cosworth YB .. strange idle behaviour / seems rich as well
16-06-2016, 02:32 PM
#1
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cosworth YB .. strange idle behaviour / seems rich as well
Hi,
I am the proud owner of a Dax Rush kitcar with a cosworth YB engine (200 block mated to a T5 BW gearbox), running dark greens, 3 bar map sensor, MSD chip with closed loop.
This winter I had a lot of mods on the car done (which included getting the engine out, had the turbo rebuild,...) Before doing all these things the car Always had an issue starting (never started the first time when cold, then started fine... when hot never an issue)
Now when I got the engine back into the car, the engine starts from the first time (I did clean the throttle body as good as possible without taking of the tps), every time even when cold. Then it idles normally, but when the car gets warmer (after a minute or so), the idle speed drops very low (almost stalls) and the ISCV kicks in picking up the rev's. and this goes on like that. As soon as I touch the throttle a bit engine speed is perfect and no dropping anymore.
I still need to set the CO screw (have no equipment here), and last time set the TPS correctly as per MSD instructions (so it would be a strange thing that would be the cause). Any ideas on how to find the solution or identify the problem?
Many thanks,
Regards,
Stijn
I am the proud owner of a Dax Rush kitcar with a cosworth YB engine (200 block mated to a T5 BW gearbox), running dark greens, 3 bar map sensor, MSD chip with closed loop.
This winter I had a lot of mods on the car done (which included getting the engine out, had the turbo rebuild,...) Before doing all these things the car Always had an issue starting (never started the first time when cold, then started fine... when hot never an issue)
Now when I got the engine back into the car, the engine starts from the first time (I did clean the throttle body as good as possible without taking of the tps), every time even when cold. Then it idles normally, but when the car gets warmer (after a minute or so), the idle speed drops very low (almost stalls) and the ISCV kicks in picking up the rev's. and this goes on like that. As soon as I touch the throttle a bit engine speed is perfect and no dropping anymore.
I still need to set the CO screw (have no equipment here), and last time set the TPS correctly as per MSD instructions (so it would be a strange thing that would be the cause). Any ideas on how to find the solution or identify the problem?
Many thanks,
Regards,
Stijn
16-06-2016, 03:01 PM
#2
Get it up to temperature, unplug the idle speed control valve, and adjust the throttle body idle screw (below the throttle body) until the rpm is around 900 rpm.
You may have inadvertently fixed a small air leak and it now just needs a little extra air to idle correctly.
It is worth checking the TPS calibration anyway as it only takes 2 minutes.
You may have inadvertently fixed a small air leak and it now just needs a little extra air to idle correctly.
It is worth checking the TPS calibration anyway as it only takes 2 minutes.
16-06-2016, 03:16 PM
#3
Hi,
I am the proud owner of a Dax Rush kitcar with a cosworth YB engine (200 block mated to a T5 BW gearbox), running dark greens, 3 bar map sensor, MSD chip with closed loop.
This winter I had a lot of mods on the car done (which included getting the engine out, had the turbo rebuild,...) Before doing all these things the car Always had an issue starting (never started the first time when cold, then started fine... when hot never an issue)
Now when I got the engine back into the car, the engine starts from the first time (I did clean the throttle body as good as possible without taking of the tps), every time even when cold. Then it idles normally, but when the car gets warmer (after a minute or so), the idle speed drops very low (almost stalls) and the ISCV kicks in picking up the rev's. and this goes on like that. As soon as I touch the throttle a bit engine speed is perfect and no dropping anymore.
I still need to set the CO screw (have no equipment here), and last time set the TPS correctly as per MSD instructions (so it would be a strange thing that would be the cause). Any ideas on how to find the solution or identify the problem?
Many thanks,
Regards,
Stijn
I am the proud owner of a Dax Rush kitcar with a cosworth YB engine (200 block mated to a T5 BW gearbox), running dark greens, 3 bar map sensor, MSD chip with closed loop.
This winter I had a lot of mods on the car done (which included getting the engine out, had the turbo rebuild,...) Before doing all these things the car Always had an issue starting (never started the first time when cold, then started fine... when hot never an issue)
Now when I got the engine back into the car, the engine starts from the first time (I did clean the throttle body as good as possible without taking of the tps), every time even when cold. Then it idles normally, but when the car gets warmer (after a minute or so), the idle speed drops very low (almost stalls) and the ISCV kicks in picking up the rev's. and this goes on like that. As soon as I touch the throttle a bit engine speed is perfect and no dropping anymore.
I still need to set the CO screw (have no equipment here), and last time set the TPS correctly as per MSD instructions (so it would be a strange thing that would be the cause). Any ideas on how to find the solution or identify the problem?
Many thanks,
Regards,
Stijn
22-06-2016, 02:47 PM
#4
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Thanks for the suggestions. finally had my hands on a mobile gas analyzer. I also checked the TPS and that has been set correctly.
When trying to lower the idle speed with ISCV disconnected and engine hot, I couldn't get the speed lower then 1200 (engine would almost stall suddenly), after adjusting the CO at that rpm a bit, I could lower the idle a bit more. But in the end it seems pretty hard to get the idle speed lower then 1100RPM. I tried adjusting the CO at that level a bit more... and got it easily below 1,5% as stated in the MSD direction for the closed loop. is that fine? or should I still try to get the idle speed lower???
Anyway, it idles normally now only at a speed a bit too high... is this ok with this CO level?
When trying to lower the idle speed with ISCV disconnected and engine hot, I couldn't get the speed lower then 1200 (engine would almost stall suddenly), after adjusting the CO at that rpm a bit, I could lower the idle a bit more. But in the end it seems pretty hard to get the idle speed lower then 1100RPM. I tried adjusting the CO at that level a bit more... and got it easily below 1,5% as stated in the MSD direction for the closed loop. is that fine? or should I still try to get the idle speed lower???
Anyway, it idles normally now only at a speed a bit too high... is this ok with this CO level?
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