RSAErick

Hi Everyone. Ok, I've researched this one extensitively, and could really use some troubleshooting assistance...

Symptoms:
1. Low/Diminished Power: It's not extremely dramatic, but is still noticeable to me. It just doesn't have the same pull up through redline that I'm used to.
2. Stalling: This has always been a problem, because of the RS flywheel and clutch. But I used to be able to prevent stalling by not engaging the clutch until the revs had dropped to about 1000 RPM. Now, even wth this technique, it still regularly stalls.

Initial Diagnosis:
Read the diagnostic fault codes using the check engine light (CEL). Gave a 1232 (Intermittent Knock Sensor II) fault code.

Corrective Action:
After searching the archives, found that this fault code could be corrected by cleaning the Knock Sensor II connector. I used a spray cleaner, sandpaper, and small screwdriver to clean the male pins. Unfortunately, there was no effect. I still get the 1232 fault code, and the engine runs poorly.

Subsequent Diagnosis:
1. Distributor belt: Good.
2. AFM: Checked that the air flow meter (AFM) wiring harness was not contacting the engine ventilation hoses (see Tech Service Bulletin 9005 http://www.pcarworkshop.com/images/b...0590geolab.pdf). Even though this TSB is for pre-91 models, I wanted to make sure - good
3. Coils: Disconnected each coil wiring harness, to make sure that the engine would start with only the primary or secondary coil connected individually - good

Questions:
1. Any other ideas as to why I can not clear the 1232 (intermittent) Knock Sensor II fault code (by holding trottle pedal to floor for 11 seconds)?
2. I do not find anything in the archives about the actual Knock Sensor II failing, so I hesitate to go about replacing that part. Has anyone seen this part acutally fail?
3. Can a defective DME Relay cause this fault and/or symptoms?
4. Does anyone have any other ideas about how correct the intermittent Knock Sensor II fault code?
5. Does anyone have any other ideas about what could be causing these symptoms?


FYI, the spark plugs, distributor cap and rotor are relatively new (~1500 miles).


Thanks in advance for your help.

johnsjmc

How old are the spark plug wires? They run close enough to each other and could be causing preignition in an adjacent cylinder. There was an issue in a Ford V8 years ago where 2 cyl were known to fail prematurely A TSB ( tech service bullitin) solved or corrected it by rerouting the plug wires. I don,t know if the 3.6 is prone to such things just an educated guess.

RSAErick

Thanks, it crossed my mind that my aging wires could be due for replacement. If I still have power and stalling issues after I get the Knock Sensor II fault code cleared, then I'll definitely consider replacing them (yuck - expensive and time consuming).

mojorizing

Erick,
I'm not sure of the procedure to clear the codes via the accelerator pedal; however, you might try disconnecting the battery for awhile to clear the ecu memory. Have you done that yet?

The CEL diagnostics are only related to emissions for the car, so that in itself is limiting.

http://members.rennlist.com/billwagner/CheckEngine.html


If you want to test your knock sensor, the output is a mv pulse when knock in the vicinity. Here's a good YT vid on toyota vehicles but it applies to p-cars.....

RSAErick

Hmmm, now that I think about it, I haven't reset the DME via the battery disconnect since I cleaned the knock sensor connector. I'll give it a shot, to see if I can get those codes cleared. Thanks.

Also, thanks for the video about how knock sensors work. Very interesting. Do you know if the 964 uses a Resonance Piezo Electric (7000Hz) knock sensor; or just a Piezo, or Mass Piezo Electric knock sensor?

mojorizing

I pulled the connector on #2 knock sensor and drove it to do errands today. I got the check engine light, read the knock sensor error with my hammer, then disconnected the battery for 10 minutes and the code was clear. That should work for you then. I didn't really notice any hesitancy, etc. but didn't drive very hard.

According to Adrain's book these sensors are tuned 5-10khz but they're sensative to the tap from a rubber mallet.

RSAErick

Great information. Thanks for performing the experiment on my behalf. I'll see if the fault code pops back up for me after I reset via battery disconnect.

The hesitancy that I'm experiencing would probably only be noticeable if you're at full throttle. It's not ultra-obvious - maybe like I'm down 30-40 hp. And the idle deterioration might not be as noticeable if you don't have an RS flywheel. I'm starting to believe that I've got something else going on (other than the knock sensor). The fuel filter is relatively new, but maybe I have failing injectors or a vacuum leak or spark plug wires or.... who knows.

RSAErick

Just an update to (hopefully) end the troubleshooting...

I disconnected the battery for a period of time to reset the DME. I also installed a new negative battery cable at this time. The fault code was cleared by this method, whereas holding the accelerator to the floor for 11 seconds did not clear the code. I took the car for a drive to see if the fault code would return. Guess what... the engine seemed to run strong with no unexpected stalling! After the test drive, I checked the fault codes, and there were none. Yay?!

I'm not sure that I understand what corrected the problem. I reset the DME previously after first experiencing the problems, and the problem remained - so I'm not sure why this DME reset resulted in the improvement.

Other ideas... the car was coming out of it's long winter hibernation, so maybe the fuel was bad or resulted in a fouled injector that finally unclogged after I put some new gas in? I re-cleaned the knock sensor II connector for a 3rd time, so maybe I finally got a good connection? Could the new negative battery cable affect the situation?

Anyway, sorry that I can't be definitive with what solved my performance problems. I was hoping that documenting this situation may help others in the future. But I don't think that there was much to learn from all of this. If the issues return, I will let you know.

Thanks for working through this with me.

Mark Preus

Glad you got it figured out

bmohr

Just wanted to bump this thread to add a few additional symptoms and to give thanks for those who contributed to this issue. I've been having an intermittant check engine light coming on for a long while now. Maybe even from the start of my purchase. I thought I was getting a MAF sensor malfunction as I was having a loss of power and the CEL coming on after revs past 4k, or when depressing the accelerator to WOT. Found this thread after doing some searches, cleaned my knock sensor contacts with metal fine grit sandpaper and added dielectric grease and voila....i got my 964 back Strong strong pulls and lots of fun. What an amazing difference it's just pure fun to drive again. So if anyone else without a hammer or 1990 models with these symptoms I would of course check the dizzy first, but then head straight to the Knock sensors for a good cleaning of the contacts. Thanks to all.

Rally Guy

Sounds exactly like my issues. Adrian's book notes that a knock system fault will retard timing 6 degrees. I don't get a CEL though, does that discount the knock sensor theory for me?

Where are the knock sensor connectors? I'm keen to clean them, and see if this is my problem.

RK