Porschenut_Lee

Starting a new thread for these new issues. I was having issues with hesitation and low power, but as I fix things, new issues are popping up. https://rennlist.com/forums/964-foru...-on-power.html I don't know if the hesitation or low top end power have been resolved yet with the ignition upgrade I have done.

For the first time I used my UDT999 software and connect my pc to the car. Did the system adaptation to fix a stalling issue. When letting off throttle or depressing the clutch at stop sign the idle does drop to 500 then bounces back up to 1000 and settles down at 800-900 RPM. Don't recall if that is normal, but it doesn't stall anymore.

So stalling is gone, but I have an intermittent vibration (fairly heavy) that feels like a misfire. Below are some screen shots of the knock counts and fault codes.

Looks like I have some injection issues? I think I read that these fault codes are normally electrical related and not necessarily clogged injectors. Makes sense if it is sporadic as shown.

Also, see the knock count. Doesn't seem right to me. Hope that number isn't correct........

964 Fault codes by HKnut, on Flickr

964 engine knock count2 by HKnut, on Flickr

964 info by HKnut, on Flickr

Porschenut_Lee

Strange thing is sometimes the car runs fine......no vibration/misfires but then a week later I get the harsh vibrations again.

I'm assuming knock count is due to vibrations or electrical noise. Wouldn't hall sensor or knock sensor issues trigger a fault code if they were bad? I don't see any fault codes for these sensors. Makes me think the injector faults / vibrations / high knock count are all related.

18T_BT

When is the last time you replaced spark plug wires and coils?

Porschenut_Lee

Just installed new 993 coils, ignition modules, cleaned ISV, new fuel filter. Plug wires need to be done still.

I did confirm that the car will start and idle with either coil module unplugged.

C4inLA

Curious to see where this leads.... Wish I could contribute to helping solve your issue. Have the UDT999 as well, will have to compare values in future.

Porschenut_Lee

Thanks C4....I'd be happy to compare screen shots anytime.

Porschenut_Lee

Started replacing wires today. What a bitch! Got the upper and lower right side done. Seems like that is the hardest part, so other side should be easier I hope. I also replaced my engine mounts with WEVO. I almost had a heart attack as I was lifting rear end by jacking beneath engine when I saw a bunch of oil start to spill on ground on left side of engine. Realized after a few minutes it was my left engine mount that ruptured.......which was already toast.

So next weekend is left side plug wires, CHT sensor, new O2 sensor, and Cat/Primary bypass once it goes back together.

Oh, here's a biggie.....I noticed when I was removing wires from dizzy caps that the whole assembly had a lot of play side to side. Then I noticed that the single nut that tightens the distributor to the block was MIA. That certainly hasn't been helping my issues I'm sure......

Can anyone confirm what size nut and washer should be holding the distributor in place?

crg53

I am pretty sure the nut and washer is 8mm.

Porschenut_Lee

Thank you Steen! Very helpful.

By the way, I love Polar silver. Had a 1991 polar silver cab with blue top. Love how polar silver has blue hues to it in darker light. Your car looks perfectly modded also!

Porschenut_Lee

Got the distributor tightened down, all plug wires replaced and fired the car up. Still had a rough vibration at idle that felt like the engine was misfiring. Drove it for a while and the rough vibration seemed to have settled down a bit. HOWEVER......still getting 5,000 knock count per 10,000 ignitions!!!!!

I don't really hear any knocks or pinging.....or any other engine noise that isn't typical of a 911. I did get a fault code "32" which is for #2 knock sensor, but I can't find any info to tell me where to go from here. I guess replace the knock sensor? Or is the excess knocking creating the fault? Chicken or the egg?

Any help would be appreciated.

Eric_Oz_S2

Possible causes for high knock

Faulty injector or injector lead (check for kinked cables, missing insulation, etc)
Faulty hall sensor will retard ignition and shouldn't affect knock (but will reduce power)
Faulty knock sensor will retard ignition and shouldn't affect knock (but will reduce power)
Faulty o2 will affect mixture and could lead to lean condition causing knock
Poor fuel quality
Poor tune (after market chip)

Porschenut_Lee

Thanks Eric, will a faulty knock sensor falsely register knocks? In this case, 1 knock for every two ignitions can't be right.........

I do have injector fault codes as well......looks like 4,5 and 6 (Curious that it is all on right bank of cylinders) so maybe I should start there. Appreciate the input!

Navaros911

I just got my UDT999 last week and will have a look.

I have similar issues of high knock count, but power is OK. Sometimes some rough running at idle, but not consistent. It tends to go away after a few minutes.

In my case I suspect low quality fuel.

Porschenut_Lee

Thanks, look forward to comparing your results to mine. My power has actuall improved significantly and is much smoother. If knocks were real I would expect power to suffer. I'm baffled. If it weren't for the rough vibration and knock count I wouldn't think twice otherwise of driving as is. I just don't want to damage the engine if there is a real knock issue.

Eric_Oz_S2

Knock sensor failures are not uncommon. I'm not sure if your setup detects a faulty sensor as knock. Normally the dme will detect a faulty sensor (due to improbable inputs) and retard ignition. I don't know if a faulty sensor necessarily will register a knock at every ignition though.

I would replace it with a new Bosch unit (not uro) and see how it goes. Best check the harness though as these can fail near the plug.