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-   -   94 chevy 4x4 truck problem (http://www.diychatroom.com/f46/94-chevy-4x4-truck-problem-54549/)

tecate1987 10-06-2009 03:36 PM

94 chevy 4x4 truck problem
 
94 chevy truck 5 speed, vortec 4.3 v6 engine.

truck is running rich, has new air filter, plugs.
What can be causing this ???

Gary_602z 10-06-2009 08:00 PM

Thermostat stuck open or a bad computer temp sensor could cause it to run rich.

Gary

tecate1987 10-06-2009 08:44 PM

truck
 
it happens pretty much from start up.
is the temp sensor the same part as this on ebay.? item #250355290617

temp control ?

Gary_602z 10-06-2009 10:45 PM

Quote:

Originally Posted by tecate1987 (Post 337288)
it happens pretty much from start up.
is the temp sensor the same part as this on ebay.? item #250355290617

temp control ?

No that is an A/C temp control.
I was talking about the Computer temp sensor that send the engine temp to the computer. There is also a sensor for your temp guage or light which would be different

Gary

Have you checked for any codes?

mspeckhem 10-07-2009 06:35 AM

another thing you might try to check is, pull the engine oil dipstick out and smell the oil on it, if it smells like gasoline, you could have a fuel injector or fuel injector line problem, those vortec engines have plastic lines inside the intake plenum that sometimes will crack, and make the engine run extremely rich, and dump fuel right down into the crankcase and evantually ruin the engine., i would also check for codes , it is very possible it could just be a coolant temp sensor, or even a different problem, i've seen bad vacuum lines to the map sensor also, although i cant think right off the top of my head if that particular one has a vacuum hose or if it is directly mounted into a vacuum port. 20 plus year ase master mechanic, just thought i'd throw some quick ideas at ya.

ratherbefishin' 10-07-2009 10:34 AM

Check the fuel pressure and pull codes. Could just be the fuel pressure regulator. If so, the only code it would throw would probably be one indicating the O2 sensor is detecting a rich condition.

tecate1987 10-07-2009 03:17 PM

chevy
 
I am going to see if my coder will read with this year truck.
If the weather clears up some today. I will also check the oil smell.
thanks for the help, I will reply with updates.

Rehabber 10-08-2009 12:32 AM

VERY high possibility of bad fuel pressure regulator. The diaphram pops and leaks fuel into the intake manifold. A pressure check may not determine this leakage.

47_47 10-08-2009 10:22 AM

A fuel pressure regulator will fail in one of two ways. Either cause high fuel pressure (measure with a gauge) or bypass internally as Rehabber stated. To check for a bypass, remove the vacuum line from the regulator and check for fuel.

I'm leaning toward a bad ECT or thermostat.

newbsauce 10-08-2009 12:14 PM

Is it showing a code? Please pull the code (or go to advanced auto/autozone) to have them pull it.

Alot of people jumping to some serious conclusions on this thread. My thoughts (in this order):

1> O2 sensor
2> FPR
3> Temp sensor
4> Dinosaur attack caused fuel problem

47_47 10-08-2009 01:15 PM

This truck has OBD. I think Autozone can read only OBDII codes. The OP did not state if the SES light is on, usually that is the first complaint stated. To read the codes on this truck, turn the key on and jumper pins A & B of the ALDL. You will count the flashes of the SES light. You always will read one flash, a brief pause then two more flashes (code 12, no RPM and is normal). The MIL will flash this code a total of three times, then proceed to the next code.

http://www.troublecodes.net/GM/

Engine control diagnosis starts with retrieving codes, undertanding what it takes to set the fault, following trouble trees and knowing what normal readings are. It does NOT mean read a code and hang a part.

I'd start by getting a scanner, measure and compare the ECT readings. If you watch the scanner, you will also know when the tstat opens at around 190. Good luck.

newbsauce 10-08-2009 01:17 PM

Quote:

Originally Posted by 47_47 (Post 337940)
This truck has OBD. I think Autozone can read only OBDII codes. The OP did not state if the SES light is on, usually that is the first complaint stated. To read the codes on this truck, turn the key on and jumper pins A & B of the ALDL. You will count the flashes of the SES light. You always will read one flash, a brief pause then two more flashes (code 12, no RPM and is normal). The MIL will flash this code a total of three time, then proceed to the next code.

http://www.troublecodes.net/GM/

Engine control diagnosis starts with retrieving codes, undertanding what it takes to set the fault, following trouble trees and knowing what normal readings are. It does NOT mean read a code and hang a part.

I'd start by getting a scanner, measure and compare the ECT readings. If you watch the scanner, you will also know when the tstat opens at around 190. Good luck.

Good information. Not sure about the setup of your car, but rather then using the scanner, I simply grab my upper radiator hose. There is a huge temperature difference when the Tstat opens :) Granted, I know my cars normal operating temp, and trust my gauge.

Clutchcargo 10-08-2009 01:57 PM

How do you know it's running rich?
Is the check engine light on?
Pull the codes for a start.
My guess would be the O2 sensor.

47_47 10-08-2009 02:07 PM

Quote:

Originally Posted by newbsauce (Post 337941)
Good information. Not sure about the setup of your car, but rather then using the scanner, I simply grab my upper radiator hose. There is a huge temperature difference when the Tstat opens :) Granted, I know my cars normal operating temp, and trust my gauge.

Yes this would tell if the tstat is opening, but will not give any information about the coolant temp the computer senses vs the actual engine temp. BTW this truck should have 2 coolant sensors, one for the gauge and the other for the ECM.

To the OP, with a scanner look at the integrator. Ideally it is at 128. With a rich running engine, the integrator will go down. Usually down around 100 I start looking for rich conditions.

tecate1987 10-09-2009 03:44 PM

truck running rich
 
ok, I havent checked must due to cold and wet weather.
But,

there is not check engine light on, it does work cuz it lights before starting engine. It has obd, and my scanner is obdII, I cant plug that in.
Also, truck is plow truck and not street legal to take to autozone.
Oil smells fine. going to try to check thermostat for sticking, and also pull vacuum line off fpr to check for extra fuel.
thanks for all the help so far, if I run into more info I will provide and any other ideas are appreciated, thanks.


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