Re: 93 Grand Cherokee - Weird surge problem

<sls5448@[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.