When my car go out of hibernation in April, I plan on replacing the knock sensors as a preventive maintenance.

While the air intake is removed, what other parts should be replaced? Anything special I should be aware of before starting this job?

Thanks.

Michel
89 928 S4 ROW
Quebec, Canada

 

TPS
Rubber hoses
Flappy actuator
Flappy bearings
Vac lines/elbows
ISV (clean it)
Fuel lines
Plastic elbows for MAF boot

I am forgetting something I'm sure.

 

ISV ?

 

Idle stabilizer valve.

 

Check with Roger, he has a flowsheet of common replacement parts for an intake R&R.

Consider having your injectors cleaned and new seals (O rings) out on. Now is also a good time to replace the thermostat and associated rubber bits.

 

If my idle is stable, I really don't need to replace the ISV do I. I have no idle issues. Pricey part to replace when you have no problem with it.

 

I did not replace mine. Once you know the intake job, pulling it all up again to change an ISV would only be a big PITA, not the end of the world ...

 

Nope. Just clean it up and you should be good to go.

 

Oh, and definitely plan to clean the MAF while it's out on your bench. Pop the screen off the top and douse the whole insides with that nifty CRC MAF cleaner in the convenient aerosol can ...

 

I would add the oil filler neck to the project and perhaps consider the water bridge gaskets /thermostat.

Operation of the knock sensors, flappy valve, TPS, MAF signal and ISV can all be checked electrically through the LH ecu.

 

+1 on the water bridge and oil filler neck. The water bridge bolts will be a PITA, but once you clean and chase them out you'll be good for another 20+ years.

T-stat and all o-rings as well.

Might I also interest you in a CPS? Those seem to crumble at the most inopportune times (like right after you replace everything around them).

Just a thought.

 

928 Specialist has it as a project page on their website--you can add/delete stuff as needed. Look under "specialist kits". Prety cool!

/ Bruce

 

Malcom,

How do you check the operation of those devices? Is the procedure described in the Service Manuals?

Thanks

Michel

 

Michel,

Yes and no............some systems can be checked through wiring harness of the LH and EZK computers. Others need the car running and access through the diagnostic port to a diagnostic system where the knock sensors, number of knocks and hall sensor.

The WSM does talk about the process using the Porsche diagnostic system which has now been superseeded by many private enterprises including some sponsers of Rennlist.

Send me a PM for further details.