[jeremymik84]

Hey, i have a 2005 nissan titan with 150k on it (dinosaur i know:serious: ) anyway, here recently my truck has started doing a weird thing at idle.. it idles at about 825-850 (turned up in bullydog) and once every 15-30 seconds it will drop rpm's to about 600-625 for about 3 seconds and then hop back up to regular idle... its not a rough idle and no other performance issues. i have a k&n CAI and bullydog with 87+2 tune running 93 octane gas. it did finally throw a code of p0171 and after clearing it a couple of times it finally showed p0171 and p0174. i replaced the passenger side o2 sensor and have the drivers side o2 sensor ready to be installed and was going to pick up a new MAF sensor.. i tried cleaning the MAF but no help.. the truck runs perfect ( other than a way too sensitive gas pedal for some reason) except for extremely bad fuel mileage when the SES light is on. I've searched around and seen these same codes alot but not with the symptoms im having. any suggestions? if i left anything unanswered i can answer ASAP, but the only other problem im having out of my baby is a really stiff steering issue.. maybe time to flush and refill with new PS fluid.

 

[dubyam]

The codes are for lean condition, as you likely already know. Start cheap on these. Replace the PCV valves. Check all the vacuum lines. Get a fuel pressure gauge or have a shop check the rail pressure. Check for misfires by cylinder (it's hiding in the deeper OBDII data). Could be a bad injector or bad plug/coil or an arcing plug due to a split plug boot. And have an exhaust back pressure test run to see if you're running lean because you have constricted cats.

I'd be curious to know why you have your idle turned up so high?

 

[jeremymik84]

i have replaced the PCV vales (about 2 months ago when i noticed they were stuck) i will check vacuum lines again ( i tried spraying carb cleaner and listening for RPM rise) and quickly checked over them but i will re check. i will work on checking the pressure at the fuel rail, i did just have the sending unit replaced by the dealer under good will warranty (probably messed something up lol) how would i know if it is a bad injector, coil or boot? its not throwing any misfire codes and not running bad other than the intermittent drop in RPMs at idle... and as for the idle im not sure, it was set at that when i went through the process of installing the tune... i can drop it back down to 650 no problem. as far as the cats, i literally just replaced the manifolds about a year ago with dorman replacements surely they wouldnt be clogged already?

thank you for your time and help, hopefully we can get this figured out! lol

 

[dubyam]

Plus and boots are easy to check. It's a visual inspection. You'll know which one is misfiring or cracked and arcing.

Testing coils is a little harder but a shop can do it, or you can buy a testing tool and do it at home. If you're not going to test a bunch, might be better to just let the shop test them. There may be an easier way than I'm thinking, so maybe Google testing coil on plug setups.

The Dorman manifolds could be part of the problem. Aftermarket manifolds are sketchy quality, from what I've heard. But they may be fine.

 

[jeremymik84]

yeah, i figured they couldnt be worse than the POS ones that they put on in the factory lol, i wont replace them again... ill slap some headers on it... i am going to install the bank 2 o2 sensor and see if that helps

 

[Nick Name]

I hate to be that guy, but there are seven areas,(not seven parts) on your truck that could be where the lean condition originates. I've seen something as evasive as a bad injector 'o' ring be the sole cause. It may be worth a few bucks to get a mechanic with a good analyzer on that truck. Just replacing a good MAF with another good MAF, which would do nothing, would more than pay for that tech's work.

My instincts...(I don't mess with tuners)....tell me your tuner is part of the problem. Return to a stock tune and see what develops before chasing an inconvenience that may not be an actual problem with your truck. If a lean condition code pops during 100 miles of driving at a stock tune, you know the truck has a problem that needs diagnosis. The way you're doing it now could cost a lot of money on nothing more than an Easter Egg hunt.

 

[jeremymik84]

couldn't hurt to try that Nick, thanks for your insight i will give it a shot.. today at lunch, i was sitting in y truck eating and the whole time it never skipped a beat on the idle. never dropped rpms or anything... so random lol

 

[jeremymik84]

it has still been doing it lately, i tried to get the d/s o2 sensor off and it was a booger so im soaking it in pb blaster until tonight when i try again. i repalced the MAF sensor and it seems to drive smoother but still drops rpms at idle ( cannot get it to throw a CEL code though) it seems rythmic... i literally JUST took my truck off +2 timing advance ( seemed to make it idle smoother and less dramatic rpm drop) and i uninstalled the whole tune back to stock. we will see what this does... any other guesses?

 

[jeremymik84]

o2 sensors fixed it.

 

[DaveyJ]

Good to know! I put on Dorman replacement manifolds last year as well (2005 LE 4x4) and I started getting a P0171 code about a week ago that keeps coming back no matter how many times I clear it. I was pondering whether it could actually be a bad sensor, or if I should look elsewhere first. After reading your post, I think I'll start with a new sensor.

 

[IMADOGMAN]

Check the downstream flange gasket too. Mine leaked and it threw that code on the upstream sensor.

 

[DaveyJ]

Check the downstream flange gasket too. Mine leaked and it threw that code on the upstream sensor.

Thanks! Had a small leak at the gasket, and after sealing it up, haven't had any more codes. I think that did the trick :big_grin: