1999 GMC Suburban - Sputtering and Backfire

[Spyder3244]

I have a 99 Suburban that all of a sudden started sputtering and backfiring. This started happening a couple of days ago I checked the common possibilities......spark plugs (which I changed), the plug wires and the distro cap still looked in good condition. Someone suggested that the ignition coil or module was going out. I took it off and had it inspected at my local parts store. I was told that the parts were still in working order. I am out of ideas as to what could be causing this issue . Any help or ideas would be greatly appreciated.

1999 GMC 4x4 Suburban
116K miles
5.7L engine

[maxwedge]

Welcome to AF, any cel on, did you check fuel pressure?

[Spyder3244]

Hi maxwedge. Thanks for the greet. I do have the CEL on. I went to Auto Zone to get the OBDII error code and was given P0300 a multi cylinder misfire. Once I explained that I had already tested or checked the usual culprits, it was suggested that I replace the fuel injectors. I haven't been able to test my fuel pressure, but I can tell that it has been affected. Before I go out and spend $300+ for the injectors, I would like to make sure that this could indeed be a cause for this issue. Could this issue be symptomatic of a bad fuel injector?

[lg69hydros]

Something to maybe check allthough should have a code, is the Mass Airflow Sensor. When those go bad it causes similar symptomns like rough running and backfire or bucking and snorting as we call it..and it is very easy to replace...Just something to check that maybe the autozone dint catch on the readout.

[smsrobertks]

i would absolutly check fuel pressure mine did just about the samething barly made it home the next morning it wouldnt start at all. sparyed carb cleaner into the air in take while someone tried to start it.it would run as long as i kept the carb cleaner going. but definatly check fuel pressure. i have been there too!

[smsrobertks]

did this make it?

[raymanjames]

I would say it could possibly be the injector Spider if it is multi cylinder misfires. you can google for a 5.7 injector spider online it comes with all new injectors I have seen them for 199.00 for that engine.

I would try that.

These engines can be a real pain in the ass though. I have 3 GMCs with 5.7 engines in my shop right now with multiple issues.