What do I fix now?

[Bobby D.]

I own a 2002 TRAILBLAZER. I am out of work so I used You Tube to stretch out the last of my money. Didn't think I could do it, but it was actually easier than I thought.
The waterpump was replaced, while doing that I checked the thermostat, it was fine. I changed out #4 coil pack, replaced the MAP sensor, replaced the battery, replaced the air filter, pulled the throttle body off and thoroghly cleaned it, replaced the catalytic converter and checked all the fuses. The problem still persist though, sputtering start off the line and rough idle and flashing SERVICE ENGINE SOON and #4 misfire. The clip on #4 does not CLICK, but still attaches. Any other ideas?

 

[djthumper]

Your thoughts are all over the place on this and you haven't provide a lot of information. how do you know that cylinder 4 is misfiring? How many miles do you have on the vehicle? Did you try moving the #4 coil pack to another location to see if it followed? What codes are you getting? Have you reset the codes? How long has this been going on? Did you reset the PCM?

It sounds to me that you have replaced a lot of parts and chasing the a problem that has not changed. You need to do some real troubleshooting and get to the root of the issue. What started this whole thing?

 

[TollKeeper]

With all that done, a compression check, which should be able to be done for free with rental tools. The only thing left after that would be to swap or change a fuel injector. I'm sure you could ohm check the injector, but that doesn't always give you the full story unless you flow check it.

And I agree with thumper.

 

[Bobby D.]

304 code came up before and after the replacement.
I did not move the coil, I figured it was already bad.
The truck has about 186K on it.
I pulled out the #10 to reset the PCM, but I do not know how to clear the codes without a code reader of my own.
It all started with a water pump going out. And I'm abusive to my second car and I was getting her ready for winter by spending time on her.
What do I do the compression test on?
I used You Tube alot and watched hours of video. I only did what I knew was bad or needed cleaning or replacing. And I don't know where to find the injectors, I also used injector cleaner

 

[Bobby D.]

Before I did anything I made sure these items were bad, the car ran rough before the water pump went out. There was just a laundry list of things to tackle, so I did my research.
Thanks for your input, anything you relay will be appreciated.
I did learn about pulling #10 and #28 to reset the PCM and turning the key to on for a couple of minutes before turning the engine.

 

[TollKeeper]

 

[Mounce]

While you had the coil out did you at least check the spark plug? Wouldn't hurt to swap it to another cylinder to see if it follows.

 

[hockeyman]

Before going any further, I'd buy a scanner and see why the CEL is flashing. A steady light is bad enough, but it's basically yelling at you when flashing.

You've spent a lot of money on parts that could have been good, but do yourself a favor and buy a scan tool. The uses for it go well beyond your truck.

Harbor Freight sells them for about $50. If you have an Android or iPhone, you can get the ELM327 scanner on ebay for about $25 and download the Torque app for compatibility. Many here, including myself, have that scanner and app. Works great!

 

[Mike w]

I had the same problem turned out to be the coil but it could be an injector or a problem with the valves or as simple as a spark plug. I have seen new coils bad straight out the box The reason for the compression test is to verify that the valves are not messed up which has been a common issue on our trucks we can only give you troubleshooting suggestions to find a fix. Did the truck ever overheat from the bad water pump?

 

[Mooseman]

Forget HF, you can get either a regular scanner or a bluetooth interface (for Android) for $15.
https://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias=aps&field-keywords=obd+scanner

For the coil, since you replaced it, we will assume it's good. You did mention it didn't click when plugged in so check the connector thoroughly. Check that the voltages are getting there. Pink should be 12v+ with the key on and black is ground. The third wire is the signal wire and would need specialized equipment to check.

An injector swap is not easy as you would have to remove the intake manifold. If everything in the ignition side is good, do a compression test as it could be misfiring due to low or no compression. If that checks out, I would recommend that you take it to a shop that can do an injector balance test. They would need either a Tech 2 or a high end Snap On scanner (i.e. Solus) to do this. This video shows this test as well as the voltage check afterwards. Ultimately, in this case, it was a broken wire.

 

[Bobby D.]

Thank you for the input.
The MAP sensor was cracked, that is why the part was replaced.
The catalytic converter was clogged and made noise.
I did take my time with replacing parts.
I will keep moving along with the input given.

 

[AzTruckGuy]

If those coils are original just replace them all, mine had 98k miles when I had one that was bad and I just replaced them all than to deal with engine issues. I replaced all 6 of mine for around $75 on Amazon, so far so good on them with a lifetime warranty too