Hello,
New to the forum and also new to owning a ZR-1. Recently purchased a 1991 Black/Black ZR-1 with 35k. All original except exhaust. I noticed two things right after purchasing the car. The first is the car has an instant high idle right after starting the car. probably 1500-1800 rpms. It really never comes down. The second is that the car just does not feel that fast. The first time I laced into it with the power key on, it just did not feel like 375 hp. I know one persons feeling may be different that another but I can try to explain it this way, From a 5mph roll, Full throttle and the rear tires do not even squeek, forget about breaking loose :-) . I have a few other cars and any of them with HP in this range would run circles around this car. Something must be wrong. I DO feel a difference when the power key is off and on. When its off, it really is bad. I am hoping something with this really high idle might have something to do with the lack of power.
I guess my first question is where to being with the high idle. No check engine light. No Backfire since I have owned it. Does sometimes feel like it has to crank for a while before firing.
I searched and found some links about check vacumn hoses. Should I look in any particular spot and should I check anything else?
Location: Fremont Ca. I will do No business with ANY company that boycotts Arizona.
Welcome to the madness.The vacuum pump may not be working,with the key on,motor off you should hear the vacuum pump come on for a few seconds and then go off and then cycle again.This is the vacuum pump when its working right but if there is a noticeable difference between the 2 key settings the pump might be the problem.There might be a vacuum leak under the plenum,common problem.If the vacuum pump is working the solenoid under the plenum might be dead.Regardles of the problems you will find an answer here,just about every problem these cars have,had has been dealt with here.The injectors in these cars are junk,if they havent been replaced they they will be,just a matter of time.
Hi John, welcome to the world of ZR1 ownership. I also have a 91 Blk/Blk. Both the high idle and the performance issues you've described are items I delt with on mine. With the high idle, you might check to make sure you've got the latest version of the GM chip. This improved the situation but the real fix is to call Marc Haibeck and buy his chip.
As I'm sure you know, there could be any number of issues affecting your performance concern. An easy, set of the pants test for the operation of your secondaries is to nail it with the power switch off. While you are into it, turn the power switch on. You should feel the difference in acceleration. Regardless of the results, I'd also measure the resistence through your injectors. A simple procedure for measuring injector resistence can also be found on Marc's web site:
If you don't have a Facotry Service Manual, you might want to get one. You won't need it often but it is a great aid for the few times when you do need something. By the way, don't think you've bought a car that will be "one problem after another". There are a few (very few) issues with the ZR1 and once you get them addressed, it's a great and highly reliable car. Secondaries and injectors are at the top of the list.
I'm in lower westchester and I know that there are alot of brothers of the beast out on L.I. that would be glad to help you get your car sorted out. Anyway if you need some help, just give a shout at me....have scanner & will travel....any excuse to use my Z.
Now to brass tax.....I assume that you went thru the car and brought all your maintenance back to a zero point.....ya know all the usual stuff for a tune up?
Study the links for the vacuum system.....the high idle could mean a vac leak. Also pull the connection on the vac pump and do a KOEO test. She should suck the system down, and stop....unplug the connection at the right water tube if it doesn't stop and cover the pump end of the line with a finger. If it stops then pump=okay and you have a secondary system leak somewhere.
Also, checking all the other vacuum connections is very important. The PCV system is #1 on the list. Check the "F"- connector and the molded hose that the two valves sit in for tightness and feel under that hose for any cracks! Check the I/H housings' rubber 90* el's for cracks also. If any of that stuff feels loose you could use zip ties to snug it up as an experiment. Alot of times it isn't one big vacuum leak, but rather a collection of small ones. A big vac leak, or a collection of small ones can lead to some pretty poor performance.
On the power subject. If you have a scanner I would scan the car & see what's going on all the way from cold start thru closed loop. I should suggest to do a KOEO fuel pump test just to be sure. Then I would check the other suggestions mentioned.
This link read it study it, then pull the plenum. Its not that difficult and you can and will get power out of that puppy.
I had the same problem with mine. after i got it fixed i almost lost control of the car with the burst of power i wasnt expecting. so dont give up.
That high idle you mentioned is Very possibly a vacuum leak in the hoses or sensors. Do a search on this site for secondary problems.
They are here and fixes posted also.
I'm in lower westchester and I know that there are alot of brothers of the beast out on L.I. that would be glad to help you get your car sorted out. Anyway if you need some help, just give a shout at me....have scanner & will travel....any excuse to use my Z.
Absolutely the best first step you can do is to have someone who is familiar with how the car should operate see it firsthand.
The high idle is certainly air leaking in from somewhere. You just have to figure out where. Could be vacuum lines, could be the throttle body butterflies (do not clean them), could be it's not tightened up properly or some intake gasket issue. Could possibly be the idle air control valve is malfunctioning.
Does it idle high all the time?
To the power issue, does the check engine light come on when you turn the key to "run"? What I mean is, is the bulb working?
If you turn the power key to "off" does it feel the same as when it is on?
If you wind it out in 1st or 2nd gear with the key "on", will the engine pull to the redline, or does it have trouble pulling past 5-6,000 rpm?
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Absolutely the best first step you can do is to have someone who is familiar with how the car should operate see it firsthand. 
