Different(?) P0171/74 symptoms

[Effieman]

Got the P0174 then the P0171 codes. The thing I've never seen before is that the fuel trims go from around 10 at idle, but increase to 21 just off idle (1500 - 2000).
Had vacuum leaks before, and trims were opposite of what I'm seeing here.
Any suggestions?

 

[franklin2]

Plugged cat?

 

[Effieman]

Doubt it, the cat is just an empty shell.

 

[bills4065]

I suggest you take your rpm to 3000 and check your fuel trims at 3000. If they are even worse- you are looking at a fuel delivery problem, possibly a pump. Have you cleaned maf sensor?

 

[Effieman]

Haven't checked trims at 3000, but have checked fuel pressure, and it seems OK even when revving the engine. Cleaned MAF sensor also. But I have also gotten some pending codes since I first posted this. One was something about O2 sensor wiring (don't remember it, but pretty sure it had a 3 in it). And also a p0401 that set along with lean codes. Replaced the DPFE sensor and hoses, but it didn't do anything. First code to always set is the 174 then 171, then the others...

 

[bills4065]

Your fuel trims at 10% at idle seem high to me. Not saying this is your problem, but worked on a Miata that had partially stuck open egr valve his short term fuel trim at idle was 11 -13%. When was fuel filter last replaced? I would still also check fuel pressure at 3000 rpm.

 

[Effieman]

Wanted to check/clean EGR valve a few years ago, but couldn't get it loose after soaking with WD40 for 3 days, so gave up. Thought I replaced the fuel filter not too long ago....but checked my records and it was December of 2018...64K miles ago. Guess I'm gonna have to get a new one out of the cupboard and put it on. Then I'm still gonna try getting the EGR off again with a better crowfoot wrench.

 

[bills4065]

I would do what you are doing, but I would check fuel trims at 3000 rpm first. Pretty easy check to get out of the way. Ignore in my previous post I said fuel pressure at 3000 rpm. I meant fuel trims at 3000 rpm.

 

[Effieman]

I'll check them again before and after getting the new fuel filter on...