R50 3.3 V6 Misfire Only 1500-2100 Rpm Specific Area

[onurgocmen]

Dear friends,

I have a big trouble last 2 years on my 1998 3.3 v6 manuel 5spd 4x4 transmission pathfinder. Pathy sometimes good but sometimes misfired only 1500-2100 rpm on the way in any gear.(neutral gear or idle position no problem this hesitation only when acceleration/on the load) 

My car accelerates at 1000-1400 rpm without hesitation. It is still unhesitating between 2200-6000 rpm.

I tried the followings but I can't figure it out for 2 years,i think i am gonna burn it.

-new spark plugs(i tried 3 set for NGK BKR6E-11-BKR5ES-11 and Platinium NGK 7090) There is no obvious defect in the spark plugs when i removed.
-new spark cables 3 set. 
-All pistons have ignition, because I tried pulling the plug cables one by one.
-new hitachi maf sensor and i tried my friends car mass air flow sensor. Values good 4.8 g/s idle and 14.5 g/s 2500 rpm
-changed before a new coil-new chamshaft position sensor (RSB56 ignition control module),rotor, cap and finaly i bought 2 new distributor during this time. Advance timing checked and adjusted with timing gun 13-15-17 btdc over and over.(i know timing adjust procedure, car always in operating temperature, tps bottom/ brown socket unplugged mode and the pulley mark is in the 4th notch from the left.)
-new throttle position sensor and i tried my friends car working tps and adjustments on the nissan service manual procedure with 0,3mm-0,4 mm feeler gauge or 0,48v trick. I tried throttle body cleaning and checked all spring bolts possible cracks connections
-I checked all grounds,tried new cables.
-I tried egr delete (I canceled the egr with sheet metal and all hoses blinded)
-I tried 2 different fuel pumps. Change it fuses and relays. I changed fuel filter 2 times.
-I tried 1 new map sensor and tried myfriends car sensor.
-I tested at 2 different times all injectors in the test machine. They dont leak or dont have bad spraying.
-I tried other fuel alternatives and i connected liquid petrol gas system. You know this have 6 new lpg injectors,tank,ecu and injector harness. But no difference.
-I checked 3 times timing marks from the camshaft and crankshaft sprockets. (40 teeth and 43 teeth verified on the belt from service manual)
-I tried another timing tensioner.
-I checked it charge unit. Normal voltage 12.2 v-car working voltage 13.7-14 v
-I tried new battery.
-I changed 2 times crankshaft sensor on the transmission bell 
-I changed knock sensor 
-I tried another air filter and air temperature sensor
-I checked fuel preassure regulator. Vacuum hose connected 34 psi and disconnected 42 psi its good. And no fuel leaks or cracks on the vacuum hose.
-I changed up 2 oxgen sensors.
-I checked evap leaks from the hoses blowing a smoke.
-I changed PCV and hoses
-I changed Engine Coolant Temperature Sensor
-Checked 2 cats its always empty.
-I tried good working car ECU(its same 1998) and i found same model ecu harness i try it 500 miles but no different.(You know the ecu harness connects to almost all sensors and distributors, this isnt bad connector or cable problem i have comfirmed)
-I tried new injector wiring harness.
-I checked brake booster for vacuum leaks
-I checked all vacuum hoses i tried spraying carburator cleaner all important points. And i try smoke machine on the intake manifold.
-İdle stable 800-850 rpm but, i changed iacv and fic selenoid. I tried it blinde a idle control valve hoses.(for possible vacuum leaks but dont solved)
-I changed oil preassure sensor.
-I tried all sensors unplugged mode. speed sensor-maf-map-o2-tps-evap-knock-crankshaft-egr-
-I checked all brakes-all u joints and rear-front shafts and rear differantial limited slip locks-bearings-teeths.
-I finally had the complate engine rebuild. Replaced piston 0,50mm, ring, valve seals,all lifters, oil&water pump, gaskets,all belts and other possible parts. Top cover grinding and adjustments were made. But no difference:(

Have you encountered such a problem before? Or another advice? I don't think so, I don't have any problems on slopes or at different speeds but maybe clutch maybe transmission maybe intake and exhaust valves? Sometimes Pathy works fine and this problem does not appear in this range itself. And this misfire has never happened for outside the 1500-2100 rpm range. My car can run fine for hours/ non stop 200-300 miles and its works always max 91 Celcius

I have a ODB scanner and i check all sensors referance values from the nissan service manual.I changed it even though i knew some parts were working.   I have 2 trouble code but its not important. (back o2 sensors because cats empty and i tried sometimes unplugged mode) I checked long and short fuel trims but no problem on the values LTFT1&2 or STFT1&2 in the +%5-%5 range.

It is very difficult and expensive to find another engine in my area. I need your suggestions to solve the problem.

[mdmellott]

Do you have a misfire trouble code reported or does it just feel like a misfire at that rpm range?

[mdmellott]

A faulty fuel injector? You've changed out and rebuilt everything else.

[onurgocmen]

unfortunately I don't get any code about misfire. only back o2 sensor heaters. Sometimes I try unplugging the rear o2s but that doesn't fix the problem. Yes, this misfire is just a feeling. It is as if the fuel is cut off and given back 15-20 times in the 1500-2100 rpm range. i changed fuel pump, fuel filter, relays and wiring. And i have secondery fuel system lpg. It can operate independently of gasoline. The LPG system I added later has its own injectors and cuts off the gasoline completely and injects its own gas. So I think it's not an injector problem.

[mdmellott]

The LPG system I added later has its own injectors and cuts off the gasoline completely and injects its own gas. So I think it's not an injector problem.

With that level of modification complexity, I wouldn't know how to verify this or related aftermarket process function augmentations to the engine controls that may be suspect.

[onurgocmen]

I added later to see if I could fix this problem with a new fuel system and injectors. I can disable it completely whenever I want, but it doesn't fix. Again, thank you very much for your suggestions.

[onurgocmen]

And update we checked last weekend, all cylinder compression 145-150 psi.

[doode]

I had nearly the same symptoms as you...my car sputtered and ran like crap between just off idle to a tick under 3k.
It drove like a bag of crap for about 3 days and then it got progressively worse, to the point flooring it would only get me to about 40 km/hr

Took it to a shop and they diagnosed it to be the distributor.

[onurgocmen]

I had nearly the same symptoms as you...my car sputtered and ran like crap between just off idle to a tick under 3k.
It drove like a bag of crap for about 3 days and then it got progressively worse, to the point flooring it would only get me to about 40 km/hr

Took it to a shop and they diagnosed it to be the distributor.

Thank you for your suggestion. I bought 2 new distributors but I guess I'll try to find the original from the junkyard. I hope it gets resolved and it's worth the effort.

[MisterH]

I had nearly the same symptoms as you...my car sputtered and ran like crap between just off idle to a tick under 3k.
It drove like a bag of crap for about 3 days and then it got progressively worse, to the point flooring it would only get me to about 40 km/hr

Took it to a shop and they diagnosed it to be the distributor.

Thank you for your suggestion. I bought 2 new distributors but I guess I'll try to find the original from the junkyard. I hope it gets resolved and it's worth the effort.

It may take some searching but I recommend you replace it with a rebuilt OEM Hitachi distributor, as that's the one that will last. That's what I purchased when my original failed a couple years ago. I paid just under $300 for it.

[mdmellott]

... Advance timing checked and adjusted with timing gun 13-15-17 btdc over and over.(i know timing adjust procedure, car always in operating temperature, tps bottom/ brown socket unplugged mode and the pulley mark is in the 4th notch from the left.)

According to the FSM, starting on page EC-35, this is true. https://www.nicoclub.com/service-manual ... 8%2Fec.pdf However, according to my Haynes Repair Manual, this is only true on 2001 and later models where the self-diagnosis mode is not possible by a mode selector at the PCM under your front passenger seat. With the system in self-diagnosis mode the, PCM control of the timing will be disabled, instead of disabling this control by unplugging the TPS. I have no idea why this would make a difference but it will cost you nothing to find out if your ignition performance improves at low RPMs if you do the ignition timing check and adjustment again by simply putting the PCM in self-diagnosis mode, start the engine, rev it to approximately 2K RPM a few times, then let the engine idle and warm up to operating temperature before aiming the timing light at the timing marks.

My old '91 Pathfinder had a similar ignition timing check routine, utilizing the mode selector on the PCM. It's been a long, long time but I do recall that when I set my timing on that old '91, the timing mark was steady and never varied even 1deg from its set position while I watched it with the timing light. It burped and spit on occasion while idling and I could see the timing mark waver a degree or two at that instant but otherwise it was rock-solid steady. If yours is a continuous variation between 13 and 17 degrees BTDC, I'd be suspicious of fast idle cam, idle speed or idle mixture ratio adjustments not being quite right.

[onurgocmen]

thank you i think oem distributor will be delayed now because currency now x11:( it would be worth it if i knew if it would improve.Unplugging the TPS will disable both the computer and the idle motor as far as I know. I'll try either way though.

Although I canceled my EGR with sheet metal, I found an uncontrolled air passage in the electronic solenoid valve that triggered the EGR. No trouble codes, but the valve is broken and is creating a vacuum leak into the manifold(stuck open). I blocked this vacuum, now it's a little better in acceleration. I still hear a sound of air around the suction pipe. I taped it all over and sprayed carburetor cleaner, but I'm not sure if it's just an ordinary air passing noise, a gust of wind on the propeller rotation, or a muffler noise. Maybe my problem is vacuum leak which I really can't find. (Next step is to check the possible map/baro switch leaks).

Egrc Selenoid Valve

[onurgocmen]

I've read dozens of articles canceling egr with sheet metal. I don't know, maybe if I replace the solenoid valve and start the system again, the problem can be solved. Maybe the system really needs an airflow in this rpm range over the EGR?

[onurgocmen]

this weekend i tried the distributor, egrc valve and air suction box and pipes of my friend's car. unfortunately there is no change.