95GTofDoom

I have done my reading and realize there are a few things I haven't checked yet (time..) but after checking/adjusting my timing, here is what I notice-

I pull the spout, fire it up, and at what was an "indicated" 6 degree advance, it idled like it had a cam.. rev it, it sounded great, and popped through the exhaust a bit (what I was used to from older cars). The previous owner claimed to lower it for regular gas.

Spout IN, the idle is more sedate, but it has a different kind of pop now.. like a periodic miss, and only at idle. Now timing reads about 22 degrees advance.

I tried 12-13 degrees and it pinged under hard throttle. Backed it off to 10 and it seems ok, but still pings when you gas it. I don't think the balancer is indicating the wrong timing..wish I could upload the videos. The car has had the idle miss the whole time.. it got worse when I set it to 13 degrees base and put the spout back in..then it was missing all over the place at idle.

Thanks.

dawson1112

Do you have a check engine light on? How hot is the thing running?

Pinging at base Idle of 10 is indicative of either
A. engine running lean
B. engine running hot
C. excessive carbon built up on piston/valves.

95GTofDoom

No CEL, and if the coolant gauge is still relatively accurate it rarely goes above the O of "normal". I will say the exhaust smells pretty strong, too... as if it had a carb.. but it still knocks down ~20 mpg in combined driving (a lot of highway, but minor traffic during the commute). It has cats but no smog pump and the air tube is crimped shut.

dawson1112

You could try some seafoam. I quite possibly could just have some carbon deposits on the valves , they get red hot and cause pre ignition knock by igniting the fuel before the engine fires. I forget the exact formula but I think most pour half a bottle of seafoam in the gas tank and the other half they pour into the intake via the brake booster vacuum line. It will smoke like crazy , but the seafoam helps to clean carbon deposits off the valves and pistons. It should not ping with the timing at 10 degrees btc.

95GTofDoom

I also don't know if any supporting mods were needed for the 75 mm TB with a stock MAF/air cleaner. Really I haven't checked any sensors or anything but the "popping" at idle is what threw me... it isn't like the pop when you rev the car up and you hear that crackle in the exhaust.. this sounds a bit like a hiccup but the idle doesn't change at all. I am lost until I look into it a bit further...

I need to pull the plug and verify that everything lines up..but if my understanding is correct, for it to indicate the timing that it does right now nothing can be THAT far out of whack to make it idle strangely..

95GTofDoom

Another point to note, though it may not be related: on cold-starts, usually for a couple of minutes of idling (or maybe the first take-off or two) the engine sputters at slightly off-idle rpms.. it stumbles around a little when you rev it, but past 1000 rpms it is fine.. then usually the first time you take off you need to keep the rpms up otherwise it bogs and almost stalls, as if it is loading up on fuel or something.. but after it is rolling the first time it is fine.

dawson1112

I would go ahead and pull the codes and see if the computer has stored anything in there. http://dfwmustangs.net/forums/showthread.php?t=7908

your 95 will use 3 digit codes. Also if you are getting any kind of preignition knock or ping it is really bad for that engine because it uses cast pistons and rods. You can damage the engine badly.

95GTofDoom

I pulled codes a couple of weeks ago and there was only one.. 334. This missing issue has been happening since I got the car. That was only key on engine off..didn't try it running yet. I was also told to check for a vacuum leak? The air pump system seems to have been haphazardly removed so I don't doubt there could be a line somewhere (or two..) wide open.. but I will check that this weekend with a gauge.