Poor idle when cold

TCGGrafix · 12-07-2001, 07:51 AM

Hello all. I have a problem with the car idling poorly when it is cold. When I start the car it runs fine. It goes to 1900 rpm then down to 800 rpm. After a few minutes the rpms hover around 650-700 and runs rough but never stalls. After the engine has warmed up it idles fine and smooth (be it at 800 rpm - little low?) I am guessing it may be the WUR.

Another problem is it is difficult to start when it is warm and has sat for over 30 minutes. I guess this to be the check valve or accumulator. If I turn the ignition key so the fuel pump is activated and give it a bit of throttle for a few seconds, then let off the throttle before starting it, will usually start without hesitation.

Any thoughts on what it may be are appreciated. Thanks!

wckrause · wckrause's Garage

Does it ever backfire while it's running rough? You can reach into the air box and gently lift the sensor plate very slowly while the car is rough idling. If this smooths out your idle, then your cold start is too lean. If the idle gets worse then your cold start is too rich.

Both problems can be trouble shot with a CIS pressure tester. You can check the WUR and adjust it if it is not enrichening the mixture enough. You can also check the pressure retention to see if that's the source of your hot start problem.

BTW... What does pressing the throttle do for an engine that isn't running? Even with the fuel pump running, you need air to lift the sensor plate to get any gas injected.

TCGGrafix · 12-07-2001, 08:52 AM

Bill - Thanks for the reply. I will try pushing the plate and see. I have to pick up a pressure testor to look into the WUR, so maybe next week.

As for as me holding in the trottle. I know this make no sense at all. Without air passing over the plate no fuel should go to the injectors. But for some reason it seems to help (?) Perhaps a slow leak just enough to supply fuel into the lines? I mentioned that I did this because I thought maybe it might be a problem in itself. Perhaps it would be resonable to assume that it is running rich for this reason? Very possible I could be imagining that it helps....I am somewhat prone to such thinking.