[unknown4u]

Have you checked the + 12 at the icv? Because that one is direct from the dme relay...


If that one is not a proper 12 volt plus. It gives the same symtoms too...i had that when I bought the car lightyears ago..


After the car warms up the icv works on the voltage at the other connectors from the motronic...
No hesitations at all.

But always hard to start either
When cold ofcourse

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[ds968]

Haven''t checked that but definitely sounds like I should . So how can that be accomplished ; the voltmeter' " clip " ends connect to what / which parts the ICV ? And even more fundamentally where is the ICV, and can it be easily accessed for that purpose ( to test the voltage ) ?

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[unknown4u]

Underside the throthlebody. 3 pin connector.

For the pins check the electric diagram.


If you pull the dme relay you can check the resistance from the relayboard to the 3 pin connector.

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[ds968]

Got it, thanks. Will do.


Of course, with my luck, the entire supercharger assembly will have to be taken off the car to even see the ICV.

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[ds968]

Well, that turned out to be a disaster; upon disconnecting the cap at the ICV two things became immediately evident : there was a lot of corrosion in there, and worse, one of the previous owners repaired - I use that term loosely- a broken wire connection ( there is a three wire split going into that cap's ports ) using the proverbial " bubble gum and rubber band " method, so that piece also disintegrated and broke off again the moment the cap came off.


The mechanic cleaned everything up and the. soldered that broken wire to its contact point , then tested it to make sure the new repair would conduct the current properly, and all that seemed to work fine, until I started the car cold the next morning ...and this morning as well ; the rpm drops to the lowest bar on idle and the car simply stalls, unless I immediately step on the gas and raise the rpm holding it there for a few minutes until everytging warms up. About 100 % worse now than it ever was ! The mechanic suspects the ICV unit itself , as wonky / sticky as it was to start with ( we're pretty sure of that because the ICV fault code came up a couple of times in the past ) probably got stuck in a poor functioning mode when the plug was disconnected , and reconnecting it did not correct the problem or even cause the unit's recovery to where it was before this . So I have to get a new ICV , which would have probably been the case no matter what, but I also need that plug-in cap , which hopefully will be available .

Ether way, with the SC in the way I'm looking at maybe $ 750 + in labor alone to get this thing replaced.


And until then, the only way to start and drive this car is to raise the idle RPM to about 1600 , which I've done ( throttle screw adjustment ) this morning . I figured since F1 cars idle around 7000 rpm, I can live with the 968 idling at 1600 for a few weeks or so until I get the parts in and able to have the job done .


I do need to stay away from any stores where sledgehammers are sold though , because that's the next fixing this car is going to get !!

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[flash]

be VERY careful about that.  repeatedly engaging the transmission into gear at that rpm can destroy your flex damper.  i would park the car until you can get the ICV changed.

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[unknown4u]

A quick question. Did he measured the volts? Coming from the dme? It seems to me that he did not tested that. An icv is not an item that will have a quick failure. Or ar the connectors inside gone?

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[ds968]

No he didn't have a chance to test either the voltage or the ohms because as soon as we saw the shape or the connector totally corroded and the one wire hanging by merely a prayer , the conclusion was that's where the problem must be, so he focused on fixing that and I suppose felt there was no point checking anything else. I was under the impression ICVs have issues all the time in thiese cars ..not as in failing completely m but getting " sticky " quite often and causing cold starting issues . No ?

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[ds968]

I don't feel even the slightest bump when shifting into gear unless the idle rpm is at least at, or above 2 K . Possibly because the flex plate is pretty new ( one year ) so it buffers everything very well ?

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[ds968]

Further to this - I spoke again to my ( now officially retired ) mechanic, who maintains that it is "highly improbable"  this specific symptom is caused by a voltage / resistance issue because if that was the case, the problem would manifest itself every single time I started the car after it sat for a while .  For that same reason he's not 100% certain it's the ICV either, though he does put greater weight on that possibility and said to first change that connection which was all messed up, and then see what happens.

He does suspect however there might be a temperature sensor that's either causing or at least contributing to this issue.   So to clarify once more :  this car can sit for days, or a week or however long without being driven and if I start it while the outside temperature is, say , above mid-60s there is NO PROBLEM whatsoever ; I can do that a hundred times without even the slightest trace of the symptom.  But when the outside temperature overnight is below 50, starting it in the morning will cause the problem to manifest itself, every single time.  Logically, this would point to an ambient temperature sensor, wouldn't it ?   But the only one I can think of is the coolant temp sensor ..is there anything else ?                                     

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[flash]

there are 2 temp sensors in the head.  one up front, and one a few inches behind it.

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[Waylander]

The one at the front sends water temp to the dme for cold running, the one behind sends oil temp to the dme for fuel vapour purge


If it's running like crap when temp is low try changing the blue one at the front

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[ds968]

Will do, seems easy to change and I think flash said he has a spare one he'll send me so that's the next process of elimination test . In the meantime I switched the MAF with the one from my other 968 which starts and runs perfectly , but that wasn't it.. I also had all the spark plugs torqued again just to make sure there wasn't a loose one which could have caused a firing issue when cold, so the front temp sensor is next .

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[ds968]

Changed the coolant temp sensor . Also changed the connection plug / cap at the ICV ( the old one was in really, really bad shape - every one of the three ports as well as the wire tips going into them were all badly corroded and looked burned up - I'd think the signal for the ICV- ECU contact must have been totally out of whack .. )! Last, we changed the O2 sensor as well - the one in there was the original ; 23 years and 135 K miles ago, so probably way overdue . It was seized and it took a two hour ordeal to remove it, but that's another story altogether .

So the first cold morning start after all those changes : about 50 -75 % better, but there's something else that still causes the initial 30 seconds to a minute to be rough going ..however, it " warms up " and normalizes a lot faster than it did before. I don't recall if I mentioned this in one of the previous posts, but the RPM didn't " hunt " much during that rough start , it just stayed at a very low point until the engine warms up and then it simply gets back to its normal level.

Crap ! Just realized I forgot to check the voltage at the ICV connection after we ell aced it with the new cap . Will do that when I go back to the shop, need to troubleshoot that rear wheel rumble issue.

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[ds968]

Ok, this is ridiculous ! ICV changed now, all electrical wiring and contacts tested , temp sensor changed, O2 sensor changed, fuel check valve changed, two different MAFs switched back and forth just to test if that could be it, three different DME relays switched, there's not much left to check but the FPR, but I have the one that came with the stage 3 SC, so not sure I can switch it with a regular OE one and test the symptoms ..can I ? And would a failing FPR cause those symptoms only in cold ambient temps , and then recover perfectly for the rest of the day's starts when the weather is a few degrees warmer ? Arrgh, WTF is going on, seems it's even getting worse that it was.

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[flash]

possible cause, but not likely.  there should be enough fuel to start regardless of regulator.  that is the lowest demand point.  

 

yes, you can swap it out for the OEM one for a test.  on the tip car, you could probably even run it full time, because you never hit the super high demand areas above 6k rpm.

 

i'm going to think on this one, and see if i come up with any ideas

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[unknown4u]

Bad to hear that the problem exist. You have changed the dme etc.


But will all the pins connect to the circuitboard/relayholder?

Is the connector inside the fuseboarf from the dme to the icv not worn?

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[flash]

i think we are over-analyzing the issue.  i spoke to dan, and reminded him that he adjusted the throttle plate position to raise the idle.  this would alter the A/F mixture during the 60 second start-up map.  the ICV not functioning would do essentially the same thing.  he has now changed the ICV.  conditions improved, but not entirely resolved.  now he needs to restore the throttle plate, and thereby the throttle position sensor, to the OEM configuration.  then, and only then, after eliminating that known variable, can any sort of diagnosis begin.

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[ds968]

The throttle position sensor is now the new prime suspect . To elaborate; we disconnected the ICV while the car was idling and instead of the RPM dropping , as it should , it went the other way..up by about 400 .

Then we removed the TPS cap and tested the pins with a voltmeter.the top and next pin down were not registering / reading correctly so we'll switch that sensor with another one from my friend's 968 to test if that's where the problem resides. Also we'll connect the Duramatric and check all the readings on cold starts to see what it may reveal . In any event, we rotated the throttle screw back to where it should be ( the factory level setting for the idle ) so the TPS can be tested when the throttle plate is at its normal resting position and not raised as it was where I set it . Always a possibility that the TPS is trying to figure out why the idle is way up on starts and sending the wrong info to the computer. But there was something else contributing to this issue, because I've always had that throttle manually set about 200+ rpm higher, ever ( since I bought the car , and this cold start problem did not occur until just recently ..

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[Waylander]

I have a few spare TPS here but I don't think it would be viable to post you one

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