idle - ZR-1 Net Registry Forums

icarus-54 · 07-15-2013

Hi guys,recently bought zr-1 #361,and have a problem with the idle taking too long to come down.It takes sometimes over a minute to return to 750.It seems to come down in stages which makes me think its the iac.These cars are a totally different animal to me as I come from the sy/ty world.I don't believe its a vacuum leak as it does come back but its a real pita to drive. If anyone has any ideas,I would be most grateful.
thanks,Jack

It is the IAC and its doing what its supposed to do, at least based on the stock calibration for the 90. It can be changed and the rpm decline sped up. However, the LT-5 wants to stall and if the Throttle Follower reacts to quickly, it will do that. Modded motors are more susceptible to this. But before doing any cal changes, make certain everything is nominal mechanically. IAC and port should be clean. Make sure throttle plates are also clean. Check TPSv at idle. Should be > .53v but < .57v.
BTW, its an SD motor so many of the Sy/Ty stuff applies. I learned using an 84 Xfire. Much applicable when it comes to tuning.

Kevin · 07-15-2013

can you drop it by tapping the gas? If so I have the same problem and I emailed Mr. Haibeck, his response was

Quote:

You might have two problems. If the idle speed can be reduced by kicking the throttle, the secondary throttle plates are probably sticking. The throttle body can be repaired.
http://www.zr1specialist.com/HAT%20W...tle%20body.htm

icarus-54 · 07-15-2013

Quote:

Originally Posted by Kevin

can you drop it by tapping the gas? If so I have the same problem and I emailed Mr. Haibeck, his response was

No,kicking the pedal or pulling back on the cable cam of the tb makes no difference.It will return to 750 but it takes forever which is a night mare in traffic.It seems to step its way down which is why I thought it might be the iac.

csx4350 · 07-19-2013

I just bought a pristine 1990 with 22k, it has only been driven 300 miles since 2000 and it was doing the same thing. The idle was between 1,000 and 1,500 RPM and wouldn't come down. I put 2 bottles of Techron in it and filled it full of Chevron premium. I then drove it (spiritedly) to a business meeting, about 80 miles total. It runs great and the idle is now silky smooth at ~800 RPM.

Letting any engine sit isn't great for it. I don't believe the fuel & additive should have effected the idle of a TPI engine, but it didn't hurt. I think the driving was more what it needed.

Schrade · 07-19-2013

You need Marc's chip (should be end of discussion)...

csx4350 · 07-20-2013

I've thought about that, but who is Marc and how do I get in contact with him about an Eprom?

07-15-2013	#1
icarus-54 Join Date: Jul 2013 Location: Mt.Bethel Pa. Posts: 72	idle Hi guys,recently bought zr-1 #361,and have a problem with the idle taking too long to come down.It takes sometimes over a minute to return to 750.It seems to come down in stages which makes me think its the iac.These cars are a totally different animal to me as I come from the sy/ty world.I don't believe its a vacuum leak as it does come back but its a real pita to drive. If anyone has any ideas,I would be most grateful. thanks,Jack It is the IAC and its doing what its supposed to do, at least based on the stock calibration for the 90. It can be changed and the rpm decline sped up. However, the LT-5 wants to stall and if the Throttle Follower reacts to quickly, it will do that. Modded motors are more susceptible to this. But before doing any cal changes, make certain everything is nominal mechanically. IAC and port should be clean. Make sure throttle plates are also clean. Check TPSv at idle. Should be > .53v but < .57v. BTW, its an SD motor so many of the Sy/Ty stuff applies. I learned using an 84 Xfire. Much applicable when it comes to tuning. Last edited by XfireZ51; 07-15-2013 at 03:54 PM.

07-19-2013	#4
csx4350 Join Date: Jul 2013 Location: Seguin TX Posts: 7	Re: idle I just bought a pristine 1990 with 22k, it has only been driven 300 miles since 2000 and it was doing the same thing. The idle was between 1,000 and 1,500 RPM and wouldn't come down. I put 2 bottles of Techron in it and filled it full of Chevron premium. I then drove it (spiritedly) to a business meeting, about 80 miles total. It runs great and the idle is now silky smooth at ~800 RPM. Letting any engine sit isn't great for it. I don't believe the fuel & additive should have effected the idle of a TPI engine, but it didn't hurt. I think the driving was more what it needed.

07-19-2013	#5
Schrade Join Date: Dec 2012 Location: NC Posts: 1,783	Re: idle You need Marc's chip (*should* be end of discussion)...

07-20-2013	#6
csx4350 Join Date: Jul 2013 Location: Seguin TX Posts: 7	Re: idle I've thought about that, but who is Marc and how do I get in contact with him about an Eprom?