3.6L Running Issue

[widebody911]

My 3.6L has started running funny, and it just came out of nowhere.

Symptoms:

• hard start - takes 2 or 3 seconds to get fired up
• won't idle for the first few minutes - have to keep my foot on the gas
• wants to die when I let off the gas; ie, driving down the freeway, all is well, but when I pull off the freeway and stop, the engine goes into some idle oscillations, then croaks.
• rough idle - there's a vibration at idle that's almost, but not quite a miss.

This started when the weather changed this week - it was nice and warm - mid 80's - for a few days, then suddenly dropped to the mid 60's.

I run Techron thru it every now and then, the last time being early last week.

Any clues? I've done the obvious hose-and-connector checks. I'm still really new to these engines.

[MMARSH]

Thom
sounds like a vacum leak to me. Mine was doing to same thing after my rebuild intil the vacum leak was found behind the the throttle body. Very frustrating. I couldnt find it, ended up taking it to a shop and they found it. Take one of those flexible mirrors and have a good look around the back of the motor. also try doing the carb cleaner trick and see if you can find it that way.

Thats what you get for trying to beat up on an early car at thunderhill

[Jack Olsen]

I had a problem like that when the four bolts for my intake manifold came lose. It was drawing air in, leaning things up, probably, and playing havoc with my idle.

[widebody911]

Which 4 bolts you talkin' 'bout, Willis?

Originally posted by JackOlsen
I had a problem like that when the four bolts for my intake manifold came lose. It was drawing air in, leaning things up, probably, and playing havoc with my idle.

[Jack Olsen]

[widebody911]

Ok, I spent some time this weekend playing with it, and I don't have those bolts. I think this is a difference between the plastic and aluminum setups. Mine has a huge rubber sleeve - perpindicular to the cross-section of the manifold. The clamp on this is of such a design that I can't tighten it any more. I tightended up all of the other intake clamps that I could get to.

I'm not sure it made a difference. It seems to run a little better, but it's hard to tell. It still has a vibration at idle, and lots of idle oscillations when the weather is cold.

[JDaniel]

I think you need more duct tape! That's what happens when you try to clean things up.

[Jack Olsen]

A different setup? Geez, and I pulled my engine so I could snap a picture to show you.

Have you reset your DME? It could be something screwy that a re-boot would fix. The correct way is to hold the throttle all the way down (so that the wide-open throttle microswitch is tripped) and turn key to on and wait 15 seconds (some people say as little as 3 seconds). Then drive the car for at least 15 minutes without turning it off.

The poor man's version is to disconnect the battery for fifteen mninutes and cross your fingers.

You may also want to try swapping in another DME relay.

[curtisaa]

Those were purdy jack stands....Jack (sic)...

[john70t]

One quick hoopty test for a lean idle would be to add some propane the air filter.

[widebody911]

Well, I'm giving in and taking it to the shop. I'm also having a problem (still) with fuel in the oil, and it's time that someone who knew what they were doing looked at it. I suspect the 2 issues could be related. Hopefully I haven't caused any undue wear. When I changed the oil this weekend, there was a small amount of grayish schmeg on the magnetic pickup.

[tholyoak]

Thom

We have a sort of similar problem with a 3.6 conversion I did on a friend's SC this past fall. The car occasionally starts hard and idles poorly/stalls with out giving it some gas. I have the check engine light hooked up and it comes on when this occurs. I have traced it to be the throttle cable solution that came with the kit. Basically if the thing is adjusted enough to get full opening of the throttle, occasionally it will hang up and not allow the throttle to return to the idle position and trip the idle micro switch.
Basically the throttle returns to the stop position, or appears to but at this positon there is very little spring tension to pull it fully closed and trip the switch.
The computer gets confused thinking the throttle is part open and negates the idle circut but obviously it isn't open far enough to keep the car running and you have the poor running problem.


Not sure if this is related to your problem but may be something to check. I think in our case it is complicated by the cruise cable that is used as the throttle cable having a slight kink and getting hung up even when the cable is loosened off.


Good Luck
Todd

[widebody911]

Just went out and checked it. Operating the throttle by hand, I can hear the switch 'click' when it lets down. I didn't test it with the gas pedal. I guess there's a remote possibilty that the cabble is hanging. Hmmm.

[tholyoak]

Thom

Yes that is what I observed as well, when I would opperate the throttle by hand it would return fine.
I believe it is the cable 'sticking inside the outer sheath, again I think our case is aggrivated by the slight kink in the inner cable.
It would happen when driving, when I dropped the gas from part throttle when tooling around town coming to a stop sign. The car would almost die the check engine light would come on and it would oscillate the idle and die unless I gave it throttle. When it happened I pulled over and checked and I could pull the throttle back ever so slightly and the switch would click, and the problem would be gone when I restarted the car.

Also noticed it would clear if I was more into the throttle and dropped it back closed it would return to idle normally.

I am going to try to re-engineer the throttle setup using the rod ends that Porsche used instead of the cable and bolt method that came with the kit. At least use a ball joint connector at the end of the cable rather than the cheap bolt. Another idea I had was to buy some of the gore-tex lined cables that are on my mountain bike and utilize those instead of the current setup. Those cables slide like a hot knife through butter compared to traditional braided cable inside a standard sheath like the stock cruise cable is.

Todd

Todd

[Mifintifin]

I decided against the "kit" type flexible shaft because of hanging problems and was going to use the standard 3.0L bell crank on my conversion (canned the project since then). It will work fine, the same holes are even there in the 3.6L shroud and block (964 & 993). (The only problem on the 964 is that the speed control throttle motor is where the bell crank goes, you have to remove it). To make the bell crank work you have to get a longer shaft to the throttle and a ball to mount on the throttle. Incidently, I have used a Teflon lined bike casing and cable for a Jeep throttle cable. Worked great.

Mifintifin

82 SC Coupe
83 SC Cab

[slakjaw]

it kind of sounds like an airflow meter to me

i dont know on a 3.6

try disconnecting it then it will be running from computer code only

just a thought

K

[widebody911]

I dropped by the shop today to check out the progress. It seems that the switch was not being activated correctly. They also found that my CO was too high, and it dropped a half a point when the changed my oil! He adjusted the AFM to bring the CO down. Tomorrow it gets the rest of the tune up, some small adjustments to the clutch and shift linkage, and putting the original crank pulley back on.

[emcon5]

Originally posted by widebody911
it dropped a half a point when the changed my oil!

Huh? What does one have to do with the other?