Coolant Sensor & misfire

[wurzel]

I have had an intermitent issue over the last couple of weeks when starting the car from cold that the idle seems slightly irratic and almost a misfire that clears as soon as you touch the accerlator.

This morning, same thing happened but nothing happened when I pressed the acclerator (other than more misfire and a cough) Straight away the coolant sensor light came on accompanied by 3 beeps. I switched off and restarted and problem disappeared. No other warning lights. (car smells rich when this happens but I think that is to be expected with a misfire)

I've done a search and found that cleaning the prongs on the coolant sensor may fix the coolant sensor light but would a faulty coolant sensor also cause a misfire or is the coil packs (never a problem when warm) or cold start system?

 

[benjiwales]

change the coolant sensor anyway as they fail very often and only cost £27 from vw/seat and is very easy to do. the 3 beeps is usually coolant level

 

[wurzel]

I will look into doing this, but would the coolant sensor cause a misfire?! (Could understand if it was MAF or Temp sender?)

 

[Funkyfin2000]

i still have this issue even after 4 brand new audi coil packs and changing the temp sender to a green one!

 

[wurzel]

My thinking is it can't be anything too serious as it runs fine as soon as I restart and only happens on really cold mornings.

 

[traumapat]

i think the sensor in the coolant tank is only gauge related. the other temp sensor on right side of the engine on pipe is the ecu/ engine temp one.

so i dont think the sensor in the tank would cause a misfire? not sure though

 

[traumapat]

TB clean? reset? might help. strange its only happening at idle...

 

[traumapat]

i had problems with moisture in the maff connector. but it was more surging revs... it dried out as the engine warmed up. dielectric grease sorted it.

could be a similar thing?

 

[wurzel]

It could be the MAF as it might be mixture realted. I can only describe like a 1.1 Fiesta with a carb when starting cold.. begins to idle ok then goes a little erratic and clears with a bit of throttle (except this morning) It didn't throw up the engine management light which I would have expected.

 

[Funkyfin2000]

yup same as mine....it sometimes starts fine...

but othertimes its very very lumpy....i blame it on my sports cat now......but maybe not...

might need a new MAF but the values on it are fine so i can't see it being a problem, its about the only thing i havn't changed.....

its dead lumpy for about 2-3 secs then blip the throttle and its all ok..

no errors thrown up on vag.com either....

 

[wurzel]

yup same as mine....it sometimes starts fine...

but othertimes its very very lumpy....i blame it on my sports cat now......but maybe not...

might need a new MAF but the values on it are fine so i can't see it being a problem, its about the only thing i havn't changed.....

its dead lumpy for about 2-3 secs then blip the throttle and its all ok..

no errors thrown up on vag.com either....

I can't speak for VAG com errors but this sounds exactly the same as mine, except today bliping the throttle didn't have any effect - very lumpy and almost died (revs between 400 - 1100)

 

[traumapat]

I can't speak for VAG com errors but this sounds exactly the same as mine, except today bliping the throttle didn't have any effect - very lumpy and almost died (revs between 400 - 1100)

when idling does the rev counter alternate between these values? but vanishes when warm?

maf would play up at all temperatures?
either a faulty engine temp sensor (green top) or moisture on the electrics is my guess.(maf connector)

 

[wurzel]

Yes, no issues when warm or even if you switch off and start again.

The lumpy idle does sound like a misfire or wrong mixture. Without asking a numpty question where would the moisture be in the electrics?

Quick question how much will a new maf & temp sensor cost? presumably these can be DIY fit?

 

[wurzel]

Doh - just read the bit about moisture in the MAF connector! Maybe a squirt of WD40 or is that not a good idea?

 

[traumapat]

no..... special grease ....from ebay....

http://www.seatcupra.net/forums/showthread.php?t=105762&highlight=dielectric+grease

 

[traumapat]

costs a couple of quid . and sorted my cold problem

 

[wurzel]

Great, thanks will give that go later

Just found this on the web

"Dielectric means, effectively, an insulator. dielectric grease will not carry an electric current.

This makes it ideal for coating electrical connections that come into contact with moisture. Remember, the cennection is carried through the actual physical contact between the two terminals. The grease should be applied after the connection is made and, thus, it will not affect that contact, which is to say that it won't, in any way, increase the contact resistance of the connection. What it will do is prevent moisture and air coming into contact with the metal and it will prevent the corrosion that moisture causes. Just about any grease is good for this... Vaseline is probably as good as any other and it is a little cleaner in use." from another forum.

Maybe vaseline is worth a go?!

 

[wurzel]

http://www.maplin.co.uk/searchtemplate.asp?criteria=DIELECTRIC GREASE

From looking on here it seems white grease is a dialelectric grease? Maybe I should pop to Maplins at lunch time? (Want to sort it ASAP rather than wait for bits from eBay

 

[kez]

i got dielectric grease from ebay. don't think halfords or maplins sell it, as i looked there first.

 

[Funkyfin2000]

how about this?

http://cgi.ebay.co.uk/Dielectric-Gr...ageNameZWD1VQQcmdZViewItem?_trksid=p1638.m118