P0300 Random Misfire And Ltft2 Lean

dansand4520 · Aug 26, 2015

Ok so I have a 2000 GT that has had a p0300 code for a while. It's only really noticeable with the A/C on, though it does die occasionally when coming to a stop. So I hooked up the code reader and here's what I've got...
At idle:
SHRTFT is within acceptable ranges (-6 to +1)
LONGFT1 is +7
LONGFT2 is +16.4
Output voltage for O2B1S1 and O2B2S1 fluctuates between about .1 and .8
Output voltage for O2B1S2 is relatively steady between .700 and .765, while O2B2S2 is between .635 and .660

At 2,500 RPM:
SHRTFT is still within acceptable ranges (close to zero)
LONGFT1 is between 10 and 11
LONGFT2 is 13.3
Output voltage for O2B1S1 and O2B2S1 fluctuates between .1 and .9
Output voltage for O2B1S2 fluctuates between .1 and .8 and O2B2S2 from .2 to .6

Additionally:
Vacuum reading is healthy (17in at idle and I'm at 5280 ft elevation)
No other codes are ever thrown
I have cleaned MAF, replaced plugs, new fuel pump, replaced EGR valve, cleaned IAC valve, cleaned TB, and some other stuff I'm probably forgetting...

Please help... Any input would be appreciated!! Thanks!

wmburns · Aug 27, 2015

The P0300 is the DTC code that's the 1000 lb Gorilla in the room. IMO chasing "other" problems while there's an outstanding misfire DTC's can be unwise.

Possible causes:

Excessive EGR flow.
loose/bad CKP sensor.
Loose/cracked crank damper. Other crank damper "issues" include incorrectly torqued damper bolt and worn/dry rotted rubber ring. Or excessive run out.
cheap under drive pulleys

The post does not state if the battery, battery cables, and alternator are in tip top shape.

Does disconnecting and plugging the EGR vacuum line improve any symptoms? This will throw an EGR related DTC but it's OK for testing. Also in my experience the EGR DPFE sensors fails more frequently than the EGR valve does.

Is this a manual or automatic? If automatic, consider that the motor quitting coming to a stop can also be a symptom of the lock up torque converter not releasing as it should.

OBTW, the higher LTFT values on the left side may indicate an intake leak on the left side. This leak could be from the EGR system as the EGR is on the left.

sigmanx · Aug 28, 2015

dansand4520 said:
Ok so I have a 2000 GT that has had a p0300 code for a while. It's only really noticeable with the A/C on, though it does die occasionally when coming to a stop. So I hooked up the code reader and here's what I've got...
At idle:
SHRTFT is within acceptable ranges (-6 to +1)
LONGFT1 is +7
LONGFT2 is +16.4
Output voltage for O2B1S1 and O2B2S1 fluctuates between about .1 and .8
Output voltage for O2B1S2 is relatively steady between .700 and .765, while O2B2S2 is between .635 and .660

At 2,500 RPM:
SHRTFT is still within acceptable ranges (close to zero)
LONGFT1 is between 10 and 11
LONGFT2 is 13.3
Output voltage for O2B1S1 and O2B2S1 fluctuates between .1 and .9
Output voltage for O2B1S2 fluctuates between .1 and .8 and O2B2S2 from .2 to .6

Additionally:
Vacuum reading is healthy (17in at idle and I'm at 5280 ft elevation)
No other codes are ever thrown
I have cleaned MAF, replaced plugs, new fuel pump, replaced EGR valve, cleaned IAC valve, cleaned TB, and some other stuff I'm probably forgetting...

Please help... Any input would be appreciated!! Thanks!

5280 sound like Denver/Colorado springs territory.

Drastang · Sep 16, 2015

know this is a older post ....I'm not sure about your codes but it sounds to me like your MAF might be completely bad. just because you have had a back back fires and the motor dying when you hit brakes. mines was doing that but worked fine after I used the MAF cleaner to also clean the electrical connection on both sides.

P0300 Random Misfire And Ltft2 Lean

dansand4520

New Member

wmburns

sigmanx

Member

Drastang

Member

Similar threads

P0300 Random Misfire And Ltft2 Lean

dansand4520

New Member

wmburns

sigmanx

Member

Drastang

Member

Similar threads

Privacy & Transparency

Privacy & Transparency