[DML] Re: Overheating, idle speed and stalling issues

["daveswingle2" <swingle_dmc@xxxxxxxxxxx>]

1 - It is not clear from your description that the fans are turning on when they should. Assuming your gauge is correct the fan should come on just below 220 and off just above the non-numbered line. Another good test for you  - jump around the otterstate (fan switch) so the fans run all the time. If that solves the problem replace the fan switch. Don't leave it so they run all the time, that causes other issues!

Otherwise, unfortunately this sounds like the beginnings of a failed head gasket to me. You can bleed it some more, but when the head gasket fails you get combustion byproduct blowing into the cooling system (i.e. exhaust gas) which displaces the coolant out the overflow and then the car overheats. Until you bleed it again.

If you still have leaks you should be seeing drips on the ground somewhere. 

1A Correct

2 - If you really have no vacuum leaks, the CO is probably set slightly too rich. But it's probably related to #3;

3 - This is hard to explain but...
First - there are also the three brass screws in the throttle body. They should all be turned in all the way, just snug.

Second - There are two idle stop screws- - the upper one for the idle microswitch and the lower one that actually stops the throttle from closing all the way.  These both need to be adjusted and there is some interaction. 

To set the idle correctly, get the engine running normal temp, i.e. hot enough that the fans run from time to time (this may be a problem due to #1).  Loosen the locknuts, back off the lower screw slightly, then turn the lower screw in until the idle speed just starts to rise, then back off about 1/2 turn. At the same time you do this, you need to make sure that the upper screw continues to hold the microswitch closed. If that switch clicks open, the vacuum advance is turned on and the idle speed will rise a lot all at once. In other words, as you turn the bottom screw in you have to turn the top screw in as well, and probably more due to the angle. 

What you are trying to do is open the throttle as wide as you can but maintain 775 rpm idle speed. This sets it up so that when the car is fully warmed and idling, the idle motor is almost closed. If you don't set it like this, when you back all the way off the throttle when driving, the idle motor can't open fast enough to keep the engine from dying. The decel valves also help with this but they can't overcome the time delay if the motor has to open all the way to get to idle speed. This also gives the idle motor the most range to keep the idle speed up with the engine cold or with high idle loads (a/c on etc.)

Dave S
DMC Midwest


--- In dmcnews@xxxxxxxxxxxxxxx, "jedimasterglenn" <jedimasterglenn@...> wrote:
>
> Need some advice (or a DeLorean mechanic to open shop in MA!!) on what to try next for what I think are 3 separate issues:
> 
> 1.  ...I bleed it until there is no air.  
> 
> After bleeding, if I start it cold and leave it running/idling, it stays around 150F.  When driving, temp stays consistent around 180F, but if I come to a stop for longer than a couple mins, the temp creeps up and will continue past 220.  For example, I drove for an hour on back roads and highway today and it ran around 180F the entire drive).  But when I got home and left it idling in the driveway, the temp started to rise as described. ---

> 
1A I have the fans wired to pull the air through the radiator from front of the car to back vs push...which I think is right...right?    
> 
> 2.  Prior to the cooling system replacement and since, my idle speed has been rough.  When I first start the car, the idle is good, hovering just below 1000rpms.  But as it warms up, it starts to seek up and down between 800-1100rpms.  I've checked the air flow meter inlet & intake manifold seals for leaks (I replaced all the manifold seals when I did the cooling system).  I think these are fine.  
> 
> 3.  And rounding out my collection of headaches is what I like to call the "downshift-stall mystery".  I have a manual transmission.  Again, this was happening prior to the cooling system overhaul.  It doesn't happen consistently, but when it does it's always when stepping on the clutch and always at low speed, when downshifting(usually from 3rd to 2nd).  I step on the clutch and the rpms abruptly drop to zero or close to it.  Before I have time to shift gears, the car has stalled.  



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