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 Vacuum in engine diagnostics

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tank2023

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PostSubject: Vacuum in engine diagnostics   Tue Jul 10, 2012 8:41 am

having problems with engines, hookup a vac gauge and look at the diagram on this site, i found it useful cheers

http://www.secondchancegarage.com/public/186.cfm
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boona575

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PostSubject: Re: Vacuum in engine diagnostics   Tue Jul 10, 2012 9:56 pm

now thats some bedtime reading!! if i think i have a vacuum leak i just spray carb cleaner on all the hoses/gasket faces on the inlet side of the engine.

but this is far more in depth to give an idea of leaks and the health of a motor! interesting stuff.
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tank2023

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PostSubject: Re: Vacuum in engine diagnostics   Tue Jul 10, 2012 10:11 pm

Ive tried carb cleaner with no results, so moved on to the tech stuff, i mite even end up havin it smoke tested if i still cant find it later
The hunt is on
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shrek
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PostSubject: Re: Vacuum in engine diagnostics   Tue Jul 10, 2012 10:27 pm

let us know how you get on mate, i'll try and give ya a buzz in a bit and give ya a hnd, we must be able to sort it Wink
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boona575

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PostSubject: Re: Vacuum in engine diagnostics   Wed Jul 11, 2012 5:41 am

why tank whats up??? i had hesitation from my motor after engine swap and....

tried refitted manifold
new fuel pressure regulator
new injector o-rings
new maf sensor
checked fuel pressure

mates got a diagnostic machine and for a tenner he gets giddy with it.

turned out i had fitted the lambda sensors on the engine loom side the wrong way round.lol

mines a 6 cylinder lump so you can imagine ecu is thinking wtf!! cylinders 1-3 trying to get fueling and air for 4-6!! haha. ran like it had 70bhp and nailed fuel. swapped em over and cleared fault codes.......nearly ripped my kidney out when i went for test drive. haha. only prob i had when i fitted the new engine and it was my first attempt. its a big un anorl so dont worry matey you will sort it.

my advice is check the obvious and basics first.

power=battery/good engine earths
fuel=good quality, no leaks, right pressure, functioning injectors
spark= functioning coilpacks/leads, good plugs/wells dry
air=no vacuum leaks/all pipes in good condition and connected including inlet itself, throttle body functioning correct, air filter clean, MAF sensor/try unplugging it and see if it makes a difference
electrics=all sensors working including ECU itself, all wires and plugs in good condition.

just work through it and you will get there, do it logically and start with the easiet to check first, dont go chucking money at it cos odds are it doesnt need it and it was something you messed up when you fitted it. everyone makes mistakes its just having the patience to solve em.

good luck dude, might c u sunday
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shrek
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PostSubject: Re: Vacuum in engine diagnostics   Wed Jul 11, 2012 6:29 am

thats a damn good point about the lamber sensor, i know hes been playing with a few when he built the manifold setup,
booner do you rekon if the back box doesn't flow fast enough then it could cause a build up of gasses inside the system and confuse the lamber sensor? bit of a long shot but played with the air/fuel mixture on tick over and got it running nicley for about ten seconds then drops of to a ruph idle, but once you rev it a little and clear the gasses its ok again for another 10 secs and so on, can't see anything obvious (anoyingly)
alien
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boona575

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PostSubject: Re: Vacuum in engine diagnostics   Wed Jul 11, 2012 8:00 am

aaahhhhhhhhhhhhhhhh berry my dear watson........think this could be the point,

a vacuum air leak will be more evident when warm as the knackered pipes are more evident. but

a lambda sensor will continously take exhaust values and tell ecu this then adjust fuel/air mixture to suit.

so if the signal is intermitantly good then good running when the values are hi/lo or out of scale then the fuelling will be rich/lean.

hows about unplugging the lambda and see if it makes a consistant running bad or good.

this should point you in the right direction! i believe we are on to something.

before you tweak the idle/fast idle and accelerator cable anymore i would try this.

the intermittant nature seems to point to a lambda value being way out.

faulty sensor, sensor plugged in wrong part of loom or like you said a back up of gases confusing the hell out of it, possibly after you try the above,

take the restrictive part of the zorst off.

remember make one change at a time and remember what you have changed.

hope this helps lads
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boona575

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PostSubject: Re: Vacuum in engine diagnostics   Wed Jul 11, 2012 8:04 am

p.s google 02 sensor testing all you need is a multimeter and some heat i reckon.

get the sensor to simulated temp and test resistance i believe.

also remember!!!!! ECU's run a cold map where the o2 values are usually not considered...........

so let the engine go stone cold and i mean stone cold, like leave it overnight.

fire it up and if the running is smooth, no misfires and rich/lean smelling then when warms goes to pot........your lambda readings are out.

if its rough from scratch and gets worse when warm i reckon you have a vacuum leak

although from you saying its good then bad then good then bad etc i reckon my moneys on the lambda's pal
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