I just have a couple of questions for experienced Blazer owners. I've been constantly experiencing performance issues, and constantly fixing problems only to have new ones arise... so hopefully I will get this thing in optimal working order soon haha. (Disclaimer: I've made a couple threads about my Blazer in the past, but now I'm experiencing new issues. Please go easy on me here).

Ok, so first thing is that I have been getting the trap code "Multiple/Random Cylinder Misfire", although now it is typically only appearing while driving highway speeds up hills. I had this before, but as I recently had to change a bad fuel pump, I believe that was the biggest cause of those issues in the past.

Recently I have:
- installed new spark plugs
- installed new plug wires
- cleaned EGR valve (it was good)
- cleaned MAF sensor (it was good)
- Installed new fuel pump
- Installed new alternator
- Changed studded winter tires to all seasons

Misfires while idling and driving, acceleration issues, etc were very noticable lately while on highway. But today I just noticed my PVC hose had fallen off the intake manifold recently, so I put it back on. Improvement was obvious, but there's still an obvious murmur occurring. Below, in the first image, is one of the new spark plugs that we installed. I noticed today that it's sticking out and, while the wire is on it firmly, I'm wondering if this is normal placement on a 4.3L Vortec engine (instead of screwed in deeper). Buddy who screwed it in insists that's as far as he could get it. Just want your thoughts.

Secondly, I found a vacuum tube with a severe cut in it (photo two: the duct tape is covering the cut). It's by the ABS module, close to driver side of hood, but I don't think it's part of that system. This part of tube connects to a T-valve where one end goes somewhere under the ABS module. Just curious if you guys know what it's for?

Third question: let's say, hypothetically, some backyard mechanics installed a new fuel pump and SOMEBODY used duct tape instead of plastic clips to secure the fuel lines to the pump... and then the pump started pissing out fuel all over the road a couple weeks later. Would this screw up the fuel pressure regulator even if it was all fixed up?

 

#1 Make sure those are the right plugs and gap them correctly. Route your plug wires so they are not rubbing anything. From your pic it looks like they're touching the exhaust manifold. Put an ac delco cap and rotor on it. Other brands will cause a misfire.

#2 The vacuum lines in your pic are rotten. Take a small piece to match the size and buy more than you think you'll need. Then replace all you can see.

#3 Hypothetically. I'm assuming the glue from the duct tape that dissolved in the fuel would clog your fuel filter before it reaches the pressure regulator. If the filter wasn't replaced with the pump. It should have been.

Don't worry about people being hard on you here. This isn't that kind of forum.

 

#1: I gapped all the plugs. Plugs and wires were all top quality from chain parts store. My main concern is that #4 plug is sticking out more than I remember seeing the previous plug in that position, so I'm wondering if this is actually its normal position. Two of us were doing these plug changes in rough weather, and the other guy screwed this plug in. He said it was in there as best he could get it, so just want to know if it should be in further.

I'm planning to check out the distributor when I get some time. I had this Blazer for a year and previous owner never indicated anything about the distributor, so who knows how long it has been in there or what brand it is. I'll figure it out eventually, but I don't have the funds to just replace it outright.

#2: The vacuum lines aren't great but I looked them over and there was only that one issue there. I'm more concerned with what it's for then the quality of the wire. Specifically if it's for 4wd, cruise control, or some essential function. If it's just for ABS, not too concerned.

#3: The duct tape was around all the fuel tubes, not in them. The problem was that one eventually slipped off, and when I finally realized what was going on I got the right clips and secured them (good thing we cut that hole in the floor from the inside).

Not really looking to turn this Blazer into a performance cash crop or anything. All my friends have 90s Chevy trucks and cars, and while they all look like crap, they run like beasts with basic maintenance. My Blazer looks great, but performance-wise it runs like it is always hungover. I haven't found anything particularly wrong with it yet but I should be able to get to 110km on the highway without any problems. But I notice small things simply on idle, and it's tough to get this thing comfortably past 90km on the highway. There has to be some stupid small issue at play here that can be a simple fix.

Engine is only at 280,000km, should be able to get another 200,000km out of it if I keep it tuned up lol (Edited)

 

Here's a picture of that plug on my 99. Looks about the same as yours I think.

 

1. Far as he can get it doesn't tell us if it is cross-threaded or not. Pull the plug out and look at the threads. This plug can be started crooked by interference of a spark plug socket with the dipstick tube. Boot looks off to one side, but could be just an artifact of the photo. Are you certain the plug wire is on good? Shine a flashlight into the boot. Is the plug wire terminal shiny or is it burned black?


2. This hose goes to the vacuum reserve tank buried in the driver's inner fender, and spits off and runs through the firewall to run the HVAC controls. You need it to be good and hooked up to both.


3. No


Like was said before, make sure ALL the vacuum lines are good. If still problem, then replace cap/rotor with Delco and check all plug wires visually and with an ohm meter. Chances are this problem is electrical in my opinion. Pull all the spark plugs out again and inspect for cracks and bent electrodes. If all good, then check out the fuel pump per instructions at the top of the page. That's about all you can do without a proper scan tool.

 

Cool thanks

 

Lesmyer-

I have a BlueDriver scan tool. I understand it's basic features, but I could do more diagnosing with tips on what to do (as I'm not a mechanic I'm not familiar with many technical terms). I'd like to know how to measure: fuel mixture (ie, too lean), O2 sensor values, individual spark plug performance, etc..

I don't have a vacuum testing device, though, or I'd be checking PSI values. For the fuel pump pressure, do you have to check right on the pump?

And no, I didn't install a new fuel filter with the new fuel pump as we were in a hurry. But I just had my fuel filter replaced a few months ago and I only put like 5km on it. It's likely that putting in that new fuel filter inevitably killed my old fuel pump, but it should still be ok.

 

I should also mention some other things. It's definitely vibrating more than it should be at low speeds. Most of all, there's definitely less of a smooth transition when it shifts gears. It's almost jumpy (hesitates then accelerates). Transmission fluid seems fine.

I do have my "SERVICE 4WD" light come on and off a lot, but it's always been like that. I just avoid using 4wd as it barely works anyway. I'm pretty sure there's and electrical issue with the automatic switch, but I don't think it really affects normal driving (or at least it didn't in the past).

Keep in mind that I bought this Blazer about a year ago and it had issues to start with, and I've been trying to kink them out when I can.

 

Just to update:

I decided to open up the distributor today. The gear clearly had a fair amount of play in it. The nodes for conducting electricity on both the gear and the cap had corrosion so I cleaned them up a bit and put it back together. The blazer was running noticeably better afterwards.

I will replace the whole distributor when I get the money for it, and I'll probably order an AC delco distributor since the usual parts store didn't have them. I'll probably post future updates just so others with similar problems can read about it.

 

You don't want an over-priced, plastic, problematic AC-Delco distributor body. If you're going to replace it, get one with a metal (aluminum) frame.

The folks on here seem to love the Skip White distributors. Check my recent threads and you'll see a bunch of folks running them, and at least one link to where to get it.

You do want to run an AC-Delco cap and rotor on whatever metal frame replacement distributor you get.

Excessive vibration and clunky shifts can be worn/broken motor mounts (and maybe the transmission/transfer case mount as well). Mine had that issue (among tons of other issues) when I got it. Everyone told me, "Don't buy cheap rubber ones, or even stock/OE rubber ones," but when I asked, "What should I buy instead," there were crickets chirping.