StratfordShark

I'd like to check the timing on my S4 auto as part of investigating some running issues.

Recently re-tensioned belt and marks on passenger side sprocket/cam cover lined up when pulley was at TDC position.

Does this mean my timing is OK? If not how would I use a timing light to check the dynamic timing? I can't find any posts where someone has done this, though have seen advice about checking with timing light in a number of posts.

jpitman2

connections depend a bit on the light. Some need you to pull a plug lead off a plug, connect that lead to the light's input and connect the light's output to the plug. Some pick up the signal by a clamp on the outside of the plug lead . All use plug no 1 AFAIK. Some also need ground and +12V connections. Ensure that there is a nice clear white line on the crank pulley at the desired timing setting. Once the above are done, keep light away from any rotating parts (Dont ask!), start engine. point light at timing marker on front cover as radially as possible to avoid parallax. You should clearly see the white line look stationary with respect to the cover pointer, and CLOSE to it.
jp 83 Euro S AT 51k

LostInSpace

I've been doing a bit of research into cam timing as it's one thing I want to check once the intake refurb is done. Try doing an advanced search for 'cam timing' and set it to search titles only - then its just a case of trawling throught the results.....

Here's one that's got some useful info:

https://rennlist.com/forums/showthre...hlight=exhaust

One thing I have learnt is the Porken timing tool could be very handy!

John Speake

The igntion timing is directly timed from the flywheel speed sensor, so is not adjustable, and is not dependant on cam timing.

Cam timing of course is "adjustable".

Jim bailey - 928 International

The all 1987 > the knock sensors and hall signal generator if not working the ignition brain retards the timing to "protect " the engine until that failure is corrected.

John Speake

What exactly are the "running issues", Adrian ?

PorKen

The marks are a poor indicator of cam timing for 32Vs. (Example.)

StratfordShark

Hi John,

Maybe more paranoia than genuine issues.

I had a chance to drive a nice 91 S4 at local Porsche club meet a couple of weeks ago and it ran much more smoothly than mine (as soon as I turned key I knew it was running smoothly) - made me even keener to keep looking for improvements. Since owning the car I've changed plug leads, plugs, distributor caps, new engine mounts, intake refurb including new ISV, new injectors, new timing belt.

Now scratching my head for what else could make a difference. At the moment it's running ok but not as keen to rev as the car I tried, and generally 'lumpier'. Idle is steady. tbh I thought it was running pretty well till I drove a much nicer one!

Yesterday (using your spanner) I found a break in the replacement plug I'd installed for Temp II (EZK sensor connection) and replaced that with a better job!

Records show new MAF was fitted in 2004 so presumably that would still be close to original calibration and not candidate for rebuild? Since repairing Temp II plug Spanner reports no faults on LH/EZK and it passes all actuator tests. Tonight I checked the CO with gas analyzer. It was indicating only about 0.5% which seemed too lean so I adjusted the pot to about 1.5%. After that I did another idle adaptation.

John Speake

MAF should be fine.....

There's not much left to "correct" except double check cam timing, fully.

I assume the other car was stock ?

StratfordShark

Forgot to add I also installed new knock sensors when doing intake job too.

The other car may have had revised exhaust (sounded more 'woofly' than standard S4 exhaust) but new owner wasn't sure.

Just goes to show you learn a lot driving other 928s! At least I've narrowed down potential issues which is progress of a sort.

I suppose I may have created intake leak when doing intake refurb. I was pretty meticulous about positioning/securing new hoses and gaskets though. I have sprayed carb cleaner around the intake and there's no change in idle speed.

StratfordShark

Hey I just thought of a possible intake leak.

After I put the intake back together (the old plastic oil filler was one of few parts I didn't replace) I found that the little pipe at side of filler which connects to the Y-shaped hose (one end goes to throttle body, one branch goes to fuel fume vent solenoid) was broken. You could just pull it out of the oil filler with hardly any pressure.

I popped it back in and forgot about it, but presumably if it pulls out so easily it could be source of leak?

I had intended to bond it to the filler with red gasket sealant but had overlooked doing this. Maybe that will help?

Charley B

You might also check your motor mounts if you haven't addressed them already. Broken mounts can, and usually do, feel like a less than smooth running engine.

StratfordShark

Thanks Charley but mounts fitted just a few months ago.

Wondering if worn shocks/coils would also affect perception of smoothness? Changing them is my next big project. They're originals and ride can be crashy even with new mounts which made a big improvement.