Bosch Idle Valves

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KAT PWR
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Joined: Mon Jan 16, 2017 2:55 pm

Bosch Idle Valves

Post by KAT PWR »

I'm currently trying to get the idle on my Nissan KA24DE correct, after doing some updates while replacing the motor. The main thing I changed was the intake manifold which required me to use a remote idle valve. Not wanting to make a plate for the factory idle valve as many with this intake do, I chose it to find a Bosch idle valve for it. Initially, I grabbed a straight barbed 3 wire idle valve off a Volvo. Once I got around to wiring it up I learned I had to use another med current output to run a 3 wire valve, so I set to find a 2 wire valve with straight fittings. The only one I could find in this configuration was the early 90s 318i m42 idle valve. At first, the idle valve did not want to adjust when the motor reached idle vacuum ~20 inhg, I ended up flipping it so the flow arrow was backward then everything seemed to be fine. but going to adjust it cant get my idle below 800rpms sometime and really it can only go down to ~700 fully closed. come to find out when fully closed ~34% duty it still flows too much for proper idle. ordered a new one, same issue. does anyone know of another 2 wire idle valve in a similar configuration that I could use? or do i just have to go 3 wire?
idle valves
idle valves
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billr
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Re: Bosch Idle Valves

Post by billr »

I wouldn't throw a different type valve at it. 20" Hg manifold vacuum is quite normal, any valve intended for IAC use should handle that fine. I think you "went off in the weeds" by turning it so flow is backwards, that may sure make it so it will never be satisfactory. Change the plumbing back so flow is in the correct direction and let's concentrate on finding what the root problem is.
KAT PWR
Helpful MS/Extra'er
Posts: 42
Joined: Mon Jan 16, 2017 2:55 pm

Re: Bosch Idle Valves

Post by KAT PWR »

I only plumbed it backwards is because when you got into idle range of vacuum, the valve would no longer move. If when idling, I put my thumb on the feed the valve would free up and adjust (had it in test mode for this). both the junkyard and the new valve acted this way till flipped.

today I toyed with the minimum idle duty value lowering it from 34% to 29%. Managing to get a stable idle all down to 650rpm, any lower and the valve like most german idle valves would start to open up, raising the idle. the new problem is lowering the idle 50rpm worsened the surging I sometimes got when adding electrical load. readjusting the afrs to be fairly stable at 13.5-13.8 didn't do much. This was the main thing I struggled with for a while with the much smaller factory idle valve and factory intake manifold it more or less oscillated then surged. Using the same methods I tried last time just aren't cutting it, anymore unless it's idling with no load. maybe I just need to play with fuel some more. I did also adjust the mild aftermarket cams while replacing the motor shifting lower so it's not past my rev limiter, it also gave me 1-2 inhg more at idle.
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