5.3 multiple misfire, any advice?
 

2001 5.3l with cylinders 4 and 6 not firing. Engine light steady blink. No spark at the wires with timing light. I traded coils and same result. I traded out the coil banks from side to side and same result...so it can't be coils or coil harness. I've seen people suggest egr, plugged cats, bad fuel regulator and stuck injectors. I don't have egr or cats, and I assume since the no fire condition is on two cylinders and not random it can't be regulator or injector related. Leaking intake gasket could do it normally but it shouldn't cause a no spark condition. Any thoughts?

Re: 5.3 multiple misfire, any advice?
 

Pull the plugs on 4+6, are they wet? Check for spark while while you have the plugs out. My guess is going to be plugged injectors.

Re: 5.3 multiple misfire, any advice?
 

That is entirely possible, I had to unclog them to get it to start. It had been sitting for 4 years and all 8 were stuck. However, would a clogged injector cause the coil to not fire? Timing light shows no spark at all on those two. Just for fun I checked the fuel regulator and it was putting gas in the vacuum line. I ran and got one and installed it and now I have a much smoother idle (smells less rich too) but I'm still not seeing fire on 4 and 6. Could a bad injector actually cause that?

Re: 5.3 multiple misfire, any advice?
 

Ummm... I don't get it. I checked plugs 4 and 6 and they were a little wet. I pulled 2 just to verify they looked the same. Then for grins I swapped out 6 and 2. The problem followed the plugs. Now 2 and 4 misfire. Is it really possible I just have 2 bad plugs? They were new NGK, and I know everyone says to run delco but I've never had a problem with NGK. I'm going to run out and get a couple and see what happens.

Re: 5.3 multiple misfire, any advice?
 

hows your plug wires

Re: 5.3 multiple misfire, any advice?
 

clogged injectors would provide no means to shut off the ignition system; I'd think you'd throw a error code for fuel injector of possibly 02 (if the mixture was out of whack from stuck injectors).

Check your plug wires or swap the coils, see if it changes.
NGK plugs are more than fine; if you start needing a different heat range, I'd say 75% run NGK's

Re: 5.3 multiple misfire, any advice?
 

Ok, I didn't read your first post very well, sorry. Sounds like you have it narrowed down to plugs and wires. I haven't ever had a problem with NGK, I had a set of bosch platinums just start to give out for no reason a few years ago.

Re: 5.3 multiple misfire, any advice?
 

I got two more plugs and they are firing fine now. I've seen other brands bad out of the box but this is an NGK first for me. Idles smooth now. I'm sure a new regulator that doesn't dump gas down the intake helps! Thanks for all the help...on to the next problem...