decreased gas milage

[99Rodeo]

my gas milage has decreased by 60 miles per tank....
I was informed that my fuel pressure regulator was bad and that by replacing it would bring my milage back to normal.
IT STILL STINKS!
Now the mechanic "suspects" that it is my fuel pump (a $700 repair).
I am not replacing that on a hunch.
Has anyone heard of or had this problem???
Please help!!!

[amigo-2k]

I have lower gas mileage what can I do?

Might be due to, colder weather, winter grade gas, dirty PCV valve, dirty EGR, dirty fuel injectors, low tire pressure, front and/or rear end needs to be aligned, dirty air filter, weak battery or weak alternator. If you replace or clean any of the above pieces make sure you disconnect the battery for at least 15 minutes so the ECU will recalibrate itself.


http://www.geocities.com/endre_rl/isuzufaq.htm

[rodeo02]

Originally Posted by 99Rodeo

my gas milage has decreased by 60 miles per tank....

How is the truck running? What codes are you getting? A blind guess would be a dirty MAF, bad O2 sensor, or like previously stated, a blown diaphragm on the fuel press regulator causing raw fuel to be drawn thru it's vacuum line into the intake (you should have starting problems if this is the case).
G/luck
Joel

[Jacquelyn]

My CEL has been on for a couple weeks now and after diagnosing the code (P1441) I had a dealer take a look at it to confirm. To the tune of $350 they would replace the fuel pressure regulator. I bought the part online for $56 and wonder how difficult it will be to install in my 99 Rodeo 3.6 4WD? What I received is not was I was expecting-this part doesn't look like it's enough to wreak the havoc it has with difficult starts and stalling..... Any advice or input from you guys? How much of an ordeal will this be to install? Thanks for your help.

[amigo-2k]

http://geocities.com/endre_rl/isuzufaq.htm#faq22
my Truck takes a long time to start (cranks an excessive length of time).

Leaking fuel pressure regulator is the common cause:

photo of the fuel pressure reg

http://forums.vmag.com/suvrodeo0300/messages/785.html

Quote from the above link:

The original symptom was a Check Engine Light with a #6 cylinder misfire code of P0306 when set at idle, or a random misfire P0300 when set while driving. The #6 was obviously running rich as indicated by the the spark plug. Eventually it became a hard start also. Here's the fix: The fuel pressure regulator was leaking fuel down it's manifold pressure vacuum line. The vacuum line attaches to the manifold right above the #6 port, that's why the richness only in that cylinder.

Fuel pressure regulator part # for 1999 Rodeo: 8-17113-398-0

Cost $54 from St. Charles Auto, http://isuzu.stcharlesauto.com/ (my local dealer's cost is $75. St. Charles Isuzu got it to me overnight for $65 which is cheaper than the local dealer sells it for. Funny that I could get it quicker and cheaper from Wisconsin than from the dealer down the street here in California). I was in contact with a guy named Merlin. Great service.

See below for tips on changing this part in a 1999 V6 Rodeo M/T.

Read the whole thing prior to starting the job. I replaced the regulator in about 40 minutes and I wasn't rushing. It seems to have completely fixed these problems:

1) Erratic Idle (needle now rock solid at 750 RPM)

2) Frequent stalling at idle - doesn't stall at all

3) Hard starting - starts like it used to. No need to give it gas

. 4) Intermittent CEL light - gone The regulator has no electrical connections.

It is a diaphragm operated relief valve mounted on the fuel rail. Before attempting to change the part, you need to ensure that you remove all fuel pressure from the system. The following procedure from the service manual works like a charm. I used this procedure and there was absolutely no fuel pressure in the system. No fuel leakage at all when I removed the regulator. Fuel Pressure Relief Procedure (works great).

1) Remove the fuel cap.

2)Remove the fuel pump relay from the underhood relay box.

3) Start the engine and allow it to stall.

4) Crank the engine for 30 seconds.

5) Disconnect the negative battery cable.

Caution - to reduce the risk of fire and injury, it is necessary to release fuel system pressure before servicing fuel system components. Even after relieving fuel system pressure, a small amount of fuel will likely be released when servicing fuel line connections. Cover fuel line fittings with a shop towel before disconnecting the fittings in order to absorb any fuel that may leak out.

Leave the fuel pump relay out and the battery disconnected while you change the part.

Changing the part on a 1999 Rodeo is a bit different than the service manual shows. The regulator does not screw into the fuel rail. It sits down into the rail and is held in place by a snap ring.

Once you have removed the fuel line and the bracket that blocks access to the regulator you will clearly see the regulator and the snap ring. Before you start the job make sure that you have a pair of snap ring pliers that fit.

Use the new snap ring that comes with the part to ensure your tool will do the job. You will also need to modify a 6mm allen wrench by cutting the short end to within approximately 1/4" of the 90 degree bend. You will need it to remove the rear most of the 2 bolts that mount the bracket that is over the regulator. Ideally you should have two 6mm allen wrenches, an unmodified one for the front bolt and the modified one for the back bolt.

For ease of removal of the snap ring that holds the regulator in place on the fuel rail, it can be easily rotated once you have access to it by hand using the fuel line nipple for leverage. This enables you to turn it to a position where the snap ring is easily maneuvered out. Make sure that you remove all parts of the old regulator from the fuel rail before attempting to install the new one. Make sure that you remove the large blue o-ring, the wire mesh screen and the small black o-ring from inside the fuel rail. Just make sure that you remove all of the parts that you see on the new regulator.

Once you have it all back together, install the fuel pump relay and hook up the negative battery cable. Also make sure that you put the fuel cap back on. Start it up. Done.

http://www.automotiveforums.com/vbul...=159663&page=2