[Scott Collins]

FAULT CODE - (title of post should be Name this "Blink" test - duh....)



OK, so here is the code that comes up when I do the "Blink" test:



__________________(long hold)



1-2-1-8



__________________(long hold)



1-2-1-8



this continues to repeat without changing.





This code does not seem to match any of the codes on the list - here is what is happening with the car



SYMPTOMS

Upon startup, no problems, engine revs freely from idle through redline. Then take 45min drive on PA TPKE, no one passing me for 40 miles - go through E-Z Pass, then next acceleration engine misses, or hesitates, and car, in gear, bucks at around 3,400 RPM. It does this about 3 times before I decide that it was not a patch of ice I drove over then hit dry pavement. I then keep the RPM's to under 3,000 and have no problem. Get to the parking lot, car in neutral, and engine continues to miss-hesitate at same RPM's when I run up the throttle quickly or slowly- no smell - coolant level stable, no "milkshake" on dipstick, but oil level is very FULL, where I normally run the car, at the top of the dipstick line.



Drove to work this morning, no symptons - outside temp during drive was 21 degrees F.



Recent work:



replace flywheel and clutch disc, new timing chain and Vario-cam pads, new main crank seal and oil pump drive gear.



Thanks for responding with your thoughts about what could be the culprit.



-Scott

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[banditsc]

Just going on what was recently done, there is a sensor on the flywheel housing that could possibly cause those symptoms.

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[flash]

intermittent RPM signal - the second digit (the "2") indicates "intermittent", where "1" would be constant

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[banditsc]

[quote name='flash' post='65468' date='Jan 12 2009, 11:06 AM']intermittent RPM signal - the second digit (the "2") indicates "intermittent", where "1" would be constant[/quote]



Which I think the RPM signal is related to that sensor on the flywheel housing.

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[PorscheDude]

According to the service manual and as stated by banditsc, the symptoms you describe lead to the reference sensor.



The gap between the flywheel and reference mark sensor my be out of spec.

The sensor gap should be .8mm =/-.2mm.



The car should be hooked to an oscilloscope to check the sinewave of the reference sensor.

This will give you the voltage of the sensor, it should be putting out 3V min.

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[flash]

sounds right - i haven't dug into all the sensors - pete could easily confirm that though

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[kwikt]

If it is the flywheel sensor, go for the cheaper unit that fits a BMW( 88 M3 I believe) and Porsche. Less than $60 instead of the $100+ for the Porsche one.



Kevin

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[Scott Collins]

Flash-



Thanks. OK - then, two questions:



1. what/where do I check/replace?



2. should the Fault Code list be edited?



Thanks.

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[flash]

done - thanks for the heads up

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[PorscheDude]

These pictures are from a 944 (sorry I'm at work) The 968 is very similar, difference being the 968 only uses 1 ref sensor on the bellhousing.

The first pic is of a 944 bellhousing. I circled the area where the ref sensor is.



The sensor looks like the ones pictured in pic 2 (only you need one)

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[PorscheDude]

Here are a few more. Again from a 944.



I have a pic at home that show the gap that needs to measured. I will try and dig it up when I get home tonight if someone else does not have it.

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[Scott Collins]

Holy smokes! You guys are just amazing. Great stuff - excellent photo's, with those arrows. I am going to have to learn how to do that...I will check this out - question - any idea why would the problem only occur when the car is warmed up?

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[PorscheDude]

Keep in mind yours only has one sensor in this location. Mounting and wiring is very close to what is pictured.



Sorry, I cannot really give a good answer to the last question.

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[S_Cal968]

I'm not fully familiar with the DME, however I do know that domestic cars [w/ an ECM] have more than one operating mode. Perhaps the DME is in open loop mode for a short time after start up and then goes to closed loop once the engine is up to temperature. If a parameter is not within spec. the DME will store the fault [after 15mins] and may go into limp-home mode depending on which sensor is malfunctioning. In limp mode an engine controller can lower the rpm limit and pull back on the timing.

Back in the days before electronic engine control, if the engine didn't run right or there was an unusual noise most would drive all the way home not knowing if they were further damaging the engine. Today controllers are smart enough to limit performance under certain conditions and thereby limiting potential damage..

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[flash]

yup - for example, our M3 won't let the engine go over somewhere around 5k until the oil is warm enough

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[Scott Collins]

I'll be getting "hammered" today at the Barn and Pete will make it all better. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[RS Barn]

Scott got Hammered and Max fixed problems.

Scott can fill in details

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[PorscheDude]

Nothing like getting hammered at the Barn!

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[Scott Collins]

Max used the Hammer to find the code for the problem I was having - car hesitating periodically - and then immediately found the problem - cracked plastic housing for RPM sensor, located between the firewall and rear of the top of motor - the cracked plastic housing was causing wires to disconnect periodically, causing the engine to hesitate. The repair was to glue and tape the unit back together. Glue and tape are not very expensive. I like that....



Feels like I gained about 100 hp. Turns out it had nothing to do with the recent flywheel and clutch disc replacement. That's why Max and Pete do what they do. And they do it very, very well. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[rob76turbo]

Scott, Can you take a picture of the area or part that was cracked, so we all know where to look if or when we experience the same thing?

Thanks!

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