One issue to the next. After sorting out my fuel issue, the truck ran fine for a week. I replaced the fuel pump relay, and rebuilt the TB. Now I've noticed that once it heats up enough to get to low idle, it will randomly stumble/almost die before reving back up to idle speed. I don't have the money to throw parts at it in a futile attempt to locate the issue. Anybody here have any ideas? I've only noticed it do this in drive, I'll idle it in park when I get home and see what happens. Could this be a bad IAC? Leaking TB base gasket? I only rebuilt the top half, didn't feel like pulling the whole thing off the intake in the cold. Maybe a map sensor or clogged ports on the TB? Any help is appreciated
I would check out anything to do with vacuum. This would include making sure all vacuum lines are in good shape and well connected. I'd remove the EGR valve and test it. If it's a newer valve, the plunger is going to be mostly enclosed, but you can depress it using a screwdriver or something. If it's older, the whole plunger will be exposed. Push it up and down to make sure it moves freely, and then push it down and hold, cap your finger over the vacuum port, and then let go to make sure it can hold vacuum. If it it moves freely and holds in place, clean the carbon off the pintle with a flathead screwdriver and reinstall. Otherwise, replace it. I would also test the brake booster. You'd have to replicate when your symptoms occur so it'd probably be best to pull the line off at the check valve and plug it then get in and put it in drive. If it still acts the same, the brake booster's good. If not, it'll be in your best interest to buy a new one instead of a remanned one. RockAuto is gonna have the best prices on that or almost anything else for that matter. Pull the PCV valve out, and shake it. If it rattles, you're good. If not, get a new one. I would change the little filter under the charcoal canister, and try running it without the fuel cap on. If it doesn't stall, you need a new fuel cap. You can test for vacuum leaks with the ole spraying starting fluid around the gaskets and hoses to see if you get anything. Do it very throughly around the TBI base gasket, but you can do it in other places, too. Another leak point is the throttle shaft area. Try to wiggle it up and down and side to side. If it has play, there's a vacuum leak there, and the only way to fix that is having a bushing pressed in there. Let me know later if that's something you want to do because I understand you're on a budget. Be very thorough with those vacuum lines. The TBI vacuum stuff isn't that bad. My Caprice has enough vacuum lining to mummify a world champion hotdog eater, but the TBI shouldn't be bad. Finally, do an IAC relearn. Jump the A and B pins on the ALDL like when you're pulling codes, turn the key on, wait thirty seconds, unplug the IAC connector, turn the key off, undo your jumper, and reconnect the IAC. If you don't find a problem, and these little tricks don't remedy anything, I would try replacing the IAC as a last resort. Go online if you end up buying this and see if there's an AC Delco. China's finest will probably cost only slightly less than OEM will online. Hope you get it, and if you do, report back on what it was. Overall, these parts would cost you several hundred dollars total, but all this isn't gonna be broken so don't get discouraged. You may come out of this spending only four dollars, but who knows? Good luck.
