Throttle body woes!

[nathanhardy]

So I have a custom intake built and I've gotten to a point that I've played with idle adjustments. I've always struggled with not getting the car to idle below 1000rpm, I'm running a mustang 5.0 T body with a Bosch idle valve found on vw's.. It's a turbo car even with the set screw lose and the plate shut it doesn't ever go below 1000. I'm running my valve at around 33 duty for closed below that it revs higher. Any thoughts shouldn't closing the plate kill the motor? Oh and the stock idle valve holes in the t body have been closed.

[kjones6039]

shouldn't closing the plate kill the motor?

In a word...... probably. This is seriously sounding like a vacuum leak somewhere.

Ken

[kaeman]

I hate to say this also, but vacuum leak is screaming right now.....
I had an issue like that once and found out that my block had been decked at the wrong angle and the bottom edge of the intake ports didn't seal to the heads, had a high idle, and oil fouled plugs...

[kjones6039]

I once had something as simple as a backfire that pushed the gaskets out........

Any number of things can cause a leak......

just another thing to consider...........

Ken

[nathanhardy]

Okay thank you all! Ill double check everything I have the head off and intake so nows the time to get it right! Wondering if there a good cheap trick to smoking it or pressure testing before my cams are in and the valves are open? Im using a single 4an vacuum line to a block that divides into the rest of my needed vacuum lines like brake booster, map sen, boost gauge, fpr, wastgate.. I wouldnt think that would be a issue unless its leaking. Wouldnt I have other drivablity issue if it was a vacuum leak espeically under boost?

[nathanhardy]

I hate to say this also, but vacuum leak is screaming right now.....
I had an issue like that once and found out that my block had been decked at the wrong angle and the bottom edge of the intake ports didn't seal to the heads, had a high idle, and oil fouled plugs...

That sucks, this engine the vr6 has been a pain too mostly due to machinist that claim they know what they are doing with it but really dont.. thats why the head is off ive had it on and off so much that the new head gaskets wont seal becuase the head wasnt done flat enough the first time!

[Rick Finsta]

Running a V8 here and I had similar problems with a low quality throttle body; I looked everywhere for vacuum leaks but it ended up that the poor fitment of the throttle blades in the bore were allowing too much air in and she wouldn't idle below 1150-1200rpm. Threw the Chicom stuff away and got an Accufab that has worked great. Just a thought, as you could be dealing with a leak in throttle shafts or something, too.

One technique that I'm not too keen on is to spray some starting fluid where you think there might be a leak; if the engine responds you found your leak. I don't like spraying flammable mist on a running engine, though...

[nathanhardy]

I'm running a accufab I believe! But I may have screwed it up when I closed the idle air valve hoes on it I used a welder instead of freeze plugs or threading them... Let's just say I've learned a lot now! Anyway I noticed the blade catches a little and if I force it more closed I can get it to idle a little lower but still not below 900 or so that's why I asked if it should kill the motor when working correctly.

[kaeman]

I hate to be the guy that suggests getting the new throttle body but.....well the welded throttle body is probably warped in the bore.... you might save yourself a lot of work and just get the new throttle body and use the freeze plugs and be done with the guess work, if the throttle body has a catch then it needs to be replaced.... it would be a shame to go through all the tuning and such and then get to do it over again when you finally replace the throttle body.....
Good luck.

[nathanhardy]

I hate to be the guy that suggests getting the new throttle body but.....well the welded throttle body is probably warped in the bore.... you might save yourself a lot of work and just get the new throttle body and use the freeze plugs and be done with the guess work, if the throttle body has a catch then it needs to be replaced.... it would be a shame to go through all the tuning and such and then get to do it over again when you finally replace the throttle body.....
Good luck.

Yep called accufab today said the same thing.. I've done some sutpid stuff but this day in general takes the cake! At least I learn from it!

[Rick Finsta]

A guy who has learned some stuff the hard way over his lifetime told me "learning occurs after repeated, demoralizing failure."

I think he's on to something...

Best of luck and let us know how it works.

[Ollie8974]

One technique that I'm not too keen on is to spray some starting fluid where you think there might be a leak; if the engine responds you found your leak. I don't like spraying flammable mist on a running engine, though...

Use WD40, not as flammable, will still get a RPM increase when leak detected.

[Rick Finsta]

Thanks!