LannyL81

So after checking the ducting after the MAF (all was tight), "PCV" hose is fine, no cracks or splits; I have a question:
Would a loose fuel tank cap cause these codes to be set? That was the only thing I could find was that the fuel cap would not twist tight and I had to replace it.

If not, then where else might I look? I did check around the intake for any cracks, different color, oily or wet area and found nothing.

I cleared the codes but have not taken it out yet to see if they return...thought I would ask here first.

corvet786c

Look for cracks or dried out rubber. Intense heat could cause this.

LannyL81

I guess I will check the ducting after the MAF, PCV hose, again. I also did not see how a loose fitting fuel tank cap could cause a lean condition, but thought I would ask.
Going to take it out on the road today and see if the codes return...same road/trip that the SES light came on last week.

Thanks for the replies.

LannyL81

Update: so I drove the same path yesterday as I did previous Sat with the only exception, that I did not fill-up with fuel. Only change I made to the car was the new fuel tank cap.....no SES light on. I am going to check for pending codes today.

LannyL81

I did check for any pending codes and there were none.

04train

I had these codes popup a couple of times when I first got my Z06. I had not driven a manual in quite some time and when I would glitch a shift they would popup along with the CEL. I cleaned the MAF and stopped missing shifts and problem solved. If you have an automatic then sorry no help.

chasb4570

About six months ago, our '04, six speed coupe was doing the same thing. 21,000 on the clock. I went through everything including replacing the MAF. One thing I did not think of was the fuel pump. It was going bad slowly. You should have ball park 60-65 PSI, this one was down to 25 PSI. Caused the same codes. Check your fuel pressure when running and after the car has sat for a day or two.
Chas
I live in Mesa. If you want to talk, PM your number.

LannyL81

Pretty sure not related to shifting, (yes it is a manual), as I was cruising at about 80 or so when the SES light came on.
I think it is fuel pressure related hence why the loose fuel cap was the problem, but could be an early sign that the delivery fuel pump is going out. I will be checking the fuel pressure later today. Thanks for the suggestion.
And chasb4570....summer is here.....just in case you had not noticed.....LOL....

chasb4570

Oh, I noticed alright. We went to Plastic Fantastic in San Diego last weekend. Spent Monday in Julian. Tuesday on the way home through Yuma, car readout showed 113F.
Chas

LannyL81

I checked fuel pressure with key on twice, engine off: gauge showed 55psig. Cleared pressure and did key on engine off: gauge showed about 50psig. Let it sit there and an hour later pressure was down to 40psig. Let it sit overnight, pressure pretty much zero.

Sooooo.....suggestions????

chasb4570

I did not stay at a Holiday Inn while in San Diego last weekend but I think you need to replace the pump assembly including the back flow valve. Your description matches what I just went through. Late '03 cars and all '04 have a driver's side tank with the pump assembly mounted through the top of the tank. This predicates dropping the tank. I decided to have the work done by a recommended shop and suffer the pain in the wallet instead of my back. Cost was under $1,100.00. Had my street tune rechecked afterwards, what a difference!
Not where I wanted to spend the money, but had to be done.
Chas

LannyL81

Let me clarify what I did:
With gauge connected to fuel rail, I turned key to ON, waited until IP self test completed, then turned to OFF, removed key, waited 15 sec, then inserted key, turned to ON, waited until IP self test completed, then turned key to OFF, removed key. That is when I checked the gauge and it showed about 55psig.

I cleared pressure and then inserted key, turned to ON, waited until IP self test completed, then turned to OFF, removed key. Gauge showed 50psig.

I then let it sit and checked back every hour or so and saw the pressure slowly drop.

Just now I went out and with gauge still connected, started engine. Gauge showed 60psig and was steady; I let it run for about 10 minutes.

Agree that there is a leak in the system and is likely the check valve, but will need to determine if engine side or tank side first. Not looking forward to dropping tank(s). Also not having any starting problems as I always let pressure build before starting engine.

Thanks for the replies.

LannyL81

Read through the thread and correct that my '04 is not leaking down like his was. I was also thinking that since I have no problems with starting or running, that the injectors are fine and not leaking which logically means it is the check valve in the left tank.

As far as dropping the tanks, no I do not have access to a lift. Have read where others were able to drop tanks without a lift; hopefully I can do the same. Not doing this right-away since not having any problems and the pump itself seems to be fine. Perhaps this Fall when it is not over 100°F in the garage.....IF car remains drive'able.

Now to save that info on the FFS fuel system....