Fuel System Issues?

[vxcp]

Got a new to me 2001 Vx (see 2001 in Florida... under vehicles for sale). Picked it up from a dealer in FL to drive to Austin, TX. Around a hundred miles into the return trip I started having trouble. The Vehicross started bucking severely under acceleration and I eventually got an engine code for low voltage on two O2 sensors. I first found some loose battery connections and reseated/tightened those but that just cleared the engine codes temporarily and the bucking under acceleration came back. Limping into Bradenton, FL for the night, I went to a Pep Boys there on Saturday. They found low pressure in the fuel line (30 (psi?) versus the recommended 50+) and replaced the fuel pump. On Sunday I was able to make it back to Austin, but it was painful.

Unfortunately I'm still having a few issues and I need help identifying the culprit:

1) After about an hour of driving the vehicle starts bucking again (thinking maybe there is a vacuum getting formed in the fuel line?) My temporary solution is to gas up every hour or so. This was tedious on a 20+ hour trip but for the hour after filling up the vx ran great.,

2) My fuel gauge is all over the place. Perhaps this is related to #1, or perhaps the sending unit on the fuel pump also needs to be replaced?

Thanks for your help!

[JAMAS]

2) My fuel gauge is all over the place. Perhaps this is related to #1, or perhaps the sending unit on the fuel pump also needs to be replaced?

This seems to be a common thing. My gauge is great after fill up, then it bounces around a little. I would not think the two are related, but anything is possible. I believe I recall reading that the sending unit has often been the culprit.

Was there a warranty provided by the dealer?

[vxcp]

Was there a warranty provided by the dealer?

Yes, a limited warranty that covered the fuel pump replacement. Hopefully it'll cover some of the other work that needs to be done...

[VX KAT]

maybe a dumb question, but did you replace the fuel filter as well? I know that caused bucking in another car I had.

[vxcp]

did you replace the fuel filter as well?

No, but looks like the dealer already replaced it as its quite new -- I'd guess less than a month or two old. Think I should go ahead and replace it?

[VX KAT]

No, but looks like the dealer already replaced it as its quite new -- I'd guess less than a month or two old. Think I should go ahead and replace it?

...could they have lied about replacing it? It's such a cheap item, I'd replace it again. With the bucking stopping when your tank is full, I have to defer to the more experienced gang here.
Hope it works out for you, I know this takes away from that new car giddy feeling...but it should be resolved pretty soon I'd think.

[vxcp]

I'd replace it again

Roger that.

With the bucking stopping when your tank is full, I have to defer to the more experienced gang here.

Yes, thats the part I can't quite figure out, thinking that maybe filling up is breaking a vacuum on the tank. What sorts of emissions hardware is there on the VX? Perhaps something is plugged?

Hope it works out for you, I know this takes away from that new car giddy feeling...but it should be resolved pretty soon I'd think.

Yes, its been a long few days. Looking forward to getting the vx up and running like a champ.

[Y33TREKker]

Low pressure on the fuel line could have also been caused by the Fuel Pressure Regulator being faulty, which is a common problem on VX's. A relatively easy replacement cost/procedure too. Irregular fuel pressures from a faulty FPR could have also caused the low voltage readings responsible for the codes you were getting from the O2 sensors.

I don't know exactly what goes wrong with the stock FPR's on VX's, but given the mileage on the one you purchased, it's likely that the original is still in place, so it would be a likely place to start.

Congrats on the purchase, and welcome to the site.

[tom4bren]

Have them clean the MAF as well. Those symptoms were very similar to some problems I had when I first got mine (including running better with a full tank).

[MSHardeman]

FPR replacement how-to:
http://www.vehicross.info/forums/sho...or+replacement
I used Dino's instructions and got the fuel pressure regulator replaced in not time with minimal knuckle damage.

[Dmitrikr]

Have them clean the MAF as well. Those symptoms were very similar to some problems I had when I first got mine (including running better with a full tank).

got four Isuzus last year in the shop with codes for both O2 sensors. But the problems were - MAF sensors on two; on other two-someone forgot to tight the clamp at air intake hose to plenum - created air leak not counted by MAF sensor

[vxcp]

Low pressure on the fuel line could have also been caused by the Fuel Pressure Regulator being faulty, which is a common problem on VX's

I don't know exactly what goes wrong with the stock FPR's on VX's, but given the mileage on the one you purchased, it's likely that the original is still in place, so it would be a likely place to start.

Okay, sounds like a good thing to replace in any case. If the FPR is the problem anyone have ideas on the mechanisms whereby it'd cause the issues I'm seeing (how would refueling get the FPR working right for an hour)?

Congrats on the purchase, and welcome to the site.

Appreciate it.

[Y33TREKker]

Okay, sounds like a good thing to replace in any case. If the FPR is the problem anyone have ideas on the mechanisms whereby it'd cause the issues I'm seeing (how would refueling get the FPR working right for an hour)?

FPR's on VX's are well known to be inhabited by irrational/irregular problem causing mechanical demons who operate under time-frames exhibiting no rhyme or reason. Historically, that's been the most regularly documented mechanism for issues on VX's like the one you're experiencing that have turned out to be FPR-related anyway.

Or in other words...not a clue.

[vxcp]

Have them clean the MAF as well.

Will do.

FPR replacement how-to:

Excellent.

[etlsport]

are you sure its filling up that helps the problem? could it be just having the vx turned off or opening the gas cap?

I remember when my FPR went, i would have starting issues, but if i opened the gas cap it would hiss, and things would work better, def try that