Ignition question, No longer thinking ignition.... Options

[1bwilson]

So I lend my jeep to a friend for a few weeks and go to drive the celica and find it running rough. After a bit of investigation Ive found the im getting a very small amount of spark from wire #4. So I did the usual swap plugs, new wires, new cap, new rotor...... Nothing, still a weak spark. So weak infact that its not even igniting fuel. Im not excited about the possibility of a pinched wire somewhere in the harness and im even less excited about the idea that I may have to hunt it down. So before I start pulling things apart let me go over what I know it isnt and hopefully someone will see light where I cannot.

out of the 3 mains (fuel,spark and air) Ive already figured out its the spark.

Its only happening on the #4 wire

Its not the plug, wire, distro cap, rotor as I have replaced them all.

I AM getting spark but its very weak and at times not there at all.

The old cap had burn/spark marks on the pins accept for the #4 one where it looked almost new.

I cant see any pinched wires but that doesnt mean something has worked itself loose some where out of view.

An option I have is running a MSD 6a ignition (if that would bypass my problem), Ive had one sitting on a shelf for almost 5 years and I have yet to install it. The only problem is I dont know how/which diagram to use for the install.

/discuss

This post has been edited by 1bwilson: Aug 29, 2008 - 7:04 PM

[presure2]

check out the coil, bryan, and the wiring going to the distributor.

[DEATH]

Wouldn't this indicate a problem within the distributer itself since he's getting strong spark to #'s 1-3? If he's getting strong spark to the distributer and to each cyl but #4 I would think it must be internal to the distributer and not back on the coil which is providing enough spark for the other cylinders.
I really suck at explanations on things like this [But I can diagnose and fix them ] - Hopefully you understand my train of thought here.

[1bwilson]

This is where I fall short on working on cars, Ive always hated the thought of electrical work.

The coil is internal on a 95 correct? How would I check if theres a issue with it?

The wires plugging into the distro look good as do the ones comming from the alt but once they get into the harness wraping I cant see if there is any hidden problems.

[x_itchy_b_x]

coil would mean bad spark on all of them.

i would have said distro cap. one pin all corroded. but you replaced it. then id say wires, and plugs.

looks like the problem is with the distro itself. check all connections. sand them down and use dielectric grease on all the pins to ensure a nice connection that wont oxidize.

[DEATH]

Essentially that's what I was trying to say - I just suck at explanations for this sort of thing.

[1bwilson]

I hope its the distro and not the wiring... man I hate wiring

[DEATH]

Just like it doesn't make sense it's the coil - it doesn't make sense it would be the wiring. If you are getting strong spark on 3 cyls and the engine is stumbling like that it sounds like the distributer [To me at least - sounds like Itchy too]. You never confirmed you have the distributer with the coil built in - is that the case?

[1bwilson]

I have the stock 95 distro that came with the car. If pictures would help I can snap a shot of it.

[DEATH]

I got what I needed from your engine pic in your profile. I see no coil under your ignitor so I assume it is the one attached to the distrbuter which to be perfectly honest - I have zero experience with. I prefer the coil mounted under the ignitor cause it's usually one of the first things I ditch in favor of an MSD Blaster II.
Maybe someone with a 94-95 will have more info but my guess is distributer from the way it's acting.

[1bwilson]

Eww you looked at those old arse pictures? Theres been many changes since then. Alot better shots of the bay are in my 5sfte thread here.

[1bwilson]

New distributer..... nadda.... sigh.


Going to pull the injectors out and reseat them hopping that theres the smallest possibility that its seated wrong and soaking the spark plug. The only problem is theres no sign of gas leak so I dont believe its going to change anything. After everything with this car its hard to believe that a weak spark may be the cause of its demise.

Edit: Reseated and no change. Im at a loss as to what can be causing this. Ive swapped the plug out, replaces the distributer, rotor, cap and wires. Adjusted the timing and looked for any faulty wires in the harness (those I can see, havent cut into the harness).... Im about done with options here. Getting a new harness is about where I draw the line of worthless replacements (spent over $550 already replacing whats listed above).

Feel free to toss any ideas out there no matter how strange.

This post has been edited by 1bwilson: Aug 28, 2008 - 7:11 PM

[x_itchy_b_x]

time to go Coil on plug! direct fire ignition. sorry man i'm at a loss of ideas. maybe just a new coil to strengthen it? even though your others are ok? wtf?

[lagos]

how did you figure out that your spark was weak?

[1bwilson]

Thinking outside the box for a mement, say the spark is weak but not the reason its not firing.... I have air and gas Im certin of. I dont believe my rings are bad...

BTW tested the plug with the new distro and its a bit stronger spark but still its running like #4 is dead. I can literally start the car and unplug the the wire and the engine doesnt even blink.

[1bwilson]

how did you figure out that your spark was weak?

I started it and drove it the other day and it was backfireing when I let off the gas. I got home and looked up symptoms and the reasons for a backfire (google ftw) and concluded that I was passing gas ( ) into my cat somehow and it was igniting causing a backfire. From there I started with the small things like checking the plugs and wires, I realized that unpluging the #4 wire didnt even phase the slightly rough idle whereas the other 3 damn near stalled it (cause its actually dropping to 2 cyl's instead of 3). I thought maybe it was the plug so I swapped it out and still it idled rough and backfired. So I pulled the plug out again and tested its spark, grounding it to metal and starting the car. The spark from #4 is considerably weaker then the other 3. I replaced the plugs wires cap and rotor figuring it was one of them and nothing changed. Replaced the distro today and still no change .

Tomorrow I think Im going to swap the injectors... put the one from 4 into another spot and see if that changes the conditions.

This post has been edited by 1bwilson: Aug 28, 2008 - 8:01 PM

[Bitter]

do a compression test.

[1bwilson]

Thats something I'll do, I hope there isnt anything wrong with the compression though. The motor has less then 5k on the rebuild.

[Dr_Tweak]

Got your PM.

Since you've replaced all of the ignition parts on that side (dist cap, rotor, wires, plugs), so I would say that Bitter hit the nail on the head: Do a compression test.

An injector not firing will cause a dead cylinder as well, thought that's pretty rare.... put a mechanic's stethoscope on the injector and listen to see if it's clicking or not.

-Doc

[Hanyo]

how would a compression test related to a bad spark plug in a cylinder? (trying to get the fundamentals down)