Check engine and tach issues

[entropy_46]

I recently bought a '95 ATX and I am enjoying it. But as is to be expected I have a few bugs that I'm trying to work out. One that arose this weekend was the check engine light coming on.

After reading through other posts similar I wasn't able to come to a definitive answer / solution, but I do have more information to provide in order to hopefully get a better understanding so as to not get screwed over by the place where I bought the car (i.e. it's under warranty, but I'm not sure of the place).

The tach in my car wasn't working properly, it would read about 500 RPM when cruising on the highway and when accelerating (about 1/4 throttle) it would hit 8000 RPM. I wasn't really scared because I could tell the engine wasn't actually revving to that range (all of my other cars have been manual so I am used to listening for shift points). But then out of the blue, my check engine light came on while on a longer highway drive. Whether pure coincidence or not, my tach then started giving me what seemed to be proper readings (from what I've read in other people's posts). After about a minute the light went out and from then on would go on and off at will. After the car sits for a while, the tach goes back to it's faulty readings however.

Another issue I noticed was that my temp gauge was showing my car as running REALLY cool. I understand that these cars usually run cool, but I'm not sure this cool. My gauge was barely above the bottom mark after driving for about an hour. I bring this up because other posts have made reference to the temp guage.

Does anyone have any ideas? I haven't run the code yet. I had planned on taking it back to the shop and having them fix that among other small things. I just don't want to go in there and have the wool pulled over my eyes, I like to have a game plan first. Not that I don't trust them ... yeah, right.

Thanks for your time.

-GJK-

 

[BeatDaSHO]

scan the codes. it is trying to tell you something. more than likely, your cam sensor probably needs replacing. just scan the codes per www.shotimes.com The colder temp might be due to a stuck open thermostat. Replace it with the motorcraft 192 degree thermostat. Do the temperature sending unit also. About 6 bucks for that.

Greg

 

[BlackOnBlackATX]

how long does it take for the car to get above that hash mark? hopefully the code will tell you whats wrong with the tach. the link to reading the code is in my signature if you want to just go right to it. i recommend saving the page

 

[sdpatt]

Here is an excellent site for information on the test hookup, procedures and the descriptions of the output codes. Running the codes is a convenient and powerful diagnostic tool for any modern automobile. Do yourself a great favor and learn how to do it. The couple of minutes required to check the codes can save a great deal of time, money and frustration.

The tach is driven by a signal from the distributorless igntion system (DIS) module mounted on the passenger side of the intake manifold. The triggers for this signal are the crankshaft position sensor (CPS or CKP) and the cylinder identification (CID or camshaft position) sensor. The DIS is very dependent upon having a secure ground path through the intake manifold and can produce error codes for both the CPS and CID if not properly grounded to the car body. Checking the ground path would be a good starting point after checking the EEC error codes.

Regarding the temperature gauge, is the needle above the lower white tick mark for the NORMAL range? If so, the temperature is normal, but the 3.2L in the ATX SHO characteristically registers around the "RM" portion of the gauge from its 190F (88C) degree thermostat. The 180F (82C) thermostat in the 3.0L (MTX) engine normally positions the needle in the "AL" range or slightly lower.

Be aware though, that the temperature gauge is not a calibrated device and it or the temperature sender could be innaccurate. The only true measure of the coolant temperature is a calibrated temperature measuring device applied to the thermostat inlet and outlet passages. If you do replace the thermostat, be careful that the rubber seal around the thermostat's perimeter is the only seal for the 'stat and its housing. Many new 'stats do not include the seal so the old seal must be reused.