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Marty
Marty, European Car Expert
Category: UK Car
Satisfied Customers: 397
Experience:  ASE & Bosch Certified Master Tech. Over 30 years experience.
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I have a 201 Nissan titan 5.6v8. Struggling with an

Customer Question

Customer: Hi roy,
I have a 201 Nissan titan 5.6v8. Struggling with an engine misfire.
JA: Thanks. Can you give me any more details about your issue?
Customer: The vehicle has had an LPG Conversion, Random misfire fault codes stored. Replaced plugs & coils, Also inlet mani seals but still present.
Dropped cats to check for break up/Blockage as well
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Customer: No problem
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Submitted: 1 year ago.
Category: UK Car
Expert:  Jay replied 1 year ago.

Hi, My name is*****'m happy to help you. During our conversation, I may be presenting you with different things to try, and ask you some Questions to get a better understand of the issue so I can answer your question properly. So stick with me to the end, and I am sure we should be able to get this issue resolved for you!

Did you have this misfire before you replaced spark plugs? What brand spark plugs did you install?

Does it run ruff all the time, or only after it warms up?

Customer: replied 1 year ago.
Plugs were replaced to try & cure the fault, Vehicle runs poorly all the time cold or warm
Customer: replied 1 year ago.
NGK Plugs were fitted
Expert:  Jay replied 1 year ago.

Two things I have seen cause this. First is the Catts break apart and cause a exhaust restriction. But it looks like you checked for that.

The other is the Fuel pump. It does not put out the proper pressure which can cause running issues and lack of power. To verify it's the fuel pump a fuel pressure gauge would be installed to monitor fuel pressure. It should be around 56 Psi and not drop lower than 35 to 40 psi when accelerating. I did one 2 weeks ago that fuel pressure dropped to 15 psi under acceleration.

Customer: replied 1 year ago.
Ok , I can check this, The fault occurs even at idle would fuel pressure drop cause this even at idle?
Expert:  Jay replied 1 year ago.

The fuel pump I worked on, had good pressure at idle. But lost it under acceleration. You could have it low at idle causing the misfire. That is one of the basic checks you do with misfire codes.

Customer: replied 1 year ago.
Hi there, Sorry for delay, Fuel pressure checks out OK, It is worth mentioning this seems to only misfire on one bank. Right side as you sit in it
Expert:  Jay replied 1 year ago.

Do you happen to have a scanner? The only thing I can think of that really may be causing this is maybe a restriction in the exhaust?

Customer: replied 1 year ago.
The exhaust has been disconnected after the 1st cat, There appears to be no restriction or break up of cat
Expert:  Jay replied 1 year ago.

You didn't do both catts?

Customer: replied 1 year ago.
The 1st cat appears to be part of the headers? so this has been left in place, Can be taken out if req.
Expert:  Jay replied 1 year ago.

Do you happen to have a scanner to graph 02 sensors? That will tell you for sure if you have a restriction or Catt issue

Customer: replied 1 year ago.
Unfortunately not
Expert:  Jay replied 1 year ago.

There is only so much you can do with out a scanner. You could have a A/F sensor not operating properly which could be causing a imbalance of fuel trim which can cause a misfire. You also want to monitor intake timing to make sure the sprocket is working properly as well.

Customer: replied 1 year ago.
I will obtain/borrow one
Expert:  Jay replied 1 year ago.

ok