OT chevy s 10 problems

Anonymous-0

Well-known Member
Hello. I've got an 88 chevy s10 with the 4.3 engine. Its been in the family since new. It has been running rough. I hooked an OBD I code reader to it and it is loaded with codes. Actually 11 of them. There is no way all of that stuff is bad. I checked the battery and it was low. Used a hydrometer and found two dead cells, the others were good. Replaced with a known good battery before checking for codes. Any idea on where to begin? Thanks
 
Clear all codes from the computers memory. Run it till the CEL comes on then read codes again and go from there.
 
Need more info. What are the codes? The lowest numbered code is the one the needs fixed first. Does it run the same all the time or changes with engine speed or load. Define running rough. I would start with a tune up if that has not been done recently.
 
Bobpa,

Perhaps a look at the EGR system is suspect. For an experiment, you may wish to block that off with a gasket and sheet metal and see what happens.

D.
 
As previously stated, erase the codes, and run until the MIL lights up again.

BUT FIRST...check over the basic engine. Plugs and their condition/age. Distributor cap and rotor. Secondary wiring (spark plug wires). Be sure that the engine is running on ALL cylinders. A compression test may also be advised. And be advised:

THERE IS NO SUCH THING AS A TUNE-UP!!!!!!!!!

Look it up in the dictionary. To tune means to adjust for peak performance or efficiency. Everything that was ever adjustable in the "old days" has been replaced by electronics. There are no points, therefore no dwell adjustment. Timing is synthesized by the PCM. No longer adjustable. Mixture, choke, and fast idle settings were part of a carburetor, which has been replaced by injectors. Nothing is left that is "tuneable" in modern engines of the last 25 years or so.

The garage that offers to sell you a "tune-up" is ROBBING YOU!!!
 
codes are
14 coolant sensor
31 cam sensor
32 electronic vacuum regulator
33 map sensor
42 electronic spark
43 electronic spark control
51 computer
52 ecm fault
53 system voltage to high
54 fuel pump circuit fault
55 ecm fault

that is about everything under the sun. The truck runs sort of rough at idle. It smooths out when driving but after about 20 mins of driving will run real rough. thought maybe it was like something was breaking down after it heats up.
I hit the erase button on this code reader but doesn't erase like with the OBD II vehicles. How would I erase the codes? I thought when the battery was disconnected would do it but not.
Thanks
 
I forgot to mention the old girl doesn't have any of the warning lights working anymore on the dash. That is why I couldn't use the old reader I had that read the blinks on the dash light. Got a new hand held unit to read.
 
What you need is an older scan tool that will let you read the sensors live. I have several of them that I have accumulated over the years.

The codes you list are hard faults. That means that they are present at the time of the test. It sounds as if you have a bigger problem with wiring harnesses and connectors. I might suggest that you start by unplugging them one at a time and looking for corrosion, broken wires, and pushed out terminals.

You are correct in that codes are not erasable as they are in OBD2. As I think about it, it occurs to me that your Vref (reference voltage) is not right. The system (sensors mainly) operate on a 5-volt reference voltage. Actuators usually operate on 12 volts. I would start by checking Vref on the TP sensor first, and then on the MAP sensor. If there is a discrepancy, trace back to the ECM and check for a corroded, pushed out, or broken connector or terminal.
 
Grab the wiring harness, at the back of the motor, near the firewall, and pull, twist, back and forth. Then check if there are more or less codes showing...
 
I had that happen on a 1986 and after weeks of trying everything under the sun, it turned out to be a broken ground wire from the rear of the engine to the firewall. I think the sensors on the engine were not comunicating with the computer.
 
I had a bad battery mess up a Firebird for a few days,just wouldn't run right,finally thought it was slow starting,put in a new battery and in a few days it was running fine...most GM s will reset themselves if you disconnect the battery and leave it disconnected for at least a minute..the computer will then reset when you connect the battery and all of those codes will disappear..have seen it many times
 
With your list of codes and further discription, I agree with the other posts that the weak battery could have been the cause of all your problems and you will find out in a few days. If you still have a problem then check grounds and connections. As you stated "that is about everything under the sun" is not far from the truth. I only know of 3 things that can cause that broad spectrum of codes; 1. bad/weak battery, 2. bad ECM/computer (unlikely) 3. Broken/poor connections (most likely bad grounds)
 
Thank you all for your help. It gives me a place to start. I wondered about that battery. I have a 14 Silverado that had all sorts of codes and dealer replaced the battery. (It was only 3 months old!). I'll try to clear the codes and look for grounds first and go from there.
Thank you.
Bob
 

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