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Join Date: Mar 2009
Posts: 1,781
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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! 
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03-12-2012, 02:16 PM
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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.
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Ed 1973.5 T Last edited by E Sully; 03-12-2012 at 03:14 PM.. Reason: Add AFM test link. |
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03-12-2012, 02:50 PM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,132
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You answered your own question I believe, "air sensor readings fall off when vane is moved".
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03-12-2012, 03:07 PM
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03-12-2012, 03:20 PM
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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! |
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03-12-2012, 03:51 PM
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Join Date: Oct 2004
Posts: 15,612
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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.
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03-12-2012, 03:59 PM
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Join Date: May 2003
Location: Manhattan Beach, CA
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"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!
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Have Fun Loren Systems Consulting Automotive Electronics '88 911 3.2 '04 GSXR1000 '01 Ducati 996 '03 BMW BCR - Gone |
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03-12-2012, 04:40 PM
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Diss Member
Join Date: Jul 2002
Location: SC - (Aiken in the 'other' SC)
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Check your PMs.
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- "Speed kills! How fast do you want to go?" - anon. - "If More is better then Too Much is just right!!!" - Mad Mac Durgeloh -- Wayne - 87 Carrera coupe -> The pooch. |
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03-12-2012, 06:55 PM
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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 |
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03-13-2012, 03:33 AM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,132
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Yeah, it looks (brake booster line) to be open by the CHT plug.
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Cory - turbo'd '87 C3.2 Guards/Blk, 3.4, 7.5:1 CR, 993SS cams, Borg-Warner S366 turbo @ 1.2-1.5 bar, Treadstone full bay IC, 70mm TB, TiAL F46 WG, HKS 1 1/2" BOV, twin 044 pumps, MicroSquirt AMP'd w/GM smart coilpack, Bilstein coilovers, Tramont replica Speedlines (285's rr, 225's frt), Big Reds frt, 993 rr., tower brace, MOMO wheel Last edited by Tippy; 03-13-2012 at 05:26 AM.. |
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03-13-2012, 05:24 AM
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Join Date: Mar 2009
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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. 
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03-17-2012, 12:00 PM
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Member 911 Anonymous
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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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03-18-2012, 12:03 PM
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The Other Woman
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