temp sensor identitys and causes.

[holmes]

Hi guys, I am still having problems with my 1.8 8v weber carbed syncro.

Setting the scene,

I am sitting in the car with the choke fully out the car runs fine at about 2500rpm, the temp gauge is still way off being even slightly warm.

I drive for ten minutes to work and in that time I push the choke in to save on the petrol, the temp gauge is just about to go over the first mark when I pull up to the usual junction, at this point the car rpm drops and the car stalls, when I restart and the car briefly idles erratically before it drops and stalls again, during the running period the engine sounds lumpy and there is a strong smell of unburnt fuel.

I next start the engine and keep my foot on the acc pedal to keep it at just over 1000rpm & when I look at the temp gauge it just starts to go over the first mark and as it does the rpm rises and I can take my foot off the acc pedal and it idles properly but still slighty smells of petrol.

Ive had the emiissions done twice and the mixture corrected and thats fine.

What I am querying is what happens when the gauge goes past this point? what sensor is telling the car that it is at the right temperature? how does it influence the idling of the car?

The problem maybe a faulty thermostat or switch but I need to understand what is happening before I can solve this problem.

The other thing I have noticed is that when I press the brake pedal hard the rpm rises a little is this common or may this also be a fault.

Thanks for any suggestions. however silly you may thing they are regards Darren

[Chris S]

Try pushing the choke in earlier, I used to have similar problems with my old Syncro Weber conversion and I found that by using the choke lever to keep the tickover speed to 1000 rpm ish as the engine warmed up it ran great, in other words only use the absolute minimum amount of choke to keep the engine from stalling.

You could check the hedgehog heater is working by turning on the ignition and not starting the motor, then after 2 minutes feel under the middle of the inlet manifold, if it feels warm then its ok.

Also check that the vacuum flap valve is working and the warm air duct to the exhaust manifold has not fallen off or rusted away.

As far as temp sensors (or for that matter any sensors on this engine) the only one that controls anything is mounted on the top hose flange, this controls the hedgehog heater and should not switch off till it sees a water temp of 65 degrees when it goes open circuit.

You really should buy Haynes manual nr 1081 Golf 2 as it makes trying to explain something so much easier.

This one is cheap enough

http://cgi.ebay.co.uk/Haynes-Manual-VW-Golf-Jetta-1984-92_W0QQitemZ200187975084

This second one is better as its the exact same one I have, (so we are both reading from the same script)

http://cgi.ebay.co.uk/HAYNES-VW-GOLF-JETTA-1984-92-SERVICE-REPAIRS-MANUAL_W0QQitemZ360009705741

[holmes]

Thank you for your suggestions Chris, I will look into them.
I do have a Haynes manual but sometimes its best to ask people that may have had similar problems and that actually own and drive the cars themselves. regards Darren

[holmes]

i left the ignition switched on for two minutes then touched under the carb heater, there was no heat. how does this thing work i take it current goes into the unit then am i right in thinking the unit works by the resistance throught the carb and manifold via a earth cable from the carb to the rocker cvr. my one didnt have an earth so i got a length of wire and attaatched it to one of the fixing nuts for the carb then attatched the other end to the rocker cvr. the wire i used was from an old household flexi wire so id imagine it would have less resistance than was intended?

[Chris S]

It is earthed through the manifold – head – block & through the engine earth cable back to the battery.
Check in your Haynes manual chapter 4 – 18, page 4A 21 this shows the hedgehog. []

[holmes]

just another thing that i have noticed, when the car behaves badly like this the engine splutters and barely holds its revs when going along so when i press the clutch pedal in the engine rpm drops straight out and stalls, but when i start the car back up it runs fine. like there may have been an electrical fault causing it or maybe the coil it also seems to happen more i think when ive had the demisters on and stereo and lights on but this may not be the case but is an observation i have made.

[Chris S]

Can you e-mail me a photo of your carb set up please as I still dont think the electrics are connected up right

[holmes]

ill try it will probably be tommorow nightish. thanks

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