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BOFH
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7,560 Posts
Discussion Starter #1
Well, after Heathcote I've found that my XR6 VCT is absolutely gutless in the low revs. Anything under 3500rpm and it wont pull the skin off warm milk :fraz:

Now, based on my limited knowledge of the AU VCT setup, the runners/cam change at idle to one position, then to the other postition until 3700rpm, then back to the first position. Considering my car is dead all the way up to 3500rpm I have to make an assumption that my runners/cam are locked into one position and causeing this problem.

Now, can anyone tell me exactly how I can test to see if this is the problem? If it is I will know what to get sorted at Ford, otherwise I'll have to look at other possible problem.

Thanks guys.
 

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RIP Sox.....
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2,580 Posts
To test the BBM, simply disconnect the vacuum line which is going to the vacuum diapragm at the front of the manifold.
Do this while the engine is idleing and if it is working the butterflies should relax back to the short position. If it doesn't move, you have a problem.

Do this simple test and post back.

Rick.
 

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BOFH
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7,560 Posts
Discussion Starter #3
Soxx, thanks, I will do this. But I am an engine idiot (yes, I work in IT - I can make a computer dance but changing oil is my engine limits.)
Can you explain exactly where the vacuum line is and what I should be looking/listening for? Then I'll go straight out and do it.

Pics are good :fraz:
 

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RIP Sox.....
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2,580 Posts
Just disconnect the small rubber hose in this picture.
The little actuator should move when you disconnect and replace the hose whilst idling. The idle itself will barely change however.
If it doesn't, you have a problem.

Rick.
 

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BOFH
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7,560 Posts
Discussion Starter #5
yep, tested and it moved. Also got wifey to rev it and it moved at the right time. So the runners are moving I assume. So why is it so gutless?

Soxx, you seem to know your stuff, can you help me?
 

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RIP Sox.....
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2,580 Posts
Yep, it's working.
Sounds like the VCT mechanism may not be working.
I've had bugger all experience fault finding these though, sorry.
Check to see if it's plugged in?

Rick.
 

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RIP Sox.....
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2,580 Posts
I had another thought, you can follow that little hose you disconnected back to a place behind the washer bottle and there will be the VSV solenoid.
Follow this back out and it should join a vacuum tree at the back of the manifold, try disconnecting it from the manifold and see if actuater at the front still stays where it is after 10 secs or so at idle.
This will tell you if the one way valve at the solenoid is stuffed or not.
What this does is let the vacuum actuater hold vacuum even at full throttle when vacuum is almost zero.

Rick.
 

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BOFH
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7,560 Posts
Discussion Starter #8
yeah, the cable that connects to the thing at the front of the head appears to all be plugged in. Looks like I have a dud. I guess my only option is to get it on a dyno and see what the numbers say.

Thanks for the help Soxx.
 

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BOFH
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7,560 Posts
Discussion Starter #9
Well, I tried to trace the cable but without pulling all sorts of things out I couldnt find the vacuum tree, I'm not 100% what I was looking for. So I resorted to the old test of revving it. Basically, the actuator appears to be moving when it should and staying open at higher revs. I can only assume that the runners "appear" to be working :fraz: Seems I have a problem somewhere else.
 

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RIP Sox.....
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2,580 Posts
Ok, just before the vacuum tree, there is (and I'm not 100% sure, because I'm looking at my ute in hope that it's similar) a rubber block with a few vacuum hoses coming out of each side. One of these is the feed for the VSV valve. This is the one which will go behind he washer bottle and needs to be disconnected while the engine is running to see whether it is holding vacuum.

I'll explain myself a little better on what the one way valves job is.

The VSV/BBM relies on engine vacuum to do it's job. When the throttle is floored at low revs, vacuum drops to almost zero. In this instance the vacuum actuater for the BBM would not be able to keep the butterflies in the long runner mode, so what is needed is a one way valve to hold vacuum at the actuater even though the engine is not actually making any vacuum.

My XH had this same problem when I first converted to BBM and the symptoms were on initial full throttle application it would accelerate great, then after about 1 second it would die and feel flat up until about 3500-4000rpm.

I only found out the problem on the dyno because I could see the actuater move about 1 second after the throttle was floored, even though it was at only 2500rpm or so, way before the 3800rpm BBM switchover.

If you are able to disconnect the correct vacuum line, just before the one way valve, you should be able to see the actuater move a second or so after you disconnect.
If the one way valve is functioning properly, it should hold vacuum for several minutes.

BTW, you can't simulate the actual problem (without disconnecting anything) whilst the car is stationary as the engine needs to be under load to simulate a no vacuum condition, such as driving or on a dyno.

Rick.
 

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BOFH
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7,560 Posts
Discussion Starter #11 (Edited)
Ok, I found the vacuum tree and, while idling disconnected it. I heard a definate change in the idle speed as soon as I did it (seemed to increase) however the acuator (in the pic you sent) did not move. I counted to about 15 and nothing happened. I then replaced the hose on the tree and the idle changed back again.
I take it this is what is meant to happen?
 

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RIP Sox.....
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2,580 Posts
Yes, if you did pull the correct vacuum hose (there are a couple) and the actuater didn't move, then you could assume the one way valve is ok.
Idle speed will alter a little when pulling vacuum hoses, though that's of no consequence to what we're chasing.

It is important to have disconnected the correct vacuum hose as one of them also goes into the cabin from the tree, this controls the vent system inside.

Rick.
 

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BOFH
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7,560 Posts
Discussion Starter #13
yep, I traced it correctly this time. Pulled off the washer bottle etc. It was the right hose. It is the right hose and the actuater did not move for at least 20 seconds before I put it back on.

Thanks for the help on this Soxx, I'm actually learning something as I go too :s6:
 

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RIP Sox.....
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2,580 Posts
Then we can safely say that the BBM is doing it's job.

Have you driven another car like yours to confirm that yours is down on power?
Has it been like this since you've owned it or is it somethin that has just come up?

Rick.
 

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BOFH
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7,560 Posts
Discussion Starter #15
Well, I havent driven another car like it but considereing that others have driven mine and I basically was the slowest car of the entire field at Heathcote (including stock E-Series) and I'm a good second slower than the commonly excepted 1/4 time all point to an issue.

As for is it new or been like that for a while, it's hard to say. Others say my car was quicker last year stuffing around at Calder so I have to assume it is something that has happened recently that I havent noticed as I dont really go out and to traffic light drags.

AU1SIXA F6 AU Forte - 16.58 @ 83.58mph ON LPG
kooky F6 AU XR6 HP - 15.77 @ 87.24mph
Casper F6 AU XR6 - 16.85 @ 83.72mph
 

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RIP Sox.....
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2,580 Posts
16.85 @ 83mph is very poor. You should be running at least low 16's @ 88mph with an auto, or mid 15's @ 90mph with a manual.
What is yours?

Is your exhaust ok? High tension leads? Air filter? Do you use premium fuels?

If the engine is in a good state of tune then it does point to the VCT thingo, I'll borrow my folks workshop manual over the next couple days and see if there is any diagnostics you can do.

Rick.
 

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BOFH
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7,560 Posts
Discussion Starter #17
16.85 is pathetic isnt it. I run an auto and was on regular unleaded (premium wouldnt have made much difference).
The exhaust is basically stock, but does not appear to be an issue, if it was I would assume the problem to be top end, not bottom end.
The leads are all pretty new, and no missing or issues have appeared
Airfilter is stock but I did a few runs with a BMC filter too yesterday without any difference.

I was expecting a 16.1 or less, possibly a 15.9 with the auto. Kooky has a HP auto and he got a 15.77 so I would not of expected higher than a 16.2 on a direct comparison.

Would really appreciate if you do get hold of the manual as I dont want to go to Ford and listen to them talk shit about it and try to charge me a fortune for something that is not the problem.
 

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BOFH
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7,560 Posts
Discussion Starter #18 (Edited)
Just out of curiosity, could the problem be caused by a restriction in the air intake?

EDIT: Nevermind, just checked the air intake with the bonnet closed and it has no restriction at all. So it's not that.
 

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Birth, Drift, Death...
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3,039 Posts
if it was a restriction it would be noticeable at high revs. due to the fact you seem to have a gutless down low problem, i reckon its the VCT solenoid that has issues.

there was another guy on here that had a stuffed one, but his was only sticking occasionally, so sometimes the car went good and other times it went crap.
 

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BOFH
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7,560 Posts
Discussion Starter #20
yeah, the air intake was a long shot.

I will be putting it on a dyno soon to see what it says.
Strangely today, I stalled it up and it felt far, far more powerful off the line then yesterday. Could be a similar intermittant problem too.

Time and a dyno will tell.
 
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