o2's are probably not the problem if it's stumbling when cold. The PCM
doesn't read them until the motor is warmed up. From what you are
describing, a vacuum leak is a very likely candidate. Or a mal-functioning
fuel injector. A can or two of really potent fuel injector cleaner may be
all you need if an injector or two are simple leaking a little. I don't
have an FSM handy so I don't know what the resistance of the coil inside the
injector should be, but I would take an Ohm meter to the terminals of all
your injectors and see if one or more is slightly higher (by an order of an
ohm or two) than the others.
The experience I'm drawing from is my '90 300zx. These cars are NOTORIOUS
for fuel injectors going bad, and mine had very similar symptoms as your
truck. Rough idle, stumbled when cold, etc. The injectors on that car are
supposed to be between 10 and 14 Ohms. I had one that was at 16.8 Ohms.
Changed it out, problem solved.
Another easy/cheap thing to try is cleaning the throttle boddy and butterfly
valve. If that's gunged up with anything, it'll act like a vacuum leak at
cold operation when the PCM is running off of a preprogrammed map.
Brian
'99 CC 4x4 5.2L
>From: "Jeff Durling" <jdurling@bellsouth.net>
>Reply-To: dakota-truck@dakota-truck.net
>To: <dakota-truck@dakota-truck.net>
>Subject: RE: DML: Hesitation when cold
>Date: Wed, 18 Jun 2003 12:01:34 -0400
>
>
>Thanks, Bernd. I'll the check the coolant temp sensor. As for the O2
>sensors, they have never been changed. After all that has mentioned
>about them in the past I didn't even think about them. Would that have
>anything to do with the rough idle? It's not aggressive cam rough it
>feels more like it's missing but there is no sign of that when you push
>on the gas.
>
>Jeff Durling
>
>-----Original Message-----
>From: owner-dakota-truck@bent.twistedbits.net
>[mailto:owner-dakota-truck@bent.twistedbits.net] On Behalf Of
>bernd@texas.net
>Sent: Wednesday, June 18, 2003 10:45 AM
>To: dakota-truck@dakota-truck.net
>Subject: Re: DML: Hesitation when cold
>
>
>
>(1) This is normal (to an extent) as the system is going from a
>Cold-Start/Open
>Loop operation into normal/closed-loop. There will be a slight "hiccup"
>on
>higher mileage vehicles during this time...especially on 5-speed
>vehicles.
>(2) Change the coolant temp sensor as they do corrode after a while and
>will
>give slower warm-up readings (or sometimes too warm at cold-start
>causing
>a "hiccup")
>(3) How old are your O2 sensors?
>
>- Bernd
>
>
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This archive was generated by hypermail 2b29 : Fri Feb 06 2004 - 11:46:28 EST