Any here had a pcm go out on them?? i have an issue with my cav..i just fixed a vacuum leak so i reset my pcm and started it up and WOW smoothest its ever ran! ..but 2 miles down the road it starts idling eratic..rpms jump UP when i push the clutch pedal ..stuff like that...so i go home,unplug the battery...an hour later i hook it up and WOW back to smooth again...2 miles down the road..CRAP...see what im sayin??? to me this is an indication of a messed up pcm ..im not sure exactly how that happens but unless someone has a better idea im gonna have to change it.....anyone know where i can get a 95 manuel Jbody pcm????
"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)
Sounds like ether another vacuum leak or the ISC is bad. Do you have a CEL?
Tach Out Motorsports
Option D Inc.
do you mean IAC? and no i have no CEL..would the IAC affect it while im driving???
"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)
forgot to mention my car is running VERY rich
"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)
PCMs are pretty reliable, I have never replaced one on any car.
- 2004 Cavalier - 124k, owned since new
i dont know anyone that replaced one either..HOWEVER the 95 Jbody had a RECALL on the pcm...a bad seal or something...of course i didnt buy the car till 03 so i dont know if it was done or not
"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)
Unplug the O2 sensor Scott. If it run better, you have your answer.
It look like a vacuum leak. It's a major leak tough like and unplug FPR, MAP or canister hose.
Gilles
2.3 Ho
^^^^^^
Is a moron. You cant say unplug a sensor and if it runs better. If anything it will run worse, especially he unplugs the O2 sensor on the manifold. The PCM wont know if it is rich or lean, and wont be able to calibrate the fuel/air mixture.
If you want to be a dumb@!#$ and unplug a sensor leik that guy would go ahead, but all it will do is make your car run worse, decreae gas mileage, and set off the CEL.
- 2004 Cavalier - 124k, owned since new
hahaha go back under your rock. You obviously don't know what the hell you're talking about. Never heard of closed loop? open loop? well, you better learn it cause it's the first thing you need to know to diagnose a CEL code.
Unpluging the O2 sensor WILL NOT make his car run rich. on the 2.3, running with the O2 sensor unplug will make the car run with the preset data. So in other words, it will work correctly. Same thing when you start the car.
Another thing, Scott's car is OBDI so a code is not the end of the worl, it take 2 min to clear.
So before trying to be a smart ass, you need to know what you are talking about.
to give an answer like your's just prove that you don't know your sh**.
Gilles
2.3 Ho
Mfk-223 wrote:hahaha go back under your rock. You obviously don't know what the hell you're talking about. Never heard of closed loop? open loop? well, you better learn it cause it's the first thing you need to know to diagnose a CEL code.
Unpluging the O2 sensor WILL NOT make his car run rich. on the 2.3, running with the O2 sensor unplug will make the car run with the preset data. So in other words, it will work correctly. Same thing when you start the car.
Another thing, Scott's car is OBDI so a code is not the end of the worl, it take 2 min to clear.
So before trying to be a smart ass, you need to know what you are talking about.
to give an answer like your's just prove that you don't know your sh**.
No @!#$ the computer is in open loop until the car has run for atleast 60 seconds and the O2 sensos have hit 600F.
So if you unplug a sensor that is used for fuel calibration and the PCM doesnt know if it to rich or lean how would the car run better? It wont.
If an O2 sensor is bad you will have a code, you may get hesitation from a dead stop, and you mpg will be down.
- 2004 Cavalier - 124k, owned since new
On an OBDII ecm yes, not OBDI.
There is only 1 wire on the OBDI sensor so it can't read temperature. Btw, I've run without an O2 sensor and everything was fine. The ecm doesn't need to know the A/F ratio. If the O2 sensor is bad, the ecm will take the other data to run the engine(IEP: IAT, MAP and TPS).
Btw, I had 2 bad sensor on my 2.3 and never got a code. Guess what, I had a bad O2 sensor, I unplug it and the car ran better(no code).
It still seem like you don't have enough experience with cars.
You can even unplug the TPS sensor and it will work. Unplug the MAP sensor and it will work. Unplug the IAC and the car will work. But going with what you THINK, it shouldn't. Spend 4 complete years under the hood of your car and you'll know enough to tell me how a 2.3 work.
For now, keep your mouth shut unless you got GOOD information.
Don't forget, what you know from OBDII is completly different than OBDI.
The Eprom could be bad and he could change only the chip but that's not the problem right now. The Eprom will run the ecm even without a few sensor unplug.
Gilles
2.3 Ho
I agree with mfk 223 I being a first gen owner.Yes a bad o2 sensor is not detected like with the obd 11 stuff.Typically u get the symptoms of a running issue and NO codes.Disconnecting the sensor in no way will harm the car if anything it would improve it if the part is faulty.I had a egr issue and just by removing the vac line going to it fixed it, the egr was bad internally, and had no codes or cel.Never hurts to look at things from a different point if u do not actually have exper with older models with diff specs at hand.Ok just being straight forward about it since I have the prehistoric cav and loads of exp from yrs of ownership.
i'd say IAC, yes it afect whiles driving (i.e. push clutch, engine revs) as metioned b4 PCM are pretty tough. i wrecked my car last winter, and my pcm was lost in 3 feet of wet snow for a week, i went back and found it, put it in my car and fired right up
wow..didnt expect all this haha ..thanks gilles im gonna try that first thing in the morning..dont know why i didnt do it earlier...and Rob..mfk is probably one of the leaders of quad info on the .org i can understand questioning him..but not going as far as you did.
and yes i have the problem while driving(no power..hesitates bad..revs when i push the clutch..and i can SMELL the fuel from the exhaust BLAH) it FEELS like a spark plug is out,thats the only thing i can relate to..but i know that wouldnt affect my rpm when i shift...ill try the sensor game tomarow and see what happens gilles thanks!
"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)
ok it stead of fighting about its this and that try this.......... your car runs great at first you said right then like crap after a mile are two then ya took the batt, off and put it back on...everytime you take the batt off your clearing the memory of the cpu the engine will run on a closed loop till it reads the cpu again normally after engine warm up.. Sounds like there is a problem and your engine light should come on right? thats memory in 1994/1995 there was the OBD 1 and OBD2 (ON-BOARD DIAGNOSTICS) a big word for problem with sensors + some 96's still had OBD1 i'm thinking there is where you'll find out where your problem lies that will tell you whats not working right first check your vehicle emission contol information label under the hood on the radiator plastic shield on the right topside there shoud be a OBDII CERTIFIED typing buy a car memory scanner at any auto parts store even walmarts in canada wallys have them! there are high cost ones and cheap ones $3000 (snap on/ mac tools) to $10 bucks mine was $120 OBD2 READER but GM wanted flat rate of $79 + tax to tell me that o2 sensor was fk ed (burned wire on the manifold) there are codes from :::
0010 TO P0849 each will set a engine light off! the scanners have a book with it and all the codes to tell ya what is the problem it beats having some one else tell you that its a $400 job when all it is . is a burned wire! oh yeah it will tell ya if it is a pcm problem!!! hope it helped.....
http://img86.imageshack.us/img86/4235/jim25ek.jpg
first off i DONT have an engine light...second its obd1 so buying a "scanner" is completely out of the question considering the price you have to pay for one that will read OBD1 especially with no CEL.....whatever is wrong is making mycar run very very rich so im gonna play around with it tomarow and see what i can find..considering i completly eliminated the vacuum leak today
"Freedom 'ought to have its limits"-George W. Bush may 31 1999 (who voted for this idiot?)
With an OBDI, you don't want a scanner. It's the best way to learn how the engine and Ecm works. You did a mistake and it throw a code, unplug the battery and plug it back, no more code. Even easier than that, you bypass the + and - from the diagnostic port. You get the code, no more CEL and your good to go.
I would start with the 02 sensor. I had the same problem with the turbo quad. Both of my bad 02 sensor were making the engine run rich like hell, no acceleration, it was bogging sometime and it would rev by itself when it was not stalling.
When I unplug the battery, the car ran better for a few min then the problem was back.
Gilles
2.3 Ho
well i think that did it man...i cut the line and it seems to be running good...the 02 sensor is covered in "soot" ..wet soot at that...and so is the tip of my muffler but it seems to be better with the 02 unhooked..cel came on but that should go off when i get the new one..good thing my 02 is still under warrenty
FACT : Statistics show that you are more likely to to be hit by lightning than to die street racing.
well...i changed the 02 and its still running smooth...but now its still wanting to die when i first start it..but after it gets that out of its system it runs good
FACT : Statistics show that you are more likely to to be hit by lightning than to die street racing.
now heres one for ya...got a brand new 02 sensor..start the car up, about 30 seconds into running it tries to die then jumps back up and runs(also does this in middle of driving and will try to die out if i give it gas)...now..if i unplug the sensor it doesnt do this ....any suggestions???
FACT : Statistics show that you are more likely to to be hit by lightning than to die street racing.
check your grounds.. i had the same problem with mine i ran 3 different 02 sensors brand new and still did same thing had trouble starting too... once i changed all the grounds it worked perfectly... the ground is probably on the tranny and there are 5 small 20gg wires 1 16 gg and a 4 gg... ground them all to the same point and your cookin..
