got an issue with my 2003 S10

[timothymoore]

at school in computerized engine controls class before finals , we put the scan tool to my truck it pulled 7 codes or so.

i have to fix the 02 sensor (got it havent installed yet)

MAF was replaced with a good one

I put new plugs, wires, distributor cap and rotor due to a P0300 random misfire

I got a thermostat i have to put in ( putting in a new water pump as well)

and im gonna put in my 2-3 shift solenoid it needs cause it wont shift by it self. i have to shift the auto trans manually.


but here is my problem: after replacing the plugs, wires, cap and rotor for the random misfire, i deleted the code off of my computer with my scan tool, and ran it for a bit afterwards and the random misfire code came up again and its boggling me. im thinking the ignition control module is going out or just about there. i also have a vacuum leak right above the transmission that i cant get to due to not having proper tools or place to work on it that is affecting the idling of the truck.

my question is about the random misfire: after replacing the said components to remedy to random misfire and then the code came back up again, would that be from the Ignition control module going bad? thats what im leaning towards because if the coil it self was bad that the distributor wouldnt get any juice i wouldnt think. thanks for the inputs guys.

[Squall67584]

Dumb question, but how's the battery? Had a civic long time ago that acted like it was misfiring and after replacing the ignition components, I figured out it was a dead cell in the battery. Wouldn't hurt to check.

[timothymoore]

battery is good with a full charge.

[Ron]

Random misfire is detected by crankshaft rotational variations (not 'sparks'). The vacuum leak is probably the cause.

If you have another leak and if your scanner will let you see which cylinders are misfiring, you can often chase it down by knowing which bank/runner/cylinder they are near. Other common causes for those engines are EGR defective or dirty (HIGH TEC DIAGNOSTIC TIP- Take a long bar or extension and hold it to the base of the valve and rap it hard a couple times with a hammer, but be careful not to break it. If the engine smooths out, clean or replace the EGR), fuel pressure/contamination, or anything that may cause the variations...I once had a bad drive belt setting P0300 on a customers car. He had a bearing lock up and didn't change the drive belt.... Skeptic, we put the old one back on and it set it again...

FYI- When getting a lot of different codes, often some of them are "false" due to something that set another code (eg a misfire code due to a bad spark plug(s) will allow raw fuel to get to the O2 sensors, which makes it think it is running rich and set a code, and when it tries to compensate, it screws up the other cylinders (lean).... You'll learn the pecking order ;-)

Also, if the vacuum leak is from a line that goes to the transmission it could cause the up-shift problem depending on the type of transmission installed (some use electronics instead). If so, fix this first as you may not need the solenoid.

[timothymoore]

thats a good explanation but i have had the random misfire before the vacuum leak occured . i could stand to get a new serpentine belt though, mines not looking good when it starts up, it seems like it idles smooth but when i give it throttle it starts shaking which made me think vacuum leak and then i heard the leak.
only reason i replaced all the plugs wires and such was for the fact my truck has 135k and all that stuff was original and thought it would help the misfire

[Ron]

I'd fix the vacuum leak, clear the codes and scan it again. Post them here if you want....

Does the scanner show individual cylinder misfire counts? ...what kind is it?

[timothymoore]

I'd fix the vacuum leak, clear the codes and scan it again. Post them here if you want....

Does the scanner show individual cylinder misfire counts? ...what kind is it?

ron, i took your advice and bought a serpentine belt for her. i planned on doing it anyway but forgot to buy one when i bought my other parts, and the random misfire is now gone. only codes i have left is the 02 sensor. my scan tool is an Innova CanOBD2 3120B. im not sure if it shows individual misfiring cylinders but i figure it does if it comes up with the PO300. i just re-read your previous post about cylinder misfire counts. i havent got that far into the scan tool myself but it has software that came with it so i will findout tommorow hopefully

[Ron]

I don't think the 3120 will show individual counts, I'm not familiar with the "B" model, but I doubt it.

A P0301 means cylinder #1 has misfired a set number of times within a set amount of time.
A P0302 means cylinder #2 ....
A P0303 means cylinder #3 ....
etc.
A P0300 means multiple cylinders have simultaneously misfired a set number of times within a set amount of time -- It will not give individual P3xx codes unless they happen during different time periods.
So, usually:
If you pull plug wires 2 and 3 and start the engine, you get a P0300.
And if you start the engine and pull 2, plug it back in, then pull 3 and plug it back in, you will get a P0302 and a P0303.
But, if you pull 2, wait, then 3, you get P0302 and a P0300, which is why counts come in handy ;-)