I'm learning about used, rebuilt vs reman. Not sure what the options will be if it comes to it. May have to just dump the car and use the truck as my DD (but 12mpg and expensive maintenance). Lucky I don't drive much anymore (aside from trips, maybe 3K miles per year?).

Not sure how to troubleshoot. Maybe just use it near home (in case it dies acutely) and watch for symptoms I can report to the shop?

It would be nice for a cheap easy fix but Murphy is usually not on my side.

quote:

The car seems to hesitate a little when going from a rolling stop. Not sure if I would say it's similar to a stall or not in the right gear. I'm pushing the pedal to go but there is brief hesitation. Seems like mostly when it cold but not sure yet.

Does it do it in gear only or while in N or Park.

If in gear then it's possibly the Trans, or some controller or vac line once a load is on the engine.

Doesn't sound like anything that will strand you yet, and it's probably not out of spec enough to set a code.

At this point you could do as suggested and get a shop with a factory level scanner to read the code and ride along scanning to see what is happening...

I'll test out N/P vs driving.

The shop can check for codes while driving / symptoms present that the OBD scanner won't see? Okay, then makes sense to bring it to the shop for them to attempt diagnosis. I missed that recommendation above.

While driving around, can I hook up the scanner and and check for some live reading? (assuming the scanner I have is capable). If so, what should I look for - what live data?

I have an Autel AL629 and a Bosch 1150.

quote:

Originally posted by konata88:

While driving around, can I hook up the scanner and and check for some live reading? (assuming the scanner I have is capable). If so, what should I look for - what live data?

I have an Autel AL629 and a Bosch 1150.

Fuel trims, should be around zero, plus or minus 2. Should show long term and short term trims. Short will vary more, but long should stay pretty much fixed. Make and model, engine size, all I see posted is a 25year old high mileage car.

LT Fuel Trim about 14%

ST Fuel trim ranged from 10 to -20 depending on load and speed. Mostly w/in 5 to -10 though. Driving from cold for about 5-10 minutes.

No hesitation symptoms though. Drove perfectly today.

It's adding fuel for a lean condition. Since you won't give me the make/model you need to tell me if it's a speed density (MAP) or mass airflow system (MAF).
Better yet, let the other pros in here help you out.
I'm done.

Your LT and ST fuel trims are very bad. Don't evaluate when cold. Fuel trim is only stable when you are in closed loop mode, which requires stable operating temperature.

14% is a huge number. Our test vehicles typically range from -4 to +8, depending on injector condition.

A very rich LTFT can also be required if the computer thinks you have a massive amount of ethanol in the fuel. Some vehicles calculate ethanol content. Some measure. If your ethanol content value is incorrect, for the fuel you are using, it can drive the LTFT to rich, and cause stumbling and poor starting.

Thanks! I'm trying to read about high LT fuel trim but haven't learned enough yet.

Basically:
1. Could the LT/ST fuel trims at this level be related to the intermittent hesitation symptoms? Or orthogonal? I ran the car for 10 minutes, then another 10 minutes resulting in the ST/LT readings. I read about something called Seafoam. Is that indicated here?

2. What are the general symptoms expected to be manifested by these trim levels? Less gas mileage? Other more dire symptoms (perhaps as something continues to degrade?)? Possibly related to the code thrown earlier?

As pointed out above, I think I had an issue with methodology. The reading above was likely biased heavily by numbers while running cold.

I ran the car much longer and the LT Trim came down to about 7% / 9% which sounds more typical. Both the Bosch and the Autel readings were consistent (as they should be).

If so, while I still haven't seen the concerning symptoms manifest again yet, perhaps the issue may be more transmission than fuel related? Not that it's a good thing - I think I'd prefer a fuel system issue (cheaper to fix?).