So for the last 5 hours or so I've been.... reading numerous otvc threads, low rpm stumble threads for the past several weeks, and had my finger on the buy button on summit racing.

My problem will sound quite familiar - flat spot/stumble at 2,000-2,500 rpms, will miss occasionally during this time (intake backfire - cough sound), especially under load (up a hill). I can push through this wall, but will often end up back behind it at the next gear. It usually doesn't happen untl closed loop, so I am thinking wires getting too hot, maybe even burning. My preferred shop ran a number of tests, put it on the dyno, test drives, ignition scope, etc. They could not get it to miss, nor found any porblem with the ignition system.

Now though I have shorty headers, on the passenger side mostly I see a few areas at the bottom by the 02 sensors, though zip tied well, are too damn close to the primaries. So this could be my problem, and I plan to do otvc top mount with boot protectors for added protection. I really wanted to do side mount because I am modifying the stock valve covers to look a little more sharp, but side mount is just not far enough away from the headers and would defeat the purpose. The wires I have on now are stock replacement wires (random napa wires). So I'd like to upgrade anyhow.

Problem is, I don't make a lot of money (quite underpaid) so I can only tackle one potential solution at a time. so the question is, is this a potential solution?

btw - would 1200* heat protectors be enough protection?

Other upgrades that could solve this that I have planned:
-bigger injectors and 255lph pump (getting close to passing 350 flywheel hp with 1.6 RR and tune, hell I'm likely at it now)
-various sensor replacements - tps, lt4 km, iac
-replace battery (because of one thread on cz28 about it)
-opti (why not, the one on it is from NAPA)
-tune - Maybe some timing issue that can be tuned out.

Thanks for reading the 673rd thread on two widely posted subjects.

 

Have you checked the fuel system? It never hurts to spend the 45.00 & get a guage, they do come in handy, change the fuel filter also, its cheap & easy, another area is the air filter, make sure its not clogged, now you mention your strapped for cash, but your list of fixes are pricey & most likely NOT your problem, the only thing i would invest in on that list (other then what i stated) is the fuel pump, remember, ALWAYS check the obvious things 1st., then go from there, the OTVC set-up is a good investment with sorty headers, the PS LTs don't really need them, you just need to route them good, i'm running 10mm wires on mine & i re-used the factory "boot caps" to prevent them from burning.

Now you had it on a scanner & they found no miss fireing, sence you changed the wires, i would run it in the dark & look under the hood to see if theres a lightning show going on, then you know for sure its the wires, also, check the charging system & battery too rule this out too, check the simple things 1st.

 

thanks LM, I'll check the fp, but I haven't seen my gauge in a long time....it's somewhere in my garage

 

I had the same stumble in lower RPM's when I first got my car. It went away after I got my LT4 KM. I never had a backfire though, so you may have a different issue.