3.9V6

Yesterday it refused to start. Would cough and garble and pop, but refused to start. Finally after working the throttle enough, I got it to catch fire. Would not idle on the way to school, would surge a couple times between 350-700 RPM them cough, sputter, die but would start right back up. If I gave it a quick slap of gas under load, it'd backfire through the intake. Slapping the gas in neutral or park was fine. Same thing coming home. Plugged my SCT when I got home, had P0302 and 0303, misfires on 2 and 3. Pull the dizzy cap off, rotor looks good, no carbon trails or anything. Put it back on, idles fine, but still backfired through the intake if I slapped the gas. Seemed drivable at least.

This morning, back to square one. Starter would spin and it would cough and garble and pop like it wanted to fire, but absolutely wouldn't. Didn't have any starting fluid, so I sprayed carb/choke cleaner down the TB. no change. A tablespoon of 112 leaded racing gas. Nothing. Unplugged the TPS/IAC/MAP. no change. Plugged MAP and TPS back in, working throttle to get starting A/F ratio. No change. Plugged in IAC and unplugged MAP, and after a good 30 seconds or so of working the throttle, I finally got it to catch with the throttle at about 3/8 open. Runs like crap of course without the MAP. Plug that back in, and it cleaned up. Still backfired through the intake on throttle slap under load on the way here to work. I put it in neutral rolling to a stop sign and slapped it twice, just fine. Put it back in drive and went to pull away from said stop sign, cackle pop burp cackle pop burp...you get the idea. No codes on scanner yet.

Dad says it sounds like a lean condition, to be backfiring through the intake/throttle body. When I was trying to get it to start this morning, blue smoke came up through the TB every time it popped/backfired. So it seems to be getting spark.

I pulled plugs 1 and 3 last night, 1 had a solid gray electrode, 3 had a gray electrode with some dark brown spots. Plus are 3942 autolite or something like that, 15,000 miles on them i think, changed them a summer or 2 ago.

I've put my finger down the IAC crevice, and I can feel it moving in and out with my finger- plus hear the whistling noise of air going around the plunger. The TPS and IAC are from my original V6 throttle body, the MAP I bought new when I switched TB's since I've read they have behave funky when they get older.

The strange part is that it's not throwing codes (other than when I unplugged all the sensors, but I cleared those). I would think if it was lean or rich, the O2's would be throwing all kinds of unhappy codes. If the injectors weren't firing/mis-timed, i would hink that's would make a code as well.

 

changed the TPS....didn't change the behavior. Actually ran a tick better with the TPS unplugged..drove it that way for a good 20 miles to GF's and back.

also seems to be heat-minded. Doesn't behave as bad when cold, could stab the throttle or go up hills fine. Once it got up to temperature (180 stat) I was lucky to get out of a rolling stop.

 

found out has a very, very weak spark, using screwdriver method.

putting new cap and rotor on it, hoping it's not coil ($$$).

 

$40 unneeded TPS, $12 cap, $6 rotor, and $5 coil wire later....all is well again.

The wire terminal completely came apart inside when I pulled it off, scattered corrosion dust everywhere.