# Need some tuning and Fuel Injection theory help **URL:** \ **Category:** NYSpeed Automotive\ **Created:** [July 18, 2006, 8:39pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767 "2006-07-18T20:39:21Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![rj-92](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rj-92/32/7310_2.png) [@rj-92](https://forums.speedlife.net/u/rj-92)\ **Post date:** [July 18, 2006, 8:39pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/1 "2006-07-18T20:39:21Z")
Alright tuning MOFOs. I got some technical and theory ish here for you. Background. My SHO, big cams with a good amount of overlap. since I had the cams my car idles like ish and often stalls. I had the idle increased and it helped but didn’t eleviate the problem. Problem has gotten worse with teh high flow heads. Also car seems to be running slightly rich at lower RPMs, sooted up tail pipes, plugs and CCs. Symptom specifics; Once it finds an idle its fine, but oftem takes a while to do so. Will surge idle searhing and oftem stall when coming to a stop with throttle close after normal driving. Seems to be worse when city style driving rather than low RPM highway driving. SHO Specifics; The car runs of a MAF and TPS and has an idle air control valve. (no MAP) Fuel pressure is regulated via the return line and manifold vacuum. More vacuum = less Fule pressure, less vacuum = more fuel pressure. Give all those are in tune and clean, ets, etc. It should idle fine given the stock cam profile. My thoery; with the larger cams and increased overlap there will be less vacuum at idle. The absence of vacuum at idle will increase the fuel pressure and (theoretically from my thought process) introduce more fuel at idle creating a rich condition at idle and hence a poor idle as this rich condition floods the engine. This would also cause sooting on the exahust, plugs and CCs. If the car was idling rich it would remain rich until higher int he RPM range when the engine can burn off the excess fuel. So, removing fuel at idle only would cure the poor idle and the rich condition with out affecting part and WOT characteristics. Thoughts please. ---
**Author:** ![focusinprogress](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/focusinprogress/32/7227_2.png) [@focusinprogress](https://forums.speedlife.net/u/focusinprogress)\ **Post date:** [July 18, 2006, 8:46pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/2 "2006-07-18T20:46:12Z")
hmmm, your thought process is logical. but i know enough about the way ford computers run an engine to tell you that might not be the culprit. ford computers have a function called dashpot. what dashpot does is controls the amount of air allowed through the IAC valve under idle conditions. when you add power with your heads and overlapping cams, this function is off by a margin of error, be it adding too much air through the valve, or not adding enough. this is normally the cause of a rough idle on the focus. other than that it could be a MAF calibration problem, but im assuming yours has not been messed with. my guess is with the new heads and the poverlapping cams, the air is obviously getting through the compression chamber faster, therefore you most likely need to add more air through the IAC at idle. what year is your SHO? if its OBD-2 i can datalog it to tell you if it is what i think it is. ---
**Author:** ![rj-92](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rj-92/32/7310_2.png) [@rj-92](https://forums.speedlife.net/u/rj-92)\ **Post date:** [July 18, 2006, 8:48pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/3 "2006-07-18T20:48:31Z")
'92, OBD-1 BTW, Off topic. I saw a Foci with a shaved rear hatch and the plate in the rear bumper, looked pretty tight. ---
**Author:** ![focusinprogress](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/focusinprogress/32/7227_2.png) [@focusinprogress](https://forums.speedlife.net/u/focusinprogress)\ **Post date:** [July 18, 2006, 8:49pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/4 "2006-07-18T20:49:39Z")
ah fuck. thought i could be sweet lol. is there any datalogging/flashing systems available for your car to tune it? IIRC sniper and tweecer are both working on something. ---
**Author:** ![rj-92](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rj-92/32/7310_2.png) [@rj-92](https://forums.speedlife.net/u/rj-92)\ **Post date:** [July 18, 2006, 8:52pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/5 "2006-07-18T20:52:18Z")
The TwEECer is available for the SHO. As far as I know Somedude is the only person with one locally and his is - the data logging feature. I guess when I get an extra $500 i should shell out for one. ---
**Author:** ![focusinprogress](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/focusinprogress/32/7227_2.png) [@focusinprogress](https://forums.speedlife.net/u/focusinprogress)\ **Post date:** [July 18, 2006, 8:59pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/6 "2006-07-18T20:59:42Z")
is this a common problem on SHO boards with guys that have done the same mods? ---
**Author:** ![rj-92](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rj-92/32/7310_2.png) [@rj-92](https://forums.speedlife.net/u/rj-92)\ **Post date:** [July 18, 2006, 9:03pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/7 "2006-07-18T21:03:27Z")
Yes most guys with the stage II cams have shitty idle. ---
**Author:** ![focusinprogress](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/focusinprogress/32/7227_2.png) [@focusinprogress](https://forums.speedlife.net/u/focusinprogress)\ **Post date:** [July 18, 2006, 9:05pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/8 "2006-07-18T21:05:12Z")
sounds like we need to come up with a sweet hack for everyone. what about grabbing a spare IAC valve from the junkyard and enlarging its passages too allow more air and see if it helps? shouldnt cost more than like $10 to try it out. cant hurt can it? ---
**Author:** ![rj-92](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rj-92/32/7310_2.png) [@rj-92](https://forums.speedlife.net/u/rj-92)\ **Post date:** [July 18, 2006, 9:14pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/9 "2006-07-18T21:14:32Z")
> [@focusinprogress](#): > > sounds like we need to come up with a sweet hack for everyone. what about grabbing a spare IAC valve from the junkyard and enlarging its passages too allow more air and see if it helps? shouldnt cost more than like $10 to try it out. cant hurt can it? Not at all I may even have a spare lying around. Thanx for the help. :tup: But wouldn’t having the idle speed raised help to aleviate that at all? it would open the IAB more then it would at stock idle speed. ---
**Author:** ![focusinprogress](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/focusinprogress/32/7227_2.png) [@focusinprogress](https://forums.speedlife.net/u/focusinprogress)\ **Post date:** [July 19, 2006, 3:35pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/10 "2006-07-19T15:35:30Z")
it depends how your “raising idle” on the focus some of the newbs think adjusting the stop screw for the throttle plate “raises” the idle, when in actuality its just holding the flap partially open when there is no throttle usage. this is actually bad for the car as it never gets to techinically “idle”. raising the idle another way WOULD help a bit, but you will probably still be rich down there, just not as stumbly and such, just more stable ---
**Author:** ![RuBiCaNT](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rubicant/32/7622_2.png) [@RuBiCaNT](https://forums.speedlife.net/u/RuBiCaNT)\ **Post date:** [July 19, 2006, 5:25pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/11 "2006-07-19T17:25:09Z")
I’ve got the same kind of setup in my ride and experience the same kind of symptoms. I do have the ability to adjust my fuel cut adjust when decerating but the 2 things that helped me the most were rebuilding my throttle body and setting the stop screw so my butterfly was open more at 0 TPS. I don’t know how the FORD tps goes, but with the DSM, you have a lit of room to play and adjust. Good luck, I have to set my idle at 1100 to get a decent amount of vacuum. ---
**Author:** ![MaximaSE98](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/maximase98/32/7600_2.png) [@MaximaSE98](https://forums.speedlife.net/u/MaximaSE98)\ **Post date:** [July 19, 2006, 7:33pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/12 "2006-07-19T19:33:32Z")
can u use any kind of piggy back to help ur fuel issues ---
**Author:** ![rj-92](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rj-92/32/7310_2.png) [@rj-92](https://forums.speedlife.net/u/rj-92)\ **Post date:** [July 19, 2006, 7:40pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/13 "2006-07-19T19:40:18Z")
I just plugged my EPROM back in this weekend and it seems to be helping. Seems to be gradually getting better like the car needs to “learn” teh program. ---
**Author:** ![MaximaSE98](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/maximase98/32/7600_2.png) [@MaximaSE98](https://forums.speedlife.net/u/MaximaSE98)\ **Post date:** [July 19, 2006, 7:50pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/14 "2006-07-19T19:50:19Z")
i was thinking like an SAFC to try and help with the low RPM richness ---
**Author:** ![focusinprogress](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/focusinprogress/32/7227_2.png) [@focusinprogress](https://forums.speedlife.net/u/focusinprogress)\ **Post date:** [July 20, 2006, 5:58pm UTC](https://forums.speedlife.net/t/need-some-tuning-and-fuel-injection-theory-help/14767/15 "2006-07-20T17:58:46Z")
^ not on ford computers, they learn over piggybacks and cancel them out.