dalemstevens wrote:
> Problem: Car has little power at low RPM, but as the RPMs climb the
> power is fine. Its almost like one should rev the engine before
> letting out on the clutch in order to get the car to take off from a
> stand still. Any ideas what could be the problem?
>
> Background: I've been helping a friend get his 89 Mustang four-
> clyinder car running again so that he can save money due to higher gas
> prices and a recent move to the country and much longer drive into
> work. This low-RPM problem remains from when he first gave up on the
> car (and let it sit for a few years because one day it wouldn't
> start). We've done the standard tune up (plugs, dist. cap and rotor,
> timming, etc.) and done OK with getting it to start fine. No engine
> codes have registered (all clear except for code 67...neutral circuit -
> when actually the car is in gear). Now I'm at a loss for the problem
> of no power at low RPM. What factors should I consider and look
> into?
>
> Thanks,
First off, I don't know this specific engine.
In general, I would try to look at ignition advance at part throttle.
Does the distributor have a vacuum can on the side? That would normally
give you an initial kick in the advance just as you begin pu****ng on the
gas pedal, so the engine would accelerate from idle. It also allows
higher ignition advance at cruising speeds, with small throttle
openings. If the diaphragm inside the can is leaking, or if the hose
connected to it has a leak somewhere, it won't give you that extra
advance and the engine won't respond well to throttle.
Also make sure all moving parts inside the distributor body are clean
and lubricated, and move well without binding. This goes for the
centrifugal weight mechanism parts too. If those are binding, the engine
won't see enough ignition advance.
To verify either the vacuum advance or the centrifugal advance
operation, use a strobe light timing gun and observe the timing changes
when the engine is running. Repeated very small throttle openings should
result in instant ignition jumps (vacuum advance).
The centrifugal advance operation can be checked with the vacuum hose
disconnected and plugged. If you get no change in timing regardless of
engine rpm, then the centrifugal mechanism is not working.
You can also try to suck on the vacuum can hose to try to detect leaks.
You should be able to suck a vacuum in the hose, and block the hose
opening with your tongue... it should stay stuck to the hose, meaning
the vac unit is able to maintain vacuum with zero leaks.
You can also buy an inexpensive manual vac pump from most auto parts
stores, if you don't like getting your mouth dirty :)
Another problem may be incorrect mixture. Troubleshooting and fixing
this may get a bit more complicated and vehicle specific, so I won't get
into that here.
Jan
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