[FullSizeBronco1990]

hello, recently my 1990 302 bronco has started acting up on me. whenever i brake harder than normal when coming to a stop my rig starts to idle really low and die out the closer i get to completing the stop. however if i brake normal the idle remains normal. i was thinking it had somthing to do with the TB, but after spraying it with crc cleaner and cleaning it the problem remains. the air filter is clean too. if you have any ideas please let me know. thanks

 

[Seth.Gatewood]

Do you have a check engine light? If so, everyone one here is gonna insist you first check codes.

You might also try cleaning the IAC valve. Not long ago I cleaned mine trying to troubleshoot another issue and although it wasn't the IAC in my case, it seemed to idle a tad smoother. There are some good write ups for cleaning the IAC valve and it's extremely easy to do.

Another thing it could be is the TPS (throttle position sensor). Assuming you have a Chiton's or other repair book, there are some instructions for testing it. It could be as simple as cleaning the terminals on the TPS, too. When I had a strange idle problem (when I tried cleaning the IAC), cleaning the TPS connection is what fixed mine.

Good luck!

 

[Jasonhughes2009]

I'd say cleaning the IAC is a good start like seth suggested, also pull codes, not every code throws a MIL at you

go from there and report back

http://www.fullsizebronco.com/forum/showpost.php?p=2719346&postcount=131

http://fordfuelinjection.com/?p=13

 

[FullSizeBronco1990]

theres no check engine light, and thanks ill clean it out later and let you know what happens. i just hope it has nothing to do with the fuel pump.

 

[jopes]

theres no check engine light, and thanks ill clean it out later and let you know what happens. i just hope it has nothing to do with the fuel pump.

pull codes anyways.

 

[Seth.Gatewood]

theres no check engine light, and thanks ill clean it out later and let you know what happens. i just hope it has nothing to do with the fuel pump.

I have to apologize FullSize... I may have slightly misinformed; I forgot the computer DOES store some codes occasionally even when the check engine light is not on. That 2nd link that Jason Hughes supplied gives you VERY easy instructions on doing a self test... and it's pretty cool!

 

[FullSizeBronco1990]

awesome, thanks for all the help guys. i will get the codes pulled tonight and clean the iac valve and let you guys know how it goes.

 

[JKossarides]

I agree here X infinity....lol lol

A. FIRST always "pull codes" to see what elec/electronic faults are indicated for initial diagnosis and FYI, there are no fault codes for FPR = fuel pressure regulator it's a vaccum issue and requires using a fuel pressure gauge testing for psi.

B. Check/test voltage settting for TPS....originally thought to be .93v -.97 volts but rather now .55v -.75 volts.

Posted by FSB member Jermil01:
Wanted to update this thread based on some TPS adjustment information I got from one of my tuning sites. This goes against the conventional wisdom of setting the TPS closer to .95 range. Thoughts??

Regarding any ECU controlled function (and idling conditions in particular), before any strategy based adjustment can be made by a computer controlled system, it must first run somewhat normally in a default and OL mode. To do this with a FORD you must first follow a few rules.
You must keep the TPS input above the deadband area and below the "tip in" area. On a FORD this equates to below approximately 0.9V and above 0.45. Anything above 0.90V the ECU thinks the throttle is starting to open. This brings into affect possible dashpot and fuel cut strategies which can turn one grey real fast. Below approx 0.40-0.45V the system suspects an incorrect input and substitutes a default figure. So first off, the TPS should be set to around 0.55-0.75V.


Most TPS sold today are the "plug & play" style with no adustment using a multimeter but there is a Ford Racing Performance Parts (Techline (800) FORD788) ~ idle setting instruction sheet steps 1-9 for IAC and suggestion to drill out the TPS = throttle position sensor mounting screw holes in order to adjust voltage setting which controls throttle body "blade angle air induction".

C. Clean, replace gasket and check/adjust IAC according to ^ the procedure above.

D. Check and replace air filters and PCV filters if need so the engine can breath properly.

E. Get a Haynes Repair Manual rather then use the Chilton, most here say it doesn't "read" as well compared to the Haynes, Red version (older) Green version (newer)

Good Luck ~ :thumbup