911 3.2 stalling occasionally
 

Hi,
My 3.2 litre 911 stalls occasionally.
Idle is a little erratic. The car idles at about 800rpm and will definitely cut out within 2 minutes of running.
Some Guys here have steered me towards the DME relay. I am going to buy one of these but are there any other reasons for poor idle?
All plugs are firing and it runs well under load.
Thanks in anticipation,
Dave:)

I would start with checking the fuel pressure. If you can get it to run, then check the fuel pressure with a gauge. Should be around 29 PSI. If it's lower, then you might have a fuel issue.

Also, 2 mins is about the time it takes for the 02 sensor to heat up and then go into closed loop. I wonder how old your 02 sensor is, and also what the baseline AFR is set at. If the fuel pressure is ok, then I'd go on to check the air fuel mixture, etc. And when it quits, can you verify spark?

I will fit a gauge to fuel pressure first and then see where to go....
Thanks for that,
Dave:D

Fuel filter.

From your other thread, it seems a lot of oil passed through the intake. How well did you clean out the throttle body and intake manifold, and what do the spark plugs look like?

Thanks All,
The car has a sketchy service history so I can't say when these components were changed. It may be no harm to change the fuel filter and the DME relay as a precaution. She is running smoother after a few runs, but backfires on deceleration (always has done...)

I would like to get her back to where she should be but have limited resources.....

Thanks,

Dave

So you swapped the fuel filter and relay?

As far as back fires, do you know if you have a cat by pass?

I have ordered the parts but they have not arrived yet.... I am away for the next two weeks so there will be nothing happening 'til after then...
The car has no cat installed as far as I can see....

Hi All,

Ok, new air and fuel filter fitted, new spark plugs too....
Idling at 500RPM and sounds a bit lumpy......

Still backfires on deceleration and occasionally cuts out, I thought she was overfuelling but plugs are straw brown.

What would you do? DME relay or fuel pump? Or tune up?:confused:

Thanks, sorry for taking time getting back, only received parts today!

Dave

Your idle is way way too low. I would probably re-set idle, and check fuel pressure as a start.

84-86 3.2 idle is 780rpm and a but lumpy. 87-88 3.2 idle is 880 with a little more timing. Smoother idle, also. Knowing which year chip/DME you have will help set your idle. Idle is controlled by the DME computer. The ICV will open or close to match this preset idle speed based on how you set idle screw on the throttle body. When you have the idle set just right there will be no step up or down when you pull the jumper wire.

Are you getting true backfiring on deceleration? Sounds like it's more burbling and popping. Make sure you get your foot all the way off the accelerator. The first couple of millimeters of throttle travel at the throttle body engage and disengage the idle switch and idle fuel maps. This is before the throttle plate opens. If your switch is working and you get your foot all the way off you should not have burbling. If you pay attention and play around with this a bit you find you can make this come and go at will. An exhaust leak will exacerbate the situation. Removing the cat makes the sound louder for sure.

Is your stalling at a flat idle or when the revs drop as you lift off the accelerator? If revs are dropping to nothing and our stalling when you cut the throttle search here for sub-idle dip. This is usually an indication of a lazy ICV. Some folks have had luck raising their idle to compensate. The DME is supposed to catch the revs around 1k in this situation and slow the fall down to idle. If the ICV is old or dirty it won't move quick enough to catch the falling revs.

As a tangent my wife and daughter and I spent a couple of weeks in Ireland and Northern Ireland in 2011. Absolutely beautiful country and everyone we met couldn't have been nicer. We'll definitely be back for another visit.

Good luck. -J

Maybe a head temp sender?

It sounds like almost a 100% vacuum leak. You need to dig in there and check every line to see where its coming from. Jar0023 says ICV and although unlikely it could be possible that its not closing all the way, but this would cause a substantial vacuum leak, and I doubt it as this is a very durable piece. Whatever you do, dont just start throwing parts at it. If the DME relay was bad your car wouldn't run, period. The same usually goes for most sensors. A faulty head temp sensor will cause hard cold or hot starts. If your fuel pressure was low then you would have bucking under hard acceleration (starved for fuel) Low, rough idle and popping on deceleration is indicative of a vacuum leak. Check all the lines on the rear of the intake, these are usually the culprits. Thats why your idle is so low.

Hi All,
Really appreciate your advice, I feel absolutely sure that one or more of the examples above will sort out my problem.
I will keep you posted on the outcome....
Ireland is a lovely place and there is no better place to be when the 911 is running well and I have wind in what is left of my hair! Please look me up when you visit, I am in Kildare, the home of horse racing... I know little of equestrian sports as I am a petrol head!

Again, BIG time appreciate your input.

Dave

BTW, I have previously looked for vacuum leaks but I am not sure whether all the pipes are going to the right places. Nothing in the manual about the vacuum system. Anyone got a component assembly!???
Go raibh maith agat,

Dave

There should be a schematic on the engine lid. There are plenty of good photos if you search here, but it can be a bear to search them out. -J

Dave, check the pipe clamps, and hose ends for cracks. Use a strong flashlight, and run your hand along the hoses to check for splits. A common source of vacuum leaks would be the intake gaskets, especially if the intake runner bolts in the heads are loose. A quick but not 100% check would be to let the engine get warm, then at idle, remove the oil cap. The rpms should drop momentarily then recover to normal. If not, then you might have a vacuum leak. You will have to remove the air cleaner box and afm to check the crankcase breather hoses. Check the small hose going from the ambient air valve near the oil tank to the intake boot near the throttle body.

I recently battled a similar problem in my 87 3.2. I felt the fuel pressure was marginal when checked it and replaced the pump and clocked the AFM up a tick but the problem still existed. I kept smelling a rich exhaust and I have no cat, but felt it was a more than normal. The CHT tested OK, but I replaced the head temp sensor and the problem was solved (the replacement involved a drill and a lot of patience, but that's another story). Runs better now, no rich smell, etc.
A week later it died and wouldn't restart...that was an unrelated failure, DME relay!
While I love my 3.2 I really hate the first generation of DME's. With no stored fault data you can really chase your tail on intermittent sensor issues.

New intake gaskets and spacers solved the minor idle and drivability issues I was having with my 60,000-mile 3.2. Had previously changed the O2 sensor (60K-mile replacement item) and performed a full tune-up, both of which helped, but the intake gaskets/spacers really helped. To determine whether they were the culprit we sprayed water on the intake runners at the heads with engine running and one hole seemed to draw water and stumble the engine slightly so we did the intake/spacers.

Again, I thank you all for your help.

I have checked all hoses around the air intake etc. but all looks good, unless something is piped wrong.

I mixed water with washing up liquid and sprayed it around the area where the air intake meets the engine. There was a lot of bubbling so that was a good find. Thanks Be911SC:D
So I'll be ordering a set of gaskets and seals ASAP.....

Thanks,
Dave

Hello Again,
I have removed the right hand inlet manifold and Have found a few issues...

Two of the three lower gaskets below the spacers are missing parts, it looks like it has been that way for a while. I can only imagine the other side is the same. Also, from over filling it with oil, there is an oily build up inside the manifold.

I guess a major clean up is in order!!

I will post pics when I can. I am amazed it actually ran as well as it did!!!

Thanks,
Dave

Here is what it looks like now...;)http://forums.pelicanparts.com/uploa...1375384213.jpg
http://forums.pelicanparts.com/uploa...1375384253.jpg
http://forums.pelicanparts.com/uploa...1375384293.jpg
http://forums.pelicanparts.com/uploa...1375384343.jpg
http://forums.pelicanparts.com/uploa...1375384362.jpg


I have a bit of work to do yet. I damaged one 'o' ring on one of the injectors so will need that. I have the gaskets and the surfaces are clean. What do you think about spraying the manifolds in silver to freshen them up?

Thanks.

Dave

http://forums.pelicanparts.com/uploa...1375384944.jpg

Hi,
I'm not sure if you can see this picture but the blue pipe runs from the upper sensor to the lower port.
The Pipe in the bottom left runs near the oil tank and is blanked.

The other pipe on the sensor is pipes along the right hand manifold and is also blanked with a screw.....:confused:

I am absolutely sure that isn't right!!?:eek::eek:

Thanks,

Dave

Hi Again,

Decided to spray the manifolds and am glad I did! Have the gaskets and spacers in place ready for the manifolds when they are dry....
Can't wait to assemble her and see if she runs better...
Dave


http://forums.pelicanparts.com/uploa...1375392289.jpg
http://forums.pelicanparts.com/uploa...1375392311.jpg

Have you serviced the "triangle of death" yet? You have it all apart so it's quite easy at this moment. Also the fuel lines are very easy when the intake is stripped.

Hi,
I like the 'triangle of death' thing!!!
I had serviced her prior to the strip down thinking that would solve the running issues....
The plug changes are a bit tedious!

Dave

You stated:

"I'm not sure if you can see this picture but the blue pipe runs from the upper sensor to the lower port.
The Pipe in the bottom left runs near the oil tank and is blanked.

The other pipe on the sensor is pipes along the right hand manifold and is also blanked with a screw...?"

While I'm not looking straight at my engine right now, I believe there should be another hose (similar diameter as the blue hose in your picture), that runs to the ambient air valve or recirculating valve depending on what diagram / name you look at. The part number of the valve I have is: 930-207-227-00. The hose that linke the two is 830MM long with p/n 999-239-010-40 Pelican Parts - Automotive Parts and Accessories - Porsche & BMW. Hope that helps.

Apologies for the slow reply.
Would I be right in saying that the one of the pipes runs to the air valve and the other returns? Also, is the function of this valve purely for cold starts and should not affect the running of the car at normal temperatures if it was left disconnected?
I have no idea where this valve is located on the engine or if it was discarded when the engine was fitted (before I owned the car).
If the above is true, are there any side effects to leaving this disconnected?:confused:
Cheers,
Dave

I don't believe so (at least not exactly). The small hose I have, runs to the top of the air valve - with larger hoses running to oil tank from one side of the valve and to the back / base of the throttle.

In the first attached picture (provided by another Pelicaner) you can see two references to the air valve. Hope it is starting to make a little more sense now.

http://forums.pelicanparts.com/uploa...1375807938.jpg

Am also attaching the vacuum line routing diagram I have - on the right you'll see a line to the Air Valve (that's the part I'm talking about (note the three different lines from it).

http://forums.pelicanparts.com/uploa...1375806848.jpg

Thanks for that Skip1, It really explains the system.
Only problem is that the air valve appears to be missing!!

Really appreciate the help,
Dave

Thats not a direct vacuum leak it's ported. (its above the throttle plate) Leaving it unpluged wont effect the idle at all. Check all the hoses that connect to anything below the throttle plate for cracks. A leak on one of these and the car will run like crap.

It's still downstream of the AFM, giving "false air" readings via vacuum leak.

Yes but not at idle which was the original problem. A vacuum leak here will have zero effect at idle.

Dave,

In one of your other pictures you showed the back of the throttle with the comment "I'm not sure if you can see this picture but the blue pipe runs from the upper sensor to the lower port. The Pipe in the bottom left runs near the oil tank and is blanked." This blanked pipe is the one that would go to the air valve I'm referring to.

Can you get a better picture of the right side of your engine bay (i.e. the oil tank cap area to see where the small diameter hose is running that comes from the above location?

In the enclosed picture, you can see the air valve above my oil cap. The small tube attaches to the top (from the smaller pipe on the back of the throttle), and the larger tube you refer to above, would fit on the side you don't see.

http://forums.pelicanparts.com/uploa...1375891455.jpg

Here's what things should look like back there. As Skip said, the braided hose attaches to the air valve on the oil tank. Mine was found to be disconnected at the throttle body so that may be where the grime there came from. (Engine drop on the to-do list this fall.)

http://i12.photobucket.com/albums/a2...psfce3004f.jpg

Found this cracked hose during the intake job so we used John Walker's trick and heat-shrinked it.

http://i12.photobucket.com/albums/a2...ps06bfb402.jpg

http://i12.photobucket.com/albums/a2...ps0efc4d9f.jpg

Hi All,
I have had a lot happen since my last post....
I also had problems with cracks on the above hose. I cut the hose clamp, got some heavy duty hydraulic hose and drilled one end 15mm and left the other end 12mm. I then used jubilee clips to keep it together.
Since the air valve is missing on my car, and it didn't run too bad without it with the pipes blanked, I decided to keep it that way until I pick up a new valve. I figure that if there are no vacuum leaks, there should be no problem once warmed up.
The rest of the vacuum system looks in order, the 'y' piece is connected to the fuel regulator and damper and all other pipes are in place.
I assembled the inlet manifolds and when all was fully assembled and checked, I connected the battery and.........DISASTER STRUCK!!!!

The engine made one turn and locked up. I thought it was a bad battery connection but it wasn't. I tried to turn the crankshaft but it would only turn one way for one revolution. This was 10pm last night so before I threw my teddy out of the pram, I quit, had a beer and went to bed feeling sick.

I thought about the issue today in work and the only conclusion I could come up with was that when I was removing the manifolds, a washer or some debris must have fallen into one of the ports with the valve open and entered the cylinder. Then when I cranked the car, the piston connected with it and locked against the head.

I was full sure I would have to remove the engine and box and strip down at least one side of the engine. I had an idea that could work but I really didn't think it would work!

I borrowed a very small magnet on an extendable stick (a bit like a car antennae) from a work colleague. When I got home, I removed the plugs and determined which cylinder was coming up to top dead centre when it locked. It turned out to be the left rearmost cylinder. I wound the crankshaft back until the valve opened fully and inserted the magnet. at first the magnet picked up nothing but I inserted an air blower in to the spark plug hole and blew with the magnet inserted beside the valve.
Lo and behold, the magnet picked up one half of a crushed washer. I tried again and the other half was retrieved!! What are the chances of doing that without an engine strip!!

The engine turned freely now but I was concerned if there was any damage to valves or piston. The only way to find out was to assemble her again.....

I was pretty nervous putting the key in the ignition..... but up she fired and she purred like a kitten! She has never ran so sweet in the 6 years I have owned her. Idle is a little high but I will correct that tomorrow.

Thanks a million to you all, especially Be911sc for the advice on the inlet manifold gaskets. It's so easy to check and makes such a difference. I haven't driven the car yet but hope to tomorrow. I will get back to you to let you know how I get on....

Dave

Here are a few photos of my engine as it is now.....

http://forums.pelicanparts.com/uploa...1375996770.jpg
I painted the fan and the cowl, what do you think?

http://forums.pelicanparts.com/uploa...1375996821.jpg

As you can see the air valve is missing. It now runs like a dream and ticks over at 800rpm without any fluctuation. It is like a different car and for the first time in six years I am really starting to enjoy 911 ownership:)

http://forums.pelicanparts.com/uploa...1375997053.jpg

Really appreciate all your help!!!

Just back from a 400 mile trip, car performed really well and is much more economical than before. I have much more interest in the car now that it ticks over and will pass gas stations without needing a drink:)

Thanks again to all here,
Dave