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

Should work fine in either case. And, if you can, send me a picture after your mods, I'd be interested on how it looks.

Thanks Richard - I'll send pics when completed.

Per the question posed by 88TSI_rob - that's interesting because I looked up the Neihoff PN 21774 on line and it showed the valve, but with what looked like a small pintle seat size as you described and like on the threaded mount IAC valve. It's just a pic and could be incorrect - but I did another look-up, this time I looked up the part by application - ie: 1992 Jeep Cherokee with 4.0L. It listed a series of identical looking valves as the previous pic, corresponding to the same Neihoff PN with differing manufacturer PNs - all but ONE.

The last one listed, AC151. It also corresponds to the PN 4637071, same as the one above it and same application as all the others - but it definitely appears different than all the rest - and it looks from the pic to have a slightly larger pintle seat diameter! It also looks identical to the valve shown: http://www.megasquirt.info/ms2/GMIAC.jpg

Not sure why different valves would be listed for the same application - but possibly on the OEM fitment the pintle seat size has more tolerance? Maybe only one manufacturers valve will work with the custom IAC housing?

Check and see what you think:
http://www.partsamerica.com/ProductList ... ntrol+Unit

Jeff

Just an FYI hear as DarkStar will be the best to answer these qestion at the moment-- but I'm working on sourcing and testing a good, affordable valve that I'll then put up for sale with the bodies. I've got one in to test, just haven't had the time yet-- I've got a new guy starting next week though so i'll be able to start ticking off all the to-do's on the list ;).

I have the illustrated parts guide and will scan the pages... give me a few minutes...

FWIW I placed an order for the AC151 IAC valve this morning. Found it at RockAuto.com for $35 which looked to be a good price.
This part is made by Standard Motor Products, as opposed to AC Delco or other manufacturer.
I'll let you know how it works out.

Jeff

Ok, here you go... I wanted to keep the resolution up so you could see the detail and words so I zipped them, they are kinda big. I have a feeling they won't be around for long so grab them while you can... Also, keep in mind anyhting labeled Niehoff is just a Standard product in a different box.

Well... I can say now that the (had my fingers crossed...) AC151 IAC valve does NOT fit the housing either.

The pintle on the valve measures 0.0475" diameter at the outer edge, and about 0.425" just under the lip. No way it'll seal in the housing - the ID of the seat is just over 0.500".

Maybe we're trying to use the wrong valve? I was sure this was going to be "the one"... Not!

Jeff

Jeff,

The pintle 'cone' doesn't seal to the bore of the housing, that's why the o-ring is there. The cone only has to seal to it's seat. The distance between the pintle cone and seat determines the idle air volume that is bypassed.

Perhaps i'm not understanding you correctly, though.

Lance.

Think I have that part straight Lance - the actual bore the IAC sits down into and seals against is quite a bit larger - 3/4" or so? I was referring to the bore of the pintle seat itself - the ID below where the pintle "seats".

Does the IAC possibly provide some level of air "leak", to compensate for a fully closed throtttle body at idle? Still, a 0.025" difference in diameters would be a pretty big leak! Working off line with Richard on this - we'll get to the bottom of it! I want this product to work - as I want to use it!

Jeff

Jeff,

Okay, I understand - yes - the seat ID needs to be a bit smaller. I have one of these units, and the seat ID is 0.500" (as near as I can measure it), as you say.

Two of the steppers I use for bench testing have actual inner seat diameters of 0.300" and 0.380" (though the seat can be a bit larger by riding up the cone a bit). The maximum cone diameter on both is 0.472".

Interestingly, the beta unit I tested worked fine, but this was with a Holley IAC stepper, which muct have a slightly larger 'cone' (or I got lucky in the production tolerances).

The IAC is not designed to have a controlled 'leak' when closed - it should seal completely against the seat. Otherwise there's no 'final' position for the pintle, and it could come out of the stepper.

Lance.