Need help solving an idle problem.

[Kwik]

I think my car has a vacuum leak. Is there any quick and easy way to check? Is this something I can do at home or will it require a mechanic? Thanks for your help!!

[bhall82]

If you have a smoke machine that is the easiest quickest way. OR you can pull the cover off and check all your vaccum hoses around the intake.

[wylde1]

what are the symptoms? there are a few things that can disguise themselves as vac leaks, and vise versa. A little more info might help us help you locate it.

if you have a vacuum guage you can pull off a line and hook up the guage to read how much your pulling. If it's low or inconsistent that's a good indication you're looking at a vac leak. If the vac reading holds solid above 9ish inHg you probably have some other issue that is manifesting with the same symptoms.

If you don't have a guage you can usually pick them up a just about any parts store for under 10 bucks, and they're very handy to have around.

it's pretty rare these days that a modern engine has vac issues. Things tend to be computer controlled now instead of all the vac lines they used to run back in the day.

[vroomapunk]

This worked for me!

When I needed to find a vacuum leak, I took brake cleaner and sprayed it in various areas, brake cleaner is flamable so when you spray it and it makes it into the cylinder it will make the engine race up and you can hear it.

I sprayed it near my fuel rails and my engine increased about 100 or 200 RPMs and I found that on the passenger side, one of my fuel injectors had a seal that deteriorated around it.

Worked like a charm, found the leak in 5 mins flat!

[Kwik]

Okay, here is what is happening. Car is fairly well modded with cam etc. Last engine work I did was change out the valve covers. Had to remove spark plug looms etc. I also replaced hose from CAI tube to the valve cover. Car was running fine. Drove from here to McKinney and back (2 hours) and no issues. Then it started. Car is set to idle at 950 RPM. SOMETIMES it does that, other times when you come to a stop, the engine revs like you are blipping the throttle. "Idle" when this is going on is around 550 RPM. When I get tired of hearing it, I turn the car off. It USUALLY goes back to a normal idle when I start it again. Any ideas? Thanks for your input guys!

[Kwik]

Would the brake cleaner mess up my FAST intake etc.? Thanks.

[vroomapunk]

If you dont douse it everything should be fine, it can disturb certain types of paint. Its okay for sensors, its pretty much just adding some fuel from outside the engine (because of the vacuum leak its getting sucked in) instead of using the injectors, its not going to do anything different than gas or alcohol would.

Dont spray it in front of your maf sensor like at the filter or anything, but even then I couldnt see it messing anything up becuase electronics cleaner is about the same thing.


And you are only using a couple light sprays. This is a cheap easy way to try, if it doesnt work you can just move on, you only wasted a dollar.

Cant really help you nail down whether your problem is a vacuum leak or not, but this is a good way to tell, if you engine is sucking in air then when it sucks in break cleaner you will know becuase it will rev up, not like a whole 1000 rpm, just enough to tell you theres a leak

[bhall82]

Originally Posted by Kwik

Okay, here is what is happening. Car is fairly well modded with cam etc. Last engine work I did was change out the valve covers. Had to remove spark plug looms etc. I also replaced hose from CAI tube to the valve cover. Car was running fine. Drove from here to McKinney and back (2 hours) and no issues. Then it started. Car is set to idle at 950 RPM. SOMETIMES it does that, other times when you come to a stop, the engine revs like you are blipping the throttle. "Idle" when this is going on is around 550 RPM. When I get tired of hearing it, I turn the car off. It USUALLY goes back to a normal idle when I start it again. Any ideas? Thanks for your input guys!

When I put my exhaust on it. My car started idling rough and dropping in and out. At about the same rpms. I think it's ok could be just the diffrence in back pressure since you've replaced the exhaust

[Kwik]

Does it sound like you are blipping the throttle and try to die?

[bhall82]

Originally Posted by Kwik

Does it sound like you are blipping the throttle and try to die?

Yes sir. It drops down very low then picks up. If I cutt the car off it is almost like it resets it. It doesn't do it anymore unless I drive it a ways. I took it to the dealer and of course they couldn't find anything. I let my guys look at it and they said they same thing. Sooo

[vroomapunk]

Edit, carb cleaner would be more appropriate now that I think about it, brake cleaner was all I had handy at the time

[Kwik]

That's exactly what is happening. If you find out the problem, please give me a shout. I will be sure and do the same for you. I'm going to try and have this thread moved to tunes / diagnostics.

[bhall82]

Originally Posted by Kwik

That's exactly what is happening. If you find out the problem, please give me a shout. I will be sure and do the same for you. I'm going to try and have this thread moved to tunes / diagnostics.

Yes sir I will. Thanks in advance

[bhall82]

kwik just got off the phone with 2 diffrent people one guys works at a tune shop another is a exhaust person. They both said the samething. It sounds like it's losing back pressure