hey there i had just changed the plenum gasket... was gettin an engine light before i fixed it not no more light. yay! but it still stumbles slightly when i let off the brake. runs good for the most part. would a new iac valve fix this?... also i notice sometimes when im driving when changing speed slightly it flucuates a tad. not bad but i notice it. would that be the timing chain? it has 193,000 miles on it, no idea if its ever been changed. for the most part it runs decent. how do i check the timing for slack without takin everything apart? thanks a million!!!!!

 

there is the rotor button trick to get an idea about your timing chain... but I won't even elaborate on it because you have the mileage you have... yes, if that critter is OEM stock, it needs to be changed..

I've read here in the past couple of days the best explanation I've ever read about timing chains- that being something like: "You don't recognize the symptoms until you replace it".. it creeps up on you like that, so slow you don't ever see the ill effects until you replace it..

I'm getting mine done tomorrow.. I'm crossing my fingers for dramatic improvement... :-)

 

IAC just controls the idle air volume that passes the closed throttle plate. it just controls idle speed when you have your foot off the gas. don't try to make it do anything more than that.

if it stumbles when you press the gas pedal, that sounds like a vac leak. to prove it, LABEL, then disconnect and cap off all vac lines at the manifold. caution, you may not have power brakes during this test. if it runs better, then it proves there is a vac leak, and you can find it by adding the lines back one at a time.

timing chain doesn't cause a major problem unless broken, jumped, or slapping the case. i doubt you have any problem with it other than some wear. i don't think this is your problem. i think its vac.

 

An easy way to check timing chain wear is to hook up a timing light, just like you were gonna set the timing, shoot the light on the crank pulley and watch the mark, if it "waves" back and forth, it's worn/wearing, if it sits steady you should be good.

 

how far can the timing flucuate before considered bad when checked. should it be spot on everytime or does it change a degree or two or 8 lol

 

In my experience, if it's waving back and forth a 1/2" or more, put it on your list of needed repairs!

 

rough idle after warm up....98 ram 1500 5.9 4x4. truck starts great idle good...till after it starts to warm up it begins to faulter and stumble. runs rough and slowly starts to die. it never dies but literally down to 200 rpm misfires and sounds like poop.now if i hit the gas to about 2000-3000rpm or a second and it clears out. usually doesnt happen again till it cools off completely and start it again. it doesnt always do this. prob once or twice a week. i put brand new y pipe with cat on it a few months ago. new o2 sensors with that. new tps, new iac, new cap rotor plugs wires. new air temp sensor, new ignition coil, did plenum gasket. doesnt use a drop of oil and no cel illumination so....hmmmmmm... i just put a new purge valve soelnoid on it too. runs great otherwise. just that little hiccup. any thoughts?

 

Just to give you an idea, I just changed mine at 170k and I had a little over 3/4 of an inch of slack on my chain. When all was said and done, I went from 10 mpg to 15 mpg.

 

If you do replace it I would recommend a double roller one, I replaced the chain with a OEM type one and there was still a bit of slack in the chain, nothing compared to the old one, but still wasn't super tight. I replaced the one in my 89 with a double roller and that sucker was TIGHT.

 

a worn out dist.bushing will cause miss fires and rough running as well.the dealer sells them for about 10 bucks a bit of a pain to change but well worth it