Check out their website I think they test them as well. I don't think they mess with vortec though.

 

OK, here is a quick review of what I’ve done so far on my 99 Suburban K1500 (130,000 miles) 5.7 liter engine:

Replaced components: cap, rotor, spark plugs, plug wires, idle air control valve, and both O2 sensors after the catalytic converter.
Cleaned: EGR valve, new gasket
Cleaned: Ran Seafoam through the intake and gas tank

Issues:
Still have the rough idle and misfire when accelerating when the engine is cold
Rough idle is not bad when the engine is warm.
Misfire code on Cyl #3, Sometimes #4

Checks:
Fuel pressure is 62 psi when pump is running and engine off.
No vacuum leaks found

I’m not sure what to do next. Suggestions are to replace fuel injectors, fuel pump, EGR valve. Each of these items are looking at $100 - $300 each so I don’t want to just continue to swap out parts that aren’t fixing the problem. Any suggestions?

Thanks,Frank

 

I may have missed it in your posts but did you check compression?

 

No, I haven't done a compression test. But I'll do one this weekend and post the results. I know that there shouldn't be much of a variance between cylinder to cylinder but about psi what should they be?

Thanks,
Frank

 

I would say 100psi or better andnote that highest to lowest reading is not more than about 20% apart.

 

Very similar symptoms with our '99 Suburban have been diagnosed as blocked catalytic converters. Failure codes indicated O2 sensor, EGR and misfire. The shop was able to run a back pressure test to confirm the cat's as the problem. You may also be able to test your vehicle by removing the O2 sensors temporarily and driving the vehicle that way. There will be noise but the open O2 sensor hole will relieve some of the pressure, if that is the problem. The cat's have not been replaced yet and I will post again to confirm the repair.

 

I just joined the thread because I am having the same problem with the same truck. Sounds like replacing the cats could be the best first move(?) Also, anyone one out there had an emission test done on this model truck WITHOUT cats in the system? Curious if it would pass.

 

I've kind of given up on it for now. The weather in Indiana has changed to very cold and when it did the rough idle went away. I did have the code for a misfire at a specific cylinder so I change that spark plug and it went away for a few weeks. then another code for a different cylinder showed up with the rough idle so I change that spark plug. Each time it goes away for a while. It does burn a little oil which might be fouling the plug, but it doesn't look too bad when I change it. So, right now I'm just living with a little bit of a rough idle when it warms up into the 40's or higher. I won't see that temperature very often until spring so I'm just waiting for warmer weather to start working on it again.

Frank

 

So my P0304 message for piston 4 misfire with Traction Control & Service Stabilitrak message led to Collapsed Lifters on the right hand side. This only uncovered after I replaced spark plugs, spark plug wire, swapped ignitors, performed fuel injection cleaning. Condition worsened while I was on vacation. I started receiving a P1175 message, constant engine clicking noise, in addition to consuming 2 qts of oil. In the end, took it to dealer after local mechanics wanted to replace the entire engine. Replaced Collapsed Lifters on the both sides and was good as new.

 

Ours will not throw a code but runs rough. Replaced the fuel filter, spark plugs and wire. Still acts bad. Could the timing be bad or bad gas??