Misfires again

[LilYellowZQ8]

I have been chasing this down since last November and thought I found the culprit. I have changed out new plugs, wires, cap, rotor, MAF, TPS, ignition module and its still missing. A guy from work had acess to a Snap-On diagnostic machine and looked into the misfire history and found cylinders 3,4, and 6 were misfiring. Number 3 was the worst one with 13,000 plus misfires with 4 and 6 not too far behind. We also did a live data and found number 4 just missing away when you hold the rpms around 1,000 to 1,500. It doesn't mis at idle, but it does when the throttle is barely opened at idle or cruising speeds. My next thought would be bad injector(s). Someone told me that a good injector should ohm out at 11-13 ohms and anything more or less is possibly bad. Any thoughts? Is this a common problem for the "new" Multec 2 fuel injectors. BTW, its on an 03 4.3L(LU3) 4l60e S10

[Sparky2263]

I have fixed many of these type misses using a CarbonClean (trademark) fuel injection cleaning machine. Even after flow testing, they seem within specs. Even though, they get the cleaning treatment and good as new. That is one piece of equipment that's worth every bit of it's $3500 cost.

Most places around here charge $100 to do it. You'll think you picked up 20 hp if you can find someone with that machine.

http://www.motorvac.com/specs/CarbonClean_MCS245.pdf

[Maximus]

Those machines are the best by far.I can't afford one for the casual use I would need it for but there are 3 shops here locally that have one and I use them on any new vehicle I get to make sure the fuel system is as new as poissible.You would be amazed the difference they can make.Especially on a car that has a lot of build up in it.Night and day difference.

[Outlaw178]

Mine was doing the same exact thing I went to autozone bought seafoam and ran about 2 bottles in it and it's as good as new. No skip and no codes!

[LilYellowZQ8]

Ok, I had the injection system cleaned, but the misfire is still there. Tonight I wanted to check for any vacuum leaks around the throttle body and found none. I did notice that I have a light show going on. The wires, cap, rotor, plugs, module are all new, but I am getting a bunch of stray sparks coming from the wires close to the coil and cap. Could this indicate a bad coil? I am at a loss here so any more info would be helpful.

[nomaboy]

if you have the old parts i would put those on one at a time until you eliminate the miss

the fact that you see sparks proves the coil is working.

[Sparky2263]

Anybody close by with a scope? That would instantly reveal any ignition problems.

As far as injector cleaning, I specified Motorvac because it is unlike any others I have used (even GM's badass set-up I use for the CPI and MPFI). It really takes it 2 steps beyond anything else out there.

[LilYellowZQ8]

OK, new issue. Now I am going through caps and rotors. The tab on the rotor looks like its grounding out on something, but what? Cruising at around 70mph turning 2,000rpms it runs fine, but take it above 2,500rpms, the SES light starts flashing. I know its going to misfire because the torque converter unlocks and will stay unlocked. The problem is intermittent, but shows up every couple of days. I am at the point where I am going to get rid of it, if I can't find out whats causing it. Could it be the sensor inside of the distributor, or the distributor itself? Crank Sensor? O2 sensor? ECM temp sensor? Faulty coil? Thats why I love the PO300 DTC, it could be anything!!!!

[Hammer Head]

Are you still experiancing sparks up by the cap? Is that what's happening? If that's the case then maybe you have a cracked cap, dry-rotted plug wires and/or just not in all the way w/ the wires into the cap. Just my thought..

[Sparky2263]

Sounds like the distributor isn't phased properly. The distributor setting procedure is here somewherer. I posted it.

If the distributor is not set properly, the spark has to jump farther to get from the rotor to the terminal. Too far and it'll take another path. Also, one bad plug wire (high resistance) can wreak havoc on a cap and rotor.

[sammy]

I had a saturn sc2 (actually I had 2) that kept sparking (lightning crackles) from the coil packs around the ends of the plug wires. Everyone told me that it was a common problem due to dust etc. that created a path of least resistance along the surface of the wires and therefore weakend over time the insulation etc. I never got it under control before selling the car. I went thru 3 sets of coil packs and plug wires.
Good luck and let us know what it takes to fix it.
Open the hood at night and watch the show, set a camera shutter to stay open. I bet it would make a great picture.

[LilYellowZQ8]

This is the only thing I could come up with as far as a distributor write-up.
http://www.s10planet.com/forum/showthread.php?t=5943

One other thing I noticed was it looked like the spark was firing just past the terminal on the inside of the cap, almost like it was too far advanced/retarted( don't remember exactly where it was). Could that be another indication of something out of sync?

[Sparky2263]

http://www.s10planet.com/forum/showthread.php?t=4916&highlight=distributor+procedure

That's it. Prolly should make it a sticky.

[THA_BAD_ONE-0]

Sounds like the distributor isn't phased properly. The distributor setting procedure is here somewherer. I posted it.

If the distributor is not set properly, the spark has to jump farther to get from the rotor to the terminal. Too far and it'll take another path. Also, one bad plug wire (high resistance) can wreak havoc on a cap and rotor.

I had this problem on my brothers 95 blazer, he had the dist. timing off and it kept throwing codes. but it never misfired? but set it in there right on time off it went

[LilYellowZQ8]

I didn't remove the distributor, only the cap and rotor. Is it possible for the CMS and the CKS to get out of sync some how? The problem started when the starter wouldn't engage or even spin because of a bad ground between the block and starter. Is there anything there that might have caused it? I don't think I tried to rotate the crank by hand, but I can't remember that far back. Would the knock sensors have anything to do with it? I do have an exhaust leak around the doughnut gasket, but only at start-up when cold. Is there anything else that could possibly be the cause of it? I have a new set of Taylor Thundervolt 8.2mm wires on order, so I can make sure thats not the cause.

[Sparky2263]

Bad ground between block and starter could have torched some smaller grounds. Ck. voltage drop from the negative post to any sensor ground and make sure it's less than a tenth of a volt. You've got a real problem if it's over 2 tenths.

[LilYellowZQ8]

What kind of problem are we talking about? Misfire, ECM damage, melted grounds? I will check tomorrow at work since I don't have my Fluke with me.

[Lastwagen]

OK, new issue. Now I am going through caps and rotors. The tab on the rotor looks like its grounding out on something, but what? Cruising at around 70mph turning 2,000rpms it runs fine, but take it above 2,500rpms, the SES light starts flashing. I know its going to misfire because the torque converter unlocks and will stay unlocked. The problem is intermittent, but shows up every couple of days. I am at the point where I am going to get rid of it, if I can't find out whats causing it. Could it be the sensor inside of the distributor, or the distributor itself? Crank Sensor? O2 sensor? ECM temp sensor? Faulty coil? Thats why I love the PO300 DTC, it could be anything!!!!

Dude I am right there with you. I have almost the same problem. I have been getting a P0300 code too. I also have done the plugs, cap, rotor. Next is the coil and the injector cleaning. Something tells me that neither of those are going to fix it....... I am at the point where nothing seems like it will work. Although my misfire has been happening at cruising speed around 2000-2500rpm with slight pressure on the gas to maintain speed. Let me know if you make any progress. I have been troubleshooting this situation for a while now

[LilYellowZQ8]

I have been running with the MAF un hooked for about a month now, and the torque converter stays locked up at cruising speeds. Now last night I was pulling a loaded enclosed trailer when it started missing whenever I would give it more throttle input when on the highway. I also noticed that when going WOT for about 2-3 seconds, it would do it. I probably need to clean the air filter next and get a new MAF. Any ideas Sparky?

[Lastwagen]

My truck is at the dealer.....ugh. I'll let you know what they tell me.

[LilYellowZQ8]

Yayyyyy, its still there!!!!! Replaced the plugs, wires, coil, cap last night and its still misfiring. I replaced my Taylor wires because they were arcing to rubber hoses, i.e. heater hoses going to the heater core right by the distributor. I put on a $30 set of Bosch wires and guess what, they're doing the same thing. What would cause the wires to arc to non-conductive items? Static? Wiring? bad ground somewhere? I'm about ready to get me a Tacoma if I can't catch this gremlin.

[Lastwagen]

It turns out that the cranks position sensor and the IAT sensor was prolly it. It makes sense because it does it a lot when it is cold ambient temperature.