I have a 2000 Blazer 4 door 4x4. Last week I was driving down the highway and when I hit 60 out felt like I lost all power, the engine started sputtering and my engine light started flashing. I thought it was my fuel pump. Towed to my mechanic. He checked the fuel pump and everything worked great, had power and good pressure. Checked Engine code it said multiple cylinder misfire, three cylinders were misfiring, he replaced the distributer cap and that fixed the misfiring except in cylinder 1. He checked the spark plug and it was completely black, he said that means it's getting to much fuel, then he checked the injector in case it was stuck open. The injector was perfect, he replaced it anyway to see if it helps but it didn't still misfires, now he says there's no other reason it should be misfiring except there's a problem with the cars computer and that it's making the injector put out to much fuel but he seems unsure of it. Please help me if there are other explanations besides replacing the computer. I really don't have $700 to pay a dealership to program a computer for me.

 

I doubt it is the computer and if you are up for a challenge, this recent thread will guide your way through diagnosing the 0300 multiple misfire code:

https://blazerforum.com/forum/engine...rogress-90856/

Two things though:

1) You are going to have to work for it! (or your mechanic will costing you lots of $$)

2) Les's bark is worse than his bite (but refer back to #1)

The problem can range from a simple fix to needing to rebuild the engine... Good Luck!!

 

Shops that want you to go away (or ones with no diagnostic skills) often diagnose a PCM problem, knowing that the cost will probably drive you away. IMHO there is very little chance the PCM is causing your problem. In any case your current mechanic is not going to do you any good so don't take it back to him. He has had his chance and has pretty much thrown up his hands.

So first thing I need to know is if you are committed to working on your vehicle and fixing this yourself (PO300s are seldom easy to diagnose and can involve a lot of time/testing) - or if you need someone to do it for you. Nothing irritates me more than someone who won't do all the indicated testing, or makes up testing results, or gives up easily. The guy in the linked thread was an 81 year old that followed through to the conclusion of a major mechanical problem with a couple of bad cylinders (per leak down testing). He was a joy to work with. Chances are that your problem is completely different.

If someone else is going to do the diagnostic and repair work for you, then you need to find someone with true diagnostic skills and the equipment to work on your vehicle. Here on this forum we don't intend to help an owner tell a shop what they need to do. That would simply never work. A given bet is that a mid to large size dealer has at least one technician that is an expert at this type of diagnosis, and that they have all the equipment and factory documentation required. Non-dealers can have the expertise and equipment, but tend to be more of a crap-shoot - after all they can always say take it to the dealer. If I sound like an ex-dealership technician, so be it. I am one. All my dealership experience was before OBD2 (1996), so I have been playing catch-up during the last year since I bought my 2001 Blazer as a Winter vehicle. I never dreamed I would have to work on my 65,000 mile creampuff as much as I did. Now I have fully bonded with it and drive it all the time. I truly enjoy it and find it extremely comfortable.

If you choose to proceed yourself, and since you are talking about a remaining sooty plug on one cylinder - start with the fuel pressure testing sticky at the top of the 2nd gen forum. This is how you tell if an injector or fuel pressure regulator is leaking gas (in addition to verifying correct fuel pump and regulator operation). Don't shortcut anything and do all the tests indicated. You can borrow a fuel pressure gauge (with deposit) at your local parts store, and the other things you will need to obtain are in the sticky. Then return and report results of all tests.

Also suspect is the ignition system (because of your comments about ca fixing some misfires) , but in your case I believe you should start with the fuel system and competely verify its operation before moving on. Note no parts replacement required to do this verification! Just work!

 

I would like to do this myself, I'm not the most mechanically inclined person but i can figure out my way around with a little guidance.

 

Alright thank you I will start there, probably get to it tomorrow and I'll post results

 

Atta Boy! (or Atta Girl!!)

 

I think I may have found the culprit! What's your guys opinion on this idea. I've been reading around and everybody says always use AC Delco parts. They said that they had misfires and replaced distributor cap with a different brand and they then only had a misfire on cylinder 1. Once they replaced it with a Delco cap it worked great, I called my mechanic and he said they just used a Napa distributer cap. Could that likely be the problem cause the misfire?

 

Great, and if it's important to get things fixed ASAP and you have an 1-2 year old Android phone or Tablet available, then you may want to go ahead and get the BAFX Bluetooth OBD2 adapter and Car Diagnostic Pro coming, both from Amazon (about $35 total - don't substitute).

Old versionof the app was named Gar Gauge Pro and is found on Google Play store. New version of same software is named Car Diagnostic Pro and is found on Amazon. Developer is having trouble getting Google Play to update like he wants. As far as I know it is the only inexpensive scan tool that will do CMP retard. Either version will work.

Know that checking CMP retard and other things will be the next step if no fuel system problems are found.

 

It could be that your remaining problem might be the CMP retard setting and/or distributor gear wear aggravated by a less than optimal distributor cap. New distributor cap could potentially temporarily cover up a problem, only to have it come back in a little while (or the new cap could truly be the cause - IMHO doubtful) - but it's all pure speculation without solid testing.

However, you have told me that the spark plug was black with carbon so we are going to begin with the fuel system, even if it looks difficult to do. Usually people take one look at the fuel tests and immediately start trying to avoid doing all of them by latching on to anything else they come across. Just know there is a lot of unsubstantiated misinformation out there.

Do the fuel system tests and report. We're not going to play the typical guessing games based on a someone said replacing this part fixed his. Diagnosis needs to be logical and complete - otherwise I'm out and don't intend to waste my time trying to drag you back on track. Fair enough?

 

Fair enough, sorry I was proposing the idea in case any of you had heard of that being a common issue. I will get the fuel gauge and do the fuel tests.