mgg

If the secondaries are not operating properly, will an SES code or warning be displayed.
The car REALLY struggles from 5grand on to reach 6 or 7k rpm.
The air duct has been modified with Haibeck braces, filter is a K&N in good shape with no obstructions and the car has only 11k on it.
I attatched the duct to the air box with set screws to eliminate it coming loose.
I read the post earlier and it sounds like a very similar problem.
Your comments would be appreciated. The car is a 90 ZR-1.

spl642

i assume the full power light is on?

Zrxmax

When you turn on the key without starting the engine, how long does the vacuum pump run ? It should stop after 3 or 4 seconds. Sounds to me like you don't have functioning secondaries. Your description sounds like a Z running on primaries only.

willyszr1

you dont have to start the car to find out if they have a leak. just turn it to on and go around and listen to see if the pump is running . or better yet have a friend turn the key while you listen . you i think will find that either the pump doesnt run or that it doesnt stop running . there is a fuse for the pump up on the the inner fender on the drivers side . may be some can take a pic and display for him . i dont have a way of doing this .

65ZR1

A malfunctioning oil temp sensor circuit can cause the secondaries to stay closed and not pull a code. The computer thinks the oil is too cold to turn them on.

willyszr1

wow , i didnt know that , but i guess it could , thanx for the info

illenema

If it struggles to get past 5K rpm the secondaries are off line.
This should be an easy fix.

mgg

Thanks for all of the responses! I guess this means I have to take the Plenum off to get to the vaccum line. I have heard that on start up it is possible to blow that line off. I have also been told that the fuel pumps could also be an issue.
I think I will start with the easiest one first.
Having never pulled the plenum, I assume I will need to purchase a new gasket set. Where would be the best place to get one of these?
I have heard of a video that might be helpful, what are your thoughts?
I was really hoping that I would not have to do this until I was ready to have the plenum and injector housings ported but it looks as if I have no choice now.
Thanks again for all of your comments and ideas!
Mike

tomtom72

Mike, You may not actually need to pull the plenum. I would check that the 2* vacuum pump is working properly first. Turn the car on, but don't start it. Then go over to the right front headlight and the pump is right there....just listen to see if it comes on. If it is working you should hear it. Then follow it's vacuum line to the connection point just at & above the right side water tube from the right I/H. Pull that connection apart and see if the pump comes on, then cover the line from the pump with a finger and see if it stops. If it runs & stops, then the pump is good. If it doesn't run, then check the fuse over at the left frnder liner, inside the motor bay, it's a 10 amop fuse. If the fuse is good then the pump is toast....usually the pumps last way long time.

Next take a vacuum pump, Mity-Vac type and apply a vacuum, 12" is enough, to the line that dissappears past the alternator & under the plenum. If that holds vacuum then your system under the plenum is good thru the in-line check valve + reserve tank + 2* control solenoid. If the vacuum gauge doesn't hold then any one of those parts copuld be bad. Simple first fix if it will not haold vacuum is to buy a check valve and insert it at the connection point where you are working and re-test or test drive the car. If that solves the issue then you found the problem.

If it passes all those simple vacuum tests, then the issue may be under the plenum. However, I would do a fuel pump pressure tyest at this point, using the flow chart in the FSM....just to make sure that my pumps are in order before assuming I have to pull the plenum. If the pumps pass the FSM diagnostic then I would swap the fuel filter just on the off chance and check the pressure regulator, pull the hose & look for gas & do the FSM checks on it before just pulling the plenum.

The MAP hose line everyone is referring to is at the back of the plenum, middle ....it is under the MAP sensor bracket. Yopu may have top climb up on a tire to get far enough over to get your had to it and feel if it is connected. You can dis-mount the MAP bracket from the plenum and/or dis-mount the MAP from the bracket to get a better eyeball on the situation. If that hopse if oil filled that could cause the issue as the oil cloggs the MAP sensor and it sends no signal to the ECM.

Sorry to sooooo long winded.:o


Tom

mgg

WOW! TomTom,
Thanks so much for all of your suggestions. I hope to be able to give it a shot this weekend. I will try the remedies in the order you described.
I really appreciate your detail in trying to slove this problem.
I have to tell you that not being familiar with the ZR-1 has been frustrating to me. It seems as if i am constantly working on my tuned port race car and over the years I have become more knowlegable as how to diagnose problems and resolve them. The ZR-1 is quite a bit intimidating to me and I am not confident as to where to get started.
I really appreciate you help and as I finally get this resolved I will let you know.
Thanks again!
Mike

tomtom72

Hey Mike, not a problem man, that's why we're called the brothers of the beast!

Keep us posted as you go so that if anything comes up & you need more help we can respond. I know when I got my Z I knew next to nothing and it was the other owners that helped me along....that's the way it will always be.


Tom