ZX 16V ACAV Problem

gjb02 · Post by **gjb02** » 17 Sep 2003, 01:32

Just purchased 16V ran fine, if a little slow, on the return journey. Looked it over properly at home only to find both the acav diaphrams where broken. Purchased new ones but they don't actuate. I checked the servo signal but it doesn't switch at 1800rpm. Read elsewhere about resetting the ecu?? Any ideas about the servo.. the vacuum pipes are in the correct position and everything appears correct. Cheers in advance[:)]

wheeler · Post by **wheeler** » 17 Sep 2003, 04:16

dont know too much about the ACAV system but have you checked that the vaccum pipes aint blocked up ? i've seen it happen on EGR & turbo electrovalves.

gjb02 · Post by **gjb02** » 17 Sep 2003, 12:18

Wheeler, Thanks for the idea but I already tried that one, I've checked for vacuum at source. Blew through the pipes, all fine. It's to do with this little servo not being actuated, it routes vacuum from the vacuum pump to the acav sys. It works after 1800rpm. Or at least it should..[:(] I think I'll try resetting the ecu?? Does this really work though?? What's the theory behind it...?

VisaGTi16v · Post by **VisaGTi16v** » 17 Sep 2003, 14:05

Not sure how to advise on fixing them but one thing I do know is that both mine and Benj's open the moment you touch the throttle, ie about 1000rpm. Mine shut just over 5000rpm as I had my dad watch whilst I revved it stationary. The haynes manual says they shouldnt open until 1800rpm though. Whether they are wrong or mine and Bens are knackered I dont know.

benj · Post by **benj** » 17 Sep 2003, 17:31

hi mate,
im a bit confused , the ecu has anything to do with the diaphragms opening or not. all the ecu does is match the mixture in the correct rpm range so i think you can rule that out,
if the are not opening its almost certainly a vacuum leak somewhere but you say you have checked that! i think you should check it all through again, at the right side of the engine( when looked at stright on) near the bottom end of the exhaust camshaft you will find a module where all the vacuum lines connect,
take out the input one from the brake servo and see if its sucking or not, if it is makesure all the other pipes are all connected and seal properly. if it still doesnt work it must be that module thingy, iv got a spare one, dont kow how much they are new tho.
you say your 16v is a little slow well soon as you fix the diaphragms u will notice a big increase, without the shorter inlets closing via this system the engine hits a brick wall above 5250 rpm, and above this rpm is where all the kick in the back power is!
if your still stuck il give u my phone number and il talk you through a proper check when i have my engine in front of me! ive rebuilt one of these now, and have a certain amount of smugness in my confidence!
cheers
Ben

wheeler · Post by **wheeler** » 18 Sep 2003, 04:34

i guess its an electrovalve that controlls them ? i.e. the ECU sends a signal to the valve which opens up & lets the suction pass through it ?? i'd imagine it has a live feed & the ECU earths it, is this happening ? if not you'll have to check the wiring between the plug on it & the ECU.you cold try supplying the e/valve direct with a live & earth (with the plug disconected of course)but you would need to check a wiring diagram to see if its a 12v or 5v operated. normally disconnecting the ECU (with the ignition off) re-sets it but i dont really see it helping any.

benj · Post by **benj** » 18 Sep 2003, 11:28

hi mate, was having a look last nite and it is like you say an electrovalve!! hard to remember these things sat at work!
if you work out what it is i have all the spare bits, such as the valve and a 16v ECU.

gjb02 · Post by **gjb02** » 18 Sep 2003, 12:30

Cheers Lads/Ladies???, It's definately something to do with the electrovalve. It is getting a 12v feed from the ECU, but this voltage doesn't change at all during the rev range. That's probably why the valve doesn't move. It must have something to do with the ECU. Doesn't it.??
BENJ might have a need for some of those bits in the near future, cheers for the offer. I'll be in touch.
Any more ideas would be appreciated, I want to get this beast on the road, but I have to change the water pump!!!!![:(!]
How critical is the belt tension? Haynes book-o-lies says take to Citroen for SEEM Guage Check. Is this necessary? Thanks all.

adrianeaton · Post by **adrianeaton** » 18 Sep 2003, 14:46

about as critical as on a BX 16V I suspect - if it's got 2 tensioners then it's pretty critical, but not essential to use a Seem gauge. I've only ever seen one once, and that belonged to my local specialist!!
The pins to hold the cams and crank are essential, and be prepared to do it all and then take it apart again in a couple of weeks to retension the cam belt. Worth fitting new tensioners too if they're anything other than perfect.
Adrian

benj · Post by **benj** » 18 Sep 2003, 18:05

i got pins turned down in work, its a bugger to all set up, if u need help in future gjb02 in future let us know.

pain · Post by **pain** » 20 Sep 2003, 00:32

hey!
i think i have the same problem with my 16v zx! those vacumes on my car do not move at all at any revs, so im guessing there must be a leakage somewhere.
before 4000rpm my car is pretty ****, once it hits that revs it goes like a beast, so do you guys reckon this could be my problem also?
i think one of the vacume is leaking so that will need replacing but the weird thing is that both of them do not open/close??
i disconnected the one that was leaking and blocked the pipe up, but still the other (working) vacume did not move.
any ideas?
ps. just incase im getting confused, the vacume thing is this yep?
http://zx-16v.tripod.com/Image1.jpg
cheers
rich

MiX · Post by **MiX** » 27 Sep 2003, 20:40

I'm also having problems with my acav. My problem i similar to pain's. The vacum things doesn't move at all, at any revs. And the car feels "slow" before 4000rpm, but after that all power comes back! [:)]
I would guess there is a vacume leak of some kind. This can probably be asociated with the leaking/hissing noise I'm hearing, increasing as the revs increase.
Think I'll check out all the pipes etc. for leaks tomorrow.
I would be gratefull to anyone who could dig up some documented info on the acav. Haynes sux!![:(!] Anyone???
---
Jarle

gjb02 · Post by **gjb02** » 10 Oct 2003, 12:29

Changed the Electrovalve Relay...£41 (Citroen Part only!!!) Vacuums now move, but as already mentioned, they too open as soon as you touch the throttle. Shutting again at around the 5000rpm mark.
What tells the ecu it's 1800rpm, is it a microswitch on the throttle crudely set up to a guesstimate? Is it a engine speed sensor? Is there life on Mars, oooohhh?? Who knows, maybe someone out there can give me and some others a clue....cheers in advance.

pain · Post by **pain** » 15 Oct 2003, 13:49

hey gareth,
so do you think it's worth me changing my 'electrovalve relay' ? any chance you could get me a picture of it?

thanks!

benj · Post by **benj** » 16 Oct 2003, 00:01

gareth, did you notice a difference?