P0174

[green99]

My 99 Flex Fuel 3.0 2WD has been running poorly for some time and now has gotten worse. Lousy milage, poor running, no guts, etc. I've pulled various codes and thrown parts at it, but to little avail. The code that consistantly comes back is P0174 indicating a lean condition bank 2. So far have replaced 4 injectors, 2 O2 sensors, MAF sensor, EGR valve, EGR sensor, fuel filter.

Seems odd that it would throw P0174 (lean left bank) and not also P0171 (lean right bank). This tells me that whatever the problem is, it's only affecting half of the engine. I'm guessing a leak in the intake manifold could possibly cause one side to run lean, if the leak were on the bank 2 side only. Any thoughts? I did take it to Pep Boys for a diagnostic, but I don't have any confidence in their results so far.

 

[Southern3.0]

I'd look for leaks round the intake gaskets or vacuum leaks, spray some starting fluid around the lower and intake gaskets and if the idle changes you found a leak. Also listen for a hissing sound and try to track down any broken vacuum lines

 

[green99]

Thanks for the tip. I've tried the starting fluid method, but did not notice any change in the rpm. I can't really get close to the intake manifold gasket because the plenum is in the way and Pep Boys said the vacuum system checked out ok.

Again, since the lean code is only for bank 2 of the V6, it would seem to rule out problems that would affect both banks. I'm pretty sure it must be a leak in the intake manifold on that side. Yes?

 

[Southern3.0]

You could have a leak in the lower intake to upper intake gasket and not affect both sides, each cylinder has its own runner in the intake so if you had a leak in a runner for for the left side that side could go lean, you see what I'm getting at

Also you could to pull the plugs to try to find out exactly which cylinder(s) are lean, the cylinder(s) that are running lean would be hotter so the plug will probably look cleaner and maybe glazed over.

You could also use a noid light to check if your getting a pulse signal at each injector

 

[green99]

Thanks again. I'm pretty much convinced that it must be the intake gasket(s). My next free weekend I think I'm going to take a swing at replacing the gaskets, however I'm tempted to have the dealer do a diagnostic first. For a fairly involved job like this (for me anyway) it might be worth $100 to be sure that I'm not barking up the wrong tree.

 

[Southern3.0]

Yea making sure what your changing out is even broke is always a good idea. If you go the dealer route for the Diagnostic make sure you go to a good dealer, I know my dad has always had better luck w/ Merc dealers Because there not as busy.


Good luck, keep us updated.

 

[green99]

I'll report back with the outcome later. I have heard that intake manifold gaskets are a common problem.

By the way, thanks for the photo! I'm happy to see that I won't have to remove the injector rails. I think I can do this!

 

[Southern3.0]

If it dose end up being an Intake gasket, the upper is pretty easy. To do the lower intake you have drain the cooling system, pull the valve covers, Remove the passenger rear and drivers front Rocker arms and pushrods in order to get the intake off.

Autozone has the repair manual for truck online tho

http://www.autozone.com/shopping/repairGuide.htm