Vacuum problem - Car works great! Crazy!

I never thought I'd be asking about this....

I have been driving The Phoenix (my rebuilt metro 3 cyl) for several months now
and am getting 48 - 50 mpg routinely. New Rings and Head rebuild.

I have about 12,000 miles on the rebuilt engine at this point. The oil looks
unused at 3,000 miles! Engine has mucho power!

Tried to install an Audiovox CCS-100 cruise control, but it won't engage.

Called the Help Line - they said must have 14 - 21 psi vacuum....I thought "no sweat!"

Well, I put my vacuum gauge on the various lines, drove the car at 55 mph and I get lousy vacuum!

The MAP Sensor vacuum line on the back barb of the TB gives 8 psi with ANY gas pedal
depression - that is - normal driving. 22 psi when coasting.

The barbs next to the Idle Adjust screw give the same thing.

Either of the two barbs in front of the TB give zero vacuum with any gas pedal
and maybe 15 psi when coasting.

In other words, my engine is essentially running at speed with 8 psi vacuum.

Coasting gives 22 psi.

No wonder the vacuum module of the Cruise Control won't work.

Does anyone have any ideas as to why the engine works so well and gives
48-50 mpg with such lousy vacuum?

Will this hurt the engine (valves)?

As such, the Cruise Control cannot operate....

DoctorBill

low vacuum is usually caused by late ignition or valve timing or low compression. can also be caused by a vacuum leak. might check vacuum on other car and see what it reads

"low vacuum is usually caused by late ignition or valve timing or low compression. can also be caused by a vacuum leak."

This engine was recently rebuilt - new Rings and Rebuilt Head.

As I understand this engine, the valves cannot be adjusted (?) and the timing
is where is is supposed to be (I will check it though).

I made a Butane Torch vacuum leak detector (plastic tubing pushed onto the
torch head) which I will try on the TB soon.

Question 1 - would the Idle Adjust Screw setting have anything to do with this?

That screw allows air into the vacuum chamber at the back side of the Throttle
Body (TB) and adjusts the idle speed.

Maybe too much air is being allowed into the TB....but then how would I control
the Idle rpms?

The MAP Sensor barb is back there near the Idle Adjust Screw area....

Question 2 - are there 12 volt vacuum pumps on some cars to generate a
vacuum for brakes or whatever that I could scrounge from a "Pull-n-Save"
lot?

If I can't get this vacuum problem fixed, I'll be damned if I will give up on
having a Cruise Control - there's more than one way to skin a cat....

Question 3 - the vacuum on The Phoenix's engine is 22 psi at idle. So I
doubt there are any leaks.

Why would just touching the throttle make me lose vacuum so badly?

Here is a Motorcycle Audiovox Cruise Control CCS-100 install with a homemade Vacuum Module - neat!
http://www.valkyrieriders.com/shoptalk/cruise-control.htm

Audiovox USED to sell a Vacuum Canister (CCS-202) but don't anymore...

DoctorBill

I installed an audiovox ccs 100 on my 95 metro manual trans 1.0 last week-end. It worked on the first time out. I have 102,000 miles on the car. I doubt if you have the cruise installed correctly. Mine is hooked up using only the tac signal. No VSS is used at all, no magnets on the drive shafts either. Are your little did switches in the servo set correctly? I will answer any questions I can on the installation. Ask away. I did not install any vacuum canistor, there was no need to. The thing works amazingly well for a $89.00 kit.

I triple checked everything.

I tried everything that the Support People told me at their 800 number and
nothing worked.

ALL of the "Trouble Shooting" readings were dead on...

So I sent the Vacuum Control Servo back to Audiovox today....

I think it is dead meat. My Karma.........

Man - it was so easy removing it!

BTW - my vacuum was 8 PSI while giving any gas. 25 PSI at idle.

So my Vacuum Canister coming from the front of the Intake Manifold and from the MAP Sensor line holds 25 PSI continuously.

I have photos of the whole process to put on this Forum when I am done...

DoctorBill