I bring your attention to this article in the Pico Newsletter.
1. Case Study: Celica brings Scope and Scan Tool together
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This month Steve Smith demonstrates how PicoScope fits within
the diagnostic jigsaw when resolving seemingly complex issues.
The analogy of a jigsaw fits well if we look at the essential
pieces required for a successful diagnosis.
~ The relevant Scan Tool
~ Accurate technical information
~ Experience gained as a direct result of training
~ PicoScope
The vehicle in question is a 2001 Toyota Celica 1.8 190 PS
utilising variable valve timing and lift. The complaint from
the customer was poor idling, heavy fuel consumption, lack of
power, periodic cutting out on over run and the all-important
engine warning light was illuminated.
As always the customer interview is vital, and in this case
revealed that extensive engine work had been carried out
including a cylinder head replacement due to severe
overheating.
At this point it is very easy to jump to conclusions and
assume "doom and gloom" when a customer arrives having
experienced numerous attempted repairs after a major engine
overhaul. However, by maintaining a methodical approach
throughout the diagnostic procedure we can present our customer
with not just a bill, but a working vehicle and the evidence
and data trail that supports the necessary rectification.
A basic inspection revealed the tell-tale signs of intrusion
about the engine to include, a new cylinder head, VVT oil
control valve, coolant temperature sensor, catalyst,
pre-catalyst O2 sensor accompanied with a punctured and
misrouted wiring harness that resembled a pincushion! A brief
road test confirmed the customer's complaint but also revealed
the engine to sound fine with no knocks or rattles, or smoke
from the exhaust and both coolant temperature and pressure to
be correct. Note: The exhaust fumes did emit the sulphur odor
associated with over fuelling or a catalyst working overtime!
It is essential to establish the engine condition before
spending the customer's money...
You can continue reading the Toyota Celica case study online:
http://www.picoauto.com/tutorials/celica-faulty-maf.html