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01-31-2020
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#1 |
 Join Date: Jan 2015
Location: Decatur, AL
Posts: 93
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5000rpm idle
Have cranked the car but not driven it in a couple months. Been running really well. Cranked it tonight and it was idling near 5000 rpm. Blipped the throttle. Went up to about 5100-5300 rpm and stayed. Did not let it warm up. Turned it off and cranked it back several times with same result. In gear it will not bog, does a burnout. Any ideas?
Sent from my iPhone using ZR-1 Net Registry
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1990 ZR1, 1987 Mustang GT (since new), 1973 DeTomaso Pantera, 1987 928S4 Passed on: 1984 930S (gray market), 1988 Mustang Coupe Trooper car(drag) |
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01-31-2020
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#2 |
 
Join Date: Mar 2007
Location: Crystal Lake, IL
Posts: 7,193
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Re: 5000rpm idle
Large vac leak... or possible TPS Sensor is messed up?
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LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359 |
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01-31-2020
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#3 |
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Join Date: Jan 2015
Location: Decatur, AL
Posts: 93
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Re: 5000rpm idle
I checked the top hoses I could see in the dark. TPS is possible, but doubt it’s a vacuum leak. Not sure how it would develop one sitting. But I’ll keep an open mind and check it. Block off the throttle body and if it still runs, good chance that’s it. I appreciate it.
Sent from my iPhone using ZR-1 Net Registry
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1990 ZR1, 1987 Mustang GT (since new), 1973 DeTomaso Pantera, 1987 928S4 Passed on: 1984 930S (gray market), 1988 Mustang Coupe Trooper car(drag) |
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01-31-2020
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#4 |
 
Join Date: Dec 2003
Location: Arcadia,OK
Posts: 3,393
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Re: 5000rpm idle
At 5000+rpm, I would remove the accordian duct & look at Throttle Body to see if any of the throttle blades are open.
Starting a cold engine running @ 5,000+rpm is not good for an engine. Putting anything over the Throttle Body of an 350 ci engine running at 5,000+ rpm could be pretty exciting.
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Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed. |
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02-01-2020
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#5 | |
 Join Date: Feb 2011
Location: Clayton, North Carolina
Posts: 1,133
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Re: 5000rpm idle
Quote:
Jerry is right, the throttle blades have to be stuck open to run at 5000 RPM’s. I had a similar problem of idling at 2500 RPM’s. I sent the throttle body to Marc H for analysis. He found some goop on the back of the throttle blades that prevented them from closing. No idea how it got on the back side of the blades. Sent from my iPhone using ZR-1 Net Registry
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Lou[COLOR="Red"][B][SIZE="4"][/SIZE][/B][/COLOR] |
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01-31-2020
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#6 |
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Join Date: Jan 2015
Location: Decatur, AL
Posts: 93
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Re: 5000rpm idle
Realize it’s not good. I will use a piece of plywood I don’t find something wrong first.
Sent from my iPhone using ZR-1 Net Registry
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1990 ZR1, 1987 Mustang GT (since new), 1973 DeTomaso Pantera, 1987 928S4 Passed on: 1984 930S (gray market), 1988 Mustang Coupe Trooper car(drag) |
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01-31-2020
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#7 |
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Join Date: Jan 2015
Location: Decatur, AL
Posts: 93
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Re: 5000rpm idle
Realize it’s not good. I will use a piece of plywood I don’t find something wrong first.
Sent from my iPhone using ZR-1 Net Registry
__________________
1990 ZR1, 1987 Mustang GT (since new), 1973 DeTomaso Pantera, 1987 928S4 Passed on: 1984 930S (gray market), 1988 Mustang Coupe Trooper car(drag) |
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02-01-2020
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#8 |
Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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Re: 5000rpm idle
5000 rpm...would be a heck of a leak. And, to appear suddenly AND burn the tires? Well, been there, done that one too - when a piece of rubber gasket broke off and got sucked into the throttle body and jammed the blades open.
So, I'm leaning toward something jamming the TB OR the return spring broke; something pretty catastrophic involving the TB is my guess. (OH! Did I mention it happened on my 327 V8 Vega and not on my Z?  )Do let us know what ya find! 
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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 Last edited by Paul Workman; 02-01-2020 at 09:16 AM. |
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02-01-2020
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#9 |
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Join Date: Nov 2014
Location: Brooklyn ny
Posts: 1,045
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Re: 5000rpm idle
This is just a guess now..Maybe you checked it already ? Throttle cable...Happened to me when I put my plenum back on once....It was hung up a little and was idling around 2,000 RPM steady....
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02-01-2020
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#10 |
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Join Date: Jan 2015
Location: Decatur, AL
Posts: 93
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Re: 5000rpm idle
The small throttle blade was open. Not sure how to post a pic. Main blades were closed. Never paid much attention to it and wasn’t sure how it was connected to throttle cable and all. Isn’t. But it was stuck open. Touched it and it closed and moves freely. Idles normally. No idea how it would have gotten stuck open like that. Also, not sure how to keep it from happening again. Spring looks and works fine. I do appreciate all the help and hope this will be good info for someone else. Any ideas are welcome on how to keep it from happening again.
Sent from my iPhone using ZR-1 Net Registry
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1990 ZR1, 1987 Mustang GT (since new), 1973 DeTomaso Pantera, 1987 928S4 Passed on: 1984 930S (gray market), 1988 Mustang Coupe Trooper car(drag) |
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