coolant temperature sensor

[WmWatt]

Getting an intermittent check engine light code 09 "coolant temperature sensor" on a carburetted engine. The Haynes manual shows it's on the underside of the intake manifold. I plan to jack up the car tomorrow when it's warmer and take a look but have a couple questions...

1. Can I drive the car like this? Haynes says how to test and fix things but not what they do. It does caution damage to the sensor can effect fuel injection function but doesn't metion carburettors.

2. Does the coolant have to be drained before removing the sensor? Haynes says remove and replace the radiator cap to release pressure and to wrap the threads with tape before reinstalling but doesn't mention coolant leaking out when removed.

Thanks.

[zoe60]

It is on the bottom side of the intake manifold. Up pretty high. Small hole too. It would probably work fine to have the new one ready to go with thread sealant, and just be quick with the ol' swaperoo! Shouldn't lose much coolant. Have a towel handy. Check to see if the wire fell off before spending money on a new one. I would think that it would tell the computer to make improper adjustments to your feedback carburetor and possibly make the fuel mixture wrong if it were bad. Yours is still all original, right?

[WmWatt]

Something has to tell the computer to go into closed (open?) loop mode. I don't know if that's a signal from the O2 senosr once it warms up or perhaps a signal from this coolant temperature sensor once the coolant warms up, or both. If it's just going ot stay in open (closed?) loop it's running rich and that I can do for a rew trips if nesseary until I can get this resolved. But not knowing it's grounded.

Did not get at it today as I was stuck indoors but am hopefull for tomorrow.

Yes, I have kept it stock. Less confusing. Although Ontario has killed it's emission testing so I could do away tithe the electronic feedback carburettor. That would be less confusing. Fewer things to go wrong.

[WmWatt]

All appears good physically. No dirt or damage. Replacement looks like a job for a one armed auto mechanic. Really tight. How do they do this? Unable to disconnect today. I'd like to test the voltage but can't see how to get the connector off so far. Just yank? Do not want to damage anything. Anyone know if there's a more accessible spot to check the voltage? |Thanks.

[firebush357]

I haven't tried but it might be easier from under the car.

[bugbor]

Thanks for postin' this thread. I think I need to do this on my '90 FI motor. Anything I should know about this? Cross my eyes right over left and stick my tongue outa the right side of my mouth? Are there any particular cuss words that make the job go any easier, or will just the standard "$#&* jiminy fudge snazzlefratz" do the trick?

[zoe60]

Way easier from below. The plug is odd and hard to figure out. certain way to squeeze it maybe. Been a long time since I messed with mine.

[WmWatt]

Only way is from below and it's tight. Only room to shove one arm up to the sensor. I examined with trouble light and mirror. Also looked at photos of replacement sensor and connector on Internet. The tabs on the sensor don't depress. There is a sort of wire clamp on rach siide of the connector which snaps over the fixed tabs on the sensor. Looks like you have to lift the wire on both sides or perhaps the connector just pulls off the sensor. Mystery.

PS Haynes manual says fuel injected engine has sensor located on top centre section of intake manifold, not underneath like on carburetted engines.

[Dragonhealer]

Catch one end of the wire spring clip and pull it around one side (so the wire rectangle is at 40 deg to the connector rectangle)

[AlaskaFestivaGuy]

The "wire clamp" to which WmWatt refers sounds like the same as the clip that attaches the connector to the air box on FI Festies.

See attached photo.

If it is, you probably need to be careful that you don't pop it off so it goes flying off into the dirt.

[firebush357]

I like to use the Harbor Freight pick tools for getting those spring clips off.

[WmWatt]

Thanks, guys, for the info on the connector. One of those tiny screwdrivers used on computers and other electronics worked to lift both the wire clips on one end and the connector pulled right off. All terminals looked clean and shiny and good.

I was able to test the sensor with an ohm meter. Mr Haynes says the resistance should be 2,000-3,000 cold and 200-400 hot. I got just under 1,000 cold so the sensor will have to be replaced. I need a 19mm deep socket to remove the old sensor. The spark plug socket is just a bit too big. I guess it's time to break down and buy a deep socket set. I have extensions of different lengths.

Thanks again.

[WmWatt]

Ran into an odd problem today. The new 19 mm deep socket would not fit until a file was shoved up under the car and used to round off the corners on the plastic of the sensor. Then the socket went on fine. Thought people should know about that.

The new part has been ordered fro Rock Auto and is due in a couple of weeks. I could have bought the part from bricks-and-mortar Canadian Tire right away for $44.06 Canadian but bought online from Rock Auto for $14.78 Candian instead. Those prices include shipping and tax.

[WmWatt]

This problem seems to have cured itself. I had some time to wait for the part to arrive so reconnected the sensor, let the car down of the stands and drove it. The check engine light didn't come on. I cleared the codes and the check engine light hasn't come on yet. The part arrived in the mail a week after I ordered it. I guess it's backup now.

[Rick the Quick]

Sometimes merely unplugging and re-connecting a sensor will cure the problem. I have been a collector of dental picks of all sizes and configurations but as of lately most of them have become junk. Found a nice set on eBay for $12 delivered. They are made in USA by Channellock. These make removing the clips found on some of our connectors a breeze and BTW are much nicer than the made in China crap from Harbor Freight.

https://www.ebay.com/itm/Channellock-HP-4A-Zinc-Coated-Hook-Pick-Set-Acetate-Handle-Includes-AWL2AB/253547670343?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649