Car running funny, AFR all over the place

[vertigasen]

It has been a while since I've been here, just getting back from Iraq and preparing for surgery has taken up all my time.

My car is an 03 GT, 91000 miles. It was running great until yesterday. I drove it on Saturday for about 2 hours, and stopped by the gas station on base and put in $10. I was going to my in-laws yesterday to pick up some stuff, and gas is about 10 cents cheaper there than here.

When I started the car, it started to spit and sputter, then went to a semi normal idle. The idle had a bucks it in, one about every 3-5 seconds. I have an AFR and it was all over the place during idle, 12.5 - 16. The tune I have is 14.6 across the board. I thought ok, I got bad gas. I went and picked up some STP water eliminator, and STP injector cleaner. I added that today and started it up, and it did pretty much the same thing. After idling for 20 minutes, I went to get more gas, off base this time. While driving, the AFR was even more nutz. I downshifted to turn out of my houseing edition, my AFR went to 11, when I gave it gas it jumped to 18. On the highway, I was in 5th @ 60 mph, if I gave it gas, it would sometimes jump up to 22 AFR, when I let off, it could go to 10.5. I stopped on the side of the highway and took off, after 1500 rpms.....it would level off at 14.6 until about 3500 rpms, then it would consistantly drop so that 4500 was a 12 AFR, all gears. I did it twice to make sure it wasnt a fluke. One last thing to add, my fuel pressure gauge is normally near 40, all day while I was driving, it was 30-35, usually around 30.

After getting new gas, it still acts the exact same way. Still the hickup in idle every 3-5 seconds, not noticable when given revs. Does anyone have any idea what could be causing this? Fuel Pump, Fuel Filter...or just bad gas that needs time to work out.

Thanks

 

[twogts4us]

Swap the (cheap) fuel filter first, but I suspect it's the pump that's acting up...

 

[SaleenGT2001]

your AFR will be all over the place at idle and cruising.

also since the car has been sittng a while you may want to swap in a new wideband sensor

 

[vertigasen]

your AFR will be all over the place at idle and cruising.

also since the car has been sittng a while you may want to swap in a new wideband sensor

I have been driving the car for the last 3 months since I got back, with no issues (I was only gone 5 months before they sent me back for surgery and it was started twice a week while I was gone). It has been running perfect. As for the AFR being all over the place, at idle, i know the AFR goes everywhere, but it has always been within a certain range. Typically 14-15. While driving, the only time it really goes anywhere other than 14.4-14.8 is when you first get on the throttle, or right after letting off the throttle. Under accel, it would stay pretty much pegged on 14.6 all the way through the band.

 

[vertigasen]

Ok, something new today. After running yesterday, today, I let it warm up for about 10 minutes, as soon as I put it in reverse and try to let out the clutch, the AFR jumps to 23 and the car dies. Yesterday, it ran for about 30 mins after I put in the fuel add's before I tried to drive it. I am letting it idle right now to see if letting it warm up for 30 mins or so, but I dont know. An interesting thing, I got it halfway back out, so when I put it in 1st and tried to pull forward, it did that fine, it didn't die.

Any one got any ideas?

 

[twogts4us]

your AFR will be all over the place at idle

Do you have a wideband? Ever seen one? At idle? It SHOULD dance around 14.7...maybe down to 14.2 or so...maybe up to 15... NOT "all over the place"

 

[poindexternasty]

My 02 GT doesn't have a wideband (stock) to my knowledge.... I just swapped out my upstream o2 sensors to fix a very slight stumbling, hitching problem. They are only $32/ea on Rockauto DOT com.

Fuel filters are only $12 or so. Have you swapped that out yet? Do it first, THEN check fuel pressure at different throttles. Check it manually, don't trust the output signal since your pump or sender unit may be on the fritz.

Perhaps your MAF is dirty and sending bad signals to the computer and it is overcompensating and dumping fuel to match. This makes sense because you said your AFR was wildly different at different levels of throttle. Pick up a $5 can of electrical parts cleaner at AutoZone or whatever and give the MAF a shot or two. You will need the tamper-resistant Torx bits to remove the screws that hold the MAF in place. Very gently remove the MAF from the intake, shoot it a few times with cleaner, let dry, shoot again with cleaner, let dry. Repeat 3 or 4 times until satisfied.

DONT USE ANYTHING BUT ELECTRICAL PARTS CLEANER ON YOUR MAF. Sorry for the caps, but its very important you use the right stuff. Anything else will leave a residue and **** it up.

I would do these two things (fuel filter, clean MAF) and then disconnect the battery to reset the PCM.

Let us know how this works for you.

 

[Stark77]

I would suggest replacing your O2 sensors as well.

 

[bhuff30]

Fuel filter or fuel pump. Just as the previous 2 people said.

 

[vertigasen]

oh yeah, def down to fuel filter/pump. I went back out to let it warm up today so I could go over to the auto craft shop on base, but it would start and die right away. I noticed that when I would turn the car on, it would take 3-5 seconds for the fuel pressure to come up to at least 35, when I would try to start it, it would jump to 40, then 0......then the car would die.

I am picking up a new SVT Focus pump either tomorrow or Friday and a new filter. I will get it swapped over the weekend and let you know how it turns out.

Thanks for the help.

J

 

[SaleenGT2001]

Do you have a wideband? Ever seen one? At idle? It SHOULD dance around 14.7...maybe down to 14.2 or so...maybe up to 15... NOT "all over the place"

do i have a wideband?? you obviously have no idea what i drive, do you?!?!? i just checked the readings on my car at idle and they were anywhere between 12.2 and 17.7

would you not call that all over?? i guess when your making less than 300 with no cams or any type of FI it is easy to peg your AFR at one number


good luck with the pump swap, it is a drop in replacement so it wont require anything special other than a fuel line disconnect tool

 

[02nightmaregt]

Oh no he didn't!

 

[SaleenGT2001]

Oh no he didn't!

yes, yes i did

 

[twogts4us]

do i have a wideband?? you obviously have no idea what i drive, do you?!?!? i just checked the readings on my car at idle and they were anywhere between 12.2 and 17.7

would you not call that all over?? i guess when your making less than 300 with no cams or any type of FI it is easy to peg your AFR at one number


good luck with the pump swap, it is a drop in replacement so it wont require anything special other than a fuel line disconnect tool

OMG, I had no idea I was in the presence of your greatness. Fact is, we're not talking about your car or my car...we're talking about the thread starters car...where the AFR should be dead on...

 

[SaleenGT2001]

well FWIW i have also checked 2 other cars with widebands and the AFR was between 12.5 and 16 at idle. both cars were FI (s/c and turbo)

 

[twogts4us]

well FWIW i have also checked 2 other cars with widebands and the AFR was between 12.5 and 16 at idle. both cars were FI (s/c and turbo)

And you point is?

Again, we are not talking about your car or any cammed or FI car(s). We're talking about the tread starter's car.

 

[Mikie]

And you point is?

Again, we are not talking about your car or any cammed or FI car(s). We're talking about the tread starter's car.

BUT,

We all give advice based on our cars or of that sort as we have never had experience with the thread starters car. Do you have personal experience with the thread starters application?
No need to come across like a ass, like in this post...
Do you have a wideband? Ever seen one? At idle? It SHOULD dance around 14.7...maybe down to 14.2 or so...maybe up to 15... NOT "all over the place"
Someone needs a time out

 

[SaleenGT2001]

i would like to see a video showing a wideband that stays on 14.7 (give or take .5)
i just don't think anyones car will stay pegged at that number. mine has ALWAYS moved drastically at idle. it has been tuned by MPH and FastLane and both idled the same.

the only time mine will stay in a certain range is WOT (10.7-11.5)

 

[SaleenGT2001]

Do you have a wideband? Ever seen one? At idle? It SHOULD dance around 14.7...maybe down to 14.2 or so...maybe up to 15... NOT "all over the place"
Someone needs a time out

glad i'm not the only one who saw that.

the question is..................DO YOU HAVE A WIDEBAND??or one of the narrowband "light show" gauges?

 

[twogts4us]

BUT,

We all give advice based on our cars or of that sort as we have never had experience with the thread starters car. Do you have personal experience with the thread starters application?
No need to come across like a ass, like in this post...
Do you have a wideband? Ever seen one? At idle? It SHOULD dance around 14.7...maybe down to 14.2 or so...maybe up to 15... NOT "all over the place"
Someone needs a time out

The advise given by Mr. "you obviously have no idea what i drive, do you?!?!?" (umm, no, why? Should I?) was most certainly based on his personal experience - which is always the best...actual first hand experience. But admittedly was of no use to the thread starter:

i guess when your making less than 300 with no cams or any type of FI it is easy to peg your AFR at one number

Now we all know at that point he was simply trying to 'one-up' the rest of us sorry folks that don't have aftermarket cams or forced induction. He might as well go over to the V6 forum and have a good giggle at the expense of the folks over there. Share his 700HP insight, his first hand experience. Will it help anyone? Not likely, but he'll probably feel better about himself.

Do I have personal experience with the thread starters application? Yes. I had a bolt-on 02 GT with a wideband and fuel pressure gauge (critical for my nitrous setup). I have personal experience with how badly the fuel filter can get clogged even with minimal mileage, let alone his high miles and after sitting for an extended time. I've swapped pumps on EFIs, but not yet on either of the GTs we owned or my Mach. I've had personal experience with the behavior of a failing pump. So you see, I too speak from experience. The difference between your insight and mine in this thread is the fact that mine is apt.

glad i'm not the only one who saw that.

the question is..................DO YOU HAVE A WIDEBAND??or one of the narrowband "light show" gauges?

Do I own a wideband? Yes...while it's back in the box now, since I removed it from my 2002 NOS Noszle'd GT after it was totaled and I have yet to add it to my new ride, I have an Innovate Motorsports LC-1 and their G2 gauge and I datalog with their Logworks2 software.
See pic below - and oh, lookie there...14.6 or so...at idle, this is where it would be (at idle) all day, anyday (+-5%).
So if I came across like an ass, well, my apologies for anyone offended. But quite honestly your self-rightous comment ("your AFR will be all over the place at idle and cruising.") is simply steering the thread starter in the wrong direction, don't you think? If you don't have anything to offer, why are you here?