3.6 running issue

[mb911]

I have owned this car for about 3000 miles over the last 6 months. When I first got it the flywheel sensor and 1 coil died. so I replaced them both and the car has run fine ever since. At the same time I replaced the DME relay as suggested on this board and rennlist.

so day before yesterday I took it for a drive in a 100 degrees and ran fine for the hour drive until about a mile from the house it kind of felt down on power. I chalked it up to extreme heat and humidity. WOT was no issue it was midrange it just seemed a bit sluggish. when I got back home I let it idle for a bit and noticed that the car now idled at about 1200 rpms instead of the normal 8-900 rpms I normally see. No big deal I assumed it was the dme's way of cooling the engine with more airflow????

So yesterday morning it raining and 20 degrees cooler so I decide to take it out for a run and it runs and drives perfect however it does start and hunt a bit for idle and then dies for the first start of the day. I drop my son off at a day camp and go home no issues. then I go later in the day to pick him up and no issues until coming home and the car dies at the stop sign no problem fires right back up but now it almost seems like it is running out of fuel but WOT no issues. about a mile from the house it is now down on power but I get home and it is idling just as it should . I check the DME relay to see if it is hot and it is to the touch which I think is very odd.

so to note the only thing I have done to the car is that I put on a stock airbox a couple of days ago and hooked up a vaccum line that was dissconnected from some sort of valve? that lead to charcoal canistor mounted on the stock airbox(PO just had it open to atomosphere.

My thoughts are that this is not the issue. I can say I have pretty extensive records on the car and the fuel pump has never been replaced the car has 102,000 miles on it with a top end about 15k ago.

just a note I did put the orginal DME relay back in the car and seemed to run much better. is the relay overheating because of a bad pump or is it a bad new relay??

[mb911]

Another thing is that up until 2 days ago part number 964 110 940 00 was disconnected PET calls it a vaccum unit and shows it connecting to a bleeder valve 944 605 240 01 but I had just connected to a vaccum resivoir on the air filter. not sure if it should be or not be? just not sure how it should be versus what is here. but this may not have anything to do with my running issue

[Joe Bob]

Who made the relay? Is it German or a "URO"?

[Jess]

Have you checked to see if your distributor belt is turning the second distributor? I believe that would cause the symptoms you describe if it's broken.

[Bill Verburg]

The relay sound as if it may have some sort of internal possible intermittent short, the quality of these over the years has been very spotty.

not sure what vacuum can you are referring to but if it's the one for the cross over flap you need it

You should have an aluminum manifold as pictured here, the resonance flap vac can is below the air meter flaper box and behind(right) of the air cleaner box

[mb911]

Unfortunately it is not a German made relay which are few and far between.

as to dizzy belt I have checked both ignitions and they are working as they should. I did the unplug each module and listen for RPM drop just like a MAG check on an airplane.

as to vacuum port all I did was take a hose that was disconnected from the 964 110 940 00 vacuum unit (seen from the back of the engine the side you see when you open the engine lid) and connect it to the vacuum canistor mounted on the air filter box ( about the size of toilet paper roll)

I still tend to think its a bad relay as well just want to be preparred. not going to get a chance to prove until friday though.

keep the input coming as the vacuum thing need to be figured out one way or another

[Bill Verburg]

Here's what a stock al. manifold 964 will look like

and another not stock though from the side showing resonance flap vac can below the air filter




another stock w/o the alt and A/C in the way

[mb911]

I need a shot of directly under the AFM thats where the unit is. I found it on PET #10 on the picture of the intake for PET. this is the one venting to atmosphere and I connected to the air filter canistor

[mb911]

oh thats the vacuum canister for the resonance flap. that was not even connected on my car previous. I need to identify the resonance flap and see where that vacuum line is going or not going. maybe missing a couple?

[Tom '74 911]

Ben,

I have a '90 964 engine that I'm planning to pull from my '74 911 this afternoon or tomorrow. I'm happy to take more photos of things that are hard to see or access for you if it helps. I wish I could help more directly w/your issue. . . .

Tom

[KTL]

Cylinder head temperature sensor? I recall 3.2L Motronic cars having a similar problem with faulty sensors. Although that issue was the 1 vs. 2 wire update.

[mb911]

In the back of my mind I am thinking Head temp as well but got really side tracked with the vacuum lines. I have now just looked and discovered the 2 parts that were previously un hooked were the resonance valve and the vacuum resivoir . Now the question is where does the resonance valve get a vacuum signal? This really ticks me off that someone removed these vacuum lines to begin with and now I have to figure out how it is suppose to be. the good news is that the car should have more power once its corrected.

so if anyone could take a picture of the resonance valve and the vaccum source and how it connects and ties into the resivoir as well it would be much appreciated. I did actuate the valve by hand and it moves freely so that is good.

Also I plan to run a resistance test on the temp sensor to rule that out. the question I have next is Does the DME relay seem the most logical item then go to fuel pump? is the AFM susspect at all?

[mb911]

I found these picture and mine does not look like this as it is a 90 aluminum intake but somewhat similar is this vacuum routing I should have?

[Steve W]

You said the only thing you did was remove and reinstall the the stock airbox. There was a TSB on the connector to the AFM for a 964 years back because the original position of the harness connector caused eventual damage to the wiring inside the harness/connector to the sensor. The TSB solution was to zip tie the harness back. Check the wiring inside the connector. Perhaps it sustained some wiring damage in the past and your movement finally broke what little wiring that was left.

[mb911]

Steve I will check that out.

Any thoughts why the relay would be so hot to the touch?

[mb911]

Ok checked out the tsb and found what they wanted however looks like my car already had the updated harness so thats not it and the wires look good. I did notice however it seems possible the AFM was may have been walking out of the boot as the air filter box seems to limit the boot and the AFM engagment. not sure I just pulled everything tight. also tested the resonance valve and it functions with vacuum on it so I need to do a test drive now. I am going to try to sneak one in yet tonight and see whats up.

[mb911]

also the relay is a german one so not sure what that could mean

[mb911]

drove the car for a few miles yesterday and ran perfect so not sure what the issue is. I am wondering if the DME relay was really the issue or if it was heat related to some other component. I am also a bit gunshy and not sure I want to get stuck somewhere.

any other thoughts?

[mb911]

Well nothing really to report. since tightening up the AFM and checking the wiring harness, hooking up the resonance valve and related vacuum hoses, and changing the new german made relay for the one the car came with it seems to run perfect. I did notice the relay does not get near as hot with the cover removed but I know I cant do that but curious. it also does not get real hot at idle but only when driving under load??

[Joeaksa]

Excellent photo Bill! Saved that one for future reference!