Plugs, wires, mpg and an SES

[bobbfrommn]

Multiple things happening to consider.

1. Cold starts in temp below about 15 degrees are difficult. It doesn't just fire up, I have to hold the key for 3 or 4 seconds.
-Put in a new 720 CCA battery, no difference.

2. Poor MPG, about 14mpg and I usually get 20-22.

3. SES light, code reads P0128- ECT (engine colant temp) below Thermostat regulating temp. Car temp seems fine and the heater works ok, coolant levels ok in fact I just had it changed out this fall so it's fresh.

I've bought a set of plugs figuring I'd start there. Question does anyone know what the gap should be on the plugs? They couldn't find it at autozone. They also said there are no plug wires on this model. Can anyone confirm that.

Any suggestions? I'm not a mechanic by any stretch but I have a least a rudimentry knowledge of this stuff and a buddy who is a grease monkey. If I can give him an idea of what to look for he can take a look. At the very minimum I'd like to have some ideas of what to expect if I take it to a shop.

2002 Vue 3.0, 77k mi, AWD

[fdryer]

SES light, code reads P0128- ECT (engine colant temp) below Thermostat regulating temp. Car temp seems fine and the heater works ok...

Although its pointing to the coolant temperature sensor reading below the thermostat regulating temperature it may be the thermostat that is causing the SES light to turn on. If a thermostat were stuck open, the coolant temps stay below the operating range and the coolant sensor is just passing on the information. Thermostats become faulty either closed or open even though you feel the heater is fine but unless you have a temperature probe to monitor water temps (apart from the dash temp gauge) you don't really know what temperature the coolant is. I doubt anyone can tell whether coolant temperatures are 150d F. or 195d F., they're both HOT to ordinary humans. The better scanner/readers will have this feature for more in-depth information but only as good as the sensor its reading from. Since the coolant sensor issue with the S-series has been corrected before the Vues were made, your Vue has the revised coolant sensor and that would leave the thermostat.

If you haven't done so, you'll find that there aren't any spark plug wires anywhere (we share the same V6 engine) but have instead ignition modules that are combination ignition coils and wires assembled three to a cylinder bank, one on each side of the V6 engine covering the spark plug holes. The modules plug into the spark plug holes directly onto the plugs eliminating the plug wires with a short length of plug boot that you'll see when removing the ignition module. Offhand I don't know the plug gap but its usually correct as is from the box or else it may be the same as the specs for the L300's.

As to the difficulty in cold starting below 15d F., have you tried allowing a few seconds to pass between turning the igntion key from the ON/RUN position to the START position? This may allow the fuel pump another second or two to prime the fuel lines.

[bobbfrommn]

Thanks, would this also be what is affecting the mpg and starting or do you think that is a different issue?

[VTchemist]

A faulty thermostat (stuck open) will cause your fuel mileage to suffer. A cold engine (below 150F) just doesn't operate as efficiently at normal (190F) temperatures.

I found this out first hand with a Astro Van. Engine was always cold, heater blew cool air in the winter, and the mpgs dropped. I put in a new thermostat, and the operations of the engine (and heater) returned to normal.

So, a broken thermostat can degrade your fuel mileage. I believe fdryer has got a good answer for you.

[BobbyP]

Thanks, would this also be what is affecting the mpg and starting or do you think that is a different issue?

An engine running cold will not be as fuel efficient as one running at optimal temperature. The cooler coolant temperature will keep the emissions systems in open loop operation, not allowing the computer to control the engine and not allowing your transmission's torque converter to lock for maximum mileage.

Listen to fdryer... change the thermostat... :)

[bobbfrommn]

Yes indeed thanks for the replys, very helpful :) I'll start with a new thermostat and go from there.
Thanks again and rep given :)

[fdryer]

As to the starting problem; if your local temperatures (some of us are shy of divulging location in their personal profile that would indicate what part of the world their in :whoa:) are consistently below freezing at this time of the year you'd have to know about gas line freezing. It might help to keep this in mind since you're more prone to subfreezing lines than the rest of us and usually might add a container of gas line anti-freeze to keep frozen lines at bay. Check with all your friends and relatives in the area for this even though we're using 10% ethanol that's assumed to keep lines from freezing.

[bobbfrommn]

I've put a couple of cans of Seafoam through hoping that will help. I'll be putting a new thermostat and some new plugs in tomorrow. That's the fun part about living in MN you always have to find someone with a heated garage this time of year.

You don't happen to know what the plugs should be gapped at for the 3.0 do you? Autozone couldn't find it.

[revue]

Plug gap should be 0.035-0.043 inches according to the service manual.

[bobbfrommn]

Thank you!

[bobbfrommn]

Ok one last question. How difficult is the thermostat to replace on the 3.0? I talked to the guy at O'riley and he said he did one once and you have to take the Plenum off. We've just stepped out of my element. I've done themostats before but on my older cars where they were pretty easy. I'm not even sure I'd recognize a plenum. My buddy is ASE certified but doesn't work as a mechanic any more so might not be as up to date. With a haynes manual I'm pretty confident but since they don't make one...

Biting off more than we can chew? Time to just take it into a shop?

[fdryer]

Take a look on rockauto.com for the replacement thermostat and the housing and then look around the engine for the usual place where its hiding; either radiator hose coming from the engine, then decide for yourself.

[bobbfrommn]

Called around for a few estimates one place said 2.5 hours so $225 plus the part which he said was $80 (grumble grumble) that was the low one, the dealer said 4 hours and $512. Thanks to those who have responded, the help is appreciated.

[03zq8]

If the Coolant Temp Sensor is telling the ECM that your car is not warmed up it will run rich (effecting fuel economy). Your heat will work normally.

My guess is replace the CTS.

[bobbfrommn]

Update. We attempted to change the t-stat and couldn't figure out how to get to it so gave up. I brought it into the shop and they also recommended the coolant temp sensor be switched before worrying about the t-stat so I had them do that.

That was friday but I haven't had much chance to put enough miles on to see if the mpg has changed consistantly. I topped it off yesterday and it was looking about 13mpg but thats was with running the autostart several times and some bad weather.

The cold starting does seem to be better. I had one air backfire the otherday while starting and the valve on the driverside of the motor got stuck open. The engine wouldn't stay running but I managed to figure it out and take the valve off for cleaning. Seems to be fine now.

[bobbfrommn]

Well the SES light is back. I checked it and it gave me three error codes. Since it was with in 200 miles of just having the sensor changed I cleared the codes thinking it might be some "left over" computer readings from the servicing or something from the remote start. It's running fine for a week and I'm back up to 18 or 19mpg and I didn't use the remote start incase that was shorting it or sending bogus readings. Today again after 200ish miles the SES is back on.

I read the code and it's my old friend; P0128- ECT (engine colant temp) below Thermostat regulating temp.

thermostat or something different?