6strngs

Hey all, just picked up an 87 NA the other day and have been trying to get the thing all tuned up and running how it should. So far I've changed the spark plugs with NGK, the fuel filter, and the oxygen sensor. I also adjusted the TPS last night using the resistance method and got resistance perfectly at 1k ohms closed and 5k ohms open, voltage read about 0.8V closed and about 4.6V open. The car seems to run a little smoother now but it has an issue where it idles at around 1500-1700 rpm, because of this I can't set timing (I hooked the timing light up and it just flashes sporadically, not rhythmically). I've already tried adjusting the idle screw but found it's already all the way down. The car also has an issue where it backfires anytime you shift after giving it more than 3/4 throttle, and sometimes the backfires are bad enough to shoot fireballs out the exhaust. That's totally badass, but I'm just trying to get the thing to run right to get it through smog first I've taken a can of carb cleaner and sprayed it around all the vacuum hoses I can see while the car is running and haven't found any vacuum leaks. I suppose it's worth noting that the car currently has an aftermarket straight pipe connecting the manifold and primary cat, the cat is gutted, and the muffler was cut off for some reason which I think is the reason for the backfire. (yes, it's ridiculously loud) I will be getting two cats on the thing before smog but I want to get it running right so as not to destroy the new cats right away. The car seems to run fine and accelerate smoothly to redline, just the high idle and backfiring concern me. Any thought on what to check?

6strngs

I appreciate all the help... Here's what I've uncovered so far: I sprayed around some more vacuum hoses with carb cleaner and finally found that if I sprayed it at the vacuum lines for the oil injectors I would get an rpm drop. I pulled off the upper intake manifold (not as bad as I thought, as I am starting to become familiar with this motor!) and started to pull vacuum lines. Every single one I touched was so brittle that it just snapped off. Same story for the 4-into-1 connector for the oil injectors, every single nipple snapped off as I tugged on the vacuum lines... So I temporarily am running 3 Tee fittings, running 4 into 2, then 2 into one. Kinda ghetto but it works, haha. So I replaced EVERY vacuum hose I could see in there and all the fuel injector O-rings and insulators (which, btw, also snapped in half while trying to remove) and now the car runs a lot better. Idle is finicky, it started out about 500, so I adjusted the screw up to 1000 (while it was still warming up) and then after a drive it was back to 1500. So I turn the screw back in, and all the way down it's at 1000, then another drive and now it pretty much sits around 1300.

I also discovered this morning that the previous owner had hooked the leading plugs to the trailing coil and vice versa! I didn't even think to check when I changed the plugs, I actually did them one at a time so as not to mix them up! I only took it for a quick drive after that but idle seemed to be around 800 and the car easily gained 10 hp and backfires a lot less now. This might have been my issue the whole time Once I set timing I expect it'll run even better.