Just did a tip to manual conversion today (see other thread). Two vacuum lines are left and I cant find where to join them!

The first comes from the three-linkage right on top of the intake. The second comes out of the blower motor tube - it has a joiner on the end that looks quite specific. Searched and looked through the PEF but cant find it....thanks in advance.

 

The bottom pic is one that connects to your distributor. The top pic is one which you have a y connector likely to a vacuum solenoid or vacuum actuator depending on your setup. The vacuum system is actually a simple system. Follow the lines until they end at the valve where the motor creates vacuum or the other end which is through a solenoid and eventually to a actuator where it terminates.

 

My 1991 C2 Tiptronic does not have the black Y piece out front. Here i the picture of my C2 taken from the same angle.

On my 1990 C4 that black Y piece connects to the throttle body directly but not sure where it is on my C2.

 

First photo...doesn’t that connect to the vacuum reservoir on the underside of the intake air filter box?

 

Yes. When I switched away from the air filter box I had to blank the Y connector.

 

The first pic shows my T junction with the white line going to the carbon canister behind the airbox (see pic 2).
The red vacuum line (pic 3 with the upside down A) goes off behind the engine up against the insulation and then to the RH rear suspension (pic 4).
Where it actually goes i have no idea. Is this vacuum line setup unique to ROW cars?

The white vacuum line goes to the carbon canister behind the airbox. The red one joins up to a black line up against the engine insulation.

Back of the airbox.

Red vacuum line joins this line (the upside down A) up against the engine insulation.

It is routed around the suspension tower and i have no idea where it goes........yet.

 

My car MY91 C2 Tip Coupe had a diagram of the vacuum lines on the underside of engine deck lid

Not a very good picture

 

I completely forgot about that diagram. Here is the one on my 1991 C2 Tip for reference. Looks the same. This is a USA car compliant with California emissions. This will be helpful for my intake rebuild in progress.

 

You guys are awesome....will connect it tomorrow.....thanks a lot.

 

Resurrecting this post and thread, partly to ask a question and partly to answer a question within.

Trying to eliminate from my troubleshooting list any possible causes or contributions to my issue - throttle response lag, which is very noticable when changing down gears (throttle blip on change-down does not work - just feels like an 'empty stab' on the foot pedal. Wondering if any part of the engine vacuum system has a play in this. Been tracing all the vacuum components and (spaghetti) pipework for anything missing or disconnected. Any pointers gratefully accepted (vacuum related or otherwise).

To answer a question posted in this thread - the small plastic pipe off the 'T' piece from the top mounted vacuum valve, that then disappears into the rear of the engine bay, connects to the vacuum operated headlight raise/lover function (from the dash mounted up/down dial). Not sure if all 964's came with this.

Now to ask my own question; the other pipe from the same 'T' piece connects to the vacuum reservoir behind the air filter box - what does this do and what if I disconnect this and cap the pipe? Does this control any (air pressure related) function or element of the throttle body that may affect throttle response?

Thanks

Marcus

 

The vacuum reservoir provides the power to actuate the resonance flap in the throttle body above 5,000rpm to improve power at high revs. The ECU actuates a solenoid to switch the power. I don’t think this would affect throttle response.

 

Thanks John. More applicable I guess in trackday scenarios. I'll continue going through a list of checks and try a few things out. One of them being to remove the (cone) intake air filter should that need cleaning to remove any build up of deposits.

 

Since you just reinstalled the engine make sure you verify that the system recognizes WOT. You need a hammer or similar to read if it is opening properly. It will make a significant difference in power. Mine was giving me issues. I tested it without the carpet in place but when I reinstalled the carpet it was keeping it from fully opening.

 

Hi Marcus,
Has it always had the same throttle response since you’ve owned it?
I have been chasing this lag for my whole 9 years ownership. Mine is only slow response at low revs once the car is up to temp. When the engine is cold, it blips perfectly. Also when the revs are higher it blips fine as well.
From my research, it’s quite a widespread problem….but if owners aren’t trying to blip, they may not notice it.
I found a thread a while back where someone managed to write it out. I’ll link below. Post #31.
I asked Steve Wong if he could help, and his response was that it would only be masking an issue somewhere, and advised against it…..
I think we have narrowed mine down to a resonance flap actuator bearing vacuum leak. My mechanic finally found it by spraying brake cleaner on it, and noticing revs change (please don’t start a fire on my account)….mine is plastic intake version and I don’t think it can be serviced. We’re going to tackle it next time engine is out.

You got me thinking again after reading your post….
I came up with an idea to try and stop the leak. It appears to have worked. It’s only day 2 but it seems to have made a difference. I have put a cap over the bearing. The outer plastic housing of the bearing is 24mm and I found a cap of 22mm inner which I managed to get a snug seal around. I trimmed it down about two thirds of the depth in the pic.

https://rennlist.com/forums/964-foru...low-rpm-3.html

 

Thanks for this useful info. No, I've owned this 964 for 12 years and only really noticed this the last year or two. But as you point out, unless you intentionally blip hard you wouldn't know. Normal driving and gear changing wouldn't show this and is not a problem. Response seems better when the oil is not fully up to temp - but then I avoid going over 3k rpm until the oil temp is where it should be. If I only blip say halfway then it's fine. It's only with that instantaneous stab to the floor does it not respond. And tbh it doesn't necessarily surprise me (although I need to compare with a friend's 964 to be sure). I'll have a good read of the topic link you provided.

If I rule out the easy and first probable checks of throttle cable, ISV, AFM rear connector plug modification (inc flap check) and vacuum pipe leaks then I'm left with looking at other key components - i.e. rotor arms (which are new), AFM potentiometer and arm (tracks cleaned and arm adjusted). Maybe I need to think about fuel press reg plus something else. I have no CAT O2 sensor as it has a Dansk cat bypass pipe. I removed the existing air filter and now have a foam replacement (more breathable CFM's) and need to do a few more miles to feel any difference (if any).

I might be left with a combo of more mare one thing conspiring; fuel/air mix provision not keeping up with instant demand, ECU thinking the same and then an old FPR making itself known. There's always been the belief and suggestion the ECU 'adapts' ign and fuel for optimal efficiency etc under normal steady driving, and stays that way. The theory written and posted in many forums being to get the engine up to temp, switch off and disconnect battery for a short while, reconnect then drive like the devil. This allegedly 're-adapts' the UCU to that style of driving. I've yet to see anyone's technical evidence of this with explanations (or data) to back this up. Maybe it works, maybe not. All the same, it might be something I should do to rule out. Possibly, a plug-in OBD will do the same (clear down of settings and back to factory). I may invest in one of the Carly OBD mobile app and plug-in offerings (assuming compatibility with a '92 engine).

For sure ITB's with their mechanical linkages will make all this go away $$$$