> I just put a V8 TB on my V6 and now have high rpm's. It's running around
> 11-14,000 rpm's. Now I did modify it to get better air flow and one of
the
> blades I shaved a hair to much and need to replace (not that much though).
> Also why I did that I cleaned the IAC sensor and might have cleaned it a
> little too rough. Should I replace the sensor? How do you adjust the
> throttle stop on the left of the TB? any other ideas...
>
> Tim Althoff
> 99 RC Dak w/ V6 5-speed
> http://go.to/yllwdkta
I found the following in the archives. There might be more pertaining to
your problem, but here's a start. BTW, did you use your v6 sensors or the v8
sensor's? I have no clue if this would make a difference, but someone here
might know. Anyway, get ready for a lot of reading ;-)
Oh, I found the following using high idle and they are in 2001 (Jan-June). I
didn't look at the other years/months using fast idle, but I did look for
fast idle back to the end of '99 but didn't find anything.
Happy New Year (&good luck ;-)
-- Chuck Robbins '99 Dakota Sport www.intense99dak.com-------------------------------------------------------------- Contributed by Jon Steiger:
The box on the front of the TB is the MAP sensor. What I would recommend doing is to take the IAC motor off the ported TB and replace it with your stock one. (The IAC is the solenoid at the back of the TB, which has the little plunger on it.) If that doesn't solve the problem, then you're getting too much air into the TB from somewhere else. Check around the base of the TB where it seals to the engine to be sure there isn't any air leaking underneath the throttle body (it would be sucked into the engine) You may be able to use smoke or baby powder to check on that, if just feeling for a leak doesn't turn up anything. Also, look down the bores of the TB, and see how well the butterflies seal off the bores. Its OK to see some light around them (assuming you're looking down the bores with the TB off the engine of course), but they should be pretty much closed. There is a stop which can be adjusted; as you are looking at the TB from the front with the throttle linkage to your left, on the front/left of the TB there should be a set screw which you can use to determine where the throttle linkage rests. If the butterfly valves aren't completely closed, you may need to back this screw out a little. (It might be covered by a plug which you would first have to drill out and remove.) The instructions from Hughes are correct in that the set screw is not the proper way to correct a *low* idle, but if its set too high, the IAC plunger could close off the IAC passage completely and still not be able to bring the idle down enough. When adjusting the screw, be sure that it is the screw which is stopping the throttle linkage, and not the contact of the butterfly vavles against the TB bores. A test you might want to try before messing with the screw is to seal off both bores while the engine is running, by covering it with your hand, or a piece of rubber, etc. (Obviously be careful of the serpentine belt system and the fan, and don't drop anything down the TB.) :-) If you seal off the bores and the idle drops down to normal, I'd say you found your problem. Also, with the engine running, put your hand over the IAC cavity at the back of the TB and see if any air is going down it. If not, its coming from somewhere else. If the set screw method doesn't solve it, its possible there is a mismatch between the butterfly valves and the TB bores, in which case Hughes should make it right.
Oh, also check to see that you didn't accidentally disconnect a vacuum hose from the intake or something.
Basically, at idle, the VAST majority of the air should be going through the IAC cavity. (There will be a *strong* vacuum at the IAC cavity.) If the truck is idling and the air isn't coming through the IAC cavity, its coming from somewhere else; somewhere its not supposed to be coming from... You need to figure out where this air is coming from and stop it, in order to force the air to enter via the IAC cavity, which the PCM can then modulate.
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Follow-up reply by John S.
Thanks for all the info. I covered the bores and sure enough the idle dropped. I'm assuming this means that either the stop is set wrong or the butterfly plates are mismatched. the plates seem to look ok. Would you recommend calling hughes before I mess with any adjustments, I guess that makes sense in case I need to send it back.
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Follow-up by John Steiger
Yep, that might not be a bad idea; especially if there is a warranty involved. They might just tell you to go ahead and adjust it, or they might want you to send it back, but either way that's probably better than risking voiding the warranty, especially if it really is a mismatch in the bores
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