Confusing Check engine light

[Sho Nutz]

OK, this is weird, It does not happen all the time, but it is becoming a little more frequent.

Driving along, vehicle runs great, but check engine light comes on. After shutting engine off, upon next start up attempt, the engine back fires without the engine running, let off and try again and it usually starts, but then the tachometer is not working, CEL returns. Within 30-60 seconds the tach starts working and then the CEL goes out.

The car does not run bad once it starts, no smoke no nothing, I have tried getting it checked, but it goes away so fast, I cant get it to dealer or work before the light goes out. I bought a code reader, but it will not deliver me any code.

Any info would be greatly aprreciated.

 

[93nighthawk]

Go to www.shotimes.com to find out how to pull codes. It sounds like there are several things wrong. One thing I know for sure is the CPS (Crankshaft Position Sensor) is on the way out on your car (that is why the tach is not moving). The other problems I would not want to hazzard a quess without more info.

Eric

 

[twr]

If the car back fires when tring to start it - then I suspect the cam sensor is going - it tells the eec what cylinder is in compression stroke so it knows when to fire the spark plug. If the sensor is going or gone bad, the eec starts fire the spark plugs randomly to figure out what stroke it's on. However, you may consider replacing the CPS, if it has more than 60k miles on it. Check your codes too, that may pin point the problem.

 

[sdpatt]

(NOTE: twrsho, your post did not exist when I started typing mine. Good analysis and sorry for the duplication.)

The CHECK ENIGNE light is not confusing, it is your beacon in the dark for analyzing engine control problems. It is your friend. Learn to read the codes. It only takes a few minutes.

http://www.dalidesign.com/hbook/eectest.html

You should check the codes because they will point directly at the source of the problem. I suspect that you will find a code 19 (2-digit) or code 214 (3-digit) depending on the year of your car. These codes name the cylinder identification sensor (aka camshaft position sensor, CID or CMP) as the source of the CHECK ENGINE light.

This sensor identifies to the EEC the location of the number one cylinder at startup so it can synchronize the ignition pulses with the crank position. Once the engine is running, this sensor is not used. If this sensor has failed, the EEC will use trial and error to determine the cylinder firing order. That is what causes the backfires.

You can get the Wells F134 from AutoZone for $29.99. It is located on the passenger side end of the rear bank exhaust camshaft and is held on by two 5.5mm (7/32") bolts.

The crankshaft position sensor, if failed, will not allow the engine to start or run since there is absolutely no spark generated without a signal from this sensor. This sensor is probably not the problem, but would be suspect if you find the 14 or 211 codes.

<small>[ August 08, 2002, 03:07 PM: Message edited by: sdpatt ]</small>

 

[NotoriusCSR]

anyone know what a code 673 on a 94 ATX means? i got it a couple months back and couldnt find it in my book or a 93 MTX manual and the guy who helped me pull it had never seen it either.

 

[twr]

Damn Scott, Do you have a note book next to your computer when you type your stuff?? Very comprehensive info. I just store my stuff in my head. BTW if you do have a note book - can I get a copy of it??

 

[Sho Nutz]

Question, your camshaft sensor sounds good, but if this is only used during start up, what would cause this light to come on after vehicle has been running for 10+ miles ?

I am not questioning your diag, you have done better than the local ford boyz, just trying to figure it out.

thanks for the info.

car info:
94 atx 70.700 miles with mods and need of 60k

 

[twr]

You need to pull the codes, if the check engine light is coming back on after 10 miles of driving (I'm assuming the car is cold) it could be a bad O2 sensor or any number of unrelated items.

 

[luigisho]

The codes will tell the tale. Pull 'em.

 

[sdpatt]

NotoriusCSR:
anyone know what a code 673 on a 94 ATX means? i got it a couple months back and couldnt find it in my book or a 93 MTX manual and the guy who helped me pull it had never seen it either.

I don't think that is a valid code. You may want to read the codes again and see what was really there.

The CHECK ENGINE light can be illuminated by a loss of signal from the CID sensor while the engine is running. While the sensor's output may not be used by the EEC after startup, the sensor's signal is still monitored by the EEC. The description of the 214 code is: Error in Cylinder ID (CID) circuit or signal. The signal should always be there if the engine is spinning.

I don't have a notebook, but I have driven 330,000 miles in two SHOs and have a great many resources available. As I have said before, working on cars is not nuclear physics (I am a nuclear engineer). I have posted the links to many of the sources that are available on the internet and emailed out several others. It is not a secret, just years of experience from an engineer's diagnostic point of view.

Scott

<small>[ August 08, 2002, 10:47 PM: Message edited by: sdpatt ]</small>

 

[ShoGuy93]

Scott you always come through with very usefull info!! I love u man!!

thumbs_u

 

[Sho Nutz]

Hey SDPATT, thanks for the great info.

I work in a chevy garage and do not have access to code reader so i used the info and you were right. I pulled the stator off ad found a very small crack in it, purchased the motorcraft part for 41 bucks ( my cost ) took 10 minutes to change cause i gots big hands and low and behold, the car runs better and starts without a prob.

Thanks again ( to everyone ) for the info.