Misfire and backfire

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires

This could be simple if this has a throttle body with two fuel injectors. If so, then the one fuel injector that feeds 2468 isn't working. Check for voltage to the fuel injectors with the key on run/engine off. Check for a pulse with a noid light while cranking the engine. Last but not least ohm the injectors to find out if one is bad.

Do a compression test. Check the fuel pressure regulator. It may be blown, dumping fuel.

How long since a tune-up? Any applicable trouble codes? Your obd1, you should be able to check codes, yourself. To check codes, you use a jumper wire between the A & B terminals at the dalalink connector. Turn key just till the dash lites come on, no further. The mil on the dash starts flashing, you count the flashes to get the codes. Your looking for two digit codes.

If the vehicle acts up under load, it is usually a restriction of some kind, whether air--fuel--exhaust, something of that nature.

Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help.

Hello,

Check out this guide

https://www.2carpros.com/articles/engine-backfires-while-running

Here is what someone said

Locate the crankshaft timing marks, most engines timing marks are at the front of the engine on the harmonic balancer. Near the balancer there is a small pointer or scale to align the balancer mark too. When the engine is running this gauge or pointer should align with the mark on the balancer. When the engine is running the timing light will strobe and illuminate the balancer mark as it spins. To adjust the timing loosen the distributor and turn slightly one way or the other to achieve the desired setting. Once an adjustment has been made re-tighten the distributor hold down bolt or bolts.

Exhaust systems have an air injection system designed to help the complete consumption of exhaust gasses. This added air is only in operation during power mode. If the air injection check valve or sometime referred to as a "gulp valve" fails it can allow extra air into the exhaust system causing system internal and external backfiring. To check your systems valve remove it and blow in ti both ways to check air flow. Air should only travel one direction hence the name: "check valve". If air travels both directions the valve has failed and needs replacement, this is a common problem.

Good to hear, please use 2Carpros anytime

Best, Ken

What repairs were done?

Sounds like a vacuum leak. Make sure all hoses are attached and not cracked. Otherwise it may be an idle air control valve failure

Roy

That's what you pay mechanics to figure out. They get to listen to the engine, look at it, and make tests. We can't do any of that. All we can do is decipher the information you give us, and you haven't provided any.