Something weird is going on with my vette. When I start it up it will accelerate while it is idling between 800 and 1000 rpms. It hasnt done this before. If I hold the throttle up to 1500 rpm it will still start to go between 1500 and 1700. I also have a hard brake pedal through out this and as a result the brakes don't really work.

Last night I changed the oil on her and accessory belt. The oil filter that I put on lookd about half as tall as the one that was on there before, but that is what was called out at autozone for the mobil one filters. When I backed the car off of the ramp it was fine though. the problem didn't start till today. My car has that hard start problem, and normally I will just turn it over for a couple seconds a few times before it starts. Today I just held it cranking till it started. I dont think any of the things I did could have created this problem. Has anyone else experienced this??

At first I was going to look into colapsed brake lines, then perhaps check the valve in the booster, but with this weird idling, I don't know if the problem would lie in the brakes or maybe manifold vacuum? I already checked for unplugged hoses and sensors. I need some tips, I have a track day next saturday and probably wont be able to work on it till after work wednessday. Help!

 

The hard brake pedal would suggest a vacuum leak, either internally in the booster or externally in the line leading from the manifold to the booster

Doubtful that changing oil lead to this condition

In any event, here's a bump

seeya

 

Do you think that a vacuum leak could affect the weird idle going on though?

 

You likely have a vacuum leak. It would explain everything. Inspect the line leading to th booster. If it is good, and strong vacuum is at the booster, change the booster. The boosters fail frequently. Especially on header cars.

 

Do you know a way to check for sure? Boosters are kinda expensive if that is not the problem. That would explain the idle too?

 

Plug the vac line going to the booster (from the intake) and this will remove that from your engine system. Examine what this action does to the running of your car. If the problem goes away with the booster removed, you have an idea that the booster may be defective. If the removed booster does not change anything, you have other problems.
The brakes on my 89 will lock up all four tires if I "get on" the pedal real hard!
SAM

 

Won't the ABS kick in????????????? The wheels shoudn't lock up!

 

JohnnyH: You are correct and I used improper words to describe the stopping ability of my 89. How about "it will stop on a dime"?
Thanks for the correction.
SAM

 

Well it is definitely the booster. What are the odds of the plastic being cracked vs. just the seals? It is much cheaper to replace the seals and valve instead of the whole thing.

 

There are two options regarding replacement. Oem type and a metal repop unit are available. Some guys prefer the metal because it does not crack from header heat. I have never seen a seal kit for them. But then again, I never looked for one.

 

I noticed that there was the metal and the plastic. The metal is even cheaper. I may have to get that one. I am guessing they are the same fit and performance?

 

I bought a used one (plastic) on Ebay for around $50 and it's worked for over a year now.

 

never heard of any seal replacements for a brake booster-WHEN mine goes it's gonna be metal for me! Also, your starting problems sounds like the fuel pump relay is shot-cheap part-about $12.
if you replace it check the wiring-the insulation has a tendency to
shrink back exposing bare wires-easy fix. Good Luck.

 

I put a Mighty Vac on my brake booster, pumped the mighty vac and found the OEM plastic booster to have a slow leak. When I tried the same test on the new metal brake booster I picked up from Hot Rods USA it held vacuum. That was the extend of checking my old/new booster.

 

I just saw the thread with everyone going with the metal booster. Whats with all the selection stuff in the master cylinder drop down (http://www.hotrodsusa.com/store/product341.html)? is that to purchase a master cylinder as well?

It looks like the part # HRB 2410908 is the one I want.

 

I don't know what all that crap is but yeah thats the BB I'm using

 

Thanks for the help!

 

Well, my experience with the metal booster was not nice. I had a failing (stock) booster in my '87 Coupe, and decided to buy a metal one from MidAmerica (metal is tougher than plastic, I figured). After the PITA of installation, I decided to test it at 40 mph. I really stepped on the brakes, I did not slam the brake pedal. A loud metallic "snap" and I was left with practically no brakes. So I limped home and removed the booster next day and returned it for a refund. Next I went to a local Pep Boys store and had them order a plastic rebuilt unit from some local warehouse. I picked it up the next day, it was cheaper than the metal one an it has been working perfectly for the last 5 months.

 

If I am not mistaking the metal one is a dichromate color which is personally ugly in the engine bay though you could paint it, when I bought my car the booster was leaking and had to drive it home with no power brakes, did a lot of searching and bought the plastic one from Advance Auto, had it for a year with no problems and braking feels excellent.

Bob