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Death to Camry's!
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Discussion Starter #1
Alright,

I have found a very odd problem, under hard acceleration, in power mode and economy mode I will find that the car will haul along until about 3500rpm, then just flatten out in power until bout 5000rpm when it gets a little jolt before changing to the next gear. I just want to know what is happening? Is it to do with the fact that it has a standard exhaust and intake so it isnt getting enough air into the engine?? your thoughts please.

Just a side note, this car is going to get a T-series intake snorkel, K&N panel filter, EL intake pipe from manafold to EF airbox, Pacemaker Extractors, 2.5 single muffler mandrel bent exhaust in the next week or so.

So would this help the situation??

The car is a 1996 EFII Fairmont Ghia, featuring 4spd auto, XR6 164kW motor and has 3.45LSD

Cheers for your help in advance,

Chris
 

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Try the fuel delivery system, specifically filter, regulator and pump.
Or the broadband module could be not operating I guess; should kick in at about 3800.
 

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Death to Camry's!
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Discussion Starter #3
how do i check that stuff?
i know the bbm moduble works, because it only occurs when the car kicks down to a lower gear when i want to accelerate, never does it from a standing start
 

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Regulator - on the back of the fuel rail, take the vacuum off (block the hose so no leak) and drive her hard.
Notice a difference?
Of course you can do it the proper way with gauges etc., but that's the easy way :)
Fuel filter - When was the last time it was changed? The easiest way to test is to change, though if it's fairly new chances are it's not that.
Pump - AFAIK, you will need to stick a pressure gauge on it, test delivery and volume. If this is put on the intake hose for the fuel rail, a low reading could mean a blocked fuel filter as well. The easy way is to let the relay power up the pump and squeeze the hose, but unless you know how it's supposed to feel this won't help much :(
 

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Australian Falcon Member
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MightyEFGhia - you're comment dismissing the BBM actually describes pretty much exactly what you'd see if it wasn't working properly - the BBM switches to long path when the engine is started, then switches back to short path whenever revs are above 3800rpm. The result of the BBM staying on long runners would be that it would feel flat at higher revs (anything from about 3500rpm up in fact) - and what happens when you kick down? - the revs bounce up.

If you pull the vacuum line off the actuator at the front of the BBM and suck on it with the engine off + ignition off then you should find it quite easy to draw air thru it.

If you then turn the ignition on BUT DON'T START THE ENGINE and suck on that vacuum line again then it should still be the same - if it feels like it's become blocked then you have a short between the solenoid and the ECU (possibly a fault inside the solenoid I guess) which is keeping the solenoid energised constantly - which will be keeping it on long path constantly whenever the engine is running.
 

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Eh...my understanding was that long path was the rest position, the solenoid opens at 3800 and allows engine vacuum to pull the butterflies open so short path is enabled.
Therefore, theoretically you shouldn't be able to suck through with the engine off?
And therefore, if it operates it's not faulty?

Is the way i always thought of it, anyway...
 

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The default position for the runners is where you see them with the engine off - ie. short path - this is where they'll stay if the BBM Solenoid (which is located behind the washer bottle and controls vacuum to the actuator on the front of the BBM) isn't energised or if there's any break in the vacuum system.

When the engine is started, the ECU energises the solenoid at about 400rpm and the runners are pulled round to long path - then at 3800rpm the ECU opens the circuit and de energises the solenoid and the runners fall back to their default short path position. When revs come back below 3800rpm the ECU closes the circuit and energises the solenoid to pull the runners round to long path again etc.

The power circuit for the solenoid is: 12V power gets supplied direct to the solenoid with ignition on (maybe even just accessory position of the key? - I'm not sure) - and then it goes thru to ground via the ECU - so the ECU controls the solenoid by opening or closing the circuit to ground. The significance of that is to recognise that it's not powered FROM the ECU - this has significance when trying to figure out troubleshooting (ie. it's not as simple as sticking a multimeter on the wire and looking for volts on and off - the voltage will be there along that wire right to the ECU whenever ignition is on).

Before posting that diagnostic suggestion I went out to my car and sucked on the actuator vac line without any power on the car and then with ignition on - in both cases it was easy to draw air thru it. I then unhooked the wire at the solenoid that goes back to the ECU and ran another wire from that connection direct to ground - and with no power it was the same as before, but with ignition on it was hard to suck thru - felt pretty much blocked (I could hear the solenoid "click" when the ignition was turned on).

One of the things that would make the BBM stay in long path is if the solenoid is staying energised when it shouldn't be - that could either be due to the ECU being faulty or because of a short in the wire that goes back to the ECU. My suck test is one very quick and very easy way to eliminate a short as being the cause - ie. if it's easy to suck thru both with ignition off and on then there's no wiring fault - which narrows it down to a control fault (ECU).

If the vac line becomes hard to suck thru with ignition on then it means a definite fault exists - and the next step is to identify whether it's just wiring or the ECU (IMO it'd almost certainly be a wiring problem - BUT, it could be the ECU tho). To narrow it down, a physical check of the wiring to the solenoid in the engine bay should be carried out - if you're lucky you'll find a spot where the wire back to the ECU from the solenoid is shorting. Otherwise, the next step will be to unplug the ECU and disconnect the BBM solenoid and use a multi meter to check for grounding in that wire from the solenoid to the ECU (it should be open circuit with both ends disconnected).

If there's no sign of a short then the problem could be either the BBM solenoid itself (the short could be internal in it) or the ECU. I don't know how you'd test either, so I myself would try and get hold of another solenoid, and if that didn't work I'd try another ECU.

Now, if the suck test seems normal then the only remaining source of fault really is the ECU - ie. it's working as it should with respect to not energising the solenoid until 400rpm but for some reason it's not opening the circuit again at and above 3800rpm.

But before buying another ECU the next step would be to definitely confirm that the reason for high rpm sluggishness is actually because the BBM is staying in long path above 3800rpm (this could be done first of course but the suck test is quick and easy and is necessary at some stage anyway so may as well have been first).

To check for this you simply need to disconnect and blank the vac line at the actuator and see if the car feels better in the top end - easy!. If it feels noticeably better - ie. back to normal - in the top end with the BBM definitely set to short path, then having already eliminated a wiring fault as being a possible cause (this includes the solenoid itself) then all you're left with is the ECU itself.

I wanted to take it in easy steps so didn't go into all this detail straight up :s6:
 

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Australian Falcon Member
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Umm, just to cause more confusion - I've been told that the other thing that can cause a problem with short path runners working right is if the check valve in the BBM vac system is faulty (or actually the problem I've heard about was related to it being fitted back to front).
 

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Yep, revving it will be another way of seeing it switch - my preference would be to still then disconnect and plug the vac line and see that it feels ok on the road. I personally didn't want to specifically suggest anyone rev the crap out of their engine - I'd hate for someone to throw a rod and come back at me saying "you said to rev it".

In spite of the length of my post, don't lose sight of the fact that my suck test suggestion takes about 30 seconds to do - it's worth trying before then starting it and revving it and/or driving it with the vac line plugged.
 

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Death to Camry's!
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Discussion Starter #11
alright, ill give the suck test a go tomorrow. If it is any help, the vaccum operated switch on the radiator end of the manafold switches when the engine is turned on, and when the engine is turned off it changes again, the same thing happens if the engine is running and you pull the vaccum hose off of the manafold... so is this the pipe im required to suck air through to see if it works?
 

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Yep - BUT DON'T DO IT WITH THE ENGINE RUNNING!!

What you should find is that it's easy to draw air thru that pipe with the engine and ignition off - and it should still feel exactly the same with the ignition on (engine still OFF). If it feels like it's become blocked when the ignition is on then it means the solenoid behind the washer bottle is getting power when it shouldn't - and you've identified a definite fault.

If it's still just as easy to suck thru with ignition on as ignition off then next you need to establish whether the manifold is actually switching at 3800 rpm. You can do that either by revving it up to 3800rpm - maybe a bit more - and watching for the manifold to move or else you can take the vac hose off and plug it and then go for a drive and see if you have your heavy throttle top end power back (the bottom end will feel soggy tho).

I know this is all sounding hugely complicated - but it's really not - just take it one small step at a time and with any luck we'll be able to work out if the BBM system has a problem and if so how to fix it.

Hey, if you like you can forget about the suck test (even tho it just takes moments to do) and just go straight to seeing if the manifold switches at about 3800rpm - by revving it and watching for it to switch (you'll need a second person so one can rev it while the other watches the manifold - else you could set up a mirror or something) - but if you don't see any switching, please DON'T BE TEMPTED TO REV IT TOO HIGH - if it hasn't happened by 4000rpm then there's a problem. I'm personally not real comfortable about neutral revving to 4000rpm, but any more than that is definitely not a good thing to do.
 

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OK looks like I got short/long path positions confused.
:doh:
 

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mongrelEB -

No you had the runner positions right as far as when long and short runers should be selected - the bit you missed was when the initial change to long path happens - I tried ta break it to ya gently :s6: - don't sweat it, the reason I've jumped into this one with both feet is that it is a fascinating and not a little tricky setup to come to terms with - and having done the full upgrade on my ED I had to do exactly that.

I met a Ford mechanic who had been working on them for years and didn't realise that the BBM's default position was short path and it powered to long path at startup.
 

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ef chaser -

No, since fitting the EL ECU and wiring up the BBM switching thru that (ie. as per factory) I haven't tried or even thought seriously about altering the changeover point - tho that was something very high on my mind when I was contemplating just using an aftermarket rpm switch to drive the BBM (until I discovered the EL ECU was a straight plug in for my car). You raise an interesting point there tho...

It wouldn't be possible to do it thru the ECU - but it should be possible to do it with an aftermarket rpm switch. The important thing is the knock sensor system, which wouldn't be affected by altering the switching point - so messing with the switching point should be quite workable. BUT - in case the ECU could be affected by disconnecting the BBM Solenoid from it, the go would be to instead run a "dummy" circuit to the ECU - ie. work out the operating resistance of the BBM Solenoid and run a parallel circuit from the power "in" wire of the Solenoid back to the ECU via a resistor that will simulate to the ECU that the Solenoid is still there - then the original wire that used to go from the Solenoid back to the ECU could instead be run thru an adjustable rpm switch. Hmmm - I think that could definitely be a project to try out.

As far as you guys that have soggy top end (MightyEFGhia and MustangNicko) - have you established yet whether the problem is actually your BBM not switching at 3800??

Keep in mind that I'm not claiming by any means that is definitely your problem - all I've tried to do is offer the info needed to establish WHETHER that's the problem (your symptoms are consistent with BBM fault but not exclusively conclusive to that). If you can establish that your BBM isn't switching at 3800rpm like it should, then we can hopefully work out why and fix it.

And I'd like to reiterate that inspite of the (HUGE) length of my posts on the subject, the actual steps you need to take to identify or eliminate the BBM switching as the source of trouble are very simple and quick to acomplish.

If the BBM is switching at 3800rpm then you need to look for other causes for the problem. One possible thing is timing slippage - ef chaser's recent experience is a good example of that.
 

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Death to Camry's!
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Discussion Starter #19
Ok, sorry about the delay in reply, i have gone and tested it, the BBM switches fine, i did give it a rev and have someone watching under the bonnet. I also put this apparent sluggishness down to paranoia, as the car actually is increasing speed, its just that the note of the car makes it sound like it isnt actually increasing i reckon. But again this only occurs in 1st, which makes me think it is something to do with gearing

thanks again for the help, I have started the first part of my induction to exhaust change over, i have fitted an AU T-Series snorkel (muccccccccccch larger) and an EL intake pipe (from throttle body to airbox lid), for the moment i havent got a K&N Filter, but i will do that in the near future. No real gains yet, but I am working on it. Also running the car on Premium Unleaded has somewhat reduced this sluggishness at top end
 

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MightyEFGhia - excellent, at least you know for certain now that your BBM is working ok - sorry it all ended up sounding so complicated, but when it came to it I trust you found it very easy to actually check out.
 
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