Hello everyone, i put a new ignition coil in the car today hoping it would
help but it didnt. As I negelected to state earlier the car really seems
like its misfiring after just starting up you almost give it full step
down and its like your not going anywhere for a few seconds. Sometimes I
hear like a heavy p.h.p.h.p.p.h noises coming from the front of the car.
I have good plugs, good cap/rotor, good wires, ect. I also use high test
fuel. What could be casuing this problem? Thanks-Chuck
TG, I also have some type of battery drainage problem....when the car is
off the SRS light comes of once in a while and the windown still work,
even with the key out... The battery is new....where would I begin to
look for a problem like this?-thanks
The O-V-P relay is a mystery to me. It has a fuse on its top. It's known
to cause strange engine behavior although I don't know why that occurs.
Look for it and, for now, give it a light tap on its side.
To review: the engine runs well once it has warmed up. You've replaced
most of the ignition parts. Have you checked the cold start system? If
it's not working the engine will start cold only with difficulty and
indeed need to be "warmed up" before the car can be driven for the air /
fuel ratio will be too lean while the engine is cold and it will have
poor throttle response - cough and sputter when you step on the accelerator.
We've speculated on the MAS (mass air sensor) and the O2 sensor. I'd set
those aside from consideration if the car passed your state's emission
test AND drives normally once the engine is warm.
I recall last year another owner had a similar problem - terrible engine
performance when the engine was cold and warming up and suddenly, with a
click, the engine ran perfectly. The over voltage relay was the cause.
So the suspicion is on the engine's cold start system and the over
voltage protection relay.
The OVP relay protects the sensitive electronic circuits, i.e. your ECU
from high voltages.
It basically consists of a fuse, followed by a relay energised by a
small circuit, which has a zener diode built-in. This relay feeds the
the SRS, ECU and ABS (any others?). If the voltage goes too high, the
zener conducts, and shunts the circuit to ground, cutting out the relay,
and if very high, blows the fuse.
These relays get tired, as basically, it has to activate continously
when the engine is running. 10 years +/- is about the lifetime.
When it cuts out, your engine reverts to "dumb" mode, and won't
compensate for temp, O2, timing, etc.
SRS, ECU and ABS, that's all. And depending on model and/or # of
systems that are protected, there are different versions of OVP relay,
between 5 - 9 pins, and 1 or 2 fuses.
A cross-cable during a jump start can easily kill this relay. That
explains how this happens.
thanks for all your help, i truly appreciate it... i have a book by a guy
named stu ritter and read the same thing about the OVP relay. I ordered a
new one lastnite. This is a long story, but I will keep it short. I gave
the car to my sister who is at college at rutgers, 27 miles away from out
home and my school, monmouth university. The 300 sat for a few days, she
claims she also left something on to drain the battery. She got one of
her "college friends" to jump the car and she tells me now that he cross
connected the cables. In Stu's book, it cleary states that if you cross
connect the cables the OVP can take a long vacation.
So i ordered the new one. I guess college doest not give you anymore
Anyone here ever change the cold start valve? -Thanks Tom and overyone
This was a teriffic answer to the OVP question. I'd just install the
relay and see if the cold starting is cured. It very well may be so I
suggest you wait before touching the cold start system.
Tom, Rutgers '65
Hello Tom and averyone else....
I would just like to thank everyone who helped me with the electrical
situation on my 300. I ordered the OVP relay and it fixed the problem.
The car also fires up on no delay, and whats even stranger the car does
NOT misfire at cold starts. Ill turn the key and it stays on. Since it
was such a beautiful day here in monmouth county nj, i moved the car in
the garage, changed the motor oil and tranny fluid/ filter, lubricated
need parts and even waxed it.- Thanks, I appreciate it...Charles Grainger,
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