Idle dies over time

[mikeatrpi]

My car is weird with the idle. MS1 v3.0 running spark and fuel; 82 NA with T conversion; datsun air regulator for fast idle.

 

It runs great when cold - rock solid idle around 8-900 RPM. Once it comes up to temp, unless I hold the throttle open it will die. Actually sometimes as its dying out, the MS sensor inputs go crazy and the car shakes. If I bump the throttle pedal a little bit it comes back to smooth-running.

 

I'm going to adjust my idle screw a little bit. I'm also going to look at my enrichment settings. Lastly, the datsun air widget... it sucks HUGE vacuum when its idling. Even when warmed up it still draws vacuum just not as much. Should I cover that thing up?

 

On the bench, I applied 12v to it and I could see the plate inside close. How do I know if its air-tight?

 

I'm attaching a data log of it going bezerk, and my MSQ. Thanks all!

badidle.zip

[TrumpetRhapsody]

So you have the "datsun air widget" connected to MS as a Fidle then. Check your settings to make sure it's open during cold starts, but closed when warmed up and idling. That could definately play into a bad idle if it's not configured properly.

 

Also sounds like a warmup enrichments problem. Set your ve's and throttle stop so it will idle when warm, then work on your warmup enrichments.

[mikeatrpi]

Actually I just have it connected to +12v from the fuel pump relay. By widget I mean the datsun auxiliary air regulator (AAR). Its easier to say widget!

 

Thanks for the tips. I stole Metro's warmup enrichments from the sticky. Maybe its time to find my own.

[RTz]

I think you have a few things going on...

 

Firstly, cold idle, useing the 'widget', should be higher than 8-900. By the time it closes down, there won't be enough air for a stable idle. If I set my car to cold idle ~1400, warm idle settles in nicely at 680 to 700.

 

Secondly, the widget should not be closeing down as soon you start the engine. That will cause the valve to close prematurely in the winter. I normally set it to begin closing down at 100F water temp. I find this to be a nice compromise between winter and summer months.

 

Chart below shows a nearly complete warm up cycle. Black trace is RPM, green is temp, and red is TPS. Ignore the orange trace. The air reg. closing is very clear (at 4:10)...

 

 

 

 

 

 

 

Lastly, as you noted, manifold pressure is substantial when the valve is open (and changes throughout the warm up cycle). It does take some fiddling to get this 'right'. You'll need to pay close attention to the active cells during warm up if you want a 'factory like' result.

[mikeatrpi]

Ron, thank you. I adjusted the cold RPM up from 900 to 1400. Cold that day was around 44 degrees F ambient temp. It now settles down to around 850-900 once warmed up. I will work on it a little more so it settles down around 700 or so RPM. Would you say 680-700 is an ideal idle RPM for the L28?

 

Now the datsun air regulator (aforementioned widget) is completely independent of the megasquirt. It is supplied with 12v switched from the fuel pump relay. This power heats a wire coil, causing a trap door to close thereby cutting off air as the wire heats. Anyway - I can't set it to open or close at a specific temp.

 

Here's a data log and MSQ. It starts at the end of my warmup... RPMs are in the 1000 range and slowly settle to 850ish. I think the thermostat must have opened up because I see the CLT (the datsun CHTS in my case) drop significantly. Now - at the very end of the log, the car stumbles and stalls. It looks like it goes into accel enrichment mode briefly at the very beginning of this. I'd appreciate any advice.

 

As a side comment, I can't rev over 3500 RPM. If I do, the RPMs spike. I believe that's an SI / noise issue on the VR line from the distributor. I mention it here incase its relevant.

msq_idle.zip

[cygnusx1]

Mike, turn off all of your accel corrections until you get a decent tune. You can do that by raising all of the thresholds for accel inputs. I like my motor to idle at 900-1000 rpms fully warm. It seems to respond to throttle better when coming off idle with the idle slightly high. You really need to get a wideband O2 in there eventually.

 

I wired my "widget" the same way you did Mike. However, I think you can make MS turn the widget on and off at setpoints with some more programming/wiring.

 

Get under the hood and add some shielding to as much of the ign signal wires as you can. Also read up here on the importance of PROPER plugs and plug wires for MSII to rule out noise.

 

After the car starts cold, watch the Warmup Wizard and dial in the AFR's manually as the engine warms up. I am not sure if you can do this with your narrowband O2 sensor, but you will be able to "tweak and feel" for a smooth idle all along the warmup process.

 

I may be available this Saturday or Sunday mid-day if you want me to swing by. PM me.

[cygnusx1]

You are getting a massive spike in the TPSdot and then some rise in the MAPdot which might be a result of the engine choking. Your Throttle position never moved.

 

Repeat the idle test with the TPS connector off. If it happens again, you are getting noise on the TPS line...possibly. If not, you might have a bad TPS sensor.

[mikeatrpi]

Hey Dave, thanks for the offer. But - I took my plates off already so I'll probably ask you to come up in the Spring so we can do some on-street tuning if needed.

 

I see that now in the log, not using the viewer. The tp-dot goes negative then really high. I can't unplug my TPS due to how I wired it in, but I am running autolite copper plugs. I will switch to NGK's. I do have NGK wires already. That should help reduce noise. And of course I'll use some coaxial shielded wire for the VR distributor.