Hey guys, Paul here. I need some help.

Ever since my marine intake manifold install last year I have been having some problems.

In open loop the truck runs fine. As soon as the engine gets some heat into it, at ide the truck will start to run rich. I mean blowing raw fuel out the side pipes rich. When teh cats light off, flames will actually roll out of the pipes, looks cool, but really isnt so cool.

If I give the throttle a quick blip, it all clears up, but as soon as the revs settle down, the move to rich happens again.
If I hold the revs at ANY rpm, like 2000, 3000 or 4000 rpm the revs will hold, but then the engine will richen up and the revs will fall again.

At WOT the truck has lots of power, its WOT running isthe best it ever has, power and torque is up everywhere. Part throttle driving is horrible, the engine loads up and I need to move to WOT to clear the engine.

New plugs, new O2 sensors, cap, rotor I installed bench tested 24 pph injectors up from the stock 19 pph poppets(I adjusted the PCM IFR for the higher flow).
the engine ran PERFECTLY before the intake swap. Other have done the swap and I am the only 1 that has these problems.

If I unplug the MAFS I get a PO102. No other codes, fuel pressure is 53 psi and jumps to 60 psi when the throttle is opened.

I had vacuum leak between the t-body and the upper intake that I fixed, but the trucks runs no better.

I am not going to give any clues as to what I think the problem is, I want some fresh thinking here.

thanks guys, I really appreciate it.

peace
Hog

 

If you can get a scan tool I would look at what your coolant temp senders are doing. If the engine thinks its colder than it is it is going to dump fuel. Do you have a cooler t-stat? if the engine doesnt recognize the fact that you have a cooler t-stat it has nothing to base its info off of as to what state the engine is temp wise.

Alex

 

Howdy Paul,

Where did you put the O2 sensors on the long tubes?
It sounds like it could be EGR related. Have you completely disabled EGR in the tuning and not just the EGR error codes?

Also, Try to figure out what the absolute maximum idle vacuum (no load, neutral/park) and the minimum idle vacuum (in drive, A/C and electric loads all on). Take your maximum vacuum value in kPa and make that the LOW Block Learn Mode Cell MAP Boundary. Make your minimum vacuum value in kPa and make that the MID BLM Cell Map Boundary. This table in in the FUEL TABLES section. Leave the high value stock.

Also, what is your idle RPM? If your idle is too low and you're getting misfires from the cam, the O2 sensors will see that as "lean" since all they are looking for is oxygen. The more rich it goes the more misfiring it does, the more oxygen, etc. Snowball effect.

Just some thoughts. To this day I'm still tweaking on my setup. I've programmed the PCM more than 200 times. Idle is the trickiest thing of all with this generation PCM. My trouble is preventing it from dippping below idle RPM returning from a quick throttle jab. (That used to be one of my favorite things to do in traffic, pulling the front wheels off the ground just to move forward 30 feet. I have to restrain myself now!)