Idle Issues

[smithy 1]

firstly a little background info,the car is a G plate 1.6 gti that had a 1.9 lump fitted in 2001 by the previous keeper the engine has not started since and has been in dry store until i purchased in august.

 

I found a badly fitted immobiliser was stopping it from starting so removed it,since then i have had head off and reconned it.

it has had all plugs filters etc replaced along with a new coil.While cylinder head was off i removed brown plug and soldered all the wires together.

fuel tank was drained and refilled with fresh super unleaded.

 

Today is the first time i have tried starting it firstly i cranked with coil unplugged to get oil flowing once oil light went out i connected coil and started it but it needs a press of throttle to get it to fire up it then goes up to 3k rpm and drops back down and cuts out,if i hold on some throttle it will run on all 4 and quite smooth but just cannot get it to idle on its own.

 

have been through the base idle and TPS set up procedure as described in haines also check AFM all resistance within tolerence,re tried starting and it will start go up to 3k rpm again and then just cut out still.

I have not been able to do much else with the impending poor weather as cooling system filled with fresh water and a flush additive so wanted to drain down to prevent freezing.

 

Is there anything likely to cause this type of problem???

[large 33]

First thing I would do is check all the air pipes and the sad (Supplementary air device ).

[smithy 1]

First thing I would do is check all the air pipes and the sad (Supplementary air device ).

 

thanks for reply should have mentioned all air pipes have been checked nothing amiss noticed.

 

whats the best way to check the SAD unit or is it a cheap enough item to just replace?

[large 33]

Have a look on the main site, in the Engine General section .

[smithy 1]

Have a look on the main site, in the Engine General section .

 

 

Once again thanks for the help,I will follow instructions to check out the sad

[smithy 1]

thanks large you were spot on the pipe from SAD to manifold was all brittle and split underneath some heatshrink that is on it,fitted new hose it now does not rev to 3k rpm.

 

 

however i have put another fault on it,the fuel pump will only run if i put a constant feed to it,when cranking the tachy relay is energising but there is no voltage on wire 76.I have had a look at the wiring on tachy relay and there are 2 white wires one is number 76 to fuel pump the other has no number but i am assuming it is the feed in to relay contact?? there is no feed on this.even with pump running the engine will start but it seems to be missing at all revs.

It is obviously something i have disturbed as the pump ran prior to having SAD off today but i cannot see anything amiss all connections are back on

has anyone got a link to some decent wiring diagrams so i can trace how the pump gets its feed? the haines ones are crap and i cannot make head nor tail of them.

 

thanks

[Anthony 1,003]

There is three thick wires on the tachymetric relay:

• The brown one is the 12v feed from the shunt box under the bonnet
  
• One white one (#76) feeds the fuel pump
  
• One white one (#18) feeds the fuel injectors
  

The wiring diagram in the Haynes manual is fine and pretty easy to understand.

 

The relay is activated under two situations - 12v on the starter solenoid wiring (ie key turned to crank) from wire 46B and from the pulse from the coil when the engine is running from wire 112A.

 

Your running issues don't sound like a tachymetric relay fault to me though.

[smithy 1]

There is three thick wires on the tachymetric relay:

• The brown one is the 12v feed from the shunt box under the bonnet
  
• One white one (#76) feeds the fuel pump
  
• One white one (#18) feeds the fuel injectors
  

The wiring diagram in the Haynes manual is fine and pretty easy to understand.

 

The relay is activated under two situations - 12v on the starter solenoid wiring (ie key turned to crank) from wire 46B and from the pulse from the coil when the engine is running from wire 112A.

 

Your running issues don't sound like a tachymetric relay fault to me though.

 

 

no i do not think tachy relay fault either,reading your post i am suspecting a fault on brown wire from shunt box as neither white wire gets a feed.the tachy relay is definately operating as i feel it click under cranking.

 

thanks for the info i will do some checking tomorrow.

[Anthony 1,003]

The wires MUST have a feed unless someone has bodged the wiring - no feed and the engine wouldn't run at all, as neither the fuel pump nor injectors would have power.

 

A "misfire" is far more likely to be related to either ignition or the air/fuel mixture being wrong, probably thanks to an airleak, and you've been working in close proximity to both parts recently.

[smithy 1]

Defo no feed I am having to put a feed on to wires direct to get running,I reckon might have 2 problems 1 on the feed from shunt box and poss a mixture adjustment.with the way it ran yesterday it would have been very difficult to tell.

 

Will check the wiring out tomorrow and if I can at least get running I stand a chance of being able to adjust AFM screw to get smoother.

 

The tachy relay is working that's why I suspect the brown wire at fault I have been in vicinity of shunt box so prob pulled plug off.

 

It started hammering down with snow so I called it a day before having a good look

[smithy 1]

just to update on the problems found.

 

 

Firstly the brown wire at tachy relay wire no 1R i think is live but when cranking losing feed traced fault to high resistance between the spade terminals and shunt blade in shunt box.cleaned up and tightened the spade terminals so that problem sorted engine will now run.

 

As for the misfire found the rotor arm has caught on posts in dizzy cap causing some damage and also the centre carbon electrode in cap pushed right in and not springing out,pi$$ed off about that as both are brand new bosch parts.I think it is the rotor arm at fault personally that has damaged the cap.

[smithy 1]

just to update on the problems found.

 

 

Firstly the brown wire at tachy relay wire no 1R i think is live but when cranking losing feed traced fault to high resistance between the spade terminals and shunt blade in shunt box.cleaned up and tightened the spade terminals so that problem sorted engine will now run.

 

As for the misfire found the rotor arm has caught on posts in dizzy cap causing some damage and also the centre carbon electrode in cap pushed right in and not springing out,pi$$ed off about that as both are brand new bosch parts.I think it is the rotor arm at fault personally that has damaged the cap.

 

 

New cap and rotor fitted starts and runs fine now idle a smoothe 1000 rpm so will do for now until

It can be tuned properly.

 

Thanks for all the help large and anthony