So this may be long bear with me. I had some mice get into my truck. Before this it ran perfectly mind you. Now its showing I have 3 cylinders misfiring and that both bank 1 Nd 2 are running lean.. the idle is a little rough but the engine light will begin flashing if the truck is pushing itself hard. Like uphill doing 60 or something. I'll lose most of my power. I've replaced my spark plugs, spark plug wires, I replaced my coil and my mass airflow sensor as most of you probably know now I'm more of a parts replacer than a mechanic. I'm cool with it nonetheless I want to know if anyone has ever experienced these same cylinders misfiring. I've been about to pull off my intake manifold to get at the manifold gasket now several times but all my mechanic friends urge me not to do this... i realize it could be fuel injectors but on this model I believe I have to pull my intake manifold off to get at them anyways correct? how loud would a vacuum leak be I've been testing it with brake fluid to try and find one. I'm pulling my hair out over here

 

Also I forgot to mention it's a year 2000

 

How did you verify lean cylinders without using a Scanner?
Guessing is not a good option.
Likely the mice has chewed wiring and hoses.
Find these things out before you tear things apart not knowing what your looking for.
Good luck.

 

I brought the truck to an auto parts store they read the codes off for me. Yeah roger I've looked all my hoses over really well and sprayed brake fluid around them because I heard that would rev your engine up a little if it came into contact with the leak.

 

You have been misled by the Brake spray reaction sources.
Brake cleaner is not generally flammable so does not result in an idle change.
You need to use a flammable like starting fluid.
This will be detected by the Ox sensors when the leak area is found.
The best way is to plug up a Scanner to monitor the short trim fuel table reaction when the flammable is detected.
Pays to know these details or you get stummped.
Good .luck.

 

Very interesting okay I will get some starter fluid and give that a whirl this afternoon

 

Okay I found the vacuum leak yesterday I believe. Replaced the hose, and now the engine runs way better my truck doesnt almost die in idle anymore. However I'm still getting codes P0171 and P0174 banks 1 and 2 lean I now only have misfires in cylinders 2 and 4 my engine light still comes on and flashes at 70. I got a printout of the codes and the computer says to replace positive crankcase vetalation and hose I'm going to look into that today and post what I find

 

Now your making progress.
Clear the misfires next.
If the CEL is flashing, loss of ignition is indicated. .May be the coils or the plug wires.
Do not go by what a Scanner or reader tells you to replace because there is more to the systems than just one part.
You still need to either find more leak area or clear the codes that maybe now 'old' history. This is because repairing a leak does not instantly clear the codes until many drive cycles past to slowly bring the long term trim tables back toward center or less than 25% shift.
Good luck.

 

The use of brake cleaner to isolate vacuum leak has not been affective since they started using "Low-Voc Formula". The use of starting fluid is definitely not RECOMENDED as it will also find any SPARK LEAKS (fire hazard). The normally excepted way to isolate vacuum leaks is with a hand held PROPANE tank with a control valve and a long, small diameter hose. Just remember that propane is a heavier than air gas. So mind you testing location and monitor the o2 sensor while testing for results, since you probably won't see an RPM change with this method. When Bluegrass 7;18602151 wrote "Pays to know these details or you get stummped." it was a true statement, but you could also get burned up! LEAVE THE STARTING FLUID FOR IT'S INTENDED PURPOSE, IT'S NOT FOR FINDING VACUUM LEAKS!!!

 

Brakleen does work
Both types
The chlorinated stuff in the red can is not flammable and that is what I use
It slows the engine down
Where the green can stuff (flammable) speeds the engine up
You can use water
You can use just about anything, all you are looking for is a "change" in idle speed

 

Even better is a smoke test. If you don't have a smoke machine, a simple 8 dollar fluid pump from Harbor Freight (like used for differential fluid) and a cheap cigar will pump smoke into your system.