Secondary Throttles Not Opening

[ericbwood]

I have a 1994 ZR1 which I purchased about 2 years ago. It had been sitting for a few years and had not been very well taken care of. It had 27,000 miles on (now has 35,000). I needed to replaced the catalytic converters to get it to pass smog. It has never felt like it had enough power except for briefly after a dealer replaced the EGR valve. Then around 3000 RPM it would open up and the front of the car wanted to "lift up" during acceleration (ie it had a LOT more power than it used to!). But then the "check engine" or "service soon" light went on and I have never had that power again even though sometimes the check engine light comes on, and sometimes it doesn't.

I've had a couple places spent a lot of time (over a week at one place, once) diagnosing and looking at it. I have had the EGR valve replaced twice. Nothing seems to help. I checked the air pump for the secondary throttles (near the passenger side headlight) and this works; it goes off when I remove the secondary line and put my finger on it to create suction).

I am pretty baffled and the most any mechanic has ever come up with is an intermittent error 61 which they didn't know what it was. I now suspect it is the secondary throttle but don't know what other things to look for?

What are other things which can cause the secondary throttles to not open up?

Any advice would be great!

Thank you,

Eric BW.

[tomtom72]

Hi Eric,

There is a very good explination of the system over at CorvetteActionCenter.com, in the C4 / ZR-1 section, it's a sticky. I urge you to go take a look. Also there is a great photo illustrated "plenum pull" at PacificNorthwestZR-1 Chapter web site(aka Jeffvette) also over at BigCountryCorvettes, the Texas ZR-1 Chapter web site. Also at this site in the tech section there is my journey, "Plenum pull Q's", might be worth reading.

I have a 90 so I don't know if the 94 DTC's are the same. I can look up your codes in my 90 Helm manual if you like. Also, I'm only an apprentice Z owner so I doubt that I have the depth of knowledge needed to diagnoise a 94 Z, sorry!:o

That said, you would need a Helm manual for your yr Z, Helminc.com is the source for Factory Service Manuals. You could do a vacuum test on the system using a hand vacuum pump. At the right front over by the alternator there is a vacuum line that services the 2* vacuum system, separate that connection and attach your pump to the end that goes under the plenum, the other end of that line goes to the car's vac pump. You would like the system to hold at least 12" of Vac, and no leak down instantly. The intermittant code could be the secondary MAP sensor but I'm not sure on a 94. The secondary MAP might be mounted under the ECM/CruiseControl brkt, it is on a 90. You may want to vac check that also, but I doubt it's that. More than likely there is a vacuum leak under the plenum but the proper book diagnostic protocol should be followed to eliminate guessing.

One of the senior guys will see this and give you better answers in a bit....hang in there we're all with you!:thumbsup:

:cheers:
Tom

I looked up Code 61 in my 90's Helm book and it just means "secondary Port Throttle Sysyem In-opperative" but usually that means a vac leak somewhere in the system. The second MAP sensor is the feed back control sensor that completes the feed back control loop to the ECM. It provides one of the "reference" signals for the 2* injector activation protocol.

[2lpzr1s]

Check the sec port throttle selinoid. Its under the plenum up front . Mine had a leak. It would activate the ck engine light. Oh yeah usually in 6th gear

[Jeffvette]

Eric what is your location?

[ericbwood]

Thanks for the quick replies! I will try these! As for the question of location, I was in Northern California but now the car and myself are on Oahu in Hawaii. I don't know if there are any good ZR-1 mechanics in Hawaii; I have yet to see another ZR-1 here!

Thanks again for such great responses. I will keep you updated with any progress made.

[Z Factor]

Thanks for the quick replies! I will try these! As for the question of location, I was in Northern California but now the car and myself are on Oahu in Hawaii. I don't know if there are any good ZR-1 mechanics in Hawaii; I have yet to see another ZR-1 here!

Thanks again for such great responses. I will keep you updated with any progress made.

Hello, and welcome to the forum.:handshak:

There are a few other ZR-1 owners from Hawaii here on the forum, though only one voted in our poll so far.

http://zr1netregistry.com/forum/showthread.php?t=1009

Hope to see you posting more soon.

:cheers:

[tf95ZR1]

Hey Mods/Z Factor
I would check out this "Margaret82499"
5 posts and telling veterans what to post.
No Profile.
Nonsense posts.
A time bomb?


I do not mind one silly post about light, but you are making to many posts that do not make sense. Please stop making all the crazy posts.





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[WB9MCW]

I would have to second that motion..see the Larry M thread!!!

Note to Eric... Craig T. aka HAWAIIZR1 on this forum is the guy u need to hook up with! send him a pm he is very active on our forum and a great ZR-1 guy! tell em WB9MCW sent ya!!! You can find him listed in the members section and he is a reg. poster here too!

I do think it is your secondaries and with some investigation and study you may be able to fix it yourself...might I suggest you go study the sections on secondaries in the main ZR-1 Net/Reg. board ( http://zr1netregistry.com/ZR1_issues.htm#35 ) and keep reporting back here to this thread with your findings...we can help u through it and hooking up with Craig will give you a local guy for support..He may know of some good mechanics on the island! There are more Hawaii vette guys on Corvette Valley ( http://www.corvettevalley.com/showthread.php?t=467&highlight=hawaii http://www.corvettevalley.com/showthread.php?t=1546&highlight=hawaii ) so you may want to join that site and get to meet them too! Just look up the Hawaii members postings and PM them! Vette guys usually have great connections and a true brotherhood for our love of vettes!

[BBBAD94ZR1]

Hey Mods/Z Factor
I would check out this "Margaret82499"
5 posts and telling veterans what to post.
No Profile.
Nonsense posts.
A time bomb?
Yeah,
Seems like a joker. She or he replied my post. :censored:
Maybe she needs to be ejected from here...
RAY

[2lpzr1s]

I wonder who this really is [Margaret} just joined[6-4-06] and it would be kind of a person to pm that type of message instead of posting to a thread. This forumis made up of folks with a wide range of mech. abilities sometimes people may not ask or give the best answers in the world how can one learn if one does not step out and get involved. The one thing we all have in common is a love for a truely amazing car