I have the 02' Z in my sig and recently upgraded from a 6 rib system to an 8 rib system. The other day the idle went up to about 1,400 rpm's at a red light and stayed there for a few more lights and then went back to around 800 rpm's at idle. When I got home I noticed that the nipple on the passenger side of the throttle body didn't have the rubber cap over it that I had replaced before I had the pulleys changed. I found it underneath the fuel rail cover but it was split so I pulled a new one out of the pack I had bought and put it on. I went for a test drive and every time I would stop the engine would die on me so I think the car must have been tuned without the cap on. I took the cap back off and have had no more idle issues since. My question is what if anything will this affect?
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02' Z06 EB/EB 4,400 miles, Longtubes, Off-road X-pipe, Pypes X-back, Blackwing CAI, Comp. Cam 238/240 - 605/609 - 112LSA, Patriot Gold Springs, Titanium Retainers, Comp. Push Rods, Hurst Short Throw, Cray 19"/20" w/ Toyo Proxes4 265/30/19's up front and 295/30/20's out back
It's a good question but I honestly don't know the answer here, bro.
Perhaps someone who does will chime in.
Mike
Thanks Mike. I hope someone can offer some insight. I just want to make sure I'm not robbing myself of some cheap HP. If it only affects the idle then I'll just leave her uncapped and enjoy the ride.
It's not unusual for someone with a wild cam to drill a small bypass hole in the throttle plate to help improve idle. This bung on the throttle body has basically the same effect, allowing a little extra air to bleed past a closed butterfly. If the car runs OK without the cap, run it without the cap. Sure, it's bypassing the air filter, but the odds of you sucking enough of anything through that little tube are low enough I'd ignore the risk.
At wider throttle settings, the amount of additional air coming through the bung isn't going to matter, it's probably a fraction of percent of WOT, well below measurement error. And it's umetered air so it'll lean you out which adds HP (up until the point that the engine explodes, of course).
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It's not unusual for someone with a wild cam to drill a small bypass hole in the throttle plate to help improve idle. This bung on the throttle body has basically the same effect, allowing a little extra air to bleed past a closed butterfly. If the car runs OK without the cap, run it without the cap. Sure, it's bypassing the air filter, but the odds of you sucking enough of anything through that little tube are low enough I'd ignore the risk.
At wider throttle settings, the amount of additional air coming through the bung isn't going to matter, it's probably a fraction of percent of WOT, well below measurement error. And it's umetered air so it'll lean you out which adds HP (up until the point that the engine explodes, of course).
Thanks RocketSled. I think the plug was inadvertenly removed during the pulley upgrade because it had a wire tie that was pretty tightly secured to it and as I stated I found the original plug under the fuel rail cover. The cam is very mild so I don't think it was intentional but it sounds like no harm no foul.
The original rubber cover thingy gets dried out and eventually cracks and falls off. I replaced mine with something I got at a car parts store. A softer, more vinyl like thing. I had to put a zip-tie around it to get it to stay on, but otherwise it's still in great shape a few years going now.
The original rubber cover thingy gets dried out and eventually cracks and falls off. I replaced mine with something I got at a car parts store. A softer, more vinyl like thing. I had to put a zip-tie around it to get it to stay on, but otherwise it's still in great shape a few years going now.
That is why I replaced it originally because I noted it was cracked pretty bad when I was detailing the engine. I just bought a multi pack on the help isle at the parts store and replaced it. Now if I put one back on it dies at idle so i'll just leave it off.
If you think the car was tuned with this vacuum cap missing, I would take it back and get the tune checked. I would guess that it was an accident and the tuner did not notice, I have never left a car with an intentional external vacuum leak for tuning purposes. I did have a procharged 383 C4 that we built go through most of it's tuning with a cracked vacuum cap off of the booster line though. I remember I was having trouble dialing in the idle and part throttle performance, nothing too crazy it was just hard to get the car to repeat itself at the same setting. When I discovered the leak and repaired it the same thing happened - the car didn't want to idle and I had to make quite a few changes to the tune to get the car to run right. I would have it checked just to be safe.
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Andrew Turner SPi
SHIFTED PERCEPTIONS INC. www.spi-performance.com
(905)-502-0833
I had that happen on my f-body a long time ago when running an s-trim vortech. It will affect idle and it will blow boost out that hole if it's not capped.
I had that happen on my f-body a long time ago when running an s-trim vortech. It will affect idle and it will blow boost out that hole if it's not capped.
Thanks man I just caught your reply. I knew that in old school technology any potential vacuum leak was bad.
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