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Mike V.
Mike V., Nissan Technician
Category: Nissan
Satisfied Customers: 20132
Experience:  Nissan factory trained and Certified Subaru Technician.
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2000 nissan frontier: v6..running fine..skips miss..under load

Customer Question

2000 nissan frontier v6 225k on car
repl tbelt
had approx 100k on old belt
car was running fine before. just did as normal upkeep
now once car warms up runs extremley bad. skips miss and or studders under load.
what could be the problem.
if belt was off wouldnt it damage the valves? or is something else wrong.

no faults stored
smoke test for any leaks non found.
Submitted: 2 years ago.
Category: Nissan
Expert:  Mike V. replied 2 years ago.
Greetings Sir or Madam and welcome to JA! I will do my very best to assist you with your problem.
HI there!
First, one tooth off will not hurt the engine. If it is off more then say 6 or so, then you can run into problems.
Since there is no check engine light, i have some additional questions. When it starts running this way, does it idle rough?
Can you get the engine to go up or over 3000 rpms during this problem?
Customer: replied 2 years ago.

As it gets worse idle is somewhat affected.

At first idle is ok

 

No cant get car over 3000 rpms

Expert:  Mike V. replied 2 years ago.
Ok, do you by chance have a scan tool and not a code reader?
Customer: replied 2 years ago.

Possibly.

what do you need me to check or do.

I have someone that has a Mentor tool if that is what you mean

Expert:  Mike V. replied 2 years ago.
Well, I would like to know what the fuel trims are when the engine is hot. I suspect one of 2 problems here. Either the distributor is heating up and dieing out on it, or the mass air flow sensor is messing up when the temp gets hot.
I have seen them both fail without causing the light to come on. The maf sensor is more common because it is sending info to the computer, the problem is it is sending wrong info. So the light won't come on.
If you can get the engine up to temp and get some rough idle out of it, sometimes you can unplug the maf sensor and if the idle smooths out, then you know it has to be replaced.
This is about the only test you can do on it without being able to read the fuel trims and the info coming to the computer from the maf sensor.
For this we need a scan tool. If you would like to try unplugging it and see if there is any improvement, let me know what happens.
Customer: replied 2 years ago.

I have tried disconnecting the mass air flow.

It did not help.

 

I will try shortly to get the info on the fuel trim info.

 

My only problem with distrubutor or mass air flow is that belt was done yesterday.

No prior problems. was running great.

 

That is why I wondered if belt could be off a notch or so and causing problem.

 

No wiring was disconnected. Yet did fold harness back slightly to access other components.

 

Even wonder if could be problem with harness.

 

Thats why I am trying to determine if I need to pull back down and reinspect. Even though had double checked when installing and had someone else also ck over me and it seemed good then as far as the timing marks

 

I will check fuel trim and get back with you shortly

Expert:  Mike V. replied 2 years ago.
Another option to try is to loosen the distributor and turn it a bit with the engine running to see if it changes anything.
With the miles you have a wire issue is possible, but it seems it would happen hot or cold. If the mass didn't change it and knowing the belt was changed yesterday, then might rather put a timing light on it and make sure the timing is correct.
Customer: replied 2 years ago.

not sure if my last message went thru.

so this may be a duplicate

 

stft bank 1 reading negitive .08 to 0.0%

stft bank 1 sensor 2 reading 99.2 %

 

stft bank 2 sensor 1 reading 4.7%

stft bank 2 sensor 2 reading 99.2%

 

short term ft bank 1 flucuates 0.0 to 0.8 %

short term ft bank 2 flucuates 5.5 to 6.2 %

Expert:  Mike V. replied 2 years ago.
Ok, see if you can compare the maf readings to what I have here

Looks like the tool should be able to find these. I am see ing a real issue here on bank #2
graphic
Customer: replied 2 years ago.

Not at car right now.

I did ck the air mass reading before and made a note yet dont have it with me now.

I do want to say it was 4 or slightly over 4 g.m/s at idle. Did not check it off idle.

The other items I am not fimilar with yet will ck and see. However it will be tommorrow before I can check. Will get bck with you asap

Customer: replied 2 years ago.

Did find picture I saved showed air mass reading at 4.0 g/s

man absolute press 9 iHg

o2 sensor 1/2 volts 0.00 v

o2 sensor 2/1 volts 0.14 v

o2 sensor 2/2 volts 0.08 v

Then the rest was the other reading earlier about short term fuel trim.

I will look tommorow for the other specs on the chart.

If I have a picture can and or how can I attatch it to this?

Expert:  Mike V. replied 2 years ago.
If you are using fire fox or IE, there should be a tool bar in the question box. Use the paper clip icon to upload a photo.
I will be on most of the day tomorrow and I will get back to you asap as well.
Customer: replied 2 years ago.

Good morning.

 

As the evening went on yesterday the truck began to run rougher than before.

Got to where you couldnt drive it at all.

A/c even quit blowing cold.

 

Let car set overnight

\A/C is fine today

Drove car approx 4 miles before noticing problem

Drove total of 8 miles before problem got bad. Yet still not as bad yet as yesterday evening but I am confident it will get worse again as the day goes on.

 

The air mass reading is the only reading I can get from the scanner.

I did test it at 2500 rpms it read 22.3.

 

You asked yesterday if the car would get over 3000 rpms.

Today when first driving it did.

Then as problem begin to act up it was more under load above 3000 rpms.

As the problem gets worse then, no the car will not get over 3000 rpms

 

When doing original repair nothing was disconnected on the wiring harness. However did remove metal pipe that runs from valve cover to valve cover. It is located somewhat under the distributor.

Then lifted harness back to access front of engine.

Thinking maybe we had bumped the connector to the distributor and it could be loose.

So I pulled the connector to inspect and reinstalled (not seeing any problem). and made no difference after doing so.

 

Was going to ohmn out the coil in the distributor yet cant get disconnected to test. How does that connector work and I am doing any good or wasting time in that direction.

 

Waiting on any new thoughts or info.

Expert:  Mike V. replied 2 years ago.
Here is the test for the coil. It should unplug by pushing the tab down.

graphic
Expert:  Mike V. replied 2 years ago.
Ok, question, 22.3 what?
voltage or g-ms
Customer: replied 2 years ago.
monitor reads 22.3 g/s
Expert:  Mike V. replied 2 years ago.
At most it should be 14.9 at 2500 rpms.
This is the problem. I bet if you watch it when it's cold, it will be in range and then as the engine warms up it starts reading out of range. I can't explain why this is occuring after the timing belt, but I can see it is feeding the wrong info to the ecm.
This is also why you can't get the engine above 3k, there is a fuel cut off at 3000 when the ecm can't feed enough fuel to catch up with the amount of air coming in.
Customer: replied 2 years ago.

Ok I had about come to the same conclusion of air mass or coil. Even though I have a hard time understanding why instantly after replacing tbelt.

I will order the air mass and repl. Part wont be in untill tomorrow. But we will give it a try.

Only question is though I would have to ass/u/me that when we disconnected the airmass yesterday it would have went to base setting and made some minor improvements but it didnt.

what do you think?

I will let you know how it turns out

Expert:  Mike V. replied 2 years ago.
Normally is should have improved the idle. Things are pointing at the maf sensor, but perhaps, it is a intake air leak. Maybe, just take some carb cleaner and with the engine running rough, spray it around the intake and throttle body and see if the idle speed increases or smooths out.
With it unplugged, it will go to the memorized fuel trim settings. Since they are off, may not see the improvement I was expecting.
Also, it is key to disconnect the battery for an hour after installing the new one. Otherwise it will still run poorly off the stored fuel trims. This will reset them.
Customer: replied 2 years ago.

I am going thru a battery reset now.

Thanks for the tip. I will do it again if replacing the air mass meter.

The engine at idle doesnt always run bad or only for a split second then is ok.

More under load is the worse.

However I have done a smoke test and no leaks detected.

I will try later with engine running and carb cleaner.

Air mass meter is on order and will arrive tomorrow around 10:30 am Central Time

Expert:  Mike V. replied 2 years ago.
Ok, now after you reset the fuel trims, it may actually run worse, if it does with the old sensor then we got it.
Customer: replied 2 years ago.

Been out of pocket most of the day.

 

No luck with airmass meter.

 

However on a hunch and had also ordered distributor with ignition coil build in.

Thats what it felt like was a coil breaking down after heating up.

But just couldnt believe it happened instantly after replacing timing belt.

Just couldnt make a mental connection between the two.

Again dont know if distributor was bumped when removing metal pipe under it that ran from valve cover to valve cover.

 

But I guess I have seen stranger things happen.

 

Thanks for your help and guidance.

 

I have never used this system before.

 

I have been hitting the "Reply to Expert" button evertime I was finished.

 

So I will do the same this time to be sure you get my responce.

 

However for you to get your pay for your time do I need to respond back and then select the "Accept Answer" button?

Expert:  Mike V. replied 2 years ago.
It is totally odd alright to have the distributor cause and issue right after the belt.
I knew it was a toss up between the 2, but the lack of check engine light, as well as the fact the truck wouldn't go over 3K rpms really had me thinking maf sensor.
Just press accept if you are satisfied with what we tried.
Thanks
Mike

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