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#1 |
Join Date: Aug 2014
Location: Trois-Rivieres (QC)
Posts: 473
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1991 ZR-1
Hello guys, I will explain my problem on this thread now. I just bought the car yesterday and I drove the 800 kms back home. Intermittent Service Engine Soon light. When I come to stops or red lights, engine has a hard time going at idle. 50% of time: engine dies. I can start it back (I need to crank a bit longer but it starts). Other 50% of time: idle goes to 500 rpm, go back a bit higher than 1,000 rpm, bounces for some seconds and then sets to normal idle (800?). When it is cold, I don't have the problem at all (tested only this morning, can't tell if it is always like that). Plus, I don't know if it has something to do with that problem, but when I go at WOT at around 75 mph (6th speed), the engine has a hard time going higher in RPM. WOT at 3,000 RPM at pretty much any speed is hard (it bucks, feels like misfires). WOT at 4,000 RPM and higher is nice and smooth. Seller said: -Plugs have been changed last year. -Injectors have been changed last year. No receipts at all. I know he's a honest guy though, no question there. Anybody can help me? These LT5s are intimidating, I've a lot of stuff to learn there. Thanks! |
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#2 | |
![]() Join Date: Aug 2006
Location: McLean, VA
Posts: 3,710
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First check the cam position sensor connector - from cam position sensor on driver side head (on the side) wrapped in 1/4" black flex conduit to a weatherpak plug above the brake booster. If connected, you may need a new sensor. |
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#3 |
Join Date: Aug 2014
Location: Trois-Rivieres (QC)
Posts: 473
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The code has been scanned with an unknown GM scanner (seems to be worth a lot of money). It showed no signal coming from the cam sensor. Cam sensor has an easy access and is connected. I'm pretty sure there's a way to measure the resistance of it to determine if it is bad or not?
If that's the problem, I'll be glad to pay $200+ for the sensor! |
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#4 |
![]() Join Date: Apr 2004
Location: ATL. GA.
Posts: 2,168
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Time to make your first tool buy and a must for any ZR-1 owner.. A FSM...
I would follow the code, check the plugs maybe ohm the wires. If all is good new Sensor.
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Steve 1990 Steel Blue/Black #2355 1990 Red/Red #1473 1991 Quasar /Black #118 Sold 1991 Turquoise/Black #766 Parted Out 1993 Yellow/White #179 Sold 1990 Black/Gray #1361 Headers/4:10s Sold |
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#5 |
Join Date: Aug 2014
Location: Trois-Rivieres (QC)
Posts: 473
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I'll test everything related to fire tomorrow. I hope coil packs have an easy access, I don't feel comfortable to pull the plenum yet.
Thank you I appreciate your help! |
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#6 | |
![]() Join Date: Aug 2006
Location: McLean, VA
Posts: 3,710
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Unfortunately, coil packs are under the plenum. Pulling the plenum, once you do it a couple of times, is no big deal. Especially with coolant passage plugged I can get in and out in less than an hour. It's a ZR-1 ownership initiation. |
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#7 |
Join Date: Dec 2007
Location: Fremont,Ca
Posts: 3,057
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CHECK ENGINE LIGHT, bucking and the present throuble code 31 is what my 91 did when the cam sensor died.
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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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Jerry's Gaskets has cam position sensors for $150. You'll want to get acquainted with Jerry - seems like most of us do, sooner or later - for all things LT5-related. (Click on the link and it should take you right to the page w/ the sensor on it!)
I agree w/ Secondchance: Pulling the plenum is "a right of passage" for a ZR-1 owner. All the crap you see on the outside of other motors is hidden under the plenum on the LT5. And*, after installing plugs in the INJECTOR HOUSING coolant ports leading to the throttlebody, and having a long nose "T" star tool or a 4" (~10 cm) Snap-On star extension and a drill makes pulling the plenum off about a 5-10 minute job - about like pulling a carb. (Oh...and get a set (or two) of the plenum gaskets from Jerry too, while your at it!) ![]() There's nothing scary about the LT5. It is different and requires certain techniques and sealants, etc; different; not intimidating, and actually FUN to work with, if having the right tools and the FSM! Welcome to the club! You've come to the right site for "all things ZR-1! Paul
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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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#9 | |
![]() ![]() Join Date: Aug 2009
Location: South Dakota/California
Posts: 3,791
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![]() Removing Plenum (including the 10 minute Plenum Removal) Injector Housing TB Coolant Blocking Jerrys Plenum Gasket Just Do It ![]() Get the right tools handy and we will be here as you go.....just post up any questions as someone will answer within a few minutes usually. If a Torx bolt does not want to move....take it easy and post up as you do not want to strip the heads of any Torx. Same goes with metric bolt. Usually not an issue however except on Injector Housing Coolant Manifold Bolts if you decide to Block TB Coolant. And.......when you get Plenum Off....there are some simple things to do list including Valley Drain Cleaning, Starter Solenoid Reconditioning, Tightening Crank Case Cover Bolts, Checking Vacuum System for Leaks...........all of which only take a few minutes each. You can even take a Pressure Washer to the Valley after the coils and starter have been removed.
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Left Clickable links ![]() -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 10-27-2015 at 08:02 AM. |
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#10 |
![]() Join Date: Jul 2007
Location: Bartlett, IL
Posts: 7,153
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Did you check to see if the SES bulb is there and not removed?
if you have no active SES light, when are you seeing the stalling?
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1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978 |
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