WHAT THE HECK controls the idle in these things?

88GeeTee · Feb 2, 2006

i think my TB is bad. i ordered a 70mm today. my Stang CONSTANTLY idles at 1,000 RPM. i have set the base idle (twice now, thanks) and the IAC is clean and timing is dead on at about 12 degrees base. hooked a scanner to it and it shows no problems. my TB does stick a tiny bit at zero throttle. like when you go to give it gas it's stuck a little bit. tried cleaning it, just can't get it to stop sticking. so i'm at the point of admitting defeat and thinking this TB is garbage. hopefully the new TB cures the problem. i put my '86 TB on it and it idles fine, just weaker because of the "straw", lol. how much performance gain do you normally notice out of a 70mm TB? i already have the 70mm spacer plate...previous owner put it on my '86 Mustang and i put it on this one.

thanks for reading my ranting!
Josh

jrichker · Feb 2, 2006

A 70 MM TB is too big for a stock engine, you may loose some low end power. A 65 MM is a much better choice. The 65 MM units were stock equipment on explorers with the GT40 style manifold. See Tmoss's writeup at http://www.veryuseful.com/mustang/tech/engine/ConvertingExplorer65mmTB.pdf for modifications to adapt the 65 MM Explorer TB to a Mustang.

88GeeTee · Feb 2, 2006

well, it's already ordered now...guess i'll just have to mod my engine to match, huh? naa, i knew it was a little big for a stocker, but i do plan future upgrades and i don't really like buying parts twice...

Josh

Mustang5L5 · Feb 2, 2006

Did you reset your computer after adjusting base idle with the IAC disconnected??

88Stangboy · Feb 2, 2006

do you have your car warmed to operating temp when you set it?

Euphoric306 · Feb 2, 2006

after you set the idle, did you set voltage on the TPS?

Kdubslugga · Feb 2, 2006

Yeah i have 70mm TB as well, im still stock as well, but ive got big plans, 65mm is a better choice but i didnt feel like buying 2 TB's, anyways i gained 1mph in the 1/4 mile, could be just more experience i dunno. But anyways, i have had idle problems for 3 years, i replaced to IAC twice, new TB, new o2 sensors, 3g conversion, fixed all vac leaks, replaced all gaskets, it ending up being my battery wasnt strong enough.

HISSIN50 · Feb 2, 2006

The computer cannot remove air to lower the idle (it can raise the IAC function to up the idle though).

Some TB's have screws on the throttle blade so you can adjust the blade to fit the bore. The hole in some blades doesnt help anything with regard to fixing a high idle either.

Good luck.

Paul Perreca · Feb 2, 2006

1000? better than 350 lol

Zero_chance · Feb 2, 2006

Hell Im begining to miss when my car idled at 1000. After I drive around for a while now it idles at 1250+. In any case, did you try resetting KAM and cleaning the electrical connections of the salt and pepper shakers? There was a TSB back in the day about idle surges being caused by poor or dirty connections there. There was even adapters you could order to connect the two together because Ford believed part of the problem was that there wasnt enough slack between the top and bottom and they wanted to pull apart on their own.

Kdubslugga · Feb 2, 2006

Zero_chance said:
Hell Im begining to miss when my car idled at 1000. After I drive around for a while now it idles at 1250+. In any case, did you try resetting KAM and cleaning the electrical connections of the salt and pepper shakers? There was a TSB back in the day about idle surges being caused by poor or dirty connections there. There was even adapters you could order to connect the two together because Ford believed part of the problem was that there wasnt enough slack between the top and bottom and they wanted to pull apart on their own.

How do you clean the salt and pepper connections?

vristang · Feb 2, 2006

Kdubslugga said:
How do you clean the salt and pepper connections?

.
Excellent question!

Another potential source of your issues is in the tb linkage, under the tb. There is a sleeve that slides over the cable. I had serious issues with this thing corroding and jamming up.
A little bearing grease fixed it for me.

jason

86bluecobra · Feb 2, 2006

many guys forget to maintain there TB. just disconnect the TB and get yourself a can of TB cleaner and go to town. lots of times the oil the pvc brings with it clogs up the tb and it tends to start sticking and sometimes it won't close properly due to sludge build up.

88Stangboy · Feb 3, 2006

vristang said:
.
Excellent question!

Another potential source of your issues is in the tb linkage, under the tb. There is a sleeve that slides over the cable. I had serious issues with this thing corroding and jamming up.
A little bearing grease fixed it for me.

jason

Yea, i had the same problem with it sticking to. Try that.

88GeeTee · Feb 3, 2006

yea, i reset the idle about 2 times now...here was my procedure...this is what i read, now i'm thinking i might have done it wrong...

disconnect battery for about 30 minutes...disconnect IAC motor.

reconnect battery, start car...adjust idle stop screw until idle is low enough (never gets there for me...900 is the best i can get)

shut car off, reconnect IAC motor...should be done...

but that can't be right, because i don't have the battery disconnected AFTER having the IAC disconnected...or am i looking at this wrong?

i have cleaned the mess out of the TB and it still has that little sticky spot in it, that's why i finally ordered a new one. i will check the connections on the S&P shakers...what are those for anyway and what is the proper name for them? thanks for all the input guys!

Josh

HISSIN50 · Feb 3, 2006

Josh, are you SD?

Caitlmt · Feb 3, 2006

Idealy what should you want your car to idle at???

88GeeTee · Feb 3, 2006

yes, it's still SD...haven't converted yet...

Josh

88GeeTee · Feb 3, 2006

idle SHOULD be about 750-900 i am pretty sure...

Josh

vristang · Feb 3, 2006

ttop5oh said:
reconnect battery, start car...adjust idle stop screw until idle is low enough (never gets there for me...900 is the best i can get)

The fact that you can't get the idle to drop low enough using this technique, suggests to me that you have a vac leak.
Go over the intake area with some Starting fluid, LIGHTLY spraying suspicious joints. Don't forget to check hoses and their connectors. This can be dangerous, but only if you are dumb enough to spray the fluid directly at the headers, for a significant amount of time. Just don't prove Darwin right. If you can't find a vac leak, then it is time to consider internal leaks. But first things first, check for external leaks.
jason

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