Intermittent miss at light load. - Page 2

blazes9395 · #16 09-20-2006, 11:18 AM

If you have arching, you have to get that fixed first. Insulating it from other things is not fixing it, it should have no arching.

534BC · #17 09-20-2006, 12:31 PM

Ya, my new coil is on the way. Insulating it was merely an attempt to see if the arching was the intermittent miss, it was not.

534BC · #18 09-24-2006, 04:12 PM

Quote:

Originally Posted by muddog321

I had replaced my cap/rotor with Wells and in 1 year it was arcing inside the palstic casting between wires (not visible even looking at the inside) so just a point to consider - many aftermarket parts are not equal as I chased and traced this for a few days - a simple cap/rotor change cured and only way to tell for sure. If all is OK you replaced already then look at the crank sensor ($60) and ign module (in dist on yours $75).

Thanks man, I did price a Wells coil. It seemed to be a cheap one. I was advised against the "cheap" coils. Lots of aftermarket stuff in junko compared to OEM.

534BC · #19 09-24-2006, 04:18 PM

As I'm learning about scanners and these computer stuffs I think I may have narrowed it down a bit more. Someone chech me out and see if this makes sense.

As I take off with a cold engine it runs without missing a beat, I hold a constant speed (42-65 mph) and the very second it goes to "closed loop" is when it falls apart and starts mis-firing. I notice it is exactly as the converter locks up.

How does one tell when it is in closed loop without a scanner? This is new term for me. Can I force it to stay in open loop so I can drive it and verify that it is not missing in open loop?

BlazerLT · #20 09-24-2006, 04:59 PM

The check engine light must be one when it does this.

I would still scan for codes, not all of them trip the light to come on.

534BC · #21 09-24-2006, 05:35 PM

No, the MIL is never on. Hasn't been on for a year or so. I may get it scanned for free or gwet the scanner myself. I am finding out it can have codes or pending codes with no light.

One shop wants it with the old coil on it, As son as my coil gets here I will install it and drive crap out of it, lol.

534BC · #22 09-27-2006, 02:01 PM

I kick my own butt, I put the new coil on and no difference, same missing, same lightshow around the coil. Most of my stray sparks are around the coil wire itself so I made another new one and will try it out.

cleanshavenrsx · #23 09-28-2006, 10:12 AM

go to somewhere that sells standard ignition they give a lifetime warranty with everything caps rotrs wires coils everything even o2 sensors...

534BC · #24 09-28-2006, 10:16 AM

I did have lifetime belden wires on there, but changed them all with the cap and rotor and plugs cuz it all had a lot of miles. The wires were free, but now that I think back the new ones looked kinda old, like they had been seting around a lot. Maybe they were very old stock.

I have scanner and some software on the way to help me, I will also check under dist cap to see spark relationship to post.

534BC · #25 09-28-2006, 08:51 PM

Coil wire , no different. No trouble codes present according to AZ, but I finally figured out something.

It only misses (at light throttle) between 5 minutes and 20 minutes of running. I think this is why I had a hard time making it act up and thought that a new coil "fixed" it or whatever I seemed to try magically fixed the problem. 95% of my drives are exactly 15-20 minutes long.

I assume that it is going to "closed loop" at around 5 minutes, but what happens at around 15-25 minutes?

I'm going to time it to see if it will repeat. Once started for the day, it will run perfect all day long as long as it is not allowed to cool off all the way. It seems to be time related (or temp) can't think odf anythinjg else can anyone else think of what happens at 20 minutes or so?

BlazerLT · #26 09-28-2006, 10:27 PM

Cpi Injector Leaking!!!

534BC · #27 09-30-2006, 06:42 PM

I'll be checking into that soon. A lean cylinder will cause a spark to "not jump the gap" or to not fire at all. One thing is for sure , it is getting worse and I am geting real good at making it act up (not like before)

One test I did do pointed to the back 3 cylinders and after seeing some nice pics here on the forum, they are all a common plenum, hmm.

The problem reminds me of increased timing advance pulling the spark away from the correct distributor post. I have my old cap and may make a "cut-away" cap to check it and see. It has also been suggested that the shaft/gears can be worn causing the rotor to pull away from the correct post (like maybe wobbly or run-out, this a new one to me, but was a possibility from a good shop)

BlackBlazOn · #28 09-30-2006, 08:00 PM

had the same problem on my 97 LS 4.3L 4WD. new plugs and wires didn't do the trick so i cleaned off the contacts in the cap/rotor and added dielectric grease to them. also cleaned out the EGR. problem solved.

BlazerLT · #29 10-01-2006, 02:17 AM

Quote:

Originally Posted by 534BC

I'll be checking into that soon. A lean cylinder will cause a spark to "not jump the gap" or to not fire at all. One thing is for sure , it is getting worse and I am geting real good at making it act up (not like before)

No, you are wrong, fuel mixtures don't control any part of how the spark jumps across the electrodes.

Quote:

Originally Posted by 534BC

The problem reminds me of increased timing advance pulling the spark away from the correct distributor post. I have my old cap and may make a "cut-away" cap to check it and see. It has also been suggested that the shaft/gears can be worn causing the rotor to pull away from the correct post (like maybe wobbly or run-out, this a new one to me, but was a possibility from a good shop)

What, advanced timing do what?! Seriously, where are you getting these ideas from?

You have a fuel problem, fix it and stop focusing so much on the cap and rotor and coil if they were replaced.

534BC · #30 10-01-2006, 12:17 PM

A lean mix, advanced timing, higher cylinder pressure can all cause a misfire. A rich mix is easy to fire, a lean mix is much harder to fire.

Setting the cap/rotor relationship at a specific advance point and then advancing or retarding spark starts to pull the spark away from the particular post. Advancing it will cause the spark to lead the post, retarding it will cause it lag behind and jump backwards towards the post.

In extreme cases such as low compression blower apps where the range of advance is very great from low vac high rpm and a lot of advance to high boost and low rpm and not much advance causes one to set the cap/rotor relationship to the hardest to fire spot (high cylinder pressure)

The problem shows up mostly on adjacent cylinders causing a cross-fire and back fire with small diameter distibutor caps. My problem never backfires, and I assume it is because there is never an adjacent cyclinder with mixture to fire, it just jumps out to a ground somewhere on the engine, another wire, or within the cap itself and simply shows up as one missed spark.

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