When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I did an engine swap from 302 to 351. This is in a 1992 f-150. Used the IAC from the 302, it has the high idle when cold run great but idles a little low and it doesn't idle up when put in park like the 302 did. My question is does the 351 use a different IAC than the 302. Does it have more air flow at the bypass on the 351 than does the 302. Other than this ,it worked out well. I the did fiveology maf conversion run good, other than my low idle.
I did notice that they use a different part # on the iac.
The IAC worked perfectly in the 302. The first thing I checked was the tps. I thought the 351 would use more air at idle than the 302. It has a mild cam, plus the maf conversion. It runs very well other than the low idle. It doesn't struggle to idle it's as smooth as cold be. I'm considering 2 options making the holes in throttle plates a little larger or doubling the gasket and cutting a channel in one in order to get more air flow. What's your opinion on that.
thanks for your reply to my question
What rpm does it idle at?
Has the throttle plate stop screw been tampered with on that TB?
The OEM warm idle speed is 650-680rpm, if that is what you have and it's stable and doesn't stall when coming to a stop leave it alone.
If you would still like to bump the idle speed up a little turn the throttle plate stop screw in just a small amount, but don't go too far if the truck has an auto trans the TC will begin to grab and vehicle will want to take off when in gear.
it idles at 5-600 at temp in drive, this engine is not broke in yet. it might come up when broke in. and wont moving "the screw change the voltage of the tps I set it at the spec for my MAF conversion at manufacturer recommendation I know it pretty close. is the other engine the iac would kick the idle up in neutral and park for just a few seconds. that's not happening on this engine. I like 700 at idle in drive. maybe I should wait till engine is fully broken in. Oh I used the comp cam you recommended it is nice and runs really good. and the sweet spot is exactly where I wanted it. If I do want the idle higher is there a way with out changing tps voltage.what's your opinion? thanks for your advice.
The PCM takes note of the TPS closed voltage at every startup so as long as it is below 1v at idle you are good, everything above that is considered "part throttle".
Again... does the stop screw look like it has been moved? The throttle blades should be open just a crack and be touching the stop screw at the closed position, if the screw isn't touching anything it has been moved, so my suggestion is to go back and reset the blades and stop screw, then adjust the TPS if necessary(anything from 0.8-0.99v is good), and then see how it behaves.
302/351w use same IAC, but it changed in 92, and they have the vent on side(throttle bodies had a coating put on to help stop sludge build up), the 91 and older dont have the vent(no coating on throttle body). vent on 92 newer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
