Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

[Response: Lincoln] I would check your power stage, it amplifies the signal from the
computer to the coil. I had the same thing happen to me two months ago. I think
another person had it happen to them too. I think I paid $90 for the part and $100 for
them to find the problem. The part is located to the right of the battery on the fender.
[Response 2: Fred Guest] In our case it is caused by a bad connection at a plug
connecting the power stage mounted on the left inner fender. We unplug the
connector, clean the spade terminals with emery cloth and squeeze the female
connectors with needlenose pliers if we have them with us, then put it back together
and it is fine for a while. [Editor’s Note: use electronic connection de-oxidizer instead]
I believe the round things on the fender have something to do with the fuel injection.
Since your tach goes to zero I expect you have a similar corroded connector problem -
but probably in the ignition system rather than in the fuel injection.
Note: faulty engine and chassis grounds can play havoc with the electrical system and
cause component failure. See the FAQ section for more information about diagnosing,
curing and preventing ground troubles.
Poor Power; Poor Engine Response. [Symptoms] Symptoms: no power under 3K
RPM; poor power after 3K RPM; no engine response, very slow response; will not
brake-boost past 2 psi; idle fluctuation between 750-1200RPM; rough idle; engine
makes loud "bog" noise from intake when throttle is opened and takes several
seconds to respond, even in neutral. Does not seem to get terrible gas mileage, but
could be better. Does not smoke white, blue or black. Spark plugs are white on the
electrode and have black carbon around the face [Duane Hoberg] Based upon an ageold
experiences, it appears that your ignition timing is off (late)and is not responding
properly contrary to what the base timing light indicates. The plugs with white center
indicate a lean fire condition, the black ring indicates a rich, incomplete burn cycle. ie,
fuel being burned late in the power stroke or after the exhaust valve is open. Late
ignition timing. The ECU via the O2 sensors is leaning the mixture out after they enter
the cycle because of the excess oxygen from the interupted incomplete burn after the
exhaust valve opens. Causes: Ignition wires not in the proper sequence. Certain
engines will run but with little power if two ignition wires are swapped. Has the flywheel
been removed and replaced lately? Flywheel off by one bolt or backwards would
cause a lot of problems. If the flywheel and everything else is on the money, the
ignition portion of the ECU is at fault. Verification via diagnoses step by step with a
Volvo Service Manual would be well worth the 20 or so dollars for the manual.
Intermittent Ignition Shutoff: FI Relay or Ignition Switch. [Inquiry:] I have had my
Volvo 760GLE for over a year. Currently it has 214K miles. Lately it has been cutting