TBI misfiring

[Lt.Del]

On my 91 3/4 ton 4x4 Sub the TBI has been acting up. I don't think it is as severe as Chris is trying to figure out, but, nevertheless, it is a problem.

My sub will run like a champ more often than not.  But, she will start to miss often.  I know it is in the TBI, because, I found that out about a month ago.  When I push down on the right TBI clip, she will idle perfectly and run well for a day or so.  She will then start to miss again.  I take the breather off and push down on the clip again, and she runs on all eight cylinders again.  



If i push on this clip with two wires while idling, she purrs again.  A few days later, she starts to miss again.

 

I pop the clip off and the gasket and wires look good.  It has to be something loose though because the problem doesn't occur all the time.  When i push down on the clip, she will purr again.


Common sense would say the clip is worn.  But it stays clipped on the two studs without problem.  I am just wondering if anyone has experienced a similar problem on their TBI system.

[Blazin]

I have seen those wires get brittle and fail. Usually the wire insulation is cracked though.

[Lt.Del]

The wires look good.  The clip snaps on firmly.  It is just when I push down, or just barley touch the plastic clip, the thing starts to run great.  I don't push hard enough to "move" the wires.  I am wondering if it is the contact points where the two studs fit inside the plastic clip. 

I don't know.

[VileZambonie]

are you sure just your hand restricting air over the TBI isn't making it seem to run better? Perhaps your TBI base gasket is leaking.

[Captkaos]

Are you taking the whole air cleaner assembly off?  A buddy of mine that I was telling about mine told me his did EXACTLY what yours is doing.  He found out accidently one day when it started acting up on him and he pulled over and leaned on the air cleaner base that one of the wires were chaffed and when he move the base it fixed it.

[Lt.Del]

hmmm, thanks for those ideas.  I will focus on these possibilities next time I need to put my magical touch on it.

And no, i haven't been taking the entire air cleaner off.  I just removed the top and the filter. 

If it is a gasket problem, could I check the gasket the same ole way of using the wd40  or starter fluid trick?  When rpms go up, maybe I will have found something.

thanks again

[VileZambonie]

don't use starting fluid
WAY too flammable. Carb clean or propane and definitely pull the whole lid off to check

[DnStClr]

I wonder what would happen if you switched the clips to see if the problem follows the clip to the other pot.

[Lt.Del]

Yeah, Don, I though about that.  If the wire length allows, just may try it.  That way i can narrow stuff down. 

[DnStClr]

Well just give a coupla big yanks..

[Lt.Del]

Well, I finally had time to play with it some, since my wife and kid went to Cinci for a few days.  I can't believe how much time i have on my hands when the family is gone visiting her side of the family....a toddler does indeed take up all your time. 

Anyway, I switched the two TBI clips.  And, yes, Don, the problem followed the one particular clip--at times, no gas spraying in that bore.  Bingo.  I knew what to do then.  After placing an order with  competitor.com, i started thinking.  That could be dangerous, me thinking.  I thought I would pay a visit to the local salvage yard and see what i could find.  I was amazed at how many of those clips are still on engines in their respective trucks. I snagged a few of them...they are only $2 each (vs. $12 at  ).  I did some cutting and splicing and replaced the clip on my TBI system.   Took her out for a spin.  For the first few miles, no misfire...I was getting happy.  But, then, i felt a misfire.  I accelerated heavily and that is when i notice the misfire the most.  However, it is no where like it was...I'd say it was about 85% better than she was before i replaced the clip.

I thought to myself, must be something else. I took her home and popped the hood.  I looked at all the spark plug wires, and, VIOLA, i saw the culprit.  It was the plug wire for #5 cylinder...laying on the exhaust manifold, burnt white and brittle.  So, I put an old plug wire on it...i never throw those puppies away, unless it was burnt through.  I took her out again and she runs like a champ.  Yeehaw!!        

I should've gone with my first instinct....

Common sense would say the clip is worn.  But it stays clipped on the two studs without problem.  I am just wondering if anyone has experienced a similar problem on their TBI system.

Those wires in the clip just may be prone to having a loose connection. 

Tommorow is Friday...gonna go down to the River House and drink a few this weekend, I mean catch a few fish this weekend.

[75 C20]

Well, I finally had time to play with it some, since my wife and kid went to Cinci for a few days. 

im only about 40 mins down the intersate from cincy- next time come up my way with ur 79 with the 383-  haha

[Lt.Del]

My brother in law lives in Mt Adams overlooking downtown...very nice place...they actually have 5 of those old 1890's row houses completly renovated.  They enjoy being landlords.  Last year i was there and we "walked" down the hill and went to watch the Reds play baseball---so neat.   
I'll bring my Stroker 383 79 truck--but it aint for sale 

[75 C20]

i just bought a 79 so i dont need another one yet...... but give me a holler if you come up this way