MicroSquirt.com read only forum (Jan.15,2018)

Hey Group,

I just fired up newly rebuilt GM 5.7 with TPI, using a brand new installation of MS. It runs really nicely, (:D!!!) but idles too slowly or stalls ( ) without manually backing out the IAC valve a bit.

There is a preset idle stop screw on the throttle body, which is sealed. Should this adjustment be set such that the engine will idle with the IAC completely closed, or is it intended that the IAC must be opened somewhat for the engine to idle?

At this point I have no automated control of the TPI IAC, and plan on using MSS, which sacrifices the fidle signal to ignition timing control. I'd just like a decent (clean, inexpensive and functional) way to set a fixed idle.

Thanks thanks thanks in advance for any thoughts or wisdom from TPI (or other wise) enthusiasts!!!

Drake

Drake,

First, congrats on firing your engine - that's cool!

Should this adjustment be set such that the engine will idle with the IAC completely closed, or is it intended that the IAC must be opened somewhat for the engine to idle?

You can do it either way. I ran with the IAC closed without problems. You can certainly pull the sealing cap off the throttle stop to adjust the idle.

MegaSquirt-II has a stepper motor IAC driver, so you'll be able to run your IAC with that shortly, if you choose.

Lance.

I aslo have a TPI setup on a 70 Camaro using MS and am experiencing a sucking sound during moderate to heavy acceleration. The noise sounds almost identical to a turbocharger spinning up. I've attributed the sound to air sucking through the IAC orifice, since I have mine open in order to set the idle where I want it.

Has anyone running a TPI setup run into the same noise? What is it and what should I do about it?

Thanks for any feedback.

Chris

http://community.webshots.com/user/cmeyer124

am experiencing a sucking sound

Here where I work that sound usually means the boss is close by.




Sorry I couldn't resist.

Sounds like some form of leak. Maybe Cracked intake tube (the big black plastic one going to the air filter). Once had a Ford Taurus that made the same noise, but at idle, turned out to be a blown out Throttle body gasket fluttering. Check for intake leaks as well, spray some wd40 or carb cleaner around the intake, while the engine is running, and see if the engine races. Also check your PCV, had one go bad (wide open) once and the sound coming from the front seal was horrendous.

Don't let my Avatar fool ya' I ve got plenty of hours working on GM Vehicles. (puttin' TPI in my Hummer, great low rpm intake)

Check that you don't have any unused vac ports that are sitting open.

Also, a "free flowing" air cleaner (like a K&N or an AirHog) will sometimes make this noise. (My camaro does)

-Brian

Thanks for the advise.

I do have a K&N cone type filter on it, but I don't think the noise is due to the filter. Like I said the noise is pretty loud.

MegaScott - Are you running MS on a TPI setup? If so what did you do about the IAC motor? I'm not sure whether I should block it off completely or leave it partially open like it is now.

Chris

My TPI is still on the bench, the Hummer still has a Standard GM ECU TBI in it, soon to change though....by the time I get around to it MS2 will have been out for months. It has a stepper drive built-in. If it were me I'd block it off for now, and use a solenoid air bypass, you can always switch over to stepper control later.

I'm using a TPI throttle body for my Holley Stealth Ram. I don't plan on using the IAC, at least not at first.

Can I just pull off the IAC and block off the whole underside area of the TB with a piece of aluminum?

-Dave

Can I just pull off the IAC and block off the whole underside area of the TB with a piece of aluminum?

Dave,

Yes, but you may have to also block the inlet port in the 'air horn' area of the throttle body as well (otherwise the IAC passage may be fully open all the time - depending on it's design - and give you a 4000 rpm idle!). A bit of aluminum tape works well for this.


Lance.

wait til u sit next to a viper idling they literally hiss