dlamb89

I've done almost everything I can think of:

engine/trans oil changes
air and fuel filter replaced
new valve cover gaskets
new full 4 set of appropriate tires
proper inflation
wheels balanced
PCV checked
new updated OEM exhuast
replaced faulty 02 sensors
hi flow cat
iridium spark plugs
premium gas
no CEL

I've gotten 24 mpg on all highway driving with a full trunk and seats. However, I can get as little as 11 mpg with city driving. When I drive city, there's no more than 1 passenger.

My only suspicion is somewhere around the exhaust manifold, collected from these facts:

The flex-pipe is still OK, however there is a visible hole. mechanic A said it's not bad at the moment, and it's not a severe leak.

Mechanic B (Meineke in hicksville NY - they're known for being excellent with exhaust work) - said that the EGR tubing is bad. he also noted that getting to it requires getting around the exhaust manifold, and that might not come out. and if not, that it would open a whole can o' worms.

I really hit a wall here. What have I missed?

Alexbenz

11 city is pretty bad...I get about 300 to a tank mixed but with a lot of city driving I get 240 ish... city the es isn't that good

LexusElite

Damn. You got a led foot driving in the city? Showing off for the ladies? Maybe fuel pump is going.

dlamb89

LOL. No sypmtoms of a bad fuel pump whatsoever. quick starts, good acceleration, no loss of power at higher rpms/speeds. But, Thanks for the input. maybe it's on its way..

Hayk

iTrader: (1)

You should check your fuel trim numbers to see if you're running rich. The CEL comes on only when it's really bad.

dlamb89

Man, the CL app is bugging on my phone. I posted a reply days ago, just realizing it never happened. Anyhow, here is a video of the fuel trims on idle, then i rev it at 2k for a few seconds

Is it gonna be a bad diagnosis since I didn't have the engine warm up completely until I shot the video? I'll do it again if so

Hayk

iTrader: (1)

Let the engine warm up for 15 minutes, or drive it and record the numbers after it reached normal operating temperature. Record the numbers at idle and then at 2k and 3k. This would simulate what your engine is doing during normal driving.

dlamb89

http://youtu.be/3kTW1NU2jpI
Fuel trims warmed up 2k+3k+idle

BDSL

How did you calculate your fuel consumption?

dlamb89

Full tank all highway , then another tank all city.

GS250

disconnect the battery to reset the ECU and pour a bottle of techron into the fule tank.?

dlamb89

how much of techron should i use per 1/2 or full tank? and which type of product, the fuel injection cleaner, or system cleaner? I'm assuming the system, but I gotta be sure. It's a 120k almost all highway mile, proper oil change intervals. Also, any downside or harm done by the product? I also saw some people debate whether to use techron right before or after an oil change (http://forums.pelicanparts.com/porsc...correctly.html)

Hayk

iTrader: (1)

Thank you for taking the time to record that. Your scanner has a refresh rate that limits how quickly each reading is updated on the display. Due to this limitation, I cannot accurately tell what your computer is seeing at every RPM range. If you would like to retake the video, hold the RPMs steady for at least 5-10 seconds, so that the Fuel Trim numbers can stabilize.

You said you went to Iridium spark plugs. On a 1997 you should only be using Dual Electrode Platinum plugs, due to the waste spark design.

To make sure that you're recording your fuel economy correctly, could you confirm that you're using the following method?
1. Fill up till the fuel nozzle turns off
2. Reset Trip meter on the odometer
3. Fill up till the fuel nozzle turns off
4. Divide miles driven between #1 and #3 by the amount of gallons in #3

p.s.: Don't let the car idle for more than 30 seconds, it's a waste of fuel. A cold engine will always run rich (use more fuel than normal) to try and warm itself up. So if you let a car sit for a while, it will burn through a lot of gas that can be used for driving. The most efficient way to warm up an engine is to idle for about 30 seconds, and then get up to highway speed as fast as possible, without going over 3k RPM.

BDSL

Did you record how many gallons of fuel that goes into the tank?

GS250

for techron i have tried the concentrate plus, i used up the whole bottle and refill the tank. for better result you may want to try with half tank fill. I wouldn't worry about using it before or after oil change though.

did you check your brake system? i asked because i had an experience with my Subaru Legacy. the piston on one of the rear wheel did not fully retract when the brake pedal was released. i realised the FC was awful and also found that the car will slow down pretty quickly when i let go the accelerator. sent it to the workshop and found that one of the piston was jammed. replace the seal on that piston and FC went back to normal.