Vacuum Problem 82 Cougar

I'm having a vacuum problem. On the lower right hand side of the diagram there is a A/CL CWM (lower right of the diagram). When this is not connected to the vacuum lines the car runs great. When connected I get hesitation, stalling and really cannot drive the car that way. If you follow the lines you'll see many parts. The following are new: EGR, purge CV. The VCV and VDV are good. The unknown and don't know how to test parts are the CWM, VRDV, VRESER. I really don't understand why this is occuring or why when I leave the vacuum lines disconnected from the CWM why the car runs fine. Oh yea the carb is new as well.

 

1) I see two CWM's. Can you swap them and see what happens?

2) Is that carb for your year/model? It might not have all the internal vacuum passages?

3) Doesn't yours have a PVS? (water temp controlled vacuum, near the alternator)?

 

On the chart there's three. They are called VCV and all three are in water passages.

 

Mine (PVS) seems to come off right below the top rad hose at the passenger side of the water pump, threaded right into the head - three vacuum lines (green, yellow, black).

 

If the VRDV is a delay type valve you could hook up a vacuum pump to one side and a vacuum guage to the other and see how it's functioning somewhat.

 

VRDV. Vacuum retard delay valve.
Delays the loss of vacuum signal during some vehicle deceleration modes.

Have no clue how to test this. It is however, not open statically.

CWM. Cold weather modulator. This is open at ambient temps. I put it in the freezer last nite and it is closed at 28*F.

VRESER. Small vacuum reservior. Open all the time. Only compensates for sudden vacuum losses and surges.

No matter what when I disconnect both hoses from the CWM the car stalls in drive or reverse while driving at steady low speed and after 15 secounds in gear, drive or reverse while not moving. This simply doesn't make sense. I very well may have to have my mechanic scratch his head for a while. I'M SOOO CONFUSED.

 

Aha! You solved it! The modulator at the tranny is vacuum operated too right? Check the hose. Check the modulator valve at the trans.

 

Wrong modulator my freind. The cold weather modulator is the two parts in the air cleaner housing.

The transmisstion modulator is fine. That's been checked and it holds vacuum during my test for 10 minutes with no leakdown.

 

You got the Chilton version for the F/Z's? Its got a good problem diagnostic 'tree' for those issues. I borrowed mine from the Library, but I went overdue and had to return it.

 

I've got the 1978 Ford Manuals (Andy's), so I can check those, but you've got a newer system. The vacuum valve readings should be similar? For instance the CWM opens (wide) at 55F and constricts at 40F. (On the air filter breather).

 

Thanks for that. That particular part appears to be good then.

 

OK, I'll have a gander this evening and in the morning for any diagnostic decision tree in the manuals and see if I can narrow it down for ya.

 

You'll have to refer back to the chart at the beginning of this thread.

I started following the vacuum hose from the carb to the aircleaner CWM and everything was tight etc. Then I started isolating things working from the air bypass valve back towards the carb. Once I disconnected and capped the line to the from port S on the carb to the middle VCV the problem stopped. I have to now isolate each part on that line and the others leading from that VCV to isolate the problem further.

It looks like I'm back to square one as that's the EGR circuit.

What happens is that at a steady 1500 rpm I can watch the vacuum go away after running about 15 seconds. The vacuum will actually go to almost zero then the engine stalls.

Apparently there's a lot happening at 1500 rpm. The air bypass valve opens allowing air to go from the A.I.R pump through the air bypass valve to the air control valve an into the exhaust.

Also the EGR valve begins to crack open at that rpm.

What I don't understand is why the vacuum is being vented off or where this is occuring. I've run all the tests on the A.I.R system and all components test correctly. I gave up last night about 9 and simply capped that vacuum control to the EGR for now. I need to drive it. I do have to solve this issue as on the 1st of December my registration extension is over. I need to get the emissions test done.

Capping the vacuum port at the EGR valve still does not fix the problem so it's in the controls somewhere.

More to follow.

 

I'm looking through the Haynes manual, Page 189, Figure 6.28 and 6.29, Distributor Vent Valve.

Here's the description:

"Some engines use a Distributor Vent Valve to both prevent fuel from migrating into the distributor advance diaphram and to act a a spark advance delay valve. During light acceleration, deceleration and idle, the vent valve dumps vacuum through a check valve (Figure 6.28 and 6.29). This keeps the distributor from advancing excessively for the load and evacuates the fuel in the spark port line."

Figure 6.28 shows this valve's cutaway drawing.

Figure 6.29 shows where it connects:
A) From carb's 'spark port' to valve's vacuum signal port (flat side of unit),
B) From's valve's raised side to distributor advance vacuum.

It's got a 'dump' valve and a 'check valve' inside the cutaway. And a filter at the dump valve. Don't know if there's anyway to test for all 3 functions, but this sounds like the culprit.

 

Could be. I'll be looking at that too.