Cooling And Emissions

[darrellnort1969]

Hi all,

Got a 1994 st202, bought it a few weeks back, done the normal, drop links, anti roll bar bushes and new cvs,

got a few niggles on the engine side,

start car, tick over is approx 1800rpm, then creaps to 2000 rpm, as tem guage rises the revs drop, but this can take 5mins plus,

normal tickover is 1000-1100 rpm, i think this is fast ?

once the temp rises to just over half on the guage, the fans kick in, trouble is there staying on and driving the temp guage back down to below a quarter, and obviously at this point the revs have climbed back up to around 1400-1500rpm because the cold start has kicked back on,

on the odd occasion the fans will go off again then back through the same cycle but usually i can drive say 40 miles pretty hard, get home and the cold start is still on, revs up, fan on and temp guage below a quarter,

could anyone tell me which of the sensors and where it is would be suspect and need replacing,

i have one with a single wire and one with two wires near the thermostat housing, is it one of these or is there one on the rad itself?

Took it for a pre mot the other day, on emissions it failed,

of the 3 readouts, the bottom 1 stayed white, top 2 were red,and suddenly after a few minutes they were all red and had very high readings,

is this an ecu problem? cat problem, ? or another sensor.

any advice would be great, love the car and just want to get it right

[Leeky]

I think someone has adjusted the throttle cable. Have you checked it?

Normal idle when warm is 750-900rpm.

I'd check the rad coolant for signs of a headgasket issue. Also i'd drain the coolant system and put fresh new mixture in for peace of mind.

If its getting hot and failing emissions i would say lambda is causing it to run too lean.

Not sure about the ST202 but on the st205 there is a sensor in the bottom of the radiator which i believe switches the fans on and off, so may be worth starting with that one.

[darrellnort1969]

Cheers,

throttle cable is ok, was the first thing i checked, have put new plugs in and i was surprised to find that the old ones were a perfect colour,

the coolant has been replaced as well as there was only rustyish water in it when i checked,proper mix in it now, and there was no signs of oil or contamination, oil is clean also, uses no oil, and no water,

its more of an over cooling problem as the fan doesnt shut down as a rule once it comes on which is why i was guessing a sensor ? .

have got a new lambda oxygen sensor which i need to fit, also got a spare ecu if push comes to shove,

have heard you can reset an ecu ? any info on how to do that ?

[Leeky]

Ah right, in that case have you checked the thermostat? Sounds like its stuck open.

Sensors on these cars dont tend to play up. They either work or totally fail in my experience.