i have a 1996 f150, it has 207xxx miles. at idle when it is warm, it has a very slight miss. and light rough idle, you can vibration is subtle, but i can tell it is there. also, on slow take off when cold, it hesitates. i have fixed all vacuum line leaks, new cap, rotor, plugs, and wires, new pcv valve, unplugged fpr and left unplugged for about five min. but no fuel was bubbling out. new maf sensor (it was bad, and doing this worse), checked timing, i am at a loss here. also, when i get up to about 1200-1400 rpms, there is a ticking/popping sound comming out of the tail pipe. i checked compression in all cylinders, (as i thought it might be a burnt valve) but all were around 125 pounds. so no big difference there. i do have a glass pack and no cat, with the pipe coming out in front of the rear tire. no exhaust leaks, it comes from the end of the tail pipe, and only under load. please help. thanks.

 

anyone? please help.

 

Ok try and seafoam to clean valves also change the fuel filter. this stumble/miss seems like its all the time

 

i did sea foam it through the brake booster, and i tried to clean the fuel filter. got a lot of black crap out of it. do you think i shoul still change it? alo at idle my rpms fluctuate a bit give or take 20-30 rpms back and forth.

 

anyone else have any ideas?

 

What motor do you have? But I would go ahead and change the fuel filter especially if you don't know the last time it was changed. The fluctuation in idle could result from the filter being plugged up and not letting fuel flow through it consistently. That could also be the ticking and popping as it isn't getting the correct ratio of fuel and air. So go ahead and do that and see if it makes a difference.

 

try cleaning out your egr valve, and if that makes things better, replace it. I had a rough idle and slight miss, and a new egr valve fixed all that for me

 

Oh, and the other suggestion I have, pull the codes and quit throwing parts at it aimlessly.

 

i changed the fuel filter last summer. as for codes, the maf sensor was the only code, and i changed it. it is a 302. cleaning the egr made no difference. what about the tps?

 

On my 300 6, I didn't diagnose burnt valves until doing a leakdown test. The compression check was good, but it still failed the leakdown.

 

leak down was good. could my timing chain be stretched? if so, how can i check?

 

Pull the plug on number one. Then put a screwdriver down the hole. Turn the crank pulley one direction until the screwdriver moves, then turn back the other way. If it immediately moves when you change direction, it's good. The farther you have to turn before it moves again, the more slack you have. But, I suspect that won't be the issue. I have zero slack in mine at 224,000 miles.

I have learned on this site that it is a common problem, but there is no one common cause. Do a search for misfire, and you will find lots of info on the topic. Start simple and work up from there.

 

Here's a good link for checking timing chain slop...
Timing Chain Slack Test


Also, what motor are we trying to diagnose?

 

also, she is guzzling gas. i am only getting around 8-9 mpg. 235/75/r15's, not sure the gearing.

 

another thing, i hooked up my scanner, and found my longft1 at -0.8, and longft2 at -6.3. any i deas?