OK...Here we go again mechanics.

[Goldeneagle]

First off, Lord only knows how bad I wish I could get a new truck, but I can't. Tuesday, my 1993 Chevy started idling really bad. I could barely keep it running at signal lights. Yesterday, I changed spark plugs, cap, rotor, fuel filter, air filter and PCV valve. No help. This morning, I reset the timing because it was off a little, but it didn't change much. I've crawled all over this thing looking for vacuum leaks and found nothing. Now, I'm wondering about either the IAC or I got some bad gas the other day. I'm going to put some Seafoam in the tank and top it off to see if that helps. Any other ideas?

[Walker]

Bad gas would be a likely suspect

[Traildust]

Plug wires. How did the timing get off? You set it with a timing light?

Truck specs and mileage?

[WItoTX]

I would check bad gas first. Then, is it smoking? How does the oil look? Have you cleaned the TBI yet? Might not hurt to rent a compression tester and check each cylinder if all those things check out.

Edit: If it's the 4.3, I had the same motor in a Blazer, and after driving long periods with the cruise set (Usually at 60), when I rolled up to a stop sign, it would want to die. I never figured out what was wrong. But I did notice once it died, it would start right back up, and rev super high.

[AgHntr10]

If you think it might be bad gas I would just drain it instead of topping off. Then you just have more bad gas.

[Goldeneagle]

Plug wires. How did the timing get off? You set it with a timing light?

Truck specs and mileage?

Wires are only about a year old. Timing was only off a couple of degrees with timing light. Truck is a '93 Silverado with a 5.7 and about 170,000 miles. The timing is probably just normal stretching of the timing chain. The issue seems to be at idle. Plugs looked to be running a little on the lean side. More of a whiteish color than they should be.

[Goldeneagle]

If you think it might be bad gas I would just drain it instead of topping off. Then you just have more bad gas.

I have no way to drain 15 gallons of gas.

[TxDispatcher]

I have no way to drain 15 gallons of gas.

Is siphoning it out not an option? I'd rather try a very small amount of bad gas after siphoning out all I could, than 15 gallons

[Traildust]

Wires are only about a year old. Timing was only off a couple of degrees with timing light. Truck is a '93 Silverado with a 5.7 and about 170,000 miles. The timing is probably just normal stretching of the timing chain. The issue seems to be at idle. Plugs looked to be running a little on the lean side. More of a whiteish color than they should be.

Is that a carb or throttle body? Vacuum leaks on old rubber can drive you crazy. Im not buy the bad gas problem, never had that issue before. Not saying it dont happen.

[kingranch]

I had the coolant temp sensor crack go bad on my old 95 z
Similar symptoms

[SAC]

Mass air flow sensor?

[Radar]

Wires are only about a year old. Timing was only off a couple of degrees with timing light. Truck is a '93 Silverado with a 5.7 and about 170,000 miles. The timing is probably just normal stretching of the timing chain. The issue seems to be at idle. Plugs looked to be running a little on the lean side. More of a whiteish color than they should be.

After your tune up did you try to turn the distributor to see if idle smoothed out. I had a 97 do the same thing and it ended up being a worn cam. The gear on the cam that drives the distributor was worn out. I could turn the distributor to retard the timing enough to make it idle.

You probably need to check some more, lots of things can cause idle issues.
Check engine light on?

[Guerrero88]

I had the same problem with my ‘92. Check into replacing the fuel pump sender assembly. You’ll have to drop the tank to do it. Worked for me.

https://m.youtube.com/watch?v=JEwdf6kEBoc

[Worksalot]

Could be intake manifold leak. Could be many things. Wouldn’t hurt to test the fuel pressure if you have the tool.

[Walker]

FYI, if you do need to change the fuel pump, get Squeeler.and a.couple of his friends a take the bed off. Easier than dropping the tank.