the 2nd gen forum is here - a different sub-forum of this site. Some of us tend to hang out in different places. 2nd Gen S-series (1995-2005) Tech - Blazer Forum - Chevy Blazer Forums

Avoid any threads that don't instruct you to first check for vacuum leaks and verify fuel system and ignition system before trying to chase a PO30x in earnest. A lot of mis-information on the Internet. You will need a scanner capable of reading cam retard, a fuel pressure gauge, and some misc fittings to block the fuel lines. Get loaner pressure gauge from local parts store, an inexpensive scanner that will do cam retard is Car Gauge Pro for Android with BAFX Bluetooth OBD2 adapter from Amazon - about $35, and the sources for fittings required are listed in the testing fuel pressure sticky at the top of the 2nd gen forum.

Hint: A vacuum leak from pulling hose off vacuum storage cannister inside rear of driver's inner fender during removal/reinstallation of the intake manifold seems to be a common recurring problem. You might want to check this before you get started.

Thanks Les Myer for sticking with me!!
 

I just downloaded Car Gauge Pro on my new smart phone that the kids gave me for my birthday a few days ago. I have the BAFX Adapter ordered and should get it by next Tuesday. I did the misting test a few minutes ago and found no sparkies. I took it for a 5 mile 50mph test drive this morning and no service engine light came on. I hooked up my Actron CP9580A and it had P0300 "pending". I thought it ran really good. No hesitation, plenty of pep. I feel I am getting closer. Thanks again. No more news until Tuesday.

Good choice, the ability to read CMP retard will help a lot! Let us know when you get it. It doesn't sound like your misfire is very severe, so I think that is a good sign that setting the CMP retard might just fix your P0300 problem. Still we will need to check the distributor gear for wear and other things, especially if the CMP retard is off significantly.

Use the CMP Retard with the single asterick after scanning the PIDs for your vehicle under Powertrain. You can save the scan to a file so you don't have to scan them each time, and so that all the Powertrain PIDs can appear when not connected to the vehicle (useful for building custom gauge screens). Here is one custom gauge screen that I have. CMP Retard, a misfire counter for each cylinder, coolant temp, rpm, & MAP sensor as digital gauges. I wish the digital gauges were smaller and not round with just only the digits and label so they are easier to place on the screen, but that's the way they are in Car Gauge Pro. Still useful to watch them all at once. Note that 20 scans/sec with 10 gauges on a screen will give you a refresh of 2 times/sec on all things including the misfire counters (so they can seem a bit jerky if counting up rapidly and cycling back to zero) . If you want things faster, you need to reduce the number of things monitored, or increase your refresh rate. OBDLINKMX bluetooth will get you 30/sec but think that will not be very noticeable. The pricier Windows software with USB OBD2 adapters are in excess of 100/sec if I remember correctly (light speed in comparison), but I find them much less convenient to use (I only drag them out when I need them).

https://blazerforum.com/forum/attach...ine=1444752438

http:// http://i1260.photobucket.com...pshshwtrwa.png

lesmyer...AMAZING TOOL
 

Got the BAFX adapter. Disappointed that there is no user manual available. At 81, I stumbled through and found the Cam Retard is 5.8. I am not sure what it should be. I did discover the misfires are all coming about equally from #3 & #4. There were more at idle than at higher rpm's. I suppose this means I should replace the plug wires and/or distributor cap?? I can't believe all the info I can now get for $33!! I haven't mastered getting the gauges on the screen. I was able to watch all 6 cyl misfires at the same time.


I said earlier the vacuum lines were intact. After checking again, I found the elusive line that you mentioned going to driver's side vacuum storage canister. I had not done any work on the left side and this short line was hanging under the ledge and concealed. I didn't notice any difference after hooking it back up. I think some of the lines need to be replaced. Some are soft and some are brittle.

Cam retard HAS to be "0" + or -2. Get that in spec and I suspect your po300 will be gone.

Glad you like the app. Yeah it sucks that there is no user guide at all. Actually I'm (independently) working on writing up a Car Gauge Pro user guide for Blazers because I think it's such a good deal for us. Hopefully enough info to get a person up and monitoring PIDs and making/saving custom screens and PID lists/profiles as well as understanding what it will and will not do on our particular vehicles.

You did use the CMP Retard PID labeled with the single asterisk? If so adjust your distributor to 0. Typically CMP retard values are off in the negative direction, presumably due to wear on distributor gear and stretch/wear of timing chain. Probably you will need to do some modification on the distributor hold down in order to do any adjustment. It is locked in place if never modified. Also fix any vacuum leaks or bad vacuum hoses and then see if the PO300 disappears.

A few misfires will be observed on the counters now and then in a normal system, but if not enough to trip a pending misfire code and it runs good then consider it fixed.

Plug wires and distributor cap can cause misfires, but probably not to be really worried about unless setting cam retard doesn't fix your problem. New ones don't hurt, though if you feel like replacing them. Use only AC Delco cap and rotor. Plug wires can be removed and inspected inside both boots at both ends for carbon tracking, the length of the wire inspected for burns and breaks - then checked with an ohm meter to be less than 2000 ohms. Should have some dielectric grease on the terminal at each end of each wire. Also watching at night is a good way to subsequently judge spark plug wire condition.

Did you say that you are 81 years old? If so, I hope to be like you at 81. My hat is off to you.

Let us know how things turn out or if you have any additional questions.

Les

Thanks to all.
 

81 is correct. I dont always act it. A big thanks to all for your good help. I am on a different errand of mercy now. I will get back to work on the Blazer later today. This vehicle is planned for a destitute family member. I think it can be saved.with a little more work.

I did use the cam retard with the single astrisk.

Almost there
 

I had to elongate the hole in the distributor clamp. Some said there was 15 degrees of movement available, but not so with this one. Anyway, the Cam Retard is now -0.5 I thought the car was running pretty good before this adjustment, but it now has more pep. I still get a few misfires on #3 & #4 when idling. If I increase the rpm's to 1200, they disappear. Also, the Service Engine Light flashed when idling, but when I took it for a test drive, the light went off within 1/4 mile and stayed off during the six mile trip. I still need to inspect the vacuum circuit. I would like a diagram to make sure I get every line. So far, I have not found one for this vehicle (2002 Blazer LS, 4WD, 4.3L). Perhaps I should now give everyone a break. Thanks again to all and especially the clue about the cheap Car Gauge Pro and BAFX adapter (can't believe only $34). Any other clues are still appreciated. Joe

What are the misfire counters getting up to (highest value observed?)

I would like you to confirm that the misfired detection system is working properly by inducing a dead miss in a different cylinder than 3 or 4. You can do this by removing a plug wire and grounding the distributor terminal so spark doesn't jump around inside distributor. In Car Gauge Pro you should be able to see the misfire counter for that cylinder count the misses. If it can't count the induced misses, then your other detected misfires are probably not real and the misfire detection system needs repair. My own Blazer had false misfires when seemingly running good, and I chased misfire issues around for a while in the wrong areas until I did this simple test.

If misfire detection is good, since you have already fixed the vacuum leak caused by the line being off of the vacuum reservoir - please post live short term fuel trims and let's throw the MAF sensor reading in there too while idling. Also same readings at 2000RPM steady in park. Should be able to confirm or deny any remaining vacuum leak severe enough to cause a misfire.

I think that's enough for now, but depending on what is found we will then continue with verification of the ignition system, followed by the fuel system.