Idle Issue EFI

[jpilcher]

Hi Guys

I am having a bit of an issue with my idle. Last year I converted my car to a SDS EFI system. I am using the 2 wire Bosch Fast idle valve. I have the fast idle set
to shut off at 51 Celsius. The idle drops to around 650 rpm. As the car warms up
the idle speed increases to 1000 rpm. I've adjusted the idle speed using the adjuster
on the throttle body. If I set it lower than 1000 rpm, the cold idle will be around 550 rpm. Do I have a leak on my injector blocks? I am also running the phenolic spacers.
Should I use a Copper Spray on the gaskets to seal them up? Or just re-torque the studs?

Thanks

John

[jpnovak]

Easy way to check for a leak is to block off the idle passageway and see if it still idles high. you could also pressurize the inlet using a vacuum line and see if you have any leaks other than through the filter side of the turbo.

I admit I am a little confused about idle speeds. Are you saying that

cold idle is 650 and warm idle is 1000? You might have the idle valve wired backwards or possibly your setting is inverted in the software. I am not sure how the SDS is wired.

Also, what intake system do you have on the car? Stock or 3.2?

[Tippy]

Easy to wire backwards as Jamie said. Is the RPM change linear, or does it change instantly from one RPM to the next? Being fast idle, I assume it instantly changes?

[jpilcher]

With the SDS system it is an on/off style fast idle valve. Once it hits the preset temperature it closes the valve. The 2 wires on the fast idle are positive and ground, wired through a relay, back to the computer.

The fast idle kicks in for the first 1 to 2 minutes at 1100 rpm, once it hits the 51 Celsius it drops down to 650 rpm. Then it starts to speed up gradually until the car is fully warmed up.
Rpm then is at 1000 rpm.

I've tried putting a restrictor in the fast idle hose filling it with JB weld and drilling a hole until I reached a suitable rpm. This created a hard start issue.

[Tippy]

Is it leaner at the 650 than the 1000 fully warmed?

[jpilcher]

It's richer at 650 rpm. 12.5 afr once fully warm 1000 rpm Afrs are 13.5.

[IMR-Merlin]

Are you verifying that the engine and ECU are seeing the same temp reading?

So, what you are saying is that the car starts fine, idle "normal" for a couple minutes, then the idle drops to 650?

[Tippy]

Originally Posted by IMR-Merlin

Are you verifying that the engine and ECU are seeing the same temp reading?

So, what you are saying is that the car starts fine, idle "normal" for a couple minutes, then the idle drops to 650?

It drops to 650 because the fast idle valve is stopped being supplied power.

The mystery is why the RPM increases.

Sounds like the idle valve is creeping back open. That'd be easy to test. Should be no power to it when warm.

[IMR-Merlin]

Or it's just getting up to operating temp and into it's sweet spot.

[IMR-Merlin]

I have my SC doing the opposite. It will high idle at 2k for about 5 minutes.. if I shut it down and let it sit for a few minutes, it will idle fine 950 RPM.

[proffighter]

I will read the thread when I have some time, sorry buisy now. Until then you may find some answer in my SDS thread, page 5 is about idle too:

Another EFI conversion

Check page 4 for my idle valve and restrictor

Update, came into my mind that I answered similar question once here:

EFI Cold Start Maps?

Hope it helps

[xbmwguy]

I don't know the sds system and whether or not it can support a 3 wire stepper motor but the 2 wire is an on/ off switch. There should be a warm up "curve" in which the valve is open during a pre determined set of temp values.it is not important for the settings to be the same as the temp on your cars dash as it is only used for warm up and enrichment if the coolant( oil) gets too hot. I would disconnect power to the valve and see what happens when cold

[jpilcher]

Thanks Guys for all the responses. I will try unplugging the fast idle valve and see if that has an effect.

[dap930]

jpilcher,

Is the idle valve being used the original CIS idle up valve or a 2 wire Bosch IAC "motor" that is controlled by PMW (pulse width modulation)?

[jpilcher]

Idle Valve is the 2 wire Bosch IAC motor. I have been doing some research on the 2 wire units.
Some units remain open until power is applied, then they only open 25%. This would explains
the slow increase in rpm from 650 to 1000 rpm. I am going to try unplugging the IAC tonight.
I understand there is an adjuster screw, to adjust the voltage going to the IAC.
Not sure if mine has this or not. My tuning software does not allow for this adjustment.

[Tippy]

Yep, unplugging or using a multimeter during cold, warm, and hot engine temps should tell you everything going on.

[jpilcher]

Well I unplugged the Fast idle valve and it doesn't seem to have had any effect. Idle was around 450 rpm. I adjusted the idle adjustment screw on throttle body up to 950 rpm. As engine warmed up rpms started to climb. I think I have an air leak. I re torqued intake manifold bolts.
They seemed loose to me. I had a couple of other issue to address. Re-route vr sensor wire away from spark plug number 1. Fix silicone coupler on turbo down pie. Any other sources for air leak?

[s5uewf]

I would plug the actual idle air circuit to eliminate the possibility air is leaking past the idle air control motor line. Then I would set AFR and idle speed at normal operating temp and see if it is stable then or if it still creeps up.

If you suspect an air leak and it is manifesting itself at idle, I would suspect your AFR's would go lean at idle as unplanned for/unmapped air is entering the system and leaning the mixture.

I have a sort of similar situation with my Bosch 2 wire IAC - if I plug that loop off and set idle and AFR's perfectly, I get a nice idle and stable AFR's - but I lose the advantage of a high idle/choke type effect. If I connect the IAC circuit and activate the IAC motor, my idle goes higher and my AFR's go leaner because some air leaks past the IAC motor even when it is closed. I need to compensate for this by adding fuel and lowering my idle stop and then I can achieve a stable idle and still get good cold start, etc.

I would say the idle air control is the most troublesome aspect of my entire EFI system. And it is not "really" needed ...

[jpilcher]

Thanks Emery, I will give this a try. I have to agree, the fast idle is my biggest annoyance.

[jpilcher]

Well I plugged the fast idle track, it seems to have made a significant difference. Idle is stable and Afrs are stable. Idle has also smoothed out. Car has never sounded so good at idle.
Thanks for all your help.