blogof alexey bass (алексей басс אלכסיי בס): May 2014

Wednesday, May 28, 2014

Notes for myself.

Inputs:
1. Air: MAP|MAF and Temperature
2. Fuel injectors pulse width.

Engine

Ouputs:
1. O2 sensor

14.7 (air) : 1 (fuel) - stoichiometry
rich at start and wide open throttle

02 sensor: 0.1-0.2V (lean) to 0.8-0.9V (rich)
not functional upto ~700 grad

STFT: immediate response
LTFT: baseline
Range -50% to +50%

Case 1. p0171 - bank1 lean
LTFT=25%, STFT=0% - vacuum leak
on idle, vac leak plays significant role. increase rpm, leak insignificant role, so LTFT should be low.
confirm by propane|carb cleaner in intake, so STFT will fall in response to rich.

Case 2. weak fuel pump, p0171 lean condition
FT can be 0% or bit above. Make load on engine as we need more fuel it will showup.
Increase RPM and see STFT, should increase too as more fuel demand and pump is weak.

Case 3. dirty MAF
Construction: heated wire to constant temperture controlled by PCM. PCM increase voltage to heat up more/less to get to set temp. When more airflow voltage vary. Also uses air temp for calculation.
LTFT around 0%.
Will behave same as in weak fuel pump. Need more inputs like fuel rail pressure or MAF readings as should be by specs.

FT +-5% regular, +-10% within spec. More than that - something wrong.

Exhaust leaks can affect O2 sensor.

Case 4. LTFT -30%. Rich condition. Maybe leaking injector.
After replacement LTFT should be updated initially with ST, later with LT.
If LTFT stays the same, problem not fixed, not injector.

Case 5. p017/4, idle, LTb1: 55%, LTb2: 2%, STb1: 55%, STb2: 0%.
Super lean at bank 1, not a fuel pump as bank 2 is ok. Vacuum hole in bank1? :-)

Also from ScannerDanner - Understanding Short Term and Long Term Fuel Trim

Monday, May 5, 2014

ISO Connector Pins Removal

Recently I was fixing issue with car multimedia system.
The problem was in poor contact in ISO connector. I was need to replace one of them.
But what if you need to reorder pins, remove ones that not in use?
I didn't find perfect guide for that, so I wrote by myself ;-)

All you need is office clip, better from thick (fat) wire.
On left normal clip, right is what you need to do from it.

There are two type of pins: with one (left) or two (right) teeth.

(Btw, left one is better it has split contacts - 4 independent instead of 2. So if you buy, choose same as left ones).

Now, how they sit and hold inside the plastic plug?

I did some awful schematics on top :-)
There is a small tooth or two that hold it in place.

Look close to your connector, try to identify them. You can also put clip inside and feel it.

Ok, how to remove?
Take the prepared clip, but before you insert it, push pin by wire as far as you can (from back to front, left to right) so the tooth will not touch plastic holder. Now, holding it in that position insert the clip easily until it stops.