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1987 930 Low Idle, Chugging, Hesitation

I have a new to me 87 930, original Canadian car. I am new to 930's but have some knowledge of 911's, but of the carb'd kind. When purchased 2000 km's ago it seemed to run fine, it now starts but then almost stalls, idles very low (400-500) almost seeming as if its chugging, I can give it some gas and it will come out of it, but then sinks back down, cold or hot. Accelerating has some low rpm bucking as if I'm loosing ignition or fuel for a second then comes back to life, then hesitation right from idle through to red line, it seemed as if it came and went at first now its just being a pain. Still boosts at 3k but again I can feel it missing up top as well.

I pulled 4 of 6 plugs, I don't have all the tools with me where I am right now, but I'm going to try and limp it home tomorrow night (140 km ) and check the other two. Wires look old as does the ignition, so I ordered a set of Clewett engineering wires, new DPO plugs, dizzy cap and rotor. I have a spare blaster and MSD 6al at home so I will try and rule these out first.

What would be my next best place to start looking?

Thanks for your time guys!

Old 06-05-2013, 01:42 PM
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Did you try to richen it up a little?
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'87, Modified WUR, Billet valve, 965 downpipe, Kokeln intercooler, GHL headers, Garrett T04B K27 hybrid, Tial w/.8 bar, WEGO IV, RarlyL8 dual out, LSD
Old 06-05-2013, 05:24 PM
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No I have not, but I will give it a shot later, just put an allen key in the spring loaded mix screw and turn clockwise correct?
Old 06-06-2013, 01:01 AM
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First of all, you must go through the formality of posting pictures of the car.

Your issue appears fuel mix related. Difficult to troubleshoot w/o an a/f ratio gauge. Get one (a decent one under $200) and then play.
Old 06-06-2013, 05:52 AM
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Quote:
Originally Posted by Miguel Antonett View Post
Your issue appears fuel mix related. Difficult to troubleshoot w/o an a/f ratio gauge. Get one (a decent one under $200) and then play.
a/f gauge is a good thing, but I would argue that the first tool in the box to reach for is a set of CIS fuel pressure test gauges. Best price on a suitable set of gauges I have seen is from JC Whitney.

For these kind of running problems, following the basic "tune-up" list will often reveal the issue:

1) verfiy CIS system pressure, cold control pressure, warm control pressure, (and with a mity vac you can also check enrichment control pressure).
2) verify fuel delivery volume is within specification
3) verify ignition timing is correctly set

if you are not familiar with CIS and its components, and basic troubleshooting of the fuel system read this:

http://jimsbasementworkshop.com/CIS/

this is not specific to turbo cars, but the principals are the same
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Last edited by jwasbury; 06-06-2013 at 06:04 AM.. Reason: add link
Old 06-06-2013, 06:02 AM
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i would like to add,
check for air leaks
and check pressures before making any adjustments
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Old 06-06-2013, 06:33 AM
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I would like to second the check for air leaks. I had a very similar issue when I purchased my car last year, WUR vacuum line was disconnected. Fixed my idle once reconnected.
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Old 06-06-2013, 08:16 AM
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Quote:
Originally Posted by jpilcher View Post
I would like to second the check for air leaks. I had a very similar issue when I purchased my car last year, WUR vacuum line was disconnected. Fixed my idle once reconnected.
The WUR vacuum line is actually the boost "signal" for the WUR. So, if its left disconneted, it can create a vacuum leak and the unmetered air entering the engine can cause bad idle. But more importantly, if not connected the WUR will not have a boost "Signal" and will not lower control pressure when the turbo generates positive maniford pressure (a/k/a boost) - thus you have no boost fuel enrichment, A/F ratio goes lean on boost, and eventually engine goes boom!

good catch!
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Old 06-06-2013, 09:08 AM
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I will have it home tomorrow to play with, however, I noticed if i push my (mix screw?) down without turning it my idle returns to where it should be but soon as i let it spring back up, down to 200 rpm or so again?
Old 06-06-2013, 10:37 AM
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Ditto the air leak check. Look for bad o rings or a hose blown off from boosting, etc.
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Old 06-06-2013, 10:55 AM
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Thank you very much guys, this is much appreciated, didn't expect so many responses!

And a picture of her, 132 000KM on the clock.


Last edited by ObrHaus; 06-06-2013 at 12:22 PM..
Old 06-06-2013, 12:18 PM
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Oh very nice! Some say different but I like the boxed rockers. Yes press down to engage and turn right to richen, I have an AFR gage myself and it's great so you know where you are.
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'87, Modified WUR, Billet valve, 965 downpipe, Kokeln intercooler, GHL headers, Garrett T04B K27 hybrid, Tial w/.8 bar, WEGO IV, RarlyL8 dual out, LSD
Old 06-06-2013, 03:19 PM
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What brand/type of AFR are you using, I see so many different ones, I just want one that doesn't look tacky.
Old 06-06-2013, 03:58 PM
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I'm using the WEGO IV ObrHaus, very simple install, especially if you have a muffler with a bung to fit the sensor done already.

This is the thread that sold me on it.

AFR Meter question
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'87, Modified WUR, Billet valve, 965 downpipe, Kokeln intercooler, GHL headers, Garrett T04B K27 hybrid, Tial w/.8 bar, WEGO IV, RarlyL8 dual out, LSD
Old 06-06-2013, 04:37 PM
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Prrrrreeettttycool!

Welcome!

Old 06-06-2013, 06:29 PM
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