We have a 99 Suburban K1500 that had an engine light on with originally a P0308 (misfire Cylinder 8). I have replaced the spark plugs, wires, coil, ECM (was also an error), but still have a light on and the idle feels that it is missing.

I also bought a fuel filter but cannot figure out how to best let fuel pressure go.

Since I noticed that the plugs seems a little wet (I think fuel), I wonder if I needf to replace the injectors or if there is something else to give the engine too much fuel. These spider injectors are quite costly and try not to replace something that is not needed.

This vehicle is my stepdaughter's car and my wife is going nuts driving her all around town and to work, so any help is appreciated.

Thanks!

 

is the check engine light on? The system works with pump delivering regulated pressure on demand to the engine, the rest is bypassed back to the tank.

 

Yes, we have a CEL, which used to be a P0308, but will have to go check it again.

 

Have cylinder #8 compression checked. If compression is good then replace the injector assembly with the updated part

 

If the misfire is random, how much play can the distributor have and what the issue with the intake gaskets? Are they prone to going bad?

 

5.7 is not prone to intake vac leaks. Play in the distributor will not cause a single cylinder misfire. Distributor problems are not common either

 

Given that its over 10yrs old its very possible the injectors and poppets need to be replaced, however It would be wise to check the fuel pressure for good measure.... the tool that you check the pressure with will most likely have a valve for releasing the pressure also...
if not let the vehicle sit for 30-60 min and it will bleed down on its own, also soon as your crack the filter seal any remaining pressure will release, no matter what you are going to get some fuel spillage so keep that in mind and don't work directly under the fuel filter....

on my 97 I was getting hard starts and rough idle but no codes, I replaced the injectors, poppets and regulator and she fired right up and ran smooth afterwards... I found that running a couple of bottles of injector cleaner through a couple of tanks provided temporary relief for the hard start and idle so that is what lead me to the injectors...

 

Thanks for the replies. One thing I wanted to mention is that under more RPM the engine sounds fine, but under idle you can feel this hesitation. I am for sure going to replace the fuel filter though.

One thing that keeps me awake is the fact that the engine light comes on once the engine is warm, not when cold. I can't stop thinking of the fact if there is a sensor that thinks that the engine needs to run rich. The MAF looks like new, so I am not convinced that is problem.

Any ideas in that matter??

Thanks again

 

Fuel filter and MAF sensor will not cause a single cylinder misfire

 

So we took the truck to a shop for diagnostics and it was determined that cylinder 8 has low pressure. I believe they said it should have 180, but was only 35.

The shop also mentioned that this is most likely a valve issue, particularly an intake valve as thetruck burns fuel, and it runs rich. They want to charge us $700 just for the labor to pull it apart, which I will do myself, but I like to know if someone can confirm it makes sense what they clain. i sounds about right to me, but I have not done too much internal engine myself.

Thanks!