Gozar

2003 vert. Vararam intake and that is about it.

Runs great until you lean on it hard. At about 3500-4000 rpm it starts detonating bad and then it starts backfiring through the intake.

Two different tanks of gas.

Fuel filter getting clogged so it is starving?

Come on experts... help me out.

lucky131969

No lean codes? What's your fuel pressure?

MTPZ06

When is the last time the fuel filter has been changed?

Gozar

Just got the car today and drove it from San Diego to Sacramento. (500 miles)

I haven't looked through the codes yet.

My guess is that the filter has never been changed.

Last C5

Check the clamp connections after the MAF.

dougbfresh

This usually happens when some RUBE installs a CAI and allows unmetered air past the MAF sensor by not installing it correctly.

jovette

dirty MAF? Agree that you need to check codes, clear all H/history codes. Fuel filter is not a bad guess, but generally better if you don't have to guess. Good luck!

Z06supercharged

2003-2004 years are not serviceable fuel filters that are outside of the tank. Its inside the tank and is considered a non serviceable item. You have to pull the tank to access the fuel pump and its parts and its a PITA...

Dirty MAF maybe so id defiantly clean it since it only takes 5 minutes or some water in the gas you got some where, or the lousy winterized higher ethanol % gasoline just hit all the stations here in Ca as well starting last week and will affect all cars with worse gas mileage and worse performance...
3700-4000 is where your MAF takes over full time so I bet its dirty.

03WhiteConv

I am having the same issue on my 03 vert. Looked for the fuel filter today and couldn't find it.

I read somewhere that the advanced fuel system without the easily accessible filter came in late 03. And looking in the GM Tech service manual 03 shows the filter replacement procedure and it is deleted for 04.

Mine was built in Dec 2002 so it should be there above the drivers exhaust on the rail, I just don't see it though.

If it's in the tank, I thought there was an access panel to the tank in the left wheel well. Any truth to that?

Here is the thread with all of the stuff I've chased. http://forums.corvetteforum.com/c5-t...-its-guts.html
I kept thinking fuel filter in the back of my head but I really didn't think it had enough miles to need one.

Z06,
If it is in the tank, is it a dealer service? What do you think that might go for?$$$$

Gozar

The former owner called me and told me it happened to him before. It is the exhaust check valve. Apparently when they stick they can cause this behavior.

He cleaned it with carb cleaner and WD40 and said it fixed it before.

I ordered a new one today. I just hope it is the easy one on the drivers side and not the one behind the intake (which has to be removed to replace).

Oh, and it has not thrown a single code.

03WhiteConv

Mine started with a P1415 drivers side air check valve. I replaced it, no dice. That only runs when the car is warming up and then the air pump shuts off. I had mine on a data logger today and once it is warm it was commanded off. I think it's just for emissions and I have read a bunch of posts where people mod their cars and delete it completely. Mine only threw the code in the morning during the first few minutes of driving.

Bill Curlee has a good procedure for cleaning that valve, http://forums.corvetteforum.com/1559066886-post18.html

Z06supercharged

Nope there is no access for it at all cept from the top. If its built after November 25th 2002 with a VIN after 114930 (last six digits) it has the FFS (I call it Fu**ed Fuel System) that is top tank accessible only. You have to pull the tank out then pull the pump out but its a non replaceable filter on the pump itself.

Here is how the FSS works and all parts:
http://www.corvetteactioncenter.com/...el+Tank+System

Z06supercharged

I tuned my AIR pump out and took it off completely cause of that code and drivers valve always sticking. No way im pulling the intake to change the stupid valve. Too bad GM engineers didnt have enough brains to put the passenger valve easily as accessible as the drivers side.. I left the lines and valves in for smog visual check though but they have no idea nor does their computer tell them its tuned out or pump removed and not working.

03WhiteConv

Drag 116831 are my last 6!!

RedRiderZR1

Actually it is the other way around. Passenger one is hard. Drivers is easy. At least that is the way it is on my 99. My passenger one was throwing the code. I just tuned the error out. No more problem.

Z06supercharged

Oh my bad! Your right what was I thinking! Drivers is the easy one and passenger is the PITA behind intake...
I stand corrected and will correct above post...

Jnape

Dealer did my 04 vert under warranty. $1885.00, a good tuner shop would be much less though....

David426

That would be my first guess and is an easy fix.. A loose clamp will let air in, causing a lean condition. This is common on cars with aftermarket air intakes. It has happened to me on my 99 and my 02.. Do you know for sure you are running lean?? Codes?? A carbon build up will cause detonation too.. When is the last time you ran Seafoam through the fuel system? Finally, when was the last time you cleaned the MAF sensor? Start with the simple stuff

myoriginal77

I'm having basically the same problem with an LS1 that I installed in my C3, check under my sig for the other post as I try and work through it. So far no solution.

Frank

03WhiteConv

Did you find it yet?? I took mine to the dealer and they found that the exhaust was restricted. They ordered it under warranty (8 years/80k miles).

You might want to check yours. Just pull the HO2 Sensors one at a time and put a low pressure gauge in its place. They should all read around 2 psi. If the before cat readings are significantly higher on one side or both, you might get a free pipe too!!

The warranty covered all of the diagnostic fees and mechanic time for my 03 Vert.