[No.15]

The whining of the belt is probably caused by the idler pulley (944 102 277 06) which should be adjusted with a 0.5mm gap clearance to the balanceshaft belt running below and a preload of the upper part with 0mm to 1mm.

 

Regards,

Jack.

So this appears to be the issue even though I have not been able to start the car yet. Belt was touching the idler pulley. I used a credit card to adjust the gap. I never could get a consistent reading with the arnworx gauge so I followed the advice of a guy named van something on YouTube. I ended up not messing with the tension for now.

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[No.15]

Well finally got the alternator cable installed and after the idler pulley adjustment it seems the whine is gone

 

Before

https://youtu.be/SvSsXwZ8E78

 

After

 

https://youtu.be/Q8sLzqDzJ0Q

 

 

It still randomly will not idle.  it's very random and often if I stop the car shut it down for a minute and restart it goes away.  It happens about 5% of the time so not that often

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[J.Elenbaas]

Sounds a lot better like this.

And this is the way to go, when the tension of the belt is done the idler adjustment follows.

 

I would not worry to much about idling like it does.

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[No.15]

So I changed the injectors tonight.

It seems to run better but not as big of a change as I hoped. One test run and it might be placebo but it was a little smoother

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[pdxmike]

Have you checked or cleaned the idle valve yet?

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[No.15]

Have you checked or cleaned the idle valve yet?

Not yet, it's on my list.  Honestly I might be expecting to much but my 951 idles beautifully and I am comparing it to that.

 

The other problem is about 5 percent of the time the car will not idle at all, if i don't  keep gassing it the car dies.  Coming to a stop sign the car dies, etc etc.  Then it magically goes away and all is good again.   Weird

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[pdxmike]

Does the car come back to life if you hit the throttle? Even for a bit before it dies? Can you drive it when its stumbling, as long as you don't let it go back to idle? 

 

Most 968s wander a little at idle but it's not that bad. It will be different than the 951 though due to the always-activated idle control valve. 

 

It's spark, fuel, or air. If you get a response from your engine when you hit the gas, it's probably not spark or fuel...

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[ds968]

Have you already changed the dme relay?

I glanced at the posts, maybe too quickly and could have missed it , but did not see an answer to this.


IMO replacing the DME relay is a must , and keep in mind that ( although very rare ) even some new relays can be faulty right out of the box. Haplened to me , I returned it and got another one which worked perfectly . So if there is a way to borrow someone else’s and see if you still get the symptoms before you buy one, try it out . The reason I’m thinking your should get another DME delay is not just the initial cold start stumble, but the car almost stalling when coming to a stop. The latter is exactly the symptom my car exhibited and a new DME relay fixed that immediately .

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[No.15]

I glanced at the posts, maybe too quickly and could have missed it , but did not see an answer to this.


IMO replacing the DME relay is a must , and keep in mind that ( although very rare ) even some new relays can be faulty right out of the box. Haplened to me , I returned it and got another one which worked perfectly . So if there is a way to borrow someone else’s and see if you still get the symptoms before you buy one, try it out . The reason I’m thinking your should get another DME delay is not just the initial cold start stumble, but the car almost stalling when coming to a stop. The latter is exactly the symptom my car exhibited and a new DME relay fixed that immediately .

I'm using the f9 solid state dme relay.  I still have the original relay, I guess it would not hurt to try it for awhile.

http://www.ftech9.com/new-products/993-ssr-pp

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[Waylander]

Just another thing or 2 to check,


The connection for the crankshaft sensor, located right at the back by the oil filler cap

The fuel pump lead there is a connector just by the fuel filter that can get corroded


See if you can get it plugged in to s Durametric to see if there are any codes like knock sensor or hall sensor

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[No.15]

Just another thing or 2 to check,


The connection for the crankshaft sensor, located right at the back by the oil filler cap

The fuel pump lead there is a connector just by the fuel filter that can get corroded


See if you can get it plugged in to s Durametric to see if there are any codes like knock sensor or hall sensor

 

I have a durametric and I am code free.  I will check the connectors you list.

One conclusion I came to, it will happen every single time on first start after I disconnect the battery.  I drive the car for 10 minutes, turn off, remove key, restart and it is ok again :wacko:

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[pdxmike]

That is quite interesting.

 

Going back to your original video, I think this is an issue with the idle air control valve circuit - or, the DME is not getting a signal telling it the throttle plate is at idle. It is behaving as if the IACV isn't actuating at all. If it was something else you would have problems at all throttle positions, not just at idle. Clearly it revs up just fine. So it's an air problem. 

<del>Have you checked the throttle position switch per the workshop manual to ensure the numbers are in spec? You should then confirm with the durametric that the throttle plate angle checks out OK. These cars have a dynamic TPS idle setting so there really isn't anything to set - but if the TPS is wonky - it could be sending erratic data back to the ECU messing with the idle mixture. </del>

 

Ignore above - forgot that the Durametric allows you to check to idle valve directly. Use your Durametric to make sure IACV (Idle air control valve) is fluctuating appropriately and that throttle plate angle checks out OK. It's still possible that you could have a sluggish IACV when cold and even though it's reporting a certain % to the Durametric it isn't actually opening to that setting. Especially as your car sat for a while. A cleaning may still be in order. It probably isn't a problem with the actual primary or secondary windings on the idle valve because that would show up as a fault code. 

 

I would also use your Durametric to see what voltage is both right before you shut it off and immediately after (told you that thing would be useful). Wondering if there is a voltage fluctuation at idle that somehow "clears up" when you reset the signal to the DME by turning the ignition off and back on - taking into account that you did of course just swap out the voltage regulator. 

 

I'm not sure but you might be able to use the "Actuation" tab on the Durametric to force the IACV open. Can't recall if that's an option for our cars. That would be interesting to see how the engine responds. 

 

It totally makes sense to try running it with the OEM - nonsolid state - DME relay to see if there is something weird with how that the SS unit is sending its signal to the ECU. 


Do you know if you have the stock ECU chip or aftermarket? 

 

Does it completely go away when the car is at operating temp? 


As always, JMO. Im just an amateur with a copy of the workshop manual who likes thinking about other peoples 968 woes

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[No.15]

So I am on my phone so I will reply to a few things. It does this with both the stock chip and the RS barn chip.


It does not seem to be temperature related. I drove the car for 25 miles and then disconnected the battery for 10 minutes and it shows the same behavior.


When it happens I constantly need to restart at lights, stop signs etc. It seems if I drive it about 5 miles then turn it off and remove the key it will then restart and run fine.


I've looked at the durametric info. The numbers change but I don't know what normal numbers are.


It very rarely will do it without a battery disconnect. In fact I don't think it has done it this way since I replaced the VR.


On another note I will say that I think the injectors have improved things more than I originally thought. Idle is smother and seems to hunt less and generally it is running smoothly.

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[pdxmike]

Have you plugged in the durametric while the rough idle thing is happening? Wonder what the DME is telling the IACV when youre actually having symptoms. Also wonder what the DME temp sensor readings are at those times - if its going full rich for some reason you would have trouble at idle that would be less prominent at other throttle positions.


Really interesting that power cycling the DME both causes the symptoms (battery disconnect) and clears it up (power cycling ignition). I cannot think of why the battery disconnect would cause the symptoms. Obviously new cars have an idle learning feature in that they require a little time after a battery disconnect to reestablish optimal mixture but I am certain our primitive cars do not operate in that way. What is the battery disconnect doing that a simple power cycle at the ignition switch isnt? If you can figure that out, that will most likely be the answer.

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[MCL968]

Do you know the history of the O2 sensor? Might be worth replacing if you don't know how new it is.

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[No.15]

Do you know the history of the O2 sensor? Might be worth replacing if you don't know how new it is.

I replaced the O2 sensor when I got the car. Durametric show's it behaving normally when I check it.

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[pdxmike]

Having combed through the internet - I take back what I said - it sounds like the 968 does have primitive adaptive idle learning.

 

After a battery disconnect, it can take 10 minutes for the ECU to "relearn" where idle is on the throttle plate and how to direct the IACV and mixture to operate at idle.

 

So the occurrence of this issue after battery disconnect is - maybe - normal? But it does not explain why you are occasionally having the problem coming up to lights, etc. Almost like your ECU is "forgetting" the idle map.

 

The fact that power cycling the ignition solves it would argue against a sticky idle valve.

 

I wonder what would happen if you swapped your ECU for another unit...

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[ds968]

As always, JMO. Im just an amateur with a copy of the workshop manual who likes thinking about other peoples 968 woes

 

Methinks you're being way too modest; based on what I've seen so far I get the distinct impression you can probably disassemble and reassemble this car while wearing a blindfold, and it'll run perfectly.      :closedeyes:  

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[pdxmike]

Just three things would work: the idle valve, the cooling fans, and the airbags. The car would be full of body filler and be covered with half-peeling vinyl wrap. You do know my car has been in the body shop for like a month due to my extraordinarily poor automotive decision making, right?

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[No.15]

either way all the help is appreciated

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