Hi all,

I rebuilt the engine of my 04 disco (4.6l) about two months back (top hat liner time) and it seems to be running good, I’ve done about 2kmiles since the build. I got some early cylinder misfire codes after the build but they went away.

Since the rebuild I have been getting sporadic codes such as p0171 and p0174 on my ultra gauge classic but they never stay long enough to be stored. They only appear as pending and then disappear.

My fuel trim numbers don’t look right though. Short term trim on both banks looks good and fluctuates at (-3 to +3) but long term fuel trim on both banks Sits steady at (+20 to +23). This definitely ain’t right from all the research that I’ve done.

Weirdly I read on another forum about a tranny fault code somehow being related and I recently got a p0734 tranny code up too. I didn’t even think it was related until I read that post earlier.

All four 02 sensors are brand new, leads are new, plugs new, running 91 octane. Car gets 11.5mpg in City with knobly 33s and a lift. MAF g/s reads 4.3 at idle and 25 at 3,000 rpm.

I did randomly get some codes indicating a vacuum leak in the fuel system but they also went away.

Could this be the maf? I heard not to clean it so haven’t done that. Maybe vacuum leak somewhere? As I say I recently rebuilt and replaced all vacuum lines. I’m kind of lost, done heaps of research but can’t move forward in this.

Help pls??

Thanks
Marc

 

 

 

 

Ok I’ve ordered a new Bosch maf for the sake of $250. If that solves this I’ll throw up the results for anyone getting a combo of p0171/4 and tranny codes in the future. It’s pretty much the only thing that ain’t new so I took a punt it was a maf.

 

That is a very nice looking truck! Nicely done.

 

Thanks dude. It’s actually my wife’s daily. After the rebuild I just said what the heck and bit the bullet on a bunch of stuff I have been wanting to do for years.

Ok for future reference: the new Bosch maf solved the issue. I could have got a Cardone for about $150 after cash back but I decided to pay $250 for a Bosch. They also don’t offer cash back but I’d rather peace of mind.

So lean codes with random tranny codes and those 20+ long term trims would indicate a maf was out. Also my four 02 sensors seemed to me modulating between 0 to 0.9 fine (I checked that before biting the bullet on the maf).

Ok the other personal lesson for me and I’ve read it a million times is the LR mafs do not like brake cleaner. Long range trim was moving between +20 to +23 so the maf was at the end of its life anyway and after trying to clean it long range trim for both banks went to the max +25 and would not budge so I think the cleaner destroyed he last working bit of the maf (Don’t try clean mafs)!!

Hope this all helps someone in the future.