Long term fuel trim is incorrect

truc0011 · #1 10-06-2008, 12:43 PM

Hi,

I have a 2000 Intrigue 3.5 with a hard starting condition. It has also stalled at low RPM's a few times. No codes and the fuel pressure seems good. 43 psi during starting. I did notice on my scan tool that the long term fuel trim is at -12% that doesn't seem correct to me. Has anybody seem this before? Do the oxygen sensors control this setting? Or is the fuel pressure regulator dumping in too much gas to cause a rich conditon?

Any help would be great.

Thanks!

panzer dragoon · #2 10-06-2008, 08:27 PM

ckp sensor: stalling at 1/4 temp
Cps sensor: hard starts

truc0011 · #3 10-07-2008, 10:27 AM

Quote:

Originally Posted by panzer dragoon

ckp sensor: stalling at 1/4 temp
Cps sensor: hard starts

So you think both are bad? Couldn't I have a leaky injector as well?

dtownfb · #4 10-08-2008, 10:36 AM

If you don't have any trouble codes, the hard starting could be the early signs of a bad ignition switch or a cps starting to go bad. The CPS generally (but not always) will throw a code when it is bad. Also problems with the ignition switch can make you think you have fuel related issues (hesitation, stalling, no starting, etc.).

Regarding the long term fuel trim, not sure what could be causing this.

truc0011 · #5 10-08-2008, 10:48 AM

Quote:

Originally Posted by dtownfb

If you don't have any trouble codes, the hard starting could be the early signs of a bad ignition switch or a cps starting to go bad. The CPS generally (but not always) will throw a code when it is bad. Also problems with the ignition switch can make you think you have fuel related issues (hesitation, stalling, no starting, etc.).

Regarding the long term fuel trim, not sure what could be causing this.

The ignition switch is new so I don't think it is that. I still think it is fuel related since the long term fuel trim is not correct. The computer is trying to compensate for some sort of fuel leak. But thanks for all the help.

dtownfb · #6 10-08-2008, 11:09 AM

Well that rules out the ignitions switch....

Here's a discussion on long term and short term fuel trim that I found using a Google search. Didn't have time to read it all the way through but hopefully this helps:

http://forums.evolutionm.net/archive.../t-166612.html

tmartin000 · #7 10-08-2008, 11:26 AM

Very interetsting post.

I would have to wonder if a guy had a clogged air filter, clogged fuel injector (really bad), o2 sensors, mass air flow sensor---might cause the fuel trim to be outta whack?

dtownfb · #8 10-08-2008, 01:58 PM

I went back and re-read it and it looks like -12% may be at the outer limit of the normal range. The fact he is having issues probably means something is probably not kosher with the fuel system. The big question is what? Good thing is he knows the fuel pressure is good.

Personally I would begin with the small, easy things like changing the air filter, cleaning the MAF, and use a bottle of Techron fuel cleaner. Then monitor the situation for a couple days before looking at the injectors and o2 sensors.

Interesting stuff. i almost feel like i have to help truc0011 find a solution now.

truc0011 · #9 10-09-2008, 09:42 AM

Quote:

Originally Posted by dtownfb

I went back and re-read it and it looks like -12% may be at the outer limit of the normal range. The fact he is having issues probably means something is probably not kosher with the fuel system. The big question is what? Good thing is he knows the fuel pressure is good.

Personally I would begin with the small, easy things like changing the air filter, cleaning the MAF, and use a bottle of Techron fuel cleaner. Then monitor the situation for a couple days before looking at the injectors and o2 sensors.

Interesting stuff. i almost feel like i have to help truc0011 find a solution now.

It turns out it was the fuel pressure regulator, really weird problem, almost like the FPR was intermitant. I finally drove around with the fuel gauge on the car and I saw the pressure drop, then if I got out of the car fast enough and pulled the vaccum hose off the fpr I saw a trickle of gas. At idle in my driveway it appeared to be fine, good pressure and no gas in the line.

Anyways its running good again, thanks for the help everybody.

Also the fuel trim is back at 0.

dtownfb · #10 10-09-2008, 09:08 PM

I'm glad you got this solved. What kind of scanner do you have that can read the fuel trim? That is good stuff to be able to check.

truc0011 · #11 10-09-2008, 10:32 PM

Quote:

Originally Posted by dtownfb

I'm glad you got this solved. What kind of scanner do you have that can read the fuel trim? That is good stuff to be able to check.

Its just a cheap Auto Xray scanner but it can read the short and long term fuel trims through the operational data menu.

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