924Board.org

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

Sigh, my 80 NA has developed an issue in the last 2 weeks. It runs rough until it warms up. By that, I mean it wants to stall at idle unless I hold the idle up. It also has got no balls. I can go WOT and it will move but feels like about half the power it has when warm. Once it's up to temp., it runs like a champ. Idle is steady at 950 and has plenty of power.

In the last two days, a new symptom has appeared. The battery light will flicker occasionally until it warms up. Once warm, no issues at any RPMs. This just started 2 days ago, but perhaps it is related to the first symptom?

Couldn't find any other threads with a similar issue, only the exact opposite (runs good UNTIL warm then runs like shit).

I've replaced the plugs, wires, and the AAV in the last 5k miles. Plugs are gapped to .40 I believe. Running an MSD 6al ignition box. Thinking maybe it's my dizzy cap, have heard of MSD boxes blowing through the dizzy caps. I have noticed that it is worse after a rain.
_________________
1980 924 NA
1982 931

musicalannette · Joined: 21 Feb 2012 Posts: 413 Location: UK

i reckon your mixture might be too lean for the k-jet to cope with during warm up. note the position of the screw BEFORE adjusting anything so you can put it back to where you found it if this doesnt help though.

If it is this you might also notice small flat spots at low throttle openings. flat out it will be fine. but at low throttle it might be too lean also.
_________________
I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

Mixture was set with a gastester. No dead spots in the throttle, and the plugs look perfect. I'm 90% positive that this is not something in the CIS. If it is, I think it has to be something with the WUR, but the symptoms don't match and the WUR has been replaced about a year ago.

Really think it is going to be something electrical. Guess I'm just gonna have to wait until my next day off and go fishing.
_________________
1980 924 NA
1982 931

staticsan · Joined: 19 Jan 2009 Posts: 450 Location: Sydney, Australia

I have a similar problem, though nowhere as bad. Mine just runs a little rough when starting for about a minute. Revving it sorts it out sooner.

It feels like one cylinder is missing, but all my plugs look fine and all the leads have correct resistance. It also happens much less since I put fuel system cleaner in a few times - makes me wonder if one of the injectors isn't quite good. Have you checked yours?

Wade.
_________________
'82 British NA - Which I think I've been very lucky with!

musicalannette · Joined: 21 Feb 2012 Posts: 413 Location: UK

i doubt it would water getting in the dizzy with where they have placed it on the engine, and as it runs fine when its warm you can probably rule out the ignition as the probelm. Ignitions tend to fail when things get warm or when the engine is reaching high rpm as the coil will be getting to its hottest and electrical breakdown can occur with the components. i it is getting damp it will be visable before you start inside the dizzy cap, this should not be a problem in summer.

Perhaps you have a poor connection or somewhere there is water getting in?

As it runs fine after warm up then the timing sounds fine.

it has to be either ignition, fuel, timing or compression.

not much help but hopefully it will let you rule things out and leave you with where to look further.
_________________
I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

I'm going to check my CSV and TTS. It kind of feels like maybe it's too much fuel, but IDK why it would stop after warming up.
_________________
1980 924 NA
1982 931

Julian · Joined: 24 Jan 2011 Posts: 74 Location: Oxford Ohio

My 78 was acting like that, until I rebuilt the Aux. Air Valve. The wires in the metallic flat rod were toast. It nuns better cold than warm almost.

Ozzie · Posted: Thu Aug 30, 2012 7:56 am Post subject:

I also say to check the AAV.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Julian · Joined: 24 Jan 2011 Posts: 74 Location: Oxford Ohio

Pull the hoses off both ends of the Aux. Air Valve and run 12volts to the terminals, you'll be able to see the movement of the shut off valve. Or no movement. I'd suspect it frozen closed.

They are a pain to open up, but simple rebuild. There needs to be about 30 to 32 inches of wire and a small "O" ring then back together.

You can set the closing time with the length of wire. It's about an ohm per inch.

joejax · Posted: Thu Aug 30, 2012 9:37 am Post subject:

"Runs Rough until Warm"

Is this not normal? What the heck have I been doing all this time? Arrrggghh!

_________________
I got nothin'
Uhhh...you got any pics?

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

AAV is brand spanking new. Not a "new to me" used one, but a brand new never been used one.

I suspected it too, so I bought a new one. No change.

My crankcase breather hose doesn't have a restrictor, think this could be causing an issue? It's been like this for awhile so I'm guessing not.
_________________
1980 924 NA
1982 931

joejax · Posted: Thu Aug 30, 2012 11:43 am Post subject:

Have you tried disconnecting the CC hose and plugging the intake?
_________________
I got nothin'
Uhhh...you got any pics?

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

No, I once plastic welded the intake hose nipple up and put a filter on the end of the breather. Oil soaked the breather, ended up buying a new intake pipe and going back to factory setup minus the restrictor.
_________________
1980 924 NA
1982 931

joejax · Posted: Thu Aug 30, 2012 1:21 pm Post subject:

Yeah, mine has never ran very good with it in place, was on when I got it, had major vac leaks, stopped leaks and it ran real bad.

I have since disconnected just about everything related to emissions, I know, I'm going to Hell, but oh well.

I am now in test mode with eliminating the vacuum limiter thingamajig, in bypass now, results are inconclusive but seem to be looking good.

Seems I have always had an issue with warm up, once warm runs OK. It has been a long time since I have been able to reach through the window and start it without feathering the gas, so i think I am getting close or close enough.
_________________
I got nothin'
Uhhh...you got any pics?

Julian · Joined: 24 Jan 2011 Posts: 74 Location: Oxford Ohio

With regard to the AAV. Make sure you're getting any power to it at start up. Seems to me I wasn't and another part, maybe a relay was causing there to be no juice to the AAV which was what, along with running rich, caused the death of the original AAV.