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Mileage problem of Mitsubishi Space Star

03.03.2005 | aktualizováno 27.07.2005 0:00:00 0 5420x

Informace o vozidle

VIN:
Výrobce:	Mitsubishi
Model:	Space Star
Rok výroby:	1999
Kód motoru:	1,3
Typ motoru:	4G13
Výkon (kW):	0 kW
Převodovka:	Manuální
Palivo:	Benzín
Najeto:	0 km

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Závěr

VOZIDLO JSEM NEOPRAVOVAL

Complaint: Poor mileage. Jerks
during the first take off.

Workflow:

After several repairs at Mitsubishi dealers' where
a customer claimed a poor mileage and jerks during
take off when cold, the situation has not changed.
No fault except wrong idle revs' stepper positioning
has been found.

But after hooking up to the scope, we could see
both firing and burn voltage as above-average high.

Looking through the pictures you
can discover the cause of excessive mileage, untraceable
with OBD system.

Pic. 1 Traces of corrosion over two spark
plugs

Pic. 2 Cylinder balance test came out well

Pic. 3 Ignition waveform

Pic.4 Burn times are definitely below
the specs.

Pic. 5 Inconvenient burn times at all cyls

Pic. 6 Distributor cap

Pic. 7 Rotor finger is the glitch

DTC's:

0= None.

Fix:

Rotor finger exchange.

Summary:

At the dealers' they usually work only with OBD
scanners not with scopes. The owner was told that
there were no DTC's and therefore all systems had
to be OK. Only the wrong idle revs' stepper positioning
was found, but it had had allegedly no relation
to the problem.

Obrázky, fotografie a soubory

Traces of corrosion over two spark plugs (556/1)

After recommended spark plugs were removed, two of them bore traces of corrosion. But it has had no influence to engine performance.

Cylinder balance test came out well (556/2)

Two corroded spark plugs did not screw up engine performance. All the cyls are in specs (±20 rpm).

Ignition waveform (556/3)

Comparing firing and burn voltage these Space Star's figures are pretty high. At the cyl #4, there is a tallish burn voltage, but it may be the result of throttle closing at the moment of rpm vertex during acceleration. At the other cyls there is the voltage approx. 2 - 3kV which is the relatively high value. The expected voltage at common cars is around 1 kV.

Burn times are definitely below the specs (556/4)

Checking burn times under acceleration is a common diagnostic method. They have spanned up to 50% bellow critical burn times at all spark plugs.

Inconvenient burn times at all cyls (556/5)

The burn time at another cyl is insufficient as at the previous cylinder.

Distributor cap (556/6)

We have found corroded plug tower terminals at the distributor cap.

Rotor finger is the glitch (556/7)

Such a burnt out rotor finger was the real glitch of poor mileage at this car. No technician before us had the idea to check ignition parameters with a scope. It is a real discredit for any shop not to use an essential diagnostic device - the oscilloscope.