<sls5448@[EMAIL PROTECTED]
> wrote in message
news:78f9959b-887d-40e9-afae-6b3dee760a2e@[EMAIL PROTECTED]
Apr 14, 12:13 pm, "Mike" <m...@[EMAIL PROTECTED]
> wrote:
> <sls5...@[EMAIL PROTECTED]
> wrote in message
>
> news:2a905b5d-e2ab-4848-bd6a-4c2f4d0962c7@[EMAIL PROTECTED]
>
>
>
>
>
> >I have a 93 grand cherokee with 200Kmiles. It idles smoothly and runs
> > ok but I cannot hold a steady rpm over 1000 RPM.It surges slightly
> > over a 300 RPM range. I've replaced cap, rotor, wires, coil, and
> > plugs. I've checked all the vac*** hoses for leaks. I even went as far
> > as to plug all the vacuun ****ts in the manifold and throttle body. It
> > still surged slightly.
> > I removed the throttle body and cleaned it thoroughly, replaced the
> > TBI gasket. I've used seafoam in the gas tank (it ran really crappy
> > until I filled up again). Cylinder compression is good considering
> > it's age (around 150psi max, 130 min).
>
> > Fuel economy is less then I expect. In a relatively hilly area I get
> > around 11MPG in mixed (mostly city) driving. Overall drievability is
> > pretty good and power is good all the way to redline. This leads me to
> > believe I have enough fuel pressure.
>
> > Any ideas?
>
> > Thanks in advance!
>
> > sls
>
> Surging is usually a sign of running lean. I would check the operation
of
> the O2 sensor(s) with a scan tool to make sure they are working
properly. To
> do so you would need a scan tool that is capble of reading sensor
values.
> You
> can also check O2 performance with a multimeter. It may be cheaper just
to
> replace the O2 sensors from the start due to the high mileage on the
> vehicle.
>
> I would check the fuel pressure as well just to rule that out as a
> possibility. The fuel pressure regulator increases fuel pressure under
power
> conditions so it could still be low at cruise.
>
> What engine do you have ? If you have a V8 they have a pan on the bottom
of
> the intake that is prone to leaking, the only way to check it is to
remove
> the
> intake.
>
> Also check your EGR valve for proper operation. If it opens too far or
at
> the wrong time that may cause a surge also.- Hide quoted text -
>
> - Show quoted text -
One more thing i didn't make clear in my original post. It's a cycling
surge. If I hold the throttle steady as if I was trying to hit
1500rpm, the engine will cycle from 1300 to 1600 RPM. Each cycle (up-
down-up) is about a second long. It does NOT do this at idle. RPM is a
steady 700 or so. Pretty much anythin above 1000 RPM will do the 300
rpm cycle.
Interestingly enough, I replaced the throttle position sensor a few
months ago. When I first started the vehicle, it idled at 1500 RPM. It
did the same 300RPM cycle even though the throttle was closed. Of
course after the computer "got used to" the new TPS it idled normally.
It definitely appears to be RPM dependent.
Thanks!
sls
Did you have this problem before you replaced the TPS ? Is the TPS
adjustable, if so did you adjust it properly ? Sounds like it could be a
TPS
problem.
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