Once warmed up engines runs like garbage....dont know what else to do

Ok so some history:

Its a 1973 CJ5 with a 304. Has an edelbrock performer manifold and carb. the carb has been jetted for my altitude. it has headers and flowmaster exhaust. My dad replaced the distributor about 4 years ago nothing fancy just replacement in kind.

Problem:

It all started after i had put all new spark plugs (gaped at .034), new wires (7mm silcone insulated), and new header gaskets. I took it out to a nearby trail, half way to it the jeep started to lose power and back fire violently (both out the exhaust and sometimes up through the carb) when id hit (don't have a tach so just guessing) 2500 rpm and higher. it did this for a few minutes then died. Would not start and had to be towed home.

Here is the order of solutions i tried:
Replaced fuel filter. Nothing
Rebuilt Carb. Nothing
Replaced the ignition coil. nothing
Replaced so old looking wires and the coil resistor. Nothing
Replaced the distributor points (gaped at .016). Nothing
Replaced the condenser on the distributor. VRROOOM

it finally started. so i take it for another drive, and again half way (about 20 minute drive) it starts losing power and having violent backfires. If i give gas slowly it will slowly rev but then again somewhere around 2500 RPM it will lose power and/or backfire. Difference now is it stays running, i turned around and made it home (very slowly).

Nexts steps i tried:
Relocated fuel filter and fuel line farther from the engine block (idea was to stop vapor lock). Nothing
Replaced fuel pump. Nothing.
Put old spark plug wires back on. Nothing
Replaced vacuum advance on distributor. Nothing.

I am at a loss. To recap jeep will start at first crank when cold (just 24rs later), after about 20 mins or when the engine gets hot it starts losing power and backfiring violently. Also after the problem starts when i get back home ill shut down and if i try and start it will not, i have to use starter fluid to get her going again. But if i wait a few hours till its cold again it will start first crank and run till its hot. It seems to be temperature related. The engine dos not get HOT hot it will stay in the middle of the gauge so its not overheating. Based on my knowledge of engines it says to me that at high temperature the engine is off its timing, but i have done everything I can think of to fix the problem but it still persists.

I have had to leave town for work but when i get back i will be timing the engine at different RPM's but until then i thought i would through this up there to see what you all thought.

Does anyone have an idea or suggestion that i haven't tried? i am literally going insane about not figuring this out.

i have also tried looking for manifold leaks, couldn't detect any. would a bad alternator when hot be giving me to low of spark? just aon out of the box thought.

Thanks for taking the time to help!

 

one thing you could chek is the distributor gear and the camshaft gear that make turn the distributor gear...it maybe start to get worn...what it could be...when cold oil flow much more than at hot temp...maybe oil come over both gear so it turn without any problem and when hot no more oil go over it and maybe from this point bot gear get little loose and youre problem appear.

Maybe another thing, look at you're advance fire on youre distributor...it depend from vaccum and maybe you have a problem with that...you should look at that...

other thing loose of vaccum could bring a engine to run bad...metal expense with heat so at cold if you got a leak it's not a big problem but when hot it get bigger the leak and the engine start run bad and could not start at all...

Maybe i'm totally wrong too just try to help

 

As a quick guess, I would say it is too lean, and is running fine while the choke is on.

But you state it started after doing plugs, wires, header gaskets, so the lean thing doesnt seem to fit into that scenario.

Could also be a timing or plug miswiring issue, hi manifold vacuum will affect the timing -----and when the choke is on, the manifold vacuum is high.

Check all vacuum hoses???

 

It may be time for a new dizzy, I think your problem is there. Check it closely . Good luck.

 

Thanks for all the quick reply's!!

it has the electric choke...i wonder if it is functioning?? i haven't checked that.

I will also check the dizzy gear when i get home...I had the same thought on the expanding metal leak theory but i can seem to find a leak. I have also replaced all the vaccum lines...but it is hard to check for leaks around the manifold especially when its hot....so it could still be a possibility

Yes i am looking into an HEI dizzy but it will be till after Christmas before that happens.

Again thanks for all your guys help and if you still have more ideas please chime in! Because this jeep has been in the family for 10 years and it has never happened before and it is really starting to erk me

 

For the choke just put it manual very cheap upgrade and you don't mess with that in the future.

 

An electric choke should have a wire connected to it that is hot, +12 VDC, when the ignition is turned on.
Take the air cleaner off and turn the ignition on, you don’t even need the engine running. After the ignition has been on for a few minutes, open the throttle by hand and the choke plates should flip wide open.

 

Thats an easy check, ill do that first thing when i get back
Thanks!

 

I was just talking to Nick Miller and mentioned this, he says to check the coil--------they can heat up and go south on you, and that figures into the 20 minute delay a lot better than the choke.

 

X2 on the coil. I bought one of those shiny chrome coils once and put it on a 68 ford truck i had. the truck would run fine for a while but then would have the same symptoms that you have. turns out that the shiny chrome coil would not disipate enough heat when the underhood temps increased and it would start crapping out. changed back to the factory coil and the problems went away.

 

for myself best thing to put on my carb...when offroading having such a position with a lot of angle...sometime engine's hard to start...just pull the choke and it start in a second...i read o lot over automatic choke...unless everything is brand new lots of people use to have problem with those type of choke...

 

In your first post, you said you replaced the coil. Was it a new one ? It started when you changed the condenser , right? Still sounds like a problem with the dizzy or ign. module . Good luck, and let us know what you find.

 

Re read your first post. Ops, no ign module, sorry.

 

yes i did replace the coil....but maybe its bad too? ill check if it has a heat rating printed on it somewhere maybe i just need a better coil.

again thanks for all the replies...ill keep you all posted!!

ps hey patrick nice to see a fellow new mexican and we share the same first name!

 

Check with O’Reilly, Auto Zone or Napa, one of them may be able to test your coil for you.

 

Ok sorry for the absence....was fishing

anyways i had the coil tested and its good.....i was thinking it all started when i replaced the plugs, could i have gotten a faulty one? and at high temps its not giving spark? i did just buy the cheap autolights...should i have dished out for a higher priced plug? my dad also told me it was a waste....i dont know.

i also pulled the dizzy and it seems to me fine, both gears look in good shape no wear that i could see....i think since i have it out though ill just replace it with electronic...either pertronix or HEI.

anyone have opinions on plugs to use? or which electronic ignition?

 

Nothing wrong with plain ole Autolites. That’s what I’m running in my engine and it never skips a beat from idle to the rev limiter. Of course I change mine out fairly regularly, at least every couple of months because 1) it helps me keep on top of how my engine is burning fuel by reading the plugs regularly and 2) because I just like the way my engine runs on fresh plugs. It already has snappy throttle response and good off idle power but the power and response is just that much crisper with fresh plugs.
So that’s why I buy the cheapo’s, I’m going to change them out in a couple of months anyway so it isn’t worth buying some expensive iridium BS.