ZX 16V ACAV Problem

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gjb02
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Post by gjb02 »

Can't really tell at the moment. It doesn't seem so thirsty though!!
The engine seems healthy enough, is the induction sound supposed to be so throaty as standard?
I think I'll try the throttle potentiometer next, try and smooth out this lack of smoothness/hesitation* at 2000-3500 rpm during normal driving.
*Feels like you're in a gale getting pushed back and forth!!
Still don't know what tells the Ecu it's 1800rpm. Throttle pot, speed sensor....anyone.
Is there a 16v Club, it's a rare beast might be worth having a meet! Maybe just a GSF (French) meet??[8D]
Worth thinking about.
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benj
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Post by benj »

yea i wouldnt mind knowing about some sort of club
pain
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Post by pain »

yo dudes..
i cable tied (ahem) my vacumes closed (well cable tied them up.. whatever that is open/closed) and that has made a hell of a difference! so it's definetly the vacume things. the acceleration is alot quicker! feels great. hope it doesnt use anymore fuel
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Post by VisaGTi16v »

I think it will only use more fuel when you are over 5000 as they normally open straight after idle it seems then shut at 5000. It will mean yours will be getting a bit too much air over 5000 and it may chuck in more fuel to try and compensate
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benj
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Post by benj »

and getting less low down and top end torque, be suprised if you can get over 110mph
pain
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Post by pain »

yeah ive noticed at high revs it seems to struggle, it was only a test to prove my vacumes where broken, so that's cool i'll get them and hopefully my ZX will be back to normal!
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Post by MiX »

gjb02, benj, pain!
Have you fixed your ACAV problems? If so, I would really like to know how..[:)]
Thanks.
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benj
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Post by benj »

hi MiX, iv never had a problem with my ACAV's my engine had more serious problems, and iv almost finished putiing it all back together
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Post by MiX »

sorry. [:)]
benj, pain??
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Post by Diagsys »

the car gets its info on revs from the phase sensor, usually located on the end of the head it counts the revolutions of the camshaft. hope this is some helps
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Post by pain »

yo dudes,
well mine is alot better after i cable tied them up, so they are always open. low revs are wicked and it hasnt messed up high revs as i had 120 outta the beast the other day? just saving up to get 2 vacumes from citroen at the end of the month.
pain
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Post by MiX »

Hi.
Cable tied my vacume-things today. Wow!!!! This thing goes like a rocket now, compared to before![:)] Smooth and quick up to 4000/4500rpm, but then it hesitates a bit, just like it did on low revs before my little modification. The "normal" power kick isn't present at 4000+rpm like it used to be.
So the conclusion is that I really need to fix this.
pain, keep me updated on your progress/problem solving. [:)]
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Post by gjb02 »

Before you go buying new Vacuums, test to see if they work. Daft I know but where the pipes, that suck on the vacuums, connect to the vacuum pump and electrovalve relay there is a t-piece. Take the pipe off that and fit it directly to the feed (from the vacuum pump) for the two vacuums. They should both be pulled open if they work, when the engine is running. The tee-piece has thick pipes on two ends, one from the pump and one to the brake vacuum unit. There is a small pipe fitted that goes to the electrovalve relay, swap this round with the other pipe fitted to the elctrovalve.
If that doesn't help change the vacuums they're scrap. If it does it might be the electrovalve relay. Changed mine and now the system works, it still opens too early but it closes at around 5000rpm.
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Post by lafanzy »

I should be late for this forum. I just got some of my VACUME problem fixed up. And yes! There is a little module (Vacume pump) that control the vacume level to the 2 diaphrams to the manifold. The little pump is right across the ECU, mounted no the passenger side of the engine bloc, right below the lead cover. It has 1 tube connected to the 2 diaphrams (points towards the top), 1 tube connected to a vacume valve that also has connections to the main vacume pump and to the breaks master cylinder (points towards the front of the car), and 1 release tube (doesn't connect to anywhere) facing towards the firewall. That gave me hell! It worked OK when the engine was cool and acts up when the engine was hot. A little advise to the 16V fellows, the vacume systems in the 16V is very, very sentitive. Sping a little hiss somewhere and loose the 16V push. After replacing my little vacume module, I now love the kick-in. However, I am getting hessitation at low revs. Also. my lights are hunting (modulating dim and bright). Don't know why. Any ideas?
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Post by pain »

hey dudes,
well.. i now have a different zx 16v and ive also cable tied up my vacumes but its not like my old zx for acceleration :( i wish there was some more information on how these things work!
my car now gives me a little rush at about 4000rpm but nothing like my old zx, the whole car seems slower! .. so i dunno what else to do :)
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