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From: Jonathan Ward on 30 Mar 2010 16:11
On Mar 30, 10:17 am, jim beam <m...(a)privacy.net> wrote:
> On 03/30/2010 05:42 AM, Jonathan Ward wrote:
>
>
>
>
>
> > I have a 1991 GMC s15 jimmy 4x4 with the 4.3L 'Z' engine.  It has 197K
> > miles and has been in the family since new.  A couple of weeks ago,
> > the idle started to run very high and the "service engine soon" light
> > came on.  The truck also became very hard or impossible to start when
> > cold, but starts okay even if it has only been sitting in the sun for
> > a couple of hours and isn't at operating temp.
>
> > Many parts have been previously replaced for preventive maintenance,
> > including:
>
> > - Everything electrical/mechanical on the throttle body injection,
> > including new injectors, throttle position sensor, idle air control.
>
> > - All ignition parts are upgraded quality and in new condition.
>
> > - Just replaced the gas tank, fuel pump, sender, and fuel filter.
> > (The old pump had failed but the replacement didn't make the vehicle
> > run any better than it had been.)
>
> > I asking here because I'm out of ideas.  Could a plugged catalytic
> > converter do this?  (It's still on the original one.)  There's no ODB
> > port to connect to or anything, so I'm stuck with old-school
> > troubleshooting.
>
> > Any thoughts?  Many thanks in advance.
>
> > -Jonathan Ward
>
> check the coolant temp sensor and its wiring.
>
> --
> nomina rutrum rutrum

Replaced the coolant temperature sensor and checked the wiring. No
improvement. Any suggestions?
From: willy on 30 Mar 2010 16:52
On Mar 30, 2:24 pm, Jonathan Ward <bigjon...(a)gmail.com> wrote:

> Really?  This is a 1991 model, which was released in 1990.  Where's
> the ODB connector?
>
> Thanks!

Up under the dash on the drivers side.

I'll have to check my books, but I believe this is the female end:
http://www.autoxray.com/xcart/files/small_thumb_86.jpg


From: willy on 30 Mar 2010 16:56
On Mar 30, 2:24 pm, Jonathan Ward <bigjon...(a)gmail.com> wrote:

> Really?  This is a 1991 model, which was released in 1990.  Where's
> the ODB connector?
>
> Thanks!

Male, (on vehicle), end:
http://www.cellcorner.com/xshp/skin1/images/aldlcarconnector.jpg

You have OBD I

From: Vic Smith on 30 Mar 2010 17:28
On Tue, 30 Mar 2010 11:24:37 -0700 (PDT), Jonathan Ward
<bigjonsan(a)gmail.com> wrote:

>On Mar 30, 12:46?pm, willy <danceswithbe...(a)embarqmail.com> wrote:
>> On Mar 30, 8:42?am, Jonathan Ward <bigjon...(a)gmail.com> wrote:
>>
>> >There's no ODB
>> > port to connect to or anything, so I'm stuck with old-school
>> > troubleshooting.
>> > -Jonathan Ward
>>
>> There is a connector.
>
>Really? This is a 1991 model, which was released in 1990. Where's
>the ODB connector?
>

Google for ODBI for your Jimmy.
I have a '90 Corsica and it will turn on the check engine light and
store codes.
Only happened once about 10 years ago, but shorting 2 terminals in a
box under the dash flashed the checked engine light to tell me it was
a bad O2 sensor. Used a paper clip because I didn't have a reader
then. But I think there is a connector for a reader. Is the check
engine bulb good? If it is you might not have a code to look at.
Hard cranking could be bad starter.
Long cranking could be fuel pressure. You have to check pressure to
eliminate that. I had that on a 2.8, but the symptoms were the
reverse of yours. It would start fine when the pump was cold.
You said you had a new pump, but it wouldn't be the first bad one.
The high idle might be unrelated or maybe not.
A bad fuel pressure regulator cold cause that, another reason to put
a pressure gage on it.
I had a bad ECU in the 2.8 that would sometimes cause long cranking,
and sometimes just kill the engine like you turned the key.
Really it just wasn't sending the right signals when temperature was
just right, or maybe a bad trace was susceptible to vibration.
Couldn't be trouble shot because it was so intermittent, and never
stored a code..
Finally just failed completely.
Work on one thing at a time. Start with fuel pressure when starting.
Don't recall if you mentioned coil packs. Might be worth considering,
though bad ones gave me different issues than you have.
Somebody mentioned tracking down vacuum leaks - maybe in this thread -
that was a good idea. And he had temp related problems too.
Keep us posted. This is interesting.

--Vic




From: ben91932 on 30 Mar 2010 22:09

> Could a plugged catalytic
> converter do this?

No.

>There's no ODB
> port to connect to or anything, so I'm stuck with old-school
> troubleshooting.

The OBD connector is above your right knee as you sit in the car.
I'd start by inspecting all the new stuff that was installed... are
the connectors clean and tight? Did the throttle body, egr valve, the
iac or the tps come loose? Are the throttle shaft bushings sloppy?
Voltage drop the ground wires at the tstat housing... below .050
volts? Corroded iat?
Make sure the throttle is closing all the way. Throttle cable too
tight? Cruise control hanging up? Block off the iac port in the
throttle body with the engine running to see if the idle speed drops a
bunch. If it does, iac problem, if it doesnt, look for vacuum leaks.
Aim a timing light on both injectors (use the coil wire for trigger),
is one of them spraying and the other dumping or streaming?
I'd also 'tap-test' the ecm while it's misbehaving, lightly whack it
with 2 fingers.
High tps voltage maybe? Should be .5 iirc
Grab a paper clip and let us know what codes come up.
Good luck and HTH,
Ben
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