Why did my "Service Engine Soon" light come on? - TCCoA Forums
 
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post #1 of 14 (permalink) Old 01-18-2005, 07:15 AM Thread Starter
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Why did my "Service Engine Soon" light come on?

I started my car this morning, and my "low coolant" light came on. Which isn't abnormal. I have to top it off (in the COLD weather) once a month, or so. Anyway, after about 5 minutes of driving the car, my "Service Engine Soon" light clicked on. I pulled over at a Gas Station and checked my oil. Other than looking a little dirty, I had plenty of oil. So "no oil" wasn't the case. Keeping in mind that I haven't done an oil change in about 3-4 thousand miles. Could that be the problem? This light has never clicked on before, and I have gone 4-5 thousand miles without changing my oil.

Something else that it might be, is my 180 T-stat that I have installed. Ever since I put this T-stat in, my engine temp gauge never goes horizontal (in cold weather). It takes my car about 25 minutes to heat up, so that I can even have heat, sometimes longer. If the T-stat was stuck open, or closed, would that throw the "service engine soon" light?

Is bad gas mileage a sign of blown head gaskets? I get terrible gas milage, and was just curious.

-Kornhaus
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post #2 of 14 (permalink) Old 01-18-2005, 08:01 AM
 
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Check engine light.

I'm not sure if this is the cause of the check engine light coming on, but your engine is running too cold. A 180 thermostat is not a good idea. Poor gas mileage comes from the ECC getting a cold engine signal from the coolant temp sensor. It then richens the mixture. This also causes piston ring wear as you are washing oil out of the rings with the extra fuel. I would replace the thermostat with a 195 and bleed the system carefully. Watch that coolant consumption though as that could indicate HG problems coming.
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post #3 of 14 (permalink) Old 01-18-2005, 08:18 AM
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IMHO, 180 is not too cold. You're telling me that a difference of 15 degrees is going to: ruin rings, mess with the EEC, etc...

I'll agree 100% with a very low 160 and lower thermostat or no thermostat at all isn't the best thing for an engine. But 180 in not a problem (IMHO).

Scott: Is it the Check Engine Light, or is there a Servive Engine Soon light that isn't on my 94 or 95 (like those that tell you to change the oil)? If it's the C/E, then I would just have it scanned (AutoZone for free) and see what the code is. And depending on what the code it, it could easily be killing your fuel economy.

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post #4 of 14 (permalink) Old 01-18-2005, 08:31 AM Thread Starter
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Quote:
Originally Posted by 94 Daily Driven 4.6L
IMHO, 180 is not too cold. You're telling me that a difference of 15 degrees is going to: ruin rings, mess with the EEC, etc...

I'll agree 100% with a very low 160 and lower thermostat or no thermostat at all isn't the best thing for an engine. But 180 in not a problem (IMHO).

Scott: Is it the Check Engine Light, or is there a Servive Engine Soon light that isn't on my 94 or 95 (like those that tell you to change the oil)? If it's the C/E, then I would just have it scanned (AutoZone for free) and see what the code is. And depending on what the code it, it could easily be killing your fuel economy.
Nope, not C/E light... just the Service Engine Soon light. I have never has the SES light come on before... so I am a little puzzled! Any idea Don?

Don, your cluster and "face plate" shipped out today. Thank you for being patient!

-Kornhaus
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post #5 of 14 (permalink) Old 01-18-2005, 08:53 AM
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Sorry Scott, but nothing I have has the SES light, so I have no idea. Do you have the owner's manual? I'll bet there is a list of what will make it come on in the owner's manual. Just a thought.

I'm about ready to start driving the Cougar back and forth to work (while my T'Bird gets the body work done) and I definintely need everything working! THANKS!!

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post #6 of 14 (permalink) Old 01-18-2005, 12:04 PM Thread Starter
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Okay... here is what my Owners Manual says:

Service Engine Soon Warning Light

This light illuminates when the engine's Emission Control System requires service. It will also illuminate when the ignition key is in the ON position and the engine is off.

I am thinking one of my O2 sensor could be bad. I wish I had a code reader!!!! How much are those?

I just got my emissions check last week, and I passed with flying colors! So something cant be correct!!!!

-Kornhaus
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post #7 of 14 (permalink) Old 01-18-2005, 12:18 PM
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Quote:
Originally Posted by scottkornhaus
....I am thinking one of my O2 sensor could be bad. I wish I had a code reader!!!! How much are those?....

-Kornhaus
Simple code readers are available at places like Harbor Freight Tools ($40 on sale, $50 regularly), or even on eBay. More elaborate readers start at ~$100-130+...

If your question pertained to the sensors: oxygen sensors vary in price, usually in the $60-70+ range (est.). Shop around!
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post #8 of 14 (permalink) Old 01-18-2005, 07:59 PM
 
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Running cold.

Looks like the problem began here -
'' Something else that it might be, is my 180 T-stat that I have installed. Ever since I put this T-stat in, my engine temp gauge never goes horizontal (in cold weather). It takes my car about 25 minutes to heat up, so that I can even have heat, sometimes longer. If the T-stat was stuck open, or closed, would that throw the "service engine soon" light?''
Still think it's your thermostat, causing the bad gas milage.
On the thermostat temperature this is a quote from the Federal Mogal site -
''If the thermostat needs to be replaced, install one with the same temperature rating as the original. Most cars and light trucks since 1971 require thermostats with 192 or 195 degree ratings. Using a cooler thermostat (160 or 180 degree) can increase fuel and oil consumption, ring wear and emissions. On newer vehicles with computerized engine controls, the wrong thermostat can cause major performance and emission problems if the engine fails to reach the proper operating temperature.'' Federal-Mogal
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post #9 of 14 (permalink) Old 01-18-2005, 08:42 PM
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ThunderCentral. The things you're saying about thermostats is basically true....for STOCK programmed cars. If you lower the thermostat in a stock car, the engine may never reach its desired temp and stay in closed loop mode permanently. This will cause it to run rich, etc. Scott's car, and many others on here, is running an SCT program. This changes the desired running temperature so that the car is just fine with a 180° thermostat.

Just thought you should know.

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post #10 of 14 (permalink) Old 01-18-2005, 08:57 PM
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Quote:
Originally Posted by scottkornhaus
Is bad gas mileage a sign of blown head gaskets? I get terrible gas milage, and was just curious.

-Kornhaus
If you let your oil become too dirty, it will indeed decrease your fuel economy. I had this very same problem. I let my oil go a little longer than usual, and watched as my mpg decreased. Once the oil was changed, it went back to where it should be.


-Brian
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SC Block, 4.2 Crank, Scat H Beam Rods, Wiseco Pistons, Custom Comp Cam, 3/8 Main Stud Girdle, Ported/Polished Split Port Heads and Lower Intake, Windstar Upper, Heavier Springs, 1.73 Roller Rockers, BBK Valve Covers, Kooks long tube headers, Aluminum Radiator.

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post #11 of 14 (permalink) Old 01-18-2005, 09:06 PM
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It says Service Engine Soon on the 97 cars, because they switched to the taurus cluster. All cars up to 96 said Check Engine


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post #12 of 14 (permalink) Old 01-19-2005, 07:00 AM
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AH, so it is the C/E light. I never thought about it being a 97 and having the Taurus cluster.

Scott: Get it scanned and let us know.

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97 Ford Aspire (Slow, but getting 36 mpg (f'n Ethenol!! )
84 F250 Dually w/6.9L Diesel (7.3L IDI pending)
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post #13 of 14 (permalink) Old 01-19-2005, 07:06 AM
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Quote:
Originally Posted by Sir William
ThunderCentral. The things you're saying about thermostats is basically true....for STOCK programmed cars. If you lower the thermostat in a stock car, the engine may never reach its desired temp and stay in closed loop mode permanently. This will cause it to run rich, etc. Scott's car, and many others on here, is running an SCT program. This changes the desired running temperature so that the car is just fine with a 180° thermostat.

Just thought you should know.
OK, now this got me thinking... Yeah, scary thought huh!!

On a stock MN12, in the EEC program, at what temperature does it go to closed loop?

Anybody know?!?

I assume programmers that have to change that when they chip a car, so what is the "starting" temp so it won't throw a P0125 code (Insufficient Coolant Temperature to enter Closed Loop)?

97 Lincoln Mark VIII LSC (Chip'd, 3.73 T/L... so far... )
97 Ford Aspire (Slow, but getting 36 mpg (f'n Ethenol!! )
84 F250 Dually w/6.9L Diesel (7.3L IDI pending)
73 Mercury Cougar Convertible w/351C 4V (Partially Restored)
69 F100 LWB w/460 Engine
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post #14 of 14 (permalink) Old 01-19-2005, 09:03 AM
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open loop is programmed to 30 seconds it doesnt go off of the heat of anything, its timed.

LOTS of people run 180* t-stats even without a chip. Does it increase wear? only very slightly. Does it decrease mileage? Not even noticeably. I've had a 180* t-stat in my car for 4 years now and I love it. It's usually right around the N or just a little before it. This increases performance and lowers the risk of detonation when running advanced timing. It is not a bad thing. Talk to any tuner and he'll tell you to get one. Talk to anyone on here and they'll recommend it too.

As for the service engine soon light, Do you have an Autozone nearby? They scan OBD-II codes for free. I dont see how a bad OBD-II o2 sensor would cause bad gas mileage if gone bad though, because those have nothing to do with engine control, only checking emissions. They're quite pointless if you ask me. But it sounds like your OBD-II sensors have caught something wrong with the motor that the eec did not catch. Possibly a rich condition or clogged cat?

-Thomas

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