jeff350373

hello i'm jeff just looking for a little help or advice I have a 98 es 300 3.0 I've been fighting with this lean condition for a while p0171 veh has new bank 1 a/f sensor new mass air flow sensor new coolant temp sensor airfilter plugs +wires, at idle if you listen too the exhaust you can hear a little stumble almost like a small misfire thud.with the scan tool hooked up it seems too misfire at hire rpm from mutiple cylinders veh has good fresh gas+numberous cans of injector cleaner + new fuel filter when i first hooked up the tool i was getting a steady misfire from number one cylinder pulled out #1 spank plug charcol black swapped plug misfire still there. just too verify bank 1 is between engine and radiator corrrect and bank 2 is between firewall? veh shoots out black soot out the exhaust too and smells.air duct is all tight no exhaust leaks this veh is driving me crazy if someone could point me in the right direction that would be awsome. This is my first time in this club THANKX jeff

jhill20

iTrader: (1)

jeff if u have a scan tool hooked up can you tell me what the fuel trim readings are at idle? both long term and short term.

GEORGE_JET

Bank 1 is the rear bank, next to the firewall. Bank 2 is next to the radiator. I looked up p0171, and it shows as a rich condition. If you can get hold of a scanner, I would suggest checking both bank 1 &2 sensor #1. My quess is that you have a leaking injector, but to properly diagnosis this you will need a fuel pressure gauge, and a pulser.

jeff350373

thankx for looking at my ad i got a hold of a scanner the fuel trim. Short term fuel trim bank 1 is +19.90% long term bank 1 is +39.9%. bank2 short term fuel is -0% and long term is +0.67% thankx again i worked on it some more today tryed cleaning maf c/k fuel pressure 55psi at idle

jhill20

iTrader: (1)

ok so first off p0171 is a LEAN code. not rich. The fuel trims definitely reflect that. The reason that they are positive or rich, is due to the the computer seeing unmetered air somewhere after the MAF....you could very well have a clogged injector. This is common to your engine. If you have a scanner that is good enough to look at a misfire counter in the datastream this could help you very much in determining which cylinder is the problem.

The other possibility is a vacuum leak, like a cracked vacuum hose or even a intake manifold gasket. Have not seen very many intake manifold gaskets leaking vacuum though. It is a double stamped metal gasket.

If this car were in my service bay, first thing I would do is let the car warm up to operating temp at idle, have your scanner hooked up watching your fuel trims. With a can of carb spray in one hand carefully introduce the carb spray around your vacuum hoses and intake manifold gasket, always keeping an eye on the fuel trims. If you do have an vacuum leak, as soon as the carb spray finds it the fuel trims will jump back down to zero or go negative possibly.

If you get no results with the crab spray. You'll need to look into a fuel issue or possibly an HO2S......

let me know if this helps....

jeff350373

thankx i'll run some more tests tomarrow

GEORGE_JET

Looking at the fuel trim, I would have to agree. I will have to look up that code again, because I am sure alldata listed that as rich. That would not be the first time the printed a error.

But I do dis-agree about a leak, if it is shooting black soot out the exhaust, I would suspect the O2 sensors are staying low. And the computer is adding fuel to enrich the mixture. A vac leak would cause the same trims numbers, but you would not have the extremely rich exhaust.

llcoolpass

ignition coil or egr malf possibly, but I'm getting confused reading this thread, so this will be my last comment in this thread until I start to understand. jeff's first post is ...... wow.

llcoolpass

ok so you pulled the wrong spark plug out ,jeff.

and the rest of the guys are debating why your cars computer is adding fuel, and clearly you smell that it runs rich.
but they are right that this means bank 1 is lean according to bank 1 upstream o2 sensor.

that means the ecu is wrong about needing more fuel . so, it made wrong conclusion based on data from its sensors. o2 and maf injectors leaking valves leaking intake gasket fuel pres anomaly [fuel filter, press reg, pump] all lead culpirits.

O2 sensor are huge culprit, especially the bank1. that is the rear head, the one near the firewall. due to the fuel trim. check this sensor out first.

since the two banks differ so significantly, its probably not the air flow meter .

it's possible there is one or more of the rear injectors acting up, or the front's, but, check the o2 at this time. also, if your o2 got 80K miles or more, its ALWAYS time to change them[upstream parts].

you can get a solid rod and use it as a stethoscope to hear your injectors, or use a piece of vacuum line.

you should also clean the maf sensor [carefuly using off teh shelf product that is for that purpose], just in case, if you used a k&n air filter. this is massively common prob on nissans and VWs

mmlex1987

I have to agree with the black smoke it is definitely a rich condition and not a lean condition.