Honda Techs!?!

[CompSyn]

I’ve been chasing the cause of 2-to-3% fuel dilution in my 1997 Honda Civic EX (1.6L Vtec). First, I had the fuel injectors professionally flow tested and cleaned. They didn’t appear to be the problem.

Then I read this thread by harry j. He was experiencing 1.5% fuel dilution with his 1993 Honda Civic and apparently corrected the problem by replacing the fuel Pressure Regulator (FPR).

I noticed that the factory FPR on my car appears to be an intake manifold vacuum assisted bellows assembly.

So the question: Would an aftermarket short ram intake with conical air filter affect intake manifold vacuum to a point of causing the FPR to meter fuel incorrectly?

 

[Mau]

fuel dilution is common on all honda's. They are tuned to run rich. Pick up a VAFC controller and reduce the fuel mixture.

 

[J. A. Rizzo]

I seriously doubt the intake setup is the cause of your fuel dilution and here's why: The FPR runs from intake vacuum inside of the throttle, on the opposite side of the throttle body from your intake setup. Since the only restriction in the intake setup 99% of the time is the throttle position, the vacuum to the FPR (and other vacuum-operated systems) is almost certainly not affected by the intake setup at any time other than WOT. Even then I have my doubts, but I feel very confident that's not the problem in your case.

Honda engines do seem to show fuel dilution frequently, and I don't know that anyone has really explained it well. If it was my car, I would be checking the PCV system (hoses and valve) and make sure the FPR is not leaking. Some FPR's, and I don't know that this is true about your Honda so someone please correct me if I'm wrong here, have a diaphragm made of flexible plastic that can rupture. If it ruptures for whatever reason, you can get fuel in the intake and dilution of the engine oil. These things can go unnoticed unless you have problems like hard hot restarts or long cranking before a start or weird codes about fuel mix at idle. Barring that possibility, I would probably chalk this up to typical Honda high fuel dilution rates.

 

[CompSyn]

Originally Posted By: J. A. Rizzo
I seriously doubt the intake setup is the cause of your fuel dilution and here's why: The FPR runs from intake vacuum inside of the throttle, on the opposite side of the throttle body from your intake setup. Since the only restriction in the intake setup 99% of the time is the throttle position, the vacuum to the FPR (and other vacuum-operated systems) is almost certainly not affected by the intake setup at any time other than WOT. Even then I have my doubts, but I feel very confident that's not the problem in your case.

Honda engines do seem to show fuel dilution frequently, and I don't know that anyone has really explained it well. If it was my car, I would be checking the PCV system (hoses and valve) and make sure the FPR is not leaking. Some FPR's, and I don't know that this is true about your Honda so someone please correct me if I'm wrong here, have a diaphragm made of flexible plastic that can rupture. If it ruptures for whatever reason, you can get fuel in the intake and dilution of the engine oil. These things can go unnoticed unless you have problems like hard hot restarts or long cranking before a start or weird codes about fuel mix at idle. Barring that possibility, I would probably chalk this up to typical Honda high fuel dilution rates.


Thanks, good thoughts regarding the FPR.

It still bothers me though that Honda, being one of the most fuel efficient auto makers on the planet seems to have issues with fuel dilution, at least in some of their vehicles.

A look back in the used oil analysis here show that many of the Honda/Acuras at
Why is that? Why would one run
I did ask Polaris Labs what the average fuel dilution is for my particular make/model and they told me 2.0%. It looks like Blackstone labs has the same average.

At any rate, my car seems to run okay, is getting decent fuel economy, and the check engine light is NOT on. If there were a trouble code, would the check engine light remain OFF?

Anyway, I did purchase a new OEM Honda FPR and PCV that I will be installing soon. Hopefully, that will get me somewhere???