Another SPFI conversion .."Idleing" question

[Petersubaru]

the conversion parts came off a car that seemed to work flawlessly..just turn the key "only" and it started immediately and ran smoothly every time...now that the conversion is done, both "starting and idleing" at 700-800rpm can only be done if the throttle plate is kept "slightly" more open, otherwise it just idles at 500-550rpm...I turned the throttle plate adjusting screw to increase the rpm so that final timing adjustments could be made..I tried adjusting the idle by turning the IAS screw and the rpm increased but now ran rough, so that didn't work..other then this slight problem, it runs very nice..

[Crazyeights]

LOTS of time invested personally with this problem. With a Highly-Modified EA81 it's even harder to find the sweet spot (if there is one). Some tips based on my tinkering. Make sure the timing isn't too far advanced, stay at a max of about 28 degrees, the stock throttle plate screw location for most of the SPFI's I've seen is about 1/2 turn clockwise after the screw just touches the stop. You will probably need to go another 1/4 to 1/2 turn open but no more. Finalize by finding the sweet spot with the Idle/Air control screw near the top of the TBI. Make sure the IAC valve is connected and working properly, no air leaks between the throttle body and the MAF and the PCV is properly routed. Idle should flair up when first started and stabilize after a few seconds.

 

Let me know if you find anything that helps even more:rolleyes:

Edited August 14, 2010 by Crazyeights

[GeneralDisorder]

You are not EVER supposed to touch the throttle plate stop screw - it is not an adjustment. It's only purpose is to keep the throttle plate from jamming in the closed position.

 

The only idle adjustment is the IAC.

 

Have you run a D-Check?

 

The crankcase is part of the metered air system of the SPFI - make sure you have no leaks - valve covers, oil dipstick, etc.

 

GD

[Crazyeights]

@GD I understand that. However there are differences between the EA81 and EA82 such as total combustion chamber size, SOHC versus OHV, CAM Shaft timing, ect and at the end of the day with everything else exhausted we have to make our cars run in a manor acceptable to us. Idling like crap at 500 rpm with a Brand new highly modified engine just doesn't work for me. A spare virgin throttle body is only about $8.50 at the local P-A-P. FSM does contain a detailed procedure for adjusting the Idle Stop screw.

 

 

Your right-ups and informative posts are the best and I have learned a lot from you. Any ideas are greatfully appriciated:)

Edited August 15, 2010 by Crazyeights

[Petersubaru]

You are not EVER supposed to touch the throttle plate stop screw - it is not an adjustment. It's only purpose is to keep the throttle plate from jamming in the closed position.

 

The only idle adjustment is the IAC.

 

Have you run a D-Check?

 

The crankcase is part of the metered air system of the SPFI - make sure you have no leaks - valve covers, oil dipstick, etc.

 

GD

..the throttle set screw has been reset and tested to within specs useing my digital voltage meter..connecting the 2 green connectors only give 5 short "bleeps" and then repeats itself..as you recommended, I did check for vac leaks and did find a leak around where the sensors and rubber tubing for the carbon canister hook into and got that repaired, (what a difference a few vacuum caps can make)...also pulled the IAC screw out and cleaned inside with a spray cleaner..now the car runs very smooth at idle and I believe this problem has been dealt with...However, there is still a little roughness, although barely noticeable, with some very faint popping or a miss that can be heard when the car reaches around 2000-2500rpm..I plan on getting a new O2 and coolant sensor plus have the injector cleaned...hopefully this might make a difference for complete smoothness...

[GeneralDisorder]

@GD I understand that. However there are differences between the EA81 and EA82 such as total combustion chamber size, SOHC versus OHV, CAM Shaft timing, ect and at the end of the day with everything else exhausted we have to make our cars run in a manor acceptable to us. Idling like crap at 500 rpm with a Brand new highly modified engine just doesn't work for me.

 

I completely understand - perhaps the solution is to enlarge the IAC passages to provide for a larger adjustment range and more air for the modded engine - the IAC was meant to supply air for an EA82 which is only slightly more than a stock EA81. It is possible your engine needs more air than it can currently provide.

 

On an otherwise stock EA81 I've been able to get the SPFI to perform very similar to stock..... but as you say it could be outside it's air/fuel limits on a modded engine. The only solution for that would be to move to MegaSquirt, use a larger throttle body from something else entirely and change things as needed to compensate.

 

GD

[Crazyeights]

Thank you for the response. I am very close to acceptable idle condition on mine especially the more I drive it (perhaps it is still too fresh). Sorry for Hi-Jacking your thread, I'll shut up and read now:grin:

 

[EDIT] @GD I need to eat some crow here. You were right. I was just lucky enough to have had 2 different SPFI units with bad injectors. Following a tip from a different thread on here I finally borrowed a 4 gas and got to the bottom of it. High HC's, High O2, and no vacuum leaks on a brand new performance build (crappy idle and low on power). I harvested a nice low mileage SPFI unit from a 91 or 92 today. I cleaned it up, bolted it on without touching any of the adjustments and it idles perfectly for the first time. I also has TONS more power now. It really snarls for an EA81 with all the mods. I would have to agree with GD now, don't touch the screw:rolleyes:

 

Thanks again!

Edited August 20, 2010 by Crazyeights

[GeneralDisorder]

Excelent! I'm really glad to hear that you got it fixed and it wasn't neccesary to change the throttle stop.

 

It's nice when we hear back from people on what does/does not work. So many posts end without a resolution .

 

I too have had issues with the IAC (seemingly) and idling too fast/too slow/hunting. Do you have any idea what was wrong with the previous two units?

 

GD

[Crazyeights]

Must be the injector itself? Not really sure. Both of the bad units had well over 200k on them. The perfect one I scored had only about 122k on it.

[Petersubaru]

as mentioned earlier, with the present set-up, everything is running ok...the injector which made the car run rough has returned from the cleaning/refurbishing shop ..installed into the other spare/original throttle body and then installed into the car..definitely the cleaning helped in this case, a very noticeable difference..for what ever reason, the injector "clicking" sound is now louder after the cleaning...sooo , I have one complete throttle body that seems to be operateing as near perfect as can be...at cold start the rpm is at 1600 and then very shortly drops in rpm ..the other complete throttle body also has a good working injector, but its behavior is somewhat different..the cold start takes the rpm to 2000 and stays there, also at times it is hunting, but when warmed up, all is good..I have changed out the coolant sensor (not sender), but, still makes no difference...I am putting the problem at this moment onto the idle control unit for not working properly and will keep it as a spare when travelling across the country..tomorrow I will install a 3 wire O2 sensor

Edited August 21, 2010 by Petersubaru

[Petersubaru]

..is there any reason why the idle drops when putting the headlights on..I lose about 60 rpm when sitting at the corner ....... also when stepping on the brake pedal, the fuel pump slows down momentarily..I am useing the fuel pump off my old turbo...

[GeneralDisorder]

..is there any reason why the idle drops when putting the headlights on..I lose about 60 rpm when sitting at the corner ....... also when stepping on the brake pedal, the fuel pump slows down momentarily..I am useing the fuel pump off my old turbo...

 

Load from the alternator. The alt only makes about half it's rated amps at idle - something like 25 amps. When you turn on accesories you are asking for more power from the alt and that drags against the engine causing a drop in RPM's - same as if you were to turn on the AC compressor. Higher draw = more mechanical load on the belt.

 

When you press the brake you are using engine vacuum via the brake booster -this affects engine speed momentarily as you are creating a metered air leak in the manifold to replenish the vacuum in the booster lost through the braking action. Basically it's a vacuum leak for a split seccond - that causes the RPM's the drop, lowering the output the alternator, and causeing the speed of the fuel pump (relative to voltage) to change.

 

If you are noticing these things then you probably have a borderline battery and possibly a weak alternator or corroded connections, etc. Check for voltage drops, check the amperage draw off the main junction and compare to the specs of the alt at idle.... a strong battery will have a capacitor like function when you are idleing - it will fill in the neccesary amps that the alternator is having trouble with and make this problem much less noticeable. But everything has to be working well for this to happen correctly.

 

GD

[Petersubaru]

Load from the alternator. The alt only makes about half it's rated amps at idle - something like 25 amps. When you turn on accesories you are asking for more power from the alt and that drags against the engine causing a drop in RPM's - same as if you were to turn on the AC compressor. Higher draw = more mechanical load on the belt.

 

When you press the brake you are using engine vacuum via the brake booster -this affects engine speed momentarily as you are creating a metered air leak in the manifold to replenish the vacuum in the booster lost through the braking action. Basically it's a vacuum leak for a split seccond - that causes the RPM's the drop, lowering the output the alternator, and causeing the speed of the fuel pump (relative to voltage) to change.

 

If you are noticing these things then you probably have a borderline battery and possibly a weak alternator or corroded connections, etc. Check for voltage drops, check the amperage draw off the main junction and compare to the specs of the alt at idle.... a strong battery will have a capacitor like function when you are idleing - it will fill in the neccesary amps that the alternator is having trouble with and make this problem much less noticeable. But everything has to be working well for this to happen correctly.

 

GD

Thankyou, and the battery was tested and found to be very weak..cranking amps are very low, so it was a good time to find this problem well ahead of the coming cold weather ..I got nine years out of the battery...