Not running right.

So I have a couple of manuals but it seems easier to ask on here. My mustang had sat for 8 years before I got it but fires up and runs (now with some parts). anyhow it runs smoothly at high rpm but the minute i try to let it idle it dies and when I just get low in rpm's it gets choppy. It doesnt sound like as if a cylinder isnt firing cause its very spuratic. Any ideas?

What have you done so far?

After 8 years fuel is going to be bad and carb is going to need to come apart for some new gaskets and a good cleaning.

Make sure the exhaust is free flowing (no critters or bent pipes)

You would want a dwell meter if its got points to make sure they are set and working right.

A compression test would be good just to make sure all 6 are sealing reasonably well.

Pulling the valve cover to look for a stuck valve or bent push rod may not be a bad idea.

I put a new starter, new gas tank, new relay, new radiator, never even adjusted the carburateor. I wonder about the points though cause it starts with out starting fluid after a couple trys and if you give it a little gas peddle it runs real good but as you let off toward idle it chops and runs rough.

my guess is a carb rebuild is in order. Too much varnish and who knows what else could be in there.

Really? it runs absolutely smooth when at anything more then about an 8th of throttle.

If you have had it running and you still need starting fluid you have a fuel problem. Time for a carb kit and lots of cleaner. The idle section is sort of separate from the main section and the 'power' section is yet another part. They are all separate but not and they do interact and work together depending on conditions. 8 years even under optimum conditions is going to be hard on any carb. That may not kill it but the chances of it being optimum are slim.

A dwell meter will tell you how well the points are adjusted. The dwell has to be within a fairly narrow window to work properly. The gap method only gets you close and only works well with new points. If the dizzy is worn the shaft could be bouncing around screwing up the dwell but at certain rpms it sort of hits a harmonic and works, again a dwell meter will easily show you if thats the problem.

No no I dont need starting fluid it starts with out it but I had to use it when I was trying to get it running before I replaced the gas tank (old one was pretty much made out of rust, oh and wasnt even attached just kinda sitting where the backseat should go) it just seems to me to be a spark problem so I can see points but im not certian about it being the carb. Every experience ive had with carb problems the motor bogs or chokes out or something similar, this sounds like its skipping cylinders but a different one each time...I dont know if that even makes sense.

By the way im not saying your wrong and if I come off as a pompus a!@ im sorry it just seems like a spark issue.

Will and I just had the same problem getting my new motor running. Fired up after some persuasion, did break in for 20 minutes at elevated RPM, then tried to lower RPM to idle speed and could not get it stay running unless it was at 2000RPM.
Will changed the metering block (the primary was corroding due to E85)and replaced gaskets. Fired right up and idles just fine now.
Just my 2cents worth.
Kelly

6=8":1z3zj3sg said:

My mustang had sat for 8 years before I got it but fires up and runs (now with some parts). anyhow it runs smoothly at high rpm but the minute i try to let it idle it dies and when I just get low in rpm's it gets choppy.

Click to expand...

Points can sit for 8 years and not be affected short of moisture/contaminents getting under the cap. A carb can develop significant varnish in just a year of sitting.

The fact that it runs 'smooth' at higher rpm's suggests that your idle circuit is hosed (dirty, gummed, varnished, etc). If it indeed idles smooth (I mean real smooth no hesitation) at higher rpm, that would not suggest ignition. Ignition problems maybe less noticeable at higher rpm's but they won't go away completely.

From personal experience, after mine sat for several years, there was so much varnish(looked like tar) in the fuel sending unit, the engine wasn't getting any gas at all (swapped out a perfectly good fuel pump for nothing). As LG & FC suggest, I'd clean the carb and install a kit, plus flush the tank if you haven't already done so.
Edit: whoops...just saw the new tank comment
Edit2: above about 1000 rpm you're on the carb's main jet (a relatively fixed a/f ratio) below ~1000 rpm you're running on idle circuit...diff part of carb as TJ mentioned

PS I ended up also having a stuck valve and subsequently a bent push rod from sitting so long...it missed throughout the rpm range.

Yeah probally that I was just figuring that since the carb was rebuilt before it was officialy parked, and the gas tank wasnt even hooked up and I doubt it even ever was, that it wouldnt be that. Plus the fact that it makes a skipping sound rather then a bogging sound and doesnt idle at all that maybe the points were just never readjusted.

Besides the carb's idle circuit, another issue could be the timing and the vacuum advance. What model carb and distributor are you running?

You may not have enough vac advance at idle to smooth out the idle. What is your timing set at with the vacuum line plugged and what is it with the vacuum line connected.

You could also have a vaccum leak that is hampering a smooth idle but is not significant enough to affect the higher rpm's.
Doug

so the carb was rebuilt 8 years ago and has not had fuel in it since? i would still open it up to see whats going on.

i think the first thing you should do is a compression test. i had a similar problem with a car i recently bought. it would get smoother as i went up in the rpm range, but the car would shake at idle, it sounded like a subaru, and it didnt want to idle less than 900-1k. i did a comp test and cylinder #1 registered no compression at all.

this is what i found when i pulled the head off.

Yeah the car doesnt shake which is another kinda weird thing. It just sounds like its half running and if it doesnt get enough throttle it just dies instantly

So I admit defeat. The carb now apears to be leaking so it deffinatly needs a rebuild regardless. I have no idea what kinda carb it is but I think its the autolite 1100. Where can I find a rebuild kit though?

okay... nevermind I found out my local napa has one for $23 before tax. Any easy ways to identify if its a 1100?