that its mechanical, the car has to do what the PCM calls for unless it is physically incapable, once you flash over the stock file then that is ALL THERE IS in the PCM, there is no stock file in there for it to say "screw this, I'm using my old image", it simply does not exist.

I would check for something physical like valve springs sticking or etc, any other ideas?

If the HPP messed up the computer, you would not be able to program it again at all. With a blower it is likely the tune is bad, does this guy know what he is doing with blowers? He is pulling timing right?

[This message has been edited by Dr.Mudge (edited September 04, 2002).]

 

It's Woodbridge Dynotech, very reputable shop....yes I think he knows what he's doing. Like I said it even has false knock at idle.....never did that before though. In fact I have never really had false knock problems with the stock tuning and FMU. It now has 42# SVO's and sans FMU. He has a wideband and the A/F is slightly on the rich side so that shouldn't be a problem....I've never had valvetrain noise or anything like that. He asssures me it is false knock as he's experimented with making it richer and removing lots and lots of timing....it seems to have absolutely zero effect so it must be false. He's tried everything and I mean everything short of simply zeroing out the knock retard in LT1 Edit.....which he wisely elected not to do even for experimental purposes. The sensor and the module have been replaced.....he has checked the ohms of almost every wire that could be connected to the knock sensor wire in some way....it is going bezerk for no apparent reason. It's really getting old because soon it will be seven weeks since I dropped the car off and this is just the tip of the iceberg concerning the problems I've had.

 

An oddball thought just came to mind.
Check your blower drive. All the pullies and balancer on the front of the engine. something loose there could cause false knock even at an idle.
Maybe even pull the blower belt and start it up and let it idle and see if that changes anything.

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Al
Blue Green Chameleon 2000 Formula Hardtop
A4, 3.42/Eaton HD posi TA cover, Raytec sleeve, ARP studs
Yank ST3500, TransGo, & cooler
FRA, Direct Flo/K&N, EGR bobbitt, HPP
!TB coolant, Just Me Thermo mod, ATI dampner
SLP resonator exhaust, ES tranny&torque arm mounts
Home Boxed LCAs/ES bushings, LCA relocators
Best 60' 1.737
Best 1/8 8.100 @ 86.45
Best 1/4 12.704 @ 106.68
Best Mph 109.72 with a tail wind
and her
Black '98 SS# 590 M6
T-tops, Leather, Loaded

 

Did you have stock injectors before and it was fine? Have you changed injector offsets?

Sounds like a toughie

 

The injectors have been tuned in. Something going wrong with the pulley system is not likely.....but possible since the crank pulley has been replaced recently (upgraded to ASP custom 6.45 inch pulley for another ~ 1.5 PSI).....thanks for the idea, I'll check it out just in case. No new news as of yet.