mbosch wrote:
> Hello all,
>
> I have a 1999 Grand Cherokee Laredo 4.0L which was running perfectly
> until tonight. I went to start it but it wouldn't turn over. I thought
> maybe I hit the gas pedal when I tried turning it over and flooded it
> or something. I then tried starting it holding the gas pedal to the
> floor and then quickly letting it off if it turned over, that worked,
> it started right up but would just stall when it hit low rpm idle
> speed. If I held my foot lightly on the pedal it ran smooth at 1000
> rpm but the second I let it off it would stall.

It's hard to flood a fuel injected vehicle, very hard. Flooding is
a thing for carbs. In fuel injected vehicles, pressing the gas pedal
all the way down signals the computer to start in safe-mode so to speak.
It will ignore a lot of sensor input and try to start.

> I also notice the steel cable running from the throttle body to
> somewhere under the battery had a lot of slack in it (that's a mystery
> zone for me since I haven't looked under there yet and have no idea
> what it runs to). Does that have some thing to do with the idle speed?
> Maybe a vacuum actuated choke?

Cruise control motor. Fuel injected vehicles don't have chokes, they
don't need them. Chokes are for helping the engine suck fuel from
a mostly empty carb.

Your idle speed is controlled by the IAC (idle air controller) like on
this page. http://revbeergoggles.com/tb/tb.html

> I would just leave the vacuum line unhooked but there's a reason it's
> hooked up to the manifold at the factory (I think?).

You need a factory service manual and vacuum diagram. A vac pump/gauge
is also handy for finding leaks. I'm guessing you have a cracked line or
one of the soft rubber connectors has gone bye-bye.

> Could I have a bad reservoir or valve that's not opening?

A bad reservoir (under the battery) is a very common problem.
You can check the hoses with one of these. http://www.mityvac.com/


> Could a vacuum problem lead to poor gas mileage? I average about 17-18
> MPG.

It sure can. So can a O2 sensor that's starting to go. They don't always
throw a code. Then again 17-18 isn't unreasonable.


--
-- DougW -- 93 ZJ 4.0 http://revbeergoggles.com
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!