rb20det timing and idle issue

[Sirsyorrz]

Hey guys so im having an issue with my timing and idle and ive searched everywhere and tried everything i can

 

so my timing is maxed out between the 4th and 5th mark so around 20degress when manual is suppose to be 15degress, my cas is turned all the way right so i cant lower it anymore. im doing the trick where you put a old ignition lead on cyl 1 but could it be that the way my timing light sensor clicks on is the wrong way around? as when it gets to 4k revs it feels like it retards the timing alot as it bogs down but still makes boost then around 4.5k it kicks in and it throws you back as its like i was brake boosting it.

my o2 sensor wiring is a little bit melted so thought that might be causing the timing issue but i unplugged it and the same issued happened or could that mean i was never getting o2 sensor data and thats why it retards timing at 4k?

 

my idle wont go any lower than 1.1k revs, ive set the ecu all the way anti clockwise ive backed out the screw on the iacv and backed it all the way in, my tps is set to 0.53v ive made sure my throttle cable is loose enough and not holding it open.

 

just looking for ideas on what else it could be, i have a friend coming over on the weekend to help but just want to try narrow it down, firstly will get a new connector on both ends of the o2 sensor.

[blind_elk]

I may be wrong, but I think that is set at about 12.5 BTDC

 

Wide / thick mark is TDC. Pulley is rotating from left to right.

[Sirsyorrz]

53 minutes ago, blind_elk said:

I may be wrong, but I think that is set at about 12.5 BTDC

 

Wide / thick mark is TDC. Pulley is rotating from left to right.

i thought first mark was 0 then 2nd 5 3rd 10 4th 15 5th 20 6th 25

[Sirsyorrz]

1 hour ago, blind_elk said:

I may be wrong, but I think that is set at about 12.5 BTDC

 

Wide / thick mark is TDC. Pulley is rotating from left to right.

even if wide mark is TDC i cant turn it anymore right to go more timing or less timing

[GTSBoy]

I do not know how many times I have to say it.....RB20 ECUs do not given a flying f**k what the TPS voltage is. That sensor is provided for the benefit of the auto trans TCU only. The ECU only looks at the closed throttle switch. Stop confusalting the RB25 with the 20.

If the idle won't come down, it would suggest that there is either a vacuum leak, the IACV is sticky/broken, the AAC is f**ked or you have the main throttle adjusted too far open. The ECU will attempt to rein in a runaway idle speed by delta control on ignition timing, meaning it will retard the timing to try to slow the engine.

You should not be trusting the TDC mark on the pulley unless you have mechanically proven to yourself that it hasn't slipped. You need to put the engine on #1 TDC (sparkplug OUT) and see whether TDC actually lines up with the mark. Then you really need to understand the marks and how many degrees they represent. This is easy, as there are only 360 of them and they are spread out evenly around the circumference of the pulley, which is easily worked out from the diameter and a number called pi.

[Sirsyorrz]

32 minutes ago, GTSBoy said:

I do not know how many times I have to say it.....RB20 ECUs do not given a flying f**k what the TPS voltage is. That sensor is provided for the benefit of the auto trans TCU only. The ECU only looks at the closed throttle switch. Stop confusalting the RB25 with the 20.

If the idle won't come down, it would suggest that there is either a vacuum leak, the IACV is sticky/broken, the AAC is f**ked or you have the main throttle adjusted too far open. The ECU will attempt to rein in a runaway idle speed by delta control on ignition timing, meaning it will retard the timing to try to slow the engine.

You should not be trusting the TDC mark on the pulley unless you have mechanically proven to yourself that it hasn't slipped. You need to put the engine on #1 TDC (sparkplug OUT) and see whether TDC actually lines up with the mark. Then you really need to understand the marks and how many degrees they represent. This is easy, as there are only 360 of them and they are spread out evenly around the circumference of the pulley, which is easily worked out from the diameter and a number called pi.

ive checked everything with the throttle body and its not set to high, i can change the revs up to 2k with the iacv screw but can't go any lower than 1.1 with the screw all the way in, dont know about any adjustments on the aac which i think is the thing right next to fuel rail? ill have to check for vaccum leaks but dont think thats it

ill also check TDC with spark plug out and ill also check and make sure the cams align up

also the retarding timing only happens while driving it will hit 4k revs and boost will still go up but it feels like i have the brakes on and it just bogs

also no idea what you mean by the 360 part

[GTSBoy]

52 minutes ago, Sirsyorrz said:

iacv screw but can't go any lower than 1.1 with the screw all the way in, dont know about any adjustments on the aac which i think is the thing right next to fuel rail? ill have to check for vaccum leaks but dont think thats it

No. The idle screw is the gross base adjustment. The IACV is a controlled valve. The ECU controls it to open and close to allow more or less air to idle up or down. If there is no control because it is not doing what it is supposed to be doing, or, if it is closed down as far as it can because there is air coming iin via another pathway, then you are shit out of luck with respect to mechanical idle control.

54 minutes ago, Sirsyorrz said:

also the retarding timing only happens while driving it will hit 4k revs and boost will still go up but it feels like i have the brakes on and it just bogs

I wasn't talking about your odd 4k engine behaviour. I was clearly talking about idle control still. Go back and read again.

 

55 minutes ago, Sirsyorrz said:

also no idea what you mean by the 360 part

If you want to work out how many degrees each mark on the pulley equates to, you just have to measure how far apart they are (dressmaker's tape measure) and compare that to the total circumference of the pulley. If the pulley was 360mm around (to use a nice simple assumption) and the marks were 10mm apart, then that would be 10mm out of 360mm and 360mm is equivalent to 360 degrees. So the 10mm is 10 degrees. If the pulley was 500mm around, then the 10mm would be only 360/500 = ~7°. For the marks to be 10 degrees apart on a 500mm circumference pulley, they'd need to be ~15mm apart. Get the idea?

[Sirsyorrz]

10 minutes ago, GTSBoy said:

If you want to work out how many degrees each mark on the pulley equates to, you just have to measure how far apart they are (dressmaker's tape measure) and compare that to the total circumference of the pulley. If the pulley was 360mm around (to use a nice simple assumption) and the marks were 10mm apart, then that would be 10mm out of 360mm and 360mm is equivalent to 360 degrees. So the 10mm is 10 degrees. If the pulley was 500mm around, then the 10mm would be only 360/500 = ~7°. For the marks to be 10 degrees apart on a 500mm circumference pulley, they'd need to be ~15mm apart. Get the idea?

yeah i get it now, the workshop manual says each mark is 5 degress 0 being first on the left 

 

10 minutes ago, GTSBoy said:

No. The idle screw is the gross base adjustment. The IACV is a controlled valve. The ECU controls it to open and close to allow more or less air to idle up or down. If there is no control because it is not doing what it is supposed to be doing, or, if it is closed down as far as it can because there is air coming iin via another pathway, then you are shit out of luck with respect to mechanical idle control.

ill check for vaccum leaks and will also give the iacv a good clean

another quick question would my idle being at 1200rpm effect me setting the timing? as right now say everything else is perfect and tdc is correct i cant adjust the cas anymore to get any less timing as per the picture of the cas?

Edited December 17, 2019 by Sirsyorrz

[GTSBoy]

If the idle is high and can't be controlled down with air, then the ECU should be trying to retard timing. Although, having said that, I don't know how much delta ignition control is done by the RB20 ECU. The 25s do it, just not as sure of the 20. Anyway, this is why it is important for you to work out if the timing marks actually are lined up with TDC properly (not the cam timing marks, the marks on the pulley). The rubber can slip on tired old balancers and the marks can be very wrong. if they are, then what you are doing with your CAS is not based on reality. We can't go about trying to solve really weird shit until we trust the numbers.