Cruise Control - Where is the Amplifier?

> My cc-unit seems to have the classic problem of not being able to maintain the
> desired speed.  I have determined from several  sources that the problem is a failed > amplifier. Now all I have to do is take the unit off the car and send it in.  Can 
> anyone tell me  where it is?

It's the silver box mounted under the radio.

Wayne Michelsen
'87 911 Targa


Chain Tensioners - Carrera upgrade

IMHO, the only way to go with tensioners is to update to the pressure-fed "Carrera" type. You can do it with the engine in the car.  It took me about six hours, but I'm slow, and I clean/inspect other things "while I'm in there". Here is the procedure I used:

1. Set cylinder #1 at TDC
2. Drain sump
3. Put rear of car on jackstands
4. Drain oil tank
5. Remove muffler (good idea to soak fasteners with penetrating oil first)
6. Remove oil filter
7. Remove AC compressor (Disconnect the AC clutch power wire, but don't disconnect the AC hoses-just remove the air cleaner and put the compressor on an old towel on the air box, where it will be out of the way)
8. Remove compressor bracket
9. Remove air hoses
10. Remove distributor (note where rotor is pointing so you can put it back in correctly)
11. Remove rear engine tin (covers area above muffler)
12. Remove cam chain covers (you may have to use a putty knife to separate them-be careful not to nick the engine cases)
13. Secure cam chains (use sturdy, soft copper wire, blocks of wood, whatever, just make sure that the chains don't go slack)
14. Remove tensioners (you may have to pry a little-just be careful what you pry against)
15. Install new tensioners (make sure to put the small rubber O-rings on the tensioners where they pass through the covers)
16. Replace cam chain covers
17. Install new oil lines
18. Install oil line braces
19. Replace tin (you will need to cut a little notch to clear the passenger side tensioner oil line-I used a Dremel tool with a cut-off wheel)
20. Reinstall air hoses
21. Reinstall AC bracket and compressor (ensure that the AC clutch power wire is reconnected)
22. Reinstall distributor
23. Replace oil filter
24. Reinstall muffler
25. Lower car
26. Refill oil tank
27. Start engine, check for leaks
28. Treat yourself to your favorite adult beverage--you just saved about $500 labor.

There is also a good article on this by our esteemed Alan Caldwell in Volume 7, page 57, of Up-Fixin'.

Bob Tindel


Clutch Cable - Adjustment 911SC

This is for models with an auxilliary clutch spring (C-Shaped spring on bottom of transmission)

Clutch play on these models cannot be measured accurately at the clutch pedal.  It must be checked at the transmission adjusting lever.

1.  Check whether the clutch cable is tight.
2.  If the cable is tight, check the play with a feeler gauge, and adjust it to 1mm +/- .1mm with the adjusting screw.  (This is on the bottom of the transmission, adjacent to the C-shaped spring.  The adjusting screw is located at the opposite end of the
clutch adjusting lever from the cable attachment.)
3.  If the cable is not tight, or when installing a new cable, detach cable, and set clearance at 1.2mm.  Reattach cable, and adjust nuts on the bowing tube until clutch play is 1mm.

Bob Tindel


Clutch Chatter - 911SC

This is for models with auxilliary clutch spring (C-Shaped spring on bottom of transmission)

In trying to fix slight, occasional clutch chatter in my SC, I chased down Technical Bulletin 8403, Subject: Clutch Chatter.  The entire text (no pictures) is: "For a complaint of clutch chatter, first check that the clutch cable guide tube is not contacting the accelerator linkage.  If contact is being made, adjust the guide tube to ensure adequate clearance will be maintained."

I replaced the clutch cable--the new one is plastic coated cable running in a plastic sheath, versus the old bare wire cable in plastic sheath. The clutch action is noticably lighter and smoother. The chatter is gone.  I think the old guide tube was rubbing
against the transmission, maybe binding on the filler plug.

Defective motor mounts also can cause chatter.  They are easy to check, just support the motor with a floor jack and remove one of the rear mounts for inspection.

If this type of cable system has inadequate bow in the bowing tube, it can cause clutch chatter.  To increase bow, adjust the cable at the pedal end (under carpet at front of tunnel, under dash) so that the threaded end of the cable just protrudes inside the yoke of the clevis.  This provides maximum cable length, and therefore maximum bow in the bowing tube.  Additionally, ensure that the clutch auxilliary spring is clean, lubricated, and free of caked-on cosmoline, as this can also contribute to chatter.

Bob Tindel


Cylinder Head Temperature Sensor - Upgrading 84-89 Carrera

The cylinder head temperature sensor measures the temp from cylinder head #3 and sends it to the DME computer. The original part (911.606.405.00) got its ground from the cylinder head and had a single wire going to the DME. Apparently this method of providing ground is unreliable, so the updated part provides its ground from a second wire (964.606.405.00 though there may be a new part number which is 930.606.013.00). Interestingly, on my car (87 Carrera), there already was a second ground wire in the car (two wires running to a 2-pin connector), even  though the original sensor had only one wire (1-pin connector) and didn't use the ground. This was good news, because it  meant that the upgrade didn't require any new wiring.

On the left side of the engine compartment towards the back, you'll see a bracket with three wire connectors on it, the top one is for the head temp sensor. If you try disconnecting the sensor while the car is running, you'll see that it does run but very roughly (and overly rich). I have heard some differing opinions on whether a faulty sensor could cause no-start conditions, but my car it definitely will not start with the sensor unplugged. It's easy to check if you have the upgraded (964-style) part in case you're wondering.

If you disconnect the sensor at the bracket in the engine tin, you'll notice that the left side (wire to DME) has two wires going to a 2-pin connector. The right side (wire to sensor) has a 1-pin connector if it's the orginal part (911.606.405.00), or a 2-pin connector it's the upgraded part (964.606.405.00). The upgraded part also has a thicker wire going to the sensor because it's really two wires (additional one for ground) under the insulation instead of the single wire on the original part.

If you are diagnosing a no-start condition and have the original sensor, you might want to test the sensor's resistance to ground with an ohmmeter. Put the positive probe on the single pin in the connector coming from the sensor (the connector on the right which is fixed to the bracket) and the negative probe on a known good ground. If the sensor is working properly, it should read in the 1-2k ohms range. If it reads zero or infinity the sensor is probably bad. Interestingly, I can't seem to get a proper resistance reading from the new sensor, but it definitely works.

Okay, here's the procedure for upgrading the sensor without using any special tools. Jack up the car (rear) and secure it on jack stands, remove the left rear wheel. Inside the wheel well you'll see an oval-shaped grommet in the engine tin with a wire coming out, then the wire runs through another grommet up higher in the wheel well (along with two other wires). Remove the lower grommet by prying it out with a screwdriver. You'll see the head temp sensor in cyclinder head #3 inside the hole in the engine tin. Normally a special tool would be required to remove and replace the sensor (a slotted socket that fits over the wire), but it's not needed.

Instead, cut the wire off the old sensor (as close as possible to the sensor itself), then extract the old sensor with a deep socket. Thread the new sensor in by hand and tighten it with some needle nose pliers (it's a bitch to get in there but works). Now pry out the top grommet with a screwdriver (this was very difficult, I actually had to cut out my old one). Feed the new wire through the bracket inside the wheel well (you'll need to remove and replace the little bracket). You'll notice that there are two additional wires that run through the top grommet (back into the engine compartment) along with the head temp sensor wire. Fortunately, the new grommet is slotted so these extra wires slip in easy. Slip the two extra wires into the new grommet and feed the wire through the hole. Don't replace the grommet till you've installed the wire in the engine compartment.

You should be able to reach into the back of the engine compartment and grab the new sensor wire. You'll see that it runs around the manifold pipes and through a bracket in the middle of the engine. This bracket can be easily removed with a 4" socket extension and wrench to feed the new wire through. To install the new wire on the bracket at the left side of the engine compartment, you need to take apart the bracket. You'll notice that there are two little screws on the face of the bracket. Remove these screws and the bracket slides apart. It's easier to get at these screws if you uplug all three wires (be sure to label them appropriately). Slide the old plug out, the new one in, replace the cover of the bracket.

You should see two pins in the connector on the DME end (left side). The top pin is for the temp signal, and the bottom pin is for ground. You may want to check that you are in fact getting a proper ground by reading the bottom pin with an ohmmeter. You'll notice that the connector on the sensor end (right side in the bracket) now has two pins instead of the original single pin. To complete the job, don't forget to reinstall the top grommet in the wheel well. This part is difficult, so be prepared to let a few profanities fly ;-)

That's it, head temp sensor 101, for the DIY mechanic. Thanks to Darrin Sacks for explaining how to do this with no special tools.

  -- Doug (87 Carrera Targa)


CIS - Reference books

I promised the titles of some reference materials on Bosch CIS fuel injection.
See the following:

Bosch "Gasoline & Diesel Injection Products Catalog" 221132 (1996)
Source: Robert Bosch Corporation
            Sales Group
            2800 South 25th Ave.
            Broadview, IL 60153

"PORSCHE Troubleshooting Guide K-Jetronic" 4533.20   2/78  (Approx 6" x 8 spiral bound book)
Porsche AG
Postfach 400 640
D7000 Stuttgart 40

Bosch "Mechanical Gasoline Fuel-Injection System with Lambda Closed-Loop Control K-Jetronic"   ISBN 1-85-226030-0.  Pamphlet with theory, pictures.

"Bosch Fuel Injection & Engine Management"  by Charles O. Probst, SAE
ISBN 0-8376-0300-5  Robert Bently, Pub.  Covers all the Bosch basic systems.

Porsche Factory Workshop Manuals covering the '74 - '83 cars.  These manuals have most of the important stuff, but there are still bits and pieces to be picked up in the other books listed.

PCNA's "Parts and Technical Reference Catalog" (911 Models 1974-1989) PNA 000 147

This last book is not a CIS book per se, but has some handy parts illustrations on the CIS parts.

Taken altogether, I don't think this reference material leaves much out.

Hopes this helps someone find answers to their CIS questions,

Jim Williams
'92 C2
'78 SC receiving a 964 engine transplant