96 Hummer turbo deisel fast idle racing

Hi Folks:
A buddy of mine has a '96 hummer that started having an intermittent
problem. At first, it just started bucking and popping when started,
after it had been running earlier. It cleared up a few times, and now
it's revving like it's full throttle at the start! We pulled the
throttle position potentiometer, which is actually three pots in one,
hacked it apart, cleaned it, put it back in, same thing. It measures
pretty smooth. He doesn't let it 'idle' after it starts for fear of
blowing it up, but it starts, races, blows loads of black soot out the
exhaust, and turns it off.
Now, this thing is all electronic. There is nothing but this
pontiometer connected to the accelerator. Does this deisel have a
throttle valve limiting air into the engine on idle, or is the fuel
injectors the only method of idle control? The CD's he has for the
Hummer don't go into specifics for the turbo deisel. Also, the
computer hasn't caught any alarms or events..
Thanks for any leads.

Take Care!
Harry

HarryHydro wrote:
>
> Hi Folks:
> A buddy of mine has a '96 hummer that started having an intermittent
> problem. At first, it just started bucking and popping when started,
> after it had been running earlier. It cleared up a few times, and now
> it's revving like it's full throttle at the start! We pulled the
> throttle position potentiometer, which is actually three pots in one,
> hacked it apart, cleaned it, put it back in, same thing. It measures
> pretty smooth. He doesn't let it 'idle' after it starts for fear of
> blowing it up, but it starts, races, blows loads of black soot out the
> exhaust, and turns it off.
> Now, this thing is all electronic. There is nothing but this
> pontiometer connected to the accelerator. Does this deisel have a
> throttle valve limiting air into the engine on idle, or is the fuel
> injectors the only method of idle control? The CD's he has for the
> Hummer don't go into specifics for the turbo deisel. Also, the
> computer hasn't caught any alarms or events..
> Thanks for any leads.
>
> Take Care!
> Harry

Looks like (if fitted) the turbo is worn and leaking oil. The oil mixes
with the intake air.
This makes diesels to run at high rev's when they are not under load. Be
carefull, not very good for the engine. Check if there is a lot of oil
on the output side of the turbo, in the hose of-course. When the hose is
off you can also check the free play of the axle or see if it is al worn
inside the turbo.
Good luck,
Erik-Jan.

On Wed, 01 Feb 2006 17:18:16 +0100, Erik-Jan Geniets
> wrote:

>
>
>> Harry
>
>Looks like (if fitted) the turbo is worn and leaking oil. The oil mixes
>with the intake air.
>This makes diesels to run at high rev's when they are not under load. Be
>carefull, not very good for the engine. Check if there is a lot of oil
>on the output side of the turbo, in the hose of-course. When the hose is
>off you can also check the free play of the axle or see if it is al worn
>inside the turbo.
>Good luck,
>Erik-Jan.

Another more likely is the PMD/FSD has failed. This solid state device
is mounted to the side of the injector pump and fails on a regular
basis.

The 'friend' should join the HML and post his question there--where
there are thousands of Hummer owners who support each other.

hi-1.bad choke? 2.bad choke-linkage? [broke-off,separated,or just
fallen-off] ?3.bad choke wires or loose push on connector?

2oo6 febber[RCA2100](2.9.1-16421) jm3 //nor.CAL.
| USGS Earthquake Hazards Program | Latest Earthquakes - Last 7 Days |
Address:http://earthquake.usgs.gov/

Hi Pete:
Thanks for the reply. The last I was there, (he's about 2 hours
drive from me) when he started it, it was reving and blowing black (not
blue) smoke and soot, so I, like you, don't think it's the turbo. Good
thought though.
I was just talking to him. He said someone else told him it was a
six hour job pulling this pump off !! He also told me that one time it
would idle, but not take the throttle. It would just start bucking and
hesitating.
You mentioned HML. What is this?
Thanks!
Harry

PeterD wrote:
> On Wed, 01 Feb 2006 17:18:16 +0100, Erik-Jan Geniets
> > wrote:
>
> >
> >
> >> Harry
> >
> >Looks like (if fitted) the turbo is worn and leaking oil. The oil mixes
> >with the intake air.
> >This makes diesels to run at high rev's when they are not under load. Be
> >carefull, not very good for the engine. Check if there is a lot of oil
> >on the output side of the turbo, in the hose of-course. When the hose is
> >off you can also check the free play of the axle or see if it is al worn
> >inside the turbo.
> >Good luck,
> >Erik-Jan.
>
> Another more likely is the PMD/FSD has failed. This solid state device
> is mounted to the side of the injector pump and fails on a regular
> basis.
>
> The 'friend' should join the HML and post his question there--where
> there are thousands of Hummer owners who support each other.

On 7 Feb 2006 06:42:57 -0800, "HarryHydro" >
wrote:

>Hi Pete:
> Thanks for the reply. The last I was there, (he's about 2 hours
>drive from me) when he started it, it was reving and blowing black (not
>blue) smoke and soot, so I, like you, don't think it's the turbo. Good
>thought though.
> I was just talking to him. He said someone else told him it was a
>six hour job pulling this pump off !! He also told me that one time it
>would idle, but not take the throttle. It would just start bucking and
>hesitating.
> You mentioned HML. What is this?

the PMD can be replaced without pulling the pump. Most put it on an
external heat sink.

Go to:

http://hummernetworkforums.com

the group is great.