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#11 | |
![]() Join Date: Jan 2009
Location: Portland Oregon metro area (Washington side)
Posts: 3,207
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Scott ![]() Vett owner since 1979._It's about the car and the people Last edited by scottfab; 07-25-2012 at 08:43 PM. |
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#12 |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,696
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Turn the ignition to ON, not start. Does SES BLINK once? I would check and make sure memcal was seated properly. Rough idle could indicate its running in Limp Home mode.
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[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
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#13 | |
![]() ![]() Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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But! Because you said it runs impressively at WOT, coils, wires, and plugs are set asside as culprits (for now - and you already eliminated plugs, you said). I say this because the dielectric constat (resistance to current flow) across the spark plug gap increases with increases in air/fuel mix - reaching its peak at WOT. (One reason top fuel dragsters use magnetos to throw vurtual lightning bolts at WOT!) Relative to your symptoms, at least three important changes occur at WOT – which makes operation significantly different than normal cruising: 1) The secondary fuel pump turns on (i.e., if fuel starvation due to a failing primary pump was the problem before WOT, that problem - the stumbling at least - would be "resolved" when the secondary pump came on. Taping a fuel pressure gauge to the windshield and going for a drive will deny or confirm a fuel delivery issue: 45+ psi at cruise and about 52ish psi at WOT = not a delivery problem. I’d still change the inline fuel filter tho… ![]() 2) The secondary injectors come on so a marginal to failing primary injector would get some help from another injector coming to the rescue - to the point of possibly masking the symptoms at least, if not loss of power. Fuel starvation in a single cylinder is serious – leading to burned valves, for example. And, unlike your daddy’s 86, pulling the heads on the LT5 is a major operation involving pulling the entire engine and re-timing the cams, etc, etc. I’d wanna eliminate fuel delivery first, before putting any more miles on ‘er. 3) Didn't you mention TPS, and ECM errors? With those kind of miles, the contact point between the wiper and the rheostat inside the TPS could by now be carbon etched or pitted. This would lead to an erratic "off-on" voltage signal to the ECM which would really confuse it. However, at WOT the contact point between the wiper and the rheostat is in a "clean" place where the wiper doesn't normally hang out constantly, so the signal is steady and the ECM is not getting mixed messages. Yeah, "more potatoes for the stew pot"… The FSM will help a lot - at least up to the point of requiring a Tech-I to manipulate something. IMO, the danger with these "I had that problem and I did this to fix it" threads is some start changing parts till the problem goes away (aka "shotgunning"), in place of methodical troubleshooting. I don't get the feeling you are that type. Whe asking for ideas, I take these scattered tidbits as reference "bookmarks" to be considered in due course rather than indication of stuff to change out. One premier exception to "shotgunning" might be the OEM injectors - especially in a 90-92 which were affected by alcohol in the fuel. But, even a 93-95 at 140k miles and 17+ years, they can have issues. Yeah, I'd want to eliminate the other stuff first, but keep changing them in the mix. BTW!! Welcome to the BROTHERHOOD OF THE BEAST! This issue of yours should be realtively simple to fix (if not simple to find). After you get this item fixed, I have a feeling your dad is gonna want to "test drive" your Z a lot, just to make sure it is running OK. ![]() P.
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry |
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