1987 930 Low Idle, Chugging, Hesitation

[ObrHaus]

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!

[oilonly]

Did you try to richen it up a little?

[ObrHaus]

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?

[Miguel Antonett]

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.

[jwasbury]

Originally Posted by Miguel Antonett

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

[T77911S]

i would like to add,
check for air leaks
and check pressures before making any adjustments

[jpilcher]

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.

[jwasbury]

Originally Posted by jpilcher

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!

[ObrHaus]

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?

[87 930]

Ditto the air leak check. Look for bad o rings or a hose blown off from boosting, etc.

[ObrHaus]

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.

[oilonly]

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.

[ObrHaus]

What brand/type of AFR are you using, I see so many different ones, I just want one that doesn't look tacky.

[oilonly]

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

[Miguel Antonett]

Prrrrreeettttycool!

Welcome!

[70tangerine]

I have a 1987 930 with some bolt on mods- turbo intercooler headers 1 bar spring and LTW flywheel and 935 clutch dist or something.

A simple issue might be Bad Gas in the Tank ???

I am sorting out the same problem with the low idle and not running just right at first. ( came out of no where )
Then once a few mins pass and I rev it up a little it catches and idols pretty normal. IF this is something that happened after storage and or putting a fuel it maybe just the Bad batch of fuel.
I will post back once I let my 930 sit for a night.

Note my problem happened 3 weeks ago after putting in 10 gallons of 93 BP Gas in Vernon NJ on a little back road rally I was on this was after car was in storage for Winter.
I put car away soon after I noticed this issue until I had time today to fig out what has happened after the tank of gas. I burned through about 7 gallons of the BP Gas so ended up today at 1/4 tank of BP 3 weeks old and gas from last Fall November. I put in a bottle of Techron Fuel treatment at around 1/2 tank can not hurt that is good stuff. It did not fix the problem but I really did not have time to drive the car so I put it away and took it out today.

1. Today I drove to Sunoco and put in 14 gallons of 93 Ultra to fill my tank up to almost full I did not turn my car off as it sometimes would not start at one point earlier today so once I got it started I left in running.
2. After tank was nearly full Jumped in the car and took off on to the highway
and got on Boost in 1st gear 5k RPM shifted to
2nd gear and took it up to 5,500k RPM maybe 6k and as I looked in the mirror I saw all sorts of nasty smoke cloud behind me. ( K27 hiflo turbo) has a good punch.
Power felt a little down but then when I shifted to 3rd the car woke up and felt much better smoother I took 3rd Gear to 4,500 RPM and then was on and off the boost keeping revs up around 3500 to 4000 RPM and higher. I even double clutched and down shifted to 2nd gear at about 45 MPH and ran 2nd gear again up to about 5500 6k RPM and NO smoke anymore. Car seemed to have all its power back and was Smooth as a baby but in all gears. Idol seems be be fine.
BIG TEST is tomorrow will it Start and will it Idol correct.
Then I stayed in 3rd gear.

[smurfbus]

Maybe you now got rid of storage time oil leaks in plugs/exhaust/. Dirty plugs work better hot

[jcvass]

First read the plug to see if your rich or lean . As someone mentioned gauges to check and verify fuel pressure . Lastly, basic tune up will be a help regardless . Check timing and remove and service the ignition distributor . The chugging , low idle could be a vacume problem , fuel adjust or tune up related . Its all basic and sounds like an easy fix . Ignition upgrade to direct fire is an excellent upgrade for your 930 . Good luck ..

[motorracer]

Surprised nobody has said to check the intercooler o rings.when they tear the car will act like that.

[Dominik 930]

please explain it in more detail, which rings do you mean? These ones ?