I have a '94 with 43,000miles, i havent had it for too long and really havent drove it much because of weather. It ran fine until one day I started it jus to let it run for a bit, everything was good when it was in the warmup period (high idle), then it settled into its normal idle and after a couple of minutes the rpms dropped way low and the car was barely running. If i tapped the gas and upped the rpms it would sputter a bit before it would respond to the gas being applied and if i put it in drive it would jus die. Im hopin someone has some kind of info that might help me locate the problem, also there is no engine light coming on to say something is wrong. Any kind of info would help, thanks.

 

Not much of an expert on 94's but I say you might try rapping on the IAC to see if the engine idle speed doen't come back to ya. Then consider a IAC and throttle body cleaning session.

-JRC-

 

mice in the garage? Water in fuel line? Check engine light on?

 

No engine light is on, no mice either. Im not sure about the water in the fuel line, is this a common problem and how does that even happen? I jus wanna set it straight that i dont feel im as educated on corvettes or cars in general than most of the people here, but im very willing to learn.

 

Could be water in the fuel line. Get some gas drier and add to gas tank. Wouldn't hurt to remove the IAC and clean it up, either. Fairly simple job.

 

i had an 85 that started running like it was on 6 cyl. and it was every time it rained finally i was refueling it on a rainy day and low and behold when i opened the gas door water was standing there the drain was plugged letting water seep into the tank not sure if this applies to you just something to think about ....

 

I dont think thats the problem, ive only driven it in the rain twice and it drove fine and it is also garage kept, but i'll keep that in mind, thanks. Im gonna change the fuel filter when i get a chance, i dont think thats the problem either, but im sure it could use it. I'll also try the other suggestions that were made when changin the filter doesnt help. Thanks to everyone for the suggestions ive gotten so far.

 

Attatch a fuel pressure guage to the schrader valve and read the pressure. The symptoms you describe are consistant with a dying fuel pump or severly restricted fuel filter.

 

Tested the pressure, it was fine. Changin the fuel filter is my next step in diagnosing this prob, i jus need to find time to do it.

 

You mention that the engine runs fine while it is in warmup "mode". This is an important clue for diagnostics of your engines problem. From an ECM/PCM point of view, during this time the engine is running in "open loop", which is to say that the AF ratio is predetermined in a "lookup table", and the PCM dis-reagrds O2 sensor outputs. When the engine temperature and the O2 sensors reach a certain "critical" temperature, then the engine switchs over to "closed loop" mode, and AF ratio is now determined by feedback from O2 sensors(typical voltages from O2 are between 0.1V(lean condition) and 1V(rich condition)). If your RPM's are dropping after warmup period, this would suggest that your AF ratio is running lean when the engine switches to "closed loop" operation. Typically what will happen, when you go to "closed loop", and your engine starts stumbling, an O2 sensor(s) has gone bad, at whic time the PCM will record an error code and disable the faulty O2 sensor(s) , and the PCM will revert back to the "lookup tables" for AF settings. You may notice your SES light go on, and then a few seconds later, your engine may start to idle nicely again. AF is also controlled by your TPS voltage output, which tells the PCM where the throttle position is, but let's not get into this sensor now. What you need to do is pull your error codes, and see if one or more of your O2 sensors is faulty. You can go to Autozone, and they will pull your codes for free, or it is quite easy for you to do it yourself. When you first turn on your "cold" engine, is your throttle response OK? If it is OK before the car reaches operating temperature(closed loop), I would suspect that you have a bad O2 sensor(s). As a starting point, you really need to pull any error codes from memory. If you want to do this yourself, I have posted the method how to do it, let me know and I can cut and paste it to this thread....But don't go replacing all sorts of parts and hope you cure your engines problem...this method could be frustrating and costly.....

UPDATE:
To pull error codes from your ECM/PCM, all you need to do is short pin A and pin B on your ALDL(12 pin connector under your right knee when sitting in driver seat).
You can use a thin wire or paper clip to short these pins, general procedure:
1- keys out of ignition
2- short the 2 pins mentioned (be careful, don't need to force hard into ALDL)
3- turn on ignition, but do not start engine
4- look at your SES light, it should start blinking, error codes must be desiphered like morris code
5- first code will be a set of three 12's ...this is not error code, only idicates start of reading
6- error codes will come after first three 12's, and they will end at next set of three 12's
7- If there are no error codes, you will only see a series of 12's
8- When finished, turn off ignition, remove shorting wire or paper clip.

NOTE: One CF member had this to say about getting codes:
"On my '92, if you short the "A" slot and the "G" slot, the codes will display as numbers on the LCD dash. No need to count flashes"

Here are a couple of URL's describing the ALDL numbering scheme(your '94 should have an OBDI style 12 pin connector, unlike newer OBDII 16 pin connectors)

use this site to understand your ALDL pin numbering scheme for OBDI type connector, and a better description of how to decode the 'blinking' SES light(remeber, only need to short pin A and pin B to read Diag codes)
http://www.obd1.com/

use this site to determine what the diagnostic codes mean for your engine type:
http://www.troublecodes.net/GM/

Your ALDL connector should look like this:

Thanks to ImageShack for Free Image Hosting

 

Thanks MikeC4, a guy at work told me that he thought it was the O2 sensors, but then i heard if that was the problem i would see an engine light come on and i didnt notice any lights. It definately sounds like you know whats up though, so im definately gonna check that out, thanks again. The car does respond fine when its first started also.

 

Mike C4, I'm impressed Dude!
Are you sure you're a Texan?

 

Hey Mike... this was a great write up. Crystal clear!!!!

 

Heh heh...... actually grew up in NY, so that is where I aquired my BS quotient!! Hope you didn't think any of that stuff in my post was true! I made it all up....

.......well....I gotta get back to my herd of sheep.........

 

My '94 says OBD1 under the hood but i have a OBD2 style 16 pin connector in the car, so i cant figure out how to read my codes. I have an OBD2 tester and it wont stop flashing error codes (8888). Im probably jus going to replace the O2 sensors, it looks like a fairly simple and inexpensive task. If anyone has any pointers or things i should know about replacing the O2 sensors i would appreciate any info, thanks.

 

for OBDII connectors, short pin 4 and 12.....

 

When you say to short 2 pins, do you mean to connect them?

 

Ive ran into a problem changing the O2 sensors. I replaced the two in the front, but the third one toward the rear on the passenger side looks impossible to get to, i cant even reach the plug to unplug it. I could sure use the help if anyone has an easy solution or any solution at all for that matter.

 

Nice job, MikeC4!

 

sounds like a opti spark....cha ching !