MISSING STROKER

[92tank]

ok here is the issue im haveing. my jeep has a miss from idle all the up to about 3,000 rpms, then it clears out. it does it when its cold and when its warm just not as bad. i have swapped all the sensors (exept idle air control) the coil, the dizzy. im running 24lb injectors in a 4.5L.

the only other thing i can think of is the timing chain is streched to far and the timing is off(the set has 187,000 miles on it) it started the missing after i took off from a stop sign and punched it and shredded the serp belt.

thanks for any advice

[SilverXJ]

I assume this is on your 92? Did you reindex the distributor? You used a timing set with 187,000 miles on a new engine? Did you degree the cam in? Why did the serp belt shred?

[amcinstaller]

ditto on the distributor

[92tank]

yes its on my 92. it runs the same way it did with the old dizzy(i didnt pull the old one out when i built it). its got the stock cam. and all i did is swap crank and rods. it was running great for the first 1500 miles or so, then the o2 sensor went out, i replaced it and that fixed the first missing issue. then when the serp belt blew it started missing again, i thought maybe because it was wet outside, so i checked dizzy cap for moisture and there was not any, changed plugs didnt help. changed o2 sensor again still no change. and im running out of things to change and its still not running like it was when i first built it and im starting to pull my hair out. or im gonna put the stock motor back in and drive a turd again. but i will miss the stroker for sure

[SilverXJ]

Reindex the distributor to start with.

[Cheromaniac]

There's an easy way to find out if the timing chain is overstretched. Remove the dizzy cap and observe the rotor while you try to turn the engine with a socket wrench. If the wrench turns several degrees before the rotor even moves, replace the timing set.
Another thing you can do while the cap is off is to see how much rotational play there is in the rotor. If it seems a lot, the dizzy drive gear probably has excessive wear.

[92tank]

the crank moves back and forth quite a bit before the rotor moves. and it done that since i buit the motor. when i had the dizzy out the gear didnt look bad(no sharp teeth and just a little shinny spot on each tooth) im going out to work on it now i will give you update as to what i find.

thanks for all the help so far

[4.whoa]

Did you put the tensioner back in?

[92tank]

yes i put the tensioner back in. and i was playing around with the dizzy today and if i moved it one tooth in the clockwise direction the idleing would sound better except that it varied between 1300 and 500 rpms. one tooth in the other direction it would not start. put it were it always has been and turn the dizzy as far as it would go it smothed out a little but you cant turn them all that far. with a wrench on the crank the belt moves about an inch or so before the rotor moves, is that to much? and the rotor only has minimal play in it. is there anything else i should try? its making me go bald

[SilverXJ]

Using the degree marks on the timing cover, how many degrees does the crank move before the rotor moves?

[Cheromaniac]

with a wrench on the crank the belt moves about an inch or so before the rotor moves, is that to much?

Sounds like the timing chain has a fair degree of slack in it. No surprise after 187k miles.

[92tank]

ok so some other info i forgot to add is that it used to miss when first started then it would almost die and then it would clear up and run fine now it doesnt do that anymore. and none of the spark plugs are black like it fouled out

[IH 392]

My jeep had a miss like you describe several years ago, it was a bad injector, with the engine idling my dad started pulling the looms off of the injectors one at a time until he isolated it to the specific cylinder, I slapped in a used one from the junkyard and ran it for several years before I put in a new set of injectors.
Popping the injector wires one cylinder at a time will help you narrow it down to a specific cylinder, I would also do a compression check to make sure you don't have a bad valve/seat???

[92tank]

well i know its not the injectors cause they are new, and i have to get the compresion tester from my uncle to check it i just havent had the time to do that yet

[Bodo]

well i know its not the injectors cause they are new,

Not necessarily true. How many products are bad from the factory? More than you'd think. Test them. Then and only then can you eliminate them.