Hi all, long story…My Sapphire Cosworth is suffering from lack of
power and is backfiring through the exhaust. I have only had the car
for a few weeks, and it was running beautifully initially. It first
developed the symptoms on the way into the main ford dealers for its
60,000 ml service, and by the time I had reached the garage, a journey
of 35 miles the car was really struggling – not accelerating, loss of
power, running roughly, etc. I explained the problem to the service
manager who assured me they would look into it. I later got a phone
call a 2.30pm that the car was ready, but when I went to pick it up,
they told me that they hadn't time to fix the problem and I would have
to book it in another day. They did, however, say that the turbo was
alright. After the 35ml journey home again I was really toiling (the
problem seems to get worse the as the journey goes on) and I was
reluctant to risk running the car back to them again. I took the car
to a local garage, who couldn't find anything much wrong, apart from a
rusty fuel tank which was leaking and subsequently replaced. The
symptoms I have now is that the car starts and ticks over ok, but
won't accelerate above 3000 rpm and backfires through the exhaust if
you do push the pedal down. The local garages aren't too keen to look
at to the car – they seem to be very apprehensive of a cossie and I
was wondering if any one has knowledge of a similar problem. The car
is unmodded and a red top, converted for unleaded. Thanks for any
In decided to enlighten our sheltered souls with a
rant as follows
Without seeing the car, it's hard to diagnose, but I narrowed it down to one
of the following.
A: Contamination of the fuel supply due the the rust, try blasting some
redex through it.
B: Turbo boost set too high, causing detonation (unlikely, but possible)
C: Spark plugs gapped incorrectly, Cosworths are *very* plug gap sensitive.
D: Pipe off somewhere.
This is a very VERY long shot but its worth mentioning i reckon.
The car that I race doesnt have electronic ignition, just has a bog standard
setup with dizzy. After we had an engine fire, and melted all the electrics,
we re-wired the car and one of the guys incorrectly wired up the dizzy. When
the ignition was turned on, a spring loaded peice of metal (inside the
dizzy, dont know what its called but as the lobe of the dizzy came around,
it pulls this spring loaded piece away and the spark is created) heated up
red hot. As a result, it lost its "springyness".
The car ran very rough but ran. We changed the timing to help it run but it
didnt solve the problem. When revved past a certain number of revs (circa
3000rpm) the metal spring thing couldnt get back to its default position
quick enough and missed a beat. The car would misfire and just not rev past
Like I said, a long shot, but worth bearing in mind. It took us best part of
a day, to-ing and fro-ing from halfords replacing bits that we thought could
be the culprit!
The spring loaded piece of metal thing is called the points. All cars had
points until the 1980s and all cars since the 1990s have not, more or
less. They used to need adjusting every few months and replacing every
year or so. A Sapphire Cosworth is pretty unlikely to have had points, so
if it has, someone has seriously messed it up. Basic electronic ignition
uses a sensor in the distributor to trigger a transistorised ignition
First place to start would be to check all of the basics, such as fuel
pressure, condition of ignition system. Then a test of the injection system
will need to be carried out. From your description, there could be a
problem with a coolant temperature sensor, causing too much fuel to be
injected into the engine. This can also cause the backfiring you mention.
I am not sure if a fault code reader can be utilised to test the ECU on your
car. It may be a case of having to test through the system manually. The
Haynes Automotive Engine Management Manual gives information on how to do
Remove eight from email to reply.
The most common fault on these that causes the running problems you have is
a faulty / failed / poor connection to the phase sensor in the dizzy. Very
carefully check the wiring to it, the multiplug and the connections from the
plug to the Hall sensor inside. They often break. Its easiest to remove the
dizzy to do this.
If you have problems getting a new one- ask the parts guy to cross reference
it with one from a Lancia Thema turbo- they use the same one.
Blocked fuel filter from the rust in the tank. Symptoms will be if you leave it
sat for a while the rust will fall to the bottom of the filter and it'll run ok
for a bit. The longer you drive the more the rust shakes back up until the
filter element is blocked and everything stops for tea. That'll be Â£35 please.
Address is on the website :)
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
I'm not at all sure why women like men. We're argumentative, childish,
unsociable and extremely unappealing naked. I'm quite grateful they do though.
email@example.com (Dave Baker) wrote in message
We thought we had the problem with the rusty tank, for the same
reasons as Dave points out but the 1st garage changed the filter, and
it still wasn't running right. The problem seems to be too much fuel
(or not enough air!) Does the Haynes Manual show you how to read the
codes without specialist equipment like you can do with Vauxhalls?
If it is the chain drive engine then I have known them jump a tooth on the
chain and slightly mistime the cams, they still run, but very badly.
However this would not usually get worse the longer the journey.
Might be worth a look though.
Almost certainly this won't be the root cause of your woes, but it may be
a contributary factor: are you using super unleaded or the cheap stuff?
May be that the timing is set up for the higher RON fuel.
Checked all pipe, plugs, etc. today and went for a run. Car appeared to be
running a bit better, but still lack of power above 3000 rpm. After around 20
miles started to lose power and misfiring eventually made it home and booked an
appointment with a local specialist in "high performance vehicle tuning" who is
confident in being able to diagnose the problem. Will report later with the
thanks for all suggestions
The garage had problems tracing the fault as it didn't show up on the
diagnosis equipment, but after a process of elimination the phase
sensor along with the temp sensor were replaced. problem almost cured!
there is still a slight hesitation under full load, and I am waiting
for a new set of Magnegor plug leads, which should solve this.
Starting to enjoy the car now - was longing for my elderly (but very
Thanks for all suggestions
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