1990 Q45 Cold Weather Power Surge, Lower fuel mileage

[slshearer]

Hello,

I have experienced a new problem with my acceleration from a dead stop when the temperature is cold at around 30 to 40 degrees, this condition only occurs when starting to drive from stopped. If I press the gas pedal a little hard the engine power surges causing the car to jump then hestitate or jerking, If I am careful and lightly touch the gas the engine runs fine, Once the car is moving at say +25mph the engine runs great and has no hestitation.when it is warmer the re is no problem with accelaeration from a dead stop.

I have noticed a decrease in my mileage in the past couple of months, I used to get about 380 miles to a tank, combined city and highway but now I get about 320, I just had my emmissions checked for my tag renewal and it passed without a hitch, the technican stated the engines emissions were very good and he did not suspect a problem with the sensors that control the engine.

Maintenance History

services were done about 1 year ago and now have about 10,000 miles since the service.

New Factory Plugsall new Infiniti belts,new fuel pump,Water PumpCooling System FlushThrottle Body CleaningK&N Air filterNAPA fuel filterShocksNew Brake Pads.Rebuilt Steering RackTires 245/45/zr18 @ 35 lbs.

Thanks for your reply!Stewart

Modified by slshearer at 11:47 AM 2/14/2008
Modified by slshearer at 11:47 AM 2/14/2008

[maxnix]

Well, first off, no maintenance history.

MPG is a variable indicator in that colder temperatures require longer warm ups times on initial cold start to reach operating temperature.

Sounds like your car has a fair degree of deferred intake and fuel system maintenance.

Luckily, you live near T-3. Might want to get a survey of conditon for your car from them and plan a triaged plan of catch up.

[qship96]

380 miles to the tank combined city/highway sounds impossible!

I average 300 per tank combined, 400 if strictly highway only,as in part of one long journey.Been consistant like that for the entire cars life.

[slshearer]

Hi,

I live in a rural area of Atlanta, most of my driving is on the Interstates probably 75% of my mileage is highway so that might explain it, I am only getting about 320 but I guess with the colder weather it would be less due to warm up times.I have owned my Q since 1992 and use Mobil1 so reliablity has been awesome.

Thanks
Modified by slshearer at 12:11 PM 2/14/2008

[slshearer]

Maintenance History

services were done about 1 year ago and now have about 10,000 miles since the service.

New Factory Plugsall new Infiniti belts,new fuel pump,Water PumpCooling System FlushThrottle Body CleaningK&N Air filterNAPA fuel filterShocksNew Brake Pads.Rebuilt Steering RackTires 245/45/zr18 @ 35 lbs.

[maxnix]

Two things.

1.) Unisnstall the K&N inferior and contaminating filter. Install the OEM one. You probably have to clean your MAF sensor. Be careful!

2.) Never run your tank below ¼ full for extended fuel pump life.

Always use OEM filters from Joe.

Notice there is no intake maintenance or fuel system maintenance other than the NAPA fuel filter and TB cleaning? Not good!

Fuel and air filter changes should occur at least annually. And now that you will be getting ethanol, time to think of ISO-Heet as well as BG44K.

[slshearer]

Hi,Actually the fuel filter was a last minute replacement as we could not find the one I purchased form Joe, Currently, there is no ethanol around Atlanta that I have seen so is the plug change necessary? Pretty expensive if not needed, Thanks for the tip on the fuel tank level, I will watch that closer, I was going to service my MAF but the mechanics at the Toyota dealership I do some work for recommended not to touch it so I left it alone, I have used Techron fuel cleaner every 2000 miles in my gas I have never had a problem with fuel till recently when it is real cold here as I described, What kind of tire pressure would you run, I have a set of 2003 18" Q45 wheels with ZR tires,the sidewall says max 50 pounds I have them set for 35

Thanks!
Modified by slshearer at 12:26 PM 2/14/2008

[maxnix]

At 35 psi you are probably in the ballpark.

I think in the Articles here or at http://www.Q45.org there is a section on cleaning the MAF.

Q45tech reports seeing ethanol in Atlanta.

Techron is aspirin, BG44K is schedule A. If you buy a Tier 1 gasoline like Chevron, it has techron in it.

[slshearer]

HiuAre you referring to BG Cleaner, It is what I used when I did all the service work, I only added the BG to my gas tank. I used a Throttle body cleaner to clean the TB, I was surprised that it was appeared very pretty clean as the car had 182000 miles on it

Thanks for all the help, I will call t-3 and have them pull any error codes and give me a diagnostic evaluation.

Thanks again!Stewart

[Q45tech]

Probably defective knock sensors and harness.

[slshearer]

Hi,Actually the fuel filter was a last minute replacement as we could not find the one I purchased form Joe, There is no ethanol around Atlanta that I have seen so is the plug change necessary? Pretty expensive if not needed, Thanks for the tip on the fuel tank level, I will watch that closer, I was going to service my MAF but the mechanics at the Toyota dealership I do some work for recommended not to touch it so I left it alone, I have used Techron fuel cleaner every 2000 miles in my gas I have never had a problem with fuel till recently when it is real cold here as I described, What kind of tire pressure would you run, I have a set of 2003 18" Q45 wheels with ZR tires,the sidewall says max 50 pounds I have them set for 35

Thanks!

[Q45tech]

Historically oem use to specify 80% of max psi as inflation pressure but when tires were made more ballon like [50-51 max psi] they didn't up grade the method.

35 psi cold undriven should expand to 38,39,40 after highway use?

[maxnix]

35 psi cold undriven should expand to 38,39,40 after highway use?

Definitely worth measuring when you arrive at your destination, providing you also have a before cold measurement.

If gain is 5 psi, you are porbably too low. Total gain whould be 2 - 3 psi at most.