81 SC Cold Idle Issue (as in will not idle)

[Mike in FL]

I've been having a cold idle issue for a bit of time. When cold, car starts right up but after a few seconds starts to get rough and dies. Sooo, I did some pressure checking with these results: 1)System pressure - 73 psi. 2)Control pressure - engine cold and running - 54 psi (!) - engine warm and running - 54 psi (?). Ambient temp during testing - 85 degrees. I have the 090 WUR. With engine cold, as I watch psi build, engine runs fine until about 45 psi or so is reached, then it starts to break up. Specs seem to call for about 36-40 psi when cold. Any thoughts? Btw the WUR is a rebuilt unit - swapping that out for the old one made no difference.
Thanks,
Mike

[boyt911sc]

Mike,

When the engine is cold, check the resistance (Ohms) of the WUR-090 including your spare WUR. It looks like both WUR's are out of spec. and your cold idle problem is a typical one when the WUR is out of spec. Keep us posted.

Tony

[Mike in FL]

what should the resistance be with a cold wur?

[Bob Kontak]

Originally Posted by Mike in FL

what should the resistance be with a cold wur?

26 ohms.

[prschmn]

Wurs came with different heating elements for euro and US spec cars. The US units have a bigger heater and tend to lean the mixture too soon-in the interests of meeting US smog tests.

[theiceman]

Originally Posted by prschmn

Wurs came with different heating elements for euro and US spec cars. The US units have a bigger heater and tend to lean the mixture too soon-in the interests of meeting US smog tests.

define " too soon" . I have a Us spec engine and it starts and idles flawlessly.

[prschmn]

If mixture is on the rich side you can bury the misfires. I'm just saying that since the author
didn't specify whether it was/is a US or Euro spec car the different WUR can be a minor problem

[prschmn]

To elaborate=I used to deal with a lot of Gray Market cars that had the WUR replaced--
and they weren't happy about it. A US spec with lower compression isn't as sensitive.

[strictly]

that sounds very lean (the idle dieing bit) and the specs on the control pressure are a very lean for cold, but just a little lean for warm! You need to set up the WUR for hot and cold (i.e take apart and adjust), check you airflow sensor plate height, and finally reset your mixture. It could also be other things (air leak, etc) but start with the basics.

In particular, start with the air flow sensor plate height (and check for binding) and then the WUR adjust. When you swapped the WUR over, what pressures did you then have? Also suck on the vac line, and watch the pressures change when in warm control mode.

30 to 87a on the fuel pump relay to hotwire it for the tests, unplug the wur heater to start, then plug it in, no need for the engine running. If you are still getting high control pressures when cold, then disconnect the return line from the WUR and run all disconnected lines into a container. Could be a blockage on the return line somewhere or the WUR itself.

[Mike in FL]

Good morning! My car is the US spec - I have an Oxygen sensor. I measured the resistance this morning on the WUR across the two terminals (I guess that's how you do it) - Cold engine - 9.2 ohms Warm engine (10 minutes running) 9.9 ohms. Outside air temp 78 degrees. Based on these, as well as no change in pressure from cold to warm engine, is my problem my "new" WUR? Thanks for the quick and great feedback!
Mike

[T77911S]

Originally Posted by theiceman

define " too soon" . I have a Us spec engine and it starts and idles flawlessly.

the engine is not warmed up completely.
more noticeable on cold days.
same thing with the AAR. it closes too soon.

[boyt911sc]

Originally Posted by Mike in FL

Good morning! My car is the US spec - I have an Oxygen sensor. I measured the resistance this morning on the WUR across the two terminals (I guess that's how you do it) - Cold engine - 9.2 ohms Warm engine (10 minutes running) 9.9 ohms. Outside air temp 78 degrees. Based on these, as well as no change in pressure from cold to warm engine, is my problem my "new" WUR? Thanks for the quick and great feedback!
Mike

Mike,

You need a working WUR. You will have this erratic cold idle unless the WUR is fixed and calibrated. I could lend you one for you to use and test. Going back home tomorrow from Sarasota, Fl.

Tony

[Mike in FL]

I contacted the supplier of the WUR that I purchased last year. As it is still under warranty he has agreed to take it back and replace it. It is now on its way to him. I'll keep this thread updated as to the results. Thanks to all for your posts and help
Mike

[Bob Kontak]

Originally Posted by Mike in FL

I contacted the supplier of the WUR that I purchased last year. As it is still under warranty he has agreed to take it back and replace it. It is now on its way to him. I'll keep this thread updated as to the results. Thanks to all for your posts and help
Mike

In the interim...........

Find the return fuel line to the tank. Make sure it has no restrictions that could allow fuel to not return freely to the tank.

A partial return restriction can cause your condition.

Originally Posted by strictly

tCould be a blockage on the return line somewhere or the WUR itself.

As mentioned. Don't disregard this.

[Dave Kost]

Originally Posted by Bob Kontak

In the interim...........

Find the return fuel line to the tank. Make sure it has no restrictions that could allow fuel to not return freely to the tank.

A partial return restriction can cause your condition.



As mentioned. Don't disregard this.

You can carefully crack the return line from the WUR to the return back to the fuel tank, if the CCP pressure goes to spec then you have a blockage in the return line. If not then of course its the WUR. (I put the WUR in a bucket and jumped the fuel pump.) Or, you can also run a long fuel line from the return line port of the WUR to a gas can outside of the engine bay.

Glad to hear the rebuild shop stood behind their work.

Good luck and keep us posted. That's how we all learn.

[boyt911sc]

Originally Posted by Mike in FL

I contacted the supplier of the WUR that I purchased last year. As it is still under warranty he has agreed to take it back and replace it. It is now on its way to him. I'll keep this thread updated as to the results. Thanks to all for your posts and help
Mike

Mike,

Good to hear that the WUR is under warranty and a replacement is coming soon. Based from your information, there is no flow restriction in your system and the problem is your out of spec WUR. When you get back the new replacement WUR, check the heater resistance and make sure it has the correct value. Keep us posted. Thanks.

Tony

[boyt911sc]

Originally Posted by Mike in FL

I contacted the supplier of the WUR that I purchased last year. As it is still under warranty he has agreed to take it back and replace it. It is now on its way to him. I'll keep this thread updated as to the results. Thanks to all for your posts and help
Mike

Mike,

Are you getting a replacement WUR or they will worked on the unit you sent back? Keep us posted. Thanks.

Tony

[Mike in FL]

Hi all. Got the replacement wur yesterday and installed it. Absolutely no change in control pressure from cold to warm (54 psi) or resistance (9.9 ohms cold or warm). I'll check the fuel return line tonight (assuming that Matthew stays east of us). Still wondering if I got another bad wur...

[boyt911sc]

Originally Posted by Mike in FL

Hi all. Got the replacement wur yesterday and installed it. Absolutely no change in control pressure from cold to warm (54 psi) or resistance (9.9 ohms cold or warm). I'll check the fuel return line tonight (assuming that Matthew stays east of us). Still wondering if I got another bad wur...

Mike,

Is this replacement WUR a different unit or it was the same one you sent back to them to fix? Give the rebuilder a call and inform them that 9.9 Ohms is not correct. I would not be surprised if they insist that there is nothing wrong with the WUR. This was the same value you had before. A good WUR-090 should read 25~26 Ohms when the engine is cold.



Request for a good working unit. You will have the same problem/s as before and you are wasting valuable time trying to make the 'out of spec. WUR' perform well. You are not alone. BTW, the return line has nothing to do with your problem (electrical resistance). The return line problem would affect fuel pressure and totally unrelated to resistance (Ohms).

Tony

[Mike in FL]

Thanks Tony. I'll keep all posted as to my progress.