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-   -   3.2 will not idle (http://forums.pelicanparts.com/porsche-911-technical-forum/665120-3-2-will-not-idle.html)

inaminit 03-12-2012 02:16 PM

3.2 will not idle
 
Hello -Last year I bought a 3.2 engine that was between a long block and a ready to run engine here on Pelican. Then I bought the remaining bits that would be needed to install it into an earlier car; DME, harness, various sensors, etc. I hate reaching into the rear of p-cars, so I fashioned a test stand from an angle iron frame that I already had here in order to test run the engine before installing it. I bought a Zalex frame to hold the starter, made a fuel tank out of a gallon can. Hooked it all up- the engine runs fine at higher rpms, but will not idle. Where to start?
I have checked the ICV-ohms are good, it hums. Compression is good. Visually-there are no leaks in the induction area. Idle switch works. Air sensor reading rises, then falls as the vane is moved. I am getting no reading on the tach. When the engine starts, it seems to run better at a lower throttle for a second, then it won't idle. I am very far away from any other Pelicans, dealers or independent shops, so I will have to noodle this thing out myself. Any ideas or directions to go in? Photos of the engine on the stand below. Thanks for any help! http://forums.pelicanparts.com/uploa...1331590521.jpg

E Sully 03-12-2012 02:50 PM

Have you tried installing the jumper to set the base idle first? There are a few threads on this. Of course you also need to make sure there are no vacuum leaks. Are the lines to the cruise control and brakes plugged?
AFM test. http://www.the944.com/afm.htm
Good point from Tippy.

Tippy 03-12-2012 03:07 PM

You answered your own question I believe, "air sensor readings fall off when vane is moved".

rusnak 03-12-2012 03:20 PM

I concur with Tippy

Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk* ©2001 www.the944.com

http://forums.pelicanparts.com/uploa...1331594375.jpg

http://forums.pelicanparts.com/uploa...1331594398.jpg

inaminit 03-12-2012 03:51 PM

Sully-The vac to brakes is plugged, and the long small dia hose connected to the intake just below the throttle is plugged-is that for cruise?
rusnak and Tippy- those readings were ohms measured at terminals 7 and 9. How do you set up to measure the variable voltage signal? thanks!

rusnak 03-12-2012 03:59 PM

No, those are input/output volts. Click the link and follow the AFM testing procedure. It's very quick. No need to open up the AFM.

Lorenfb 03-12-2012 04:40 PM

"No, those are input/output volts."

- rusnak -

The 1984 & 1986 AFMs are the same and as such produce the same outputs.
Let's not further confuse the guy!

Quicksilver 03-12-2012 06:55 PM

Check your PMs.

Chuck.H 03-13-2012 03:33 AM

Love the test stand!

The brake booster line seems to be just hanging near the gas can... is it plugged? If not big vacuum leak = too lean at idle...

Just at thought,
Chuck.H
'89 TurboLookTarga, 332k miles

Tippy 03-13-2012 05:24 AM

Yeah, it looks (brake booster line) to be open by the CHT plug.

inaminit 03-17-2012 12:00 PM

it idles
 
Well Duh! Now I am going to have to sit in the front of the class! It was a vaccum leak after all, on the clamp joint to the bellows rubber piece. But I did go through the applied voltage test for the AFM-nice and linear response. And I have learned a whole lot more than I had planned about testing the various sensors that feed engine data to the DME, and I have a personal relationship with each and every wire in my wiring harness!
The only thing left is to figure out the non response of the Tach.
Thanks for all the responses to my post. Photo of the idling engine below. I will heartily recommend building a test stand to sort out issues prior to installing an engine, particularly in a different MY car.http://forums.pelicanparts.com/uploa...1332014374.jpg

DRACO A5OG 03-18-2012 12:03 PM

That is a cool rig you have there, more details after install?

As far as the Tach, I see the RPM sensor is hooked up and if it was failing you could not start or even keep it running. Is the tach grounded?


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