# Fuel Trim is always positive? **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [February 26, 2021, 4:45am UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447 "2021-02-26T04:45:08Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![sciconf](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@sciconf](https://community.cartalk.com/u/sciconf)\ **Post date:** [February 26, 2021, 4:45am UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/1 "2021-02-26T04:45:08Z")
1999 integra LS 145k My FT is always positive. LTFT is fixed at 6.25% at idle and at 2k. STFT @2k rpm: B1, B1S1 B2S2 7, 1.6, 9.4 8.6, 8.6, 10.1 Ie total \> 10% At idle B1, B1S1 B2S2 7, 7.8, 8.6 8.6, 7.8, 7 Ie total \> 10% Is this expected? ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [February 26, 2021, 1:01pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/2 "2021-02-26T13:01:06Z")
How are you getting this info? And you believe it’s correct? ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [February 26, 2021, 2:04pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/3 "2021-02-26T14:04:30Z")
> [@sciconf](#): > > Is this expected? No, zero is expected. A 145k mile 21 year old car a slightly positive STFT and LTFT would not be unusual. A weak fuel pump or fuel pressure regulator could cause this. But the numbers won’t throw a CEL. Ignore it, you are fine. ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [February 26, 2021, 2:41pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/4 "2021-02-26T14:41:29Z")
The real question is can this 1999 Integra LS with 145000 miles be sold on EBAY for $30000.00 plus. ---
**Author:** ![sciconf](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@sciconf](https://community.cartalk.com/u/sciconf)\ **Post date:** [February 26, 2021, 2:47pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/5 "2021-02-26T14:47:39Z")
> [@Mustangman](#): > > No, zero is expected. A 145k mile 21 year old car a slightly positive STFT and LTFT would not be unusual. A weak fuel pump or fuel pressure regulator could cause this. But the numbers won’t throw a CEL. > > Ignore it, you are fine. @Mustangman - you hit the nail on the head! I was just getting to the fuel pressure regulator when I called it a day. I was also smelling gas when I start the car. I still need to get to the bottom of the issue and get the car smoked! Its throwing high NO. When you say “slightly positive” - did you have a value in mind? ---
**Author:** ![sciconf](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@sciconf](https://community.cartalk.com/u/sciconf)\ **Post date:** [February 26, 2021, 2:51pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/6 "2021-02-26T14:51:56Z")
> [@Cavell](#): > > How are you getting this info? > And you believe it’s correct? I am using OBDII device from Thinkcar. The values are correct and align with the symptoms - but the software is not calibrated for the model yr. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [February 26, 2021, 3:04pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/7 "2021-02-26T15:04:36Z")
> [@sciconf](#): > > did you have a value in mind? A LTFT between +25% and -25% there will not be a CEL set. A +6% STFT or LTFT is a small number that should not cause an error light. If, however the STFT can show short term trends that be used to determine a problem. See attached article. > **[The Evolving A/C Service Picture | MOTOR](https://www.motor.com/magazine-summary/fuel-trimming-diagnostic-time/)** > > The year is 2006, and for those who may have overlooked it, this is the 10th anniversary of On-Board Diagnostics II (OBD II). I believe it’s cause for celebration. Here’s an example of how it used to be: I was recently called to help a shop with a... Why do you want a smoke test? That is usually used to determine evap leaks. You can test the fuel pressure regulator by removing the vacuum line on the regulator when the engine is running. If it squirts fuel, it is bad! Here is a listing of causes for high HC, CO and NO. > **[Failed Smog: What causes high emissions, HC,CO,NO | JUST SMOGS® + REPAIR](http://justsmogs.com/2013/05/high-hydrocarbon-hc-carbon-monoxide-co-nitrogen-oxide-no-smog-failure/)** > > What causes high smog emissions. Failed HC, cO, NO at a California smog check I don’t thing the low STFT you are reading is your NOX problem. If I remember some of your earlier posts correctly, I’d say the cat converter is shot and that is your NOX problem. ---
**Author:** ![sciconf](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@sciconf](https://community.cartalk.com/u/sciconf)\ **Post date:** [February 26, 2021, 9:22pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/8 "2021-02-26T21:22:00Z")
Thanks @Mustangman Here is the chart for **O2 Sensor** : ![Screenshot_20210226-122000_ThinkCar](https://global.discourse-cdn.com/cartalk/original/3X/b/7/b76dce829e47a6fc481a021e5c25b344017bb888.jpeg) This is for **Fuel Trim** : ![Screenshot_20210226-123615_ThinkCar](https://global.discourse-cdn.com/cartalk/original/3X/1/0/10afa36e938568678d5757b13f29b0a2441071a4.jpeg) **Anything obvious?** ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [February 26, 2021, 9:32pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/9 "2021-02-26T21:32:55Z")
To greatly simplify the first article in this post, the computer has a graph stored of what an ideal engine will use for the pulse width of the injectors for all the various loads the engine will encounter when in closed loop. Small differences from engine to engine during manufacture and as engines age and wear will cause the actual pulse width to vary from the graph. Many things cause variation from cylinder wear, tolerances in the O2 sensors, tolerances in the MAF or MAP sensors, coolant temp and coolant temp sensors and wear of the injectors themselves. I would be very suspicious of an engine that stayed at 0% over a long time period. I would think that something isn’t working right, mainly because the closed loop system is a hunting system. A hunting system constantly creates an error, senses it and corrects it, maintaining a very small deviation from ideal. This especially for STFT. Less so for LTFT. Edit: it was a good article though. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [February 26, 2021, 9:57pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/10 "2021-02-26T21:57:09Z")
> [@sciconf](#): > > Anything obvious? Yes, none of these values should throw a check engine light. And they don’t. As I posted earlier… > [@Mustangman](#): > > Ignore it, you are fine. And this earlier comment, too… > [@Mustangman](#): > > If I remember some of your earlier posts correctly, I’d say the cat converter is shot and that is your NOX problem. ---
**Author:** ![sciconf](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@sciconf](https://community.cartalk.com/u/sciconf)\ **Post date:** [February 26, 2021, 10:06pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/11 "2021-02-26T22:06:33Z")
Thanks @Mustangman Someone looked at the graph, he was looking for better resolution but couldn’t since its a smart phone. He said O2 (front) is lazy! I also managed to measure CAT temp - there is a 100 degree difference. If “lazy O2” is correct, then CataClean fuel additive caused it, I believe. **Update:** The 100 degree temp difference on CAT is in line with properly working CAT. ---
**Author:** ![It\_s-Me](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/it_s-me/32/12660_2.png) [@It\_s-Me](https://community.cartalk.com/u/It_s-Me)\ **Post date:** [February 26, 2021, 10:10pm UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/12 "2021-02-26T22:10:11Z")
> [@VOLVO-V70](#): > > The real question is can this 1999 Integra LS with 145000 miles be sold on EBAY for $30000.00 plus. No, because it’s a “LS”, not a “Type R” ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [February 27, 2021, 12:26am UTC](https://community.cartalk.com/t/fuel-trim-is-always-positive/175447/13 "2021-02-27T00:26:03Z")
E10 vs pure gasoline will shift fuel trims a few points. I’ve seen the trims shift a bit from one tank of gas to the next.