Idle transition issues - ZR-1 Net Registry Forums

Matt B · 06-14-2023

So far my Z runs and idles as silk. But there is some heavy stumbling / hesitation during the transition from idle up into higher revs.
I can feel it slightly when I just rev her up. But with a gear engaged the effect is pretty strong. Let's say I let her crawl in first gear idle and then push the throttle (no matter if carefully or flooring it) the transition out of idle has no power and the beast stumbles.

North of 1000 revs she runs great, idle is smooth as well.

Any ideas?

1977CamaroZ28 · 06-14-2023

Hi Matt, with my car in last 2015 I had similar symptoms. My problem was with two coils with intermitent failure and two spark wires... I don't know if this can help you...

XfireZ51 · 06-14-2023

You should check TPS for dead spot.

phrogs · 06-14-2023

How much has this car been driven and has it seen 7K rpm shifts lately

Might need a Italian tune up

Matt B · 06-15-2023

Thanks, I will go through all those points.
I drove her rather hard recently, with coasting sections as well es full throttle accelerations north of 6k.
But in general I drive my Z about 20-30 times a year only with an average of 50 miles per ride. And given my local roads the majority is relaxed back country road driving whereas I take care for WOT accelerations and secondaries engagement as often as possible. Secondaries operation is monitored by my secondary indicator lamp

My guts say it's a sensor or something similar. Just not sure how much my guts know about LT5 engines...

Thomas ZR-1 · 06-20-2023

Measure out Matthias: the TPS signal must be at 0.50 volts at idle with the oem software on the memcal? Haibeck recommends 0.53 V with his chips. Other voltages can cause your problem.

06-14-2023	#1
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 517	Idle transition issues So far my Z runs and idles as silk. But there is some heavy stumbling / hesitation during the transition from idle up into higher revs. I can feel it slightly when I just rev her up. But with a gear engaged the effect is pretty strong. Let's say I let her crawl in first gear idle and then push the throttle (no matter if carefully or flooring it) the transition out of idle has no power and the beast stumbles. North of 1000 revs she runs great, idle is smooth as well. Any ideas? __________________ ZR-1 #638/1991

06-14-2023	#2
1977CamaroZ28 Join Date: Jul 2015 Location: Jerica - SPAIN Posts: 207	Re: Idle transition issues Hi Matt, with my car in last 2015 I had similar symptoms. My problem was with two coils with intermitent failure and two spark wires... I don't know if this can help you... __________________ 1.990 Chevrolet Corvette ZR-1 #2342 - Black/Black - March 1.990 - OBX Headers and OBX complete Exhaust Line (No Cats). K&N Air Filter with open Air Box. Jerry's Gaskets Silicone Air Duct. DeWitts Two Row Pro Series Radiator. Samco's Hose Coolant Kit. ECM/EPROM Improved. MSD Spark Plug Wires 8,5mm Super Conductor. EBC Brakes YellowStuff with EBC D-Series Rotors and Raybestos hoses.

06-14-2023	#3
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,661	Re: Idle transition issues You should check TPS for dead spot. __________________ [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

06-14-2023	#4
phrogs Join Date: Jul 2004 Location: Kalamazoo MI Posts: 1,738	Re: Idle transition issues How much has this car been driven and has it seen 7K rpm shifts lately Might need a Italian tune up __________________ JOHNNY P Currently own 90 ZR-1 #845 DRM 500 engine package 90 #226 Might be a parts car not sure yet

06-15-2023	#5
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 517	Re: Idle transition issues Thanks, I will go through all those points. I drove her rather hard recently, with coasting sections as well es full throttle accelerations north of 6k. But in general I drive my Z about 20-30 times a year only with an average of 50 miles per ride. And given my local roads the majority is relaxed back country road driving whereas I take care for WOT accelerations and secondaries engagement as often as possible. Secondaries operation is monitored by my secondary indicator lamp My guts say it's a sensor or something similar. Just not sure how much my guts know about LT5 engines... __________________ ZR-1 #638/1991

06-20-2023	#6
Thomas ZR-1 Join Date: Oct 2012 Location: Germany Posts: 227	Re: Idle transition issues Measure out Matthias: the TPS signal must be at 0.50 volts at idle with the oem software on the memcal? Haibeck recommends 0.53 V with his chips. Other voltages can cause your problem. __________________ Best thing in life is a ZR-1 ride