Possible CPS problem

[MDE3]

I have posted on this problem before, but some events have taken place that may help narrow the problem down.

Symptioms:

Car is rough starting..sometimes, and when it is..engine light comes on, tach does not work.

Car suddenly develops the same symptoms while driving..runs rough, bucking, tach does not work CE light comes on.

Symptoms are not constant..car may run fine for days without exhibiting the problem

New information....car seems to be doing this 1) in the rain, 2) after the car has come out of a car wash, or has recently been pressure washed at home...not necessarily right away..maybe 10 - 30 minutes later. Hence I did not make the connection right away.

Is there a "boot" around the CPS input lead that gets cracked or worn, and could water leaking in be causing the problem.....where do I look?

 

[Mr Anonymous]

The CEL (Check Engine Light) is trying to tell you something. You just need to ask it the right question. There are links to sites with instructions on how to read your own codes in my signature, and you can do it yourself, with something as simple as a paperclip or short piece of wire.

Read your codes, and let us know what you find. The answer might be right there just waiting for you to ask!

 

[MDE3]

reply to check codes

had the codes checked when I was in to get the strut links changed...two codes, both unrelated...nothing else. However the CE light was not on, nor was the problem "active" when we checked the codes.

 

[John]

i am experiencing the same problem .... the bucking and rpm gauge mostly. usually occurs while the car is cold . after it gets warmed up i dont notice anything. i remember my 91 SHO had an oil leak from a camshaft or crankshaft seal and it was leaking on to the CPS sensor which screwed the thing all up and would stall the car and cause it not to start.

im gonna replace mine when i get the chance ill let you know how it works out. those damn sensors are a pain in the *** to change though ... makes me sick thinking about it

John

 

[projectSHO89]

Both of you are describing classic cam sensor faults.

Unplug the sensor and run without it to see if the drivability issues are corrected. Youe will have a CEL, no tach, and may require several attempts at starting the engine to get it to fire correctly.

...or just replace the sensor.

Steve

 

[autobahnsho]

CPS going out usually causes the engine to die completely. And especially causes the engine to run worse when warm, not when cold.

Check the codes. Even if they symptoms aren't present, the stored codes should give some ideas of what's wrong.

 

[MDE3]

Codes were 214 Cyl Id fault, and 225 ..no knock sensor during self test..but none of the replies I have seen addresses why this only happens a bit after the car gets wet.....

 

[rangerj]

If you do a search under my signature, and some others, there is a series of test that can be done to test the DIS (Distributorless Ignition System). The test are done with a DMM (digital multi meter) and/or a LED (light emiting diode) test light. DO NOT do these test with an "Analog Meter (swing needle)" NOR an "Incandescent Circuit Tester".

The test will cover the crankshaft position sensor, the camshaft position sensor (Cylinder Identification sensor), coil power, etc. So, stop guessing!

And now a word about "fault codes", or codes. The computer sets a code when it does not get the information it is programmed expect. The information is in the form of an electrical impulse of either volts, milivolts, ohms resistance, or in a few instances an electrical "open" or "ground".

A code relative to a particular sensor DOES NOT necessarily mean that the sensor is bad or not functioning properly. For example, the code that indicates an O-2 sensor is showing a continuous lean condition may be because of a vacuum leak. Thus the O-2 sensor is working as it should, and the problem is not the sensor. If there is not a vacuum leak then the O-2 sensor is not working properly and is stuck in the "lean" mode.

Another reason a code may be set is because the sensor connection or wire may be "open", grounded, or corroded so that the resistace is causing a problem with the signal to the computer.

The above is a very simplified explanation of the "system". In diagnosing a problem based upon a "code", do not automatically assume that the sensor is bad. Make sure the connections are good, and clean, and that there are no shorts or opens in the wiring between the sensor and the computer. DO THE DIAGNOSTICS. You will learn more about your cars, and you will not replace parts unnecessarily. rangerj