DR

Hi Harvey,

Whoever you get to do it down there (Jim is great and so is Brad Moyer at Digital Chassis)... makes sure they not only replace the TT...BUT, as we discussed, find/fix the root cause of it's breakage.

This is the TSB I mentioned to you, make sure you mention it to them.

TSB
Broken Central Tube Shaft Vehicles With A/T

9228porsche01
July 7, 1992
Model 928 S4
Group 3
Part Identifier 3903
Number 9206

Subject: Broken Central Tube Shaft Vehicles with Automatic Transmission

ATTENTION: Service Manager/Service Technician

Models Affected: 928 S4 Model Year 1989 to 1991

Concern: Activation of the ignition monitoring system (injection circuit switched off fault codes 1131 or 1231) can lead to breakage of the central tube drive shaft.

General Information: Oscillations in the central tube system that occur when the ignition monitoring system has switched (flywheel effect) can lead to breakage of the central tube drive shaft. This can occur only in vehicles with automatic transmission where the vehicle is operated at an engine speed of approximately 1000 RPM. Possible causes are:

- Damaged or defective exhaust gas temperature sensors.

- Possible damage to the ignition coil wire left side (in driving
direction) between the ignition coil and distributor cap.

- Poor grounding of the mounting plate for the ignition final stages.

- Poor physical connection of the electrical plugs on the ignition final stages.

Parts Information: A new version temperature sensor, central tube and coil wire are installed in production.
Temperature sensor, Part Number 928 606 155 02 Central tube with changed material for drive shaft, Part Number 960 421
012 07
New coil wire with hose covering (for left side), Part Number 928 602 040 01

Repair Information:
1. If the central tube drive shaft is broken, replace the central tube with the new version part (see parts information). Refer to Technical Bulletin Group 3, Number 9203, dated May 5, 1992 for hints on central tube installation.

2. Replace the left side ignition coil wire with the part number listed in this bulletin. Be certain the coil wire is routed freely and not under tension.

3. Check all ignition components and connectors for corrosion, tightness, correct connection and damage. Repair or replace as necessary. If an ignition circuit has malfunctioned, an LED indication will be given by the ignition monitor relay located on the L-H control unit mounting plate.

Ignition circuit I (cyl. 1-7-6-4) Red diode Ignition circuit II (cyl. 3-2-5-8) Green diode

4. Replace both temperature sensors located in the exhaust ports:
Model '89-'90, cyl. 4 and 8
Model '91 cyl. 3 and 7
Use the new version temperature sensors listed in this bulletin.

The function of the ignition circuits and light diodes located in the ignition monitor relay remains unchanged. It is not possible to determine from the LED display of the ignition monitor relay if one or both temperature sensors are defective or which temperature sensor has failed.

When installing temperature sensors, coat the sensor adapter threads with molykote paste HTP (white) and torque sensors to 10 N-m.

5. After the temperature sensors are installed, the voltage difference of the sensors must be checked in order to ensure proper operation of the ignition monitor system.

Checking sensor voltage difference:

- Start engine and bring to operating temperature.

- Loosen the mounting bolt for the ignition monitor relay and pivot the relay up to gain access to the plug terminals Do not disconnect the relay plug.

- Set volt meter to the millivolt range and connect leads between E1 and
E2 of ignition monitor relay (Figure 3, white wires). A digital volt meter must be used. Polarity is not important.

- Measure voltage with the engine idling and again at approximately 2000 RPM. A maximum difference of +2.5 mV or -2.5 mV (depending on polarity) is permitted. If the voltage difference is above 2.5 mV, stop the engine, loosen and rotate one temperature sensor. Retighten sensor and check voltage difference. If the difference is above 2.5 mV, stop the engine and rotate the other sensor. If after rotating the sensors to different positions, the voltage difference is too high (above 2.5 mV) the temperature sensors are defective and must be replaced.

Cheers,

Harvey928

Dave,

Thanks for the tech note, and the full explanation. I will make sure that whomever does the work fixes the issue as well.

You guys are the best, and I hope to be friends with for a long time.

Harvey

NC928S4

Ray Munsch of RAM Automotive in North Raleigh is top notch and his shop is equipped like none other.

Chuck Z

Hendrick Porsche has a couple of really good Porsche Techs, one (Eric E) was there when Jim was there and knows a great deal about 928s. He worked on Kermit a couple times when I couldn't get in to see Jim. They have also been promoting a $85/hour labor rate for our cars but you'll want to check with them to make sure it's still available - I cannot speak for them...... Given that Jim is no longer working on customer cars any longer and the fact they moved to the other side of the world from Charlotte I will be taking my GTS to Hendrick from this point on.

cold_beer839

+1 on Ray Munch or Brad Moyer in Raleigh/Durham area. Both are known 928 wrenches with lots of experience.

Jim @ EuroWerks

Hey guys, just to let you know, I’m still around!

Also, Chuck – I’d think you’d know by now that we have a pretty good group of guys here. The experience that is in our shop is a collective experience. As a whole, a shop’s body of knowledge is stronger than that of any one tech.

And, you should know that Eric is also now in a supervisory position – an eventuality for all experienced techs in a business environment.

Dan, I will send you a PM about the work we did for you during our move. I hope if anyone has any questionable experiences that it's brought up to me or one of my partners – we can’t address what we aren’t aware of, and on the rare occasions when something needs to be readdressed, we pride ourselves on making good on our work and meeting our customers’ expectations.

Chuck Z

Everyone should know that Jim has worked on all of my 928s for the last 15+ years. Jim, I hope you understand that when I found out you were no longer going to be working on cars I was very disappointed (and a bit concerned about where I would take the GTS). I feel you are one of the most talented I've ever met when it comes to all things 928. You also know "how I am and what I expect" when it comes to who takes care of my 928s when they are in their hands. When you add everything up, the travel distance, unknown tech (too me anyway....) working on my car, I no longer have that level of comfort I once did.