diag codes

[pimpstang18]

i've got a 93 coupe with the 2.3 engine. the check engine light is on most of the time, sometimes it goes out and the car runs better, when it's on it usually eaither idles too high (around 1800) or it will drop the idle down to norm (about 700) but it starts to sputter and feels like it's going to stall.

scanned it and came up with these codes:
51
95
42

i tried looking these up in the book but mostly they said up through 91, mine is a 93 or otherwise i just couldn't make sense of them, any help would be appreciated. if anyone could tell me what these codes mean that would be great

 

[goland55]

91-93 uses 3 digit codes if I remember correctly... perhaps the codes were supposed to be 519 (Power steering pressure switch circuit open) and 542 (fuel pump secondary circuit failure:ECA to ground)?

The chiltons I have also lists 2 digit codes from 89-93...
51 - ECT/ACT circuit open
95 - fuel pump secondary circuit failure:ECA to ground
42 - no oxygen sensor switching detected, reads rich

Sputtering and sluggishness when trying to accelerate is a sign of a bad o2 sensor usually. The factory o2's usually die somewhere after 70k miles and the aftermarket sensors, on average, don't last nearly that long.

 

[pimpstang18]

could it be a bad cat? sometimes it idles real rough and there's a knocking sound, thought it was lifter knock at first but then it went away it's probably an exhaust leak...i'm thinking the cat is taking a crap, that would make it run lean right? or should i just try replacing the o2 sensors first?....

when i changed the plugs last week the tips of the old ones were white so i'm thinking the car is running a little lean, not rich

 

[goland55]

If the check engine code shows the computer is seeing the o2 as reading rich but you're showing signs of the engine running lean then it's possible the o2 could be toast and is reading rich no matter what.

A knocking sound could possibly be the engine knocking (detonating) which can happen when you run too lean. An exhaust leak could also cause a knocking but wouldn't cause the engine to run lean.

If you get good pressure out the tailpipe then the cat is most likely ok. Low pressure could mean the exhaust is restricted or leaking somewhere.

I believe the O2 sensors are 3 wire units on the 93's. There should be a power wire (5 volt I believe), a ground wire, and a O2 signal wire. If you stick two small pins through the insulation on the signal wire and ground* you can connect a voltmeter between the terminals. At idle it should be going from 0v to 1v, switching back and forth quickly...the voltmeter probably won't give you a steady reading. If it reads a steady 1v or steady 0v then the O2 is toast.

* I believe the computer reads the sensor wire with reference to ground...if you get a voltage higher than 1v then you might want to try taking a voltage reading between power and the signal wire.

 

[pimpstang18]

so what determines good pressure? do i just cup my hand over it to see if there's pressure coming out?

an engine knock wouldn't be intermitant though would it? i sure hope it's not an engine knock, i just got the car and need it for daily transportation, i'd hate to have to put a new engine in it already, especially before i have the time and $ to do my 5.0 conversion

thanks for the info, i'll test the voltage in a week of so when i go back home, i just moved to a different city and all of my tools are in my dad's garage back home, unfortunatly my 5 foot tall craftsman toolbox wouldn't fit in my new apartment, although it would make a nice addition to my living room kinda sucks especially when i'm trying to fix up my "new" car with a vey limited tool selection.

 

[goland55]

Cup your hand over the exhaust and it should push your hand off so the gases can escape. If it doesn't push your hand off then the exhaust gases are probably escaping somewhere else.

If your knock sensor is plugged in and functioning it will pull the timing when it detects a knock. I'm not sure how long it pulls the timing before reverting back to 'normal' timing or what strategy the EEC uses for that.

How loud of a knock is it? If it's more of a ticking it could just be a sticky hydraulic lifter.

I know what you mean about the tools. I'm driving cross country next month to live in CA. I'm going to be leaving all my air tools, all my jacks, and a two post 10,000lbs lift here. It kinda gives me an empty feeling in my stomach if I think about it too much...ugh.

Anyway, I would definitely check the voltage on the O2 sensor asap as that can either eliminate one major possibility or point to what's wrong.

Also, even though they're not throwing any codes, you may want to check out the TPS, IAC and EGR. A faulty TPS can cause weird throttle response (can be checked with a volt meter). An sticky IAC can also cause the car to rev higher than normal at times and stutter (clean it with some carb cleaner). A gunked up EGR can cause lean or rich conditions depending whether it's stuck open or closed (again with the carb cleaner).

 

[pimpstang18]

cool, thanks for the help man, it may be a few weeks before i can get to my tools but i'll be checking all of the above and can hopefully eliminate the problem without spending too much $

come to think of it i had just changed the oil when it started knocking, the level was ok but is it possible that the sending unit or oil pickup is going bad? it hasen't done it since that weekend though and i'm not sure that draining the oil would take any more of it out of the system than just letting the car set overnight right? unless it's slow to drain out of the valvecover for some reason and flooded it temporarily....any thoughts on this?