OK so I'm getting the pesky P1171 P1174 P0171 P0174 codes on my 04 Discovery 2, I've changed all 4 o2 sensors, the MAF, the airbox cover (old one had broken clips and didn't seal). Anyone have any other suggestions for getting rid of these damn codes?

My normal mechanic doesn't have any idea other than what I've already done, and I would rather not get bent over at a dealership if there's something simple I'm missing.

I had my mechanic do a test for vacuum leaks, and he didn't find anything.

I'm using high test gas so I don't think it's fuel.

Thanks

 

Are these new codes that have re-appeared or old resident stored codes? If old codes have them cleared and start afresh before you spend anymore hard earned cash. A mechanic with a code reader/scanner can clear all the codes and then after a week of use take the truck back for a re-scan of the ECU's and see what new codes, if any, have re-appeared. Before you clear all of the old codes store them or take a print out of them to be able to compare later when you have a re-scan.

 

I'm a novice, but earlier today I power washed the engine bay at a self-service car wash. The yellow service engine soon light came on. I read through this forum and noticed a particularly easy fix so I tried it and it worked for me. One poster wrote, "dirty battery cables have been known to be a problem for service engine lights (sic)"

I removed both battery cables, and thoroughly cleaned them with a battery wire brush cleaner. The service engine light did not return when I restarted the car.

It worked for me. Good luck.

 

OK this issue is caused by three major possibilities
1. Bad fuel pressure. ...
major cause would be a bad fuel pump and/ or filter.

2. unmeasured air going in the the cylinders,
major cause a vacuum leak

3. the meter that measures air not working
major cause MAF or MAF plug


First thing to do is to get a good code read, a code could help you pin point the issue, an example is a scanner can tell you is the signal from the MAf is is present. bad or intermintant.

Next smoke test your air intake. this is a good video that explains vacuum leak possibilities

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finally have some ine pressure test your fuel.

 

so this should be your thought process

 

The Plenum is held to the manifold with 6 bolts.
One is under the alternator.

I would make sure the inner 4 bolts are just snug and not loose.
Too tight and you snap them.

Make sure the MAF is fitted well.
Make sure the IAC motor is fitted well to the rubber hoses.

Make sure the vac lines for the brake going into the Plenum is fit.
There is a small vac line next to it.
Check that one as well.

 

Ok, the codes are new. I have one of those ODB2 readers. I cleared the codes after replacing the MAF then let the wife drive it for a few days to get a drive cycle in.

I'll have to check the bolts to make sure they're tight I never messed with them before. I am worried that I am getting a small leak at the intake manifold, how rough is this to do myself?

Also, if it's low fuel pressure and is the pump, please tell me it's not in the tank...

Thanks for all the places to check. I'll let you know what I find.

 

The fuel pump is easy to access. There is a plate in the load deck at the rear with access below to the fuel tank pump. Bearing in mind yours is no doubt petrol go careful but you can check the pump pressure here or in the engine bay fuel delivery pipe.

Definitely worth smoke testing the system before you rip off the intake manifold as there may be other leaks. The smoke test should take less than 30 minutes and is pretty useful and conclusive.