Erratic idle - 97 v8 disco

A

Ariel

Guest
Hello

lately having some troble with my truck, the damn thing wont idle right , if i start it in the morning it idles fine while it cold but when engine temp starting to raise it idles rough at 700 rpm (drops to about 450-500 and then raises to about 900-1100 and all over again accompanimented with vibrations)
in addition i noticed that i has slower engine response and poor preformence.
some times (not in any regular tendency - once in a few days) it has some backfireing at idle,
another thing is that some times i getting very poor engine response under 1800-2000 rpm but if i go over 2000 i get the feeling that some think released and the engine will work fine.
the car runs on unleaded fuel and LPG , and has the same symptoms on both.

new coil , new amp. , new roter arm , new dis cap , new ignition wires , new fuel pump, new filters.

thanks.


edit -
if i set the idle speed to about 1100 it idles fine and smoth.
 
Last edited:

derrickalda

Well-known member
Olered said:
There is/was a tsb on replacing a chip in 97s. Do a search.


yeah i had about the same problem and spend alot of money narrowing it down to the TPS (throttle position sensor). its on the front side of the throttle body attached with two screws.......worth taking a look at.
 

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A

Ariel

Guest
Mark , for some erotic ection to take place it should at lest be runing, YeH now it wont even start.

today got up , brushed my teeth , drank my coffee, started my disco.... no start.

it starts goes to about 1000-1100 rpm for a sec or so and dies again. if you floer it/ play with the gas pedal it will die faster.

fuel presure is ok
spark is ok
so it can be the mixture or the air (can belive it has some think to do with the compression)
checked the ECT - about 1900 oham - sounds right
cleand the air control valve and the maf
Ptschram and Derrickalda - checked the TPS- output voltege from about 0.6 up to 4.6 - smoothly.
Chris-St Louis - what you mean by breather hoses ? pipes from where to where? is it the air control valve pipe or pipes or some thinke else?

any ideas?! or should i take out the fuel and the matches ...
 
Last edited:
Oct 27, 2004
3,000
4
On each valve cover, there is a Black Rubber hose connecting to intake plenium. They are good for about 30,000 miles. They can suck shut and cause a breather problem, or they can tear and cause a vacuum leak.
 

derrickalda

Well-known member
Ariel said:
Mark , for some erotic ection to take place it should at lest be runing, YeH now it wont even start.

today got up , brushed my teeth , drank my coffee, started my disco.... no start.

it starts goes to about 1000-1100 rpm for a sec or so and dies again. if you floer it/ play with the gas pedal it will die faster.

fuel presure is ok
spark is ok
so it can be the mixture or the air (can belive it has some think to do with the compression)
checked the ECT - about 1900 oham - sounds right
cleand the air control valve and the maf
Ptschram and Derrickalda - checked the TPS- output voltege from about 0.6 up to 4.6 - smoothly.
Chris-St Louis - what you mean by breather hoses ? pipes from where to where? is it the air control valve pipe or pipes or some thinke else?

any ideas?! or should i take out the fuel and the matches ...

man im telling you your problems sound exactly like what my truck was doing. somethings id turn the key and NOTHING....a TPS is easy to get too and about 80 bucks.....worth looking into
 

Lutzgaterr

Well-known member
Apr 23, 2004
578
0
LUTZ, Florida
Your description says 97, yet you have mentioned distributor parts being replaced.
That is rather odd to say the least... anyways, I had the same issues, however the hoses were good, TPI good, blah blah blah... it was the VSS for my issues.
She acted fine one moment and the next I prayed to get home.
 

DiscoveryXD

Well-known member
May 1, 2004
3,617
0
37
where i'm at right now, duh...
Check the thermostat...? From what ive heard the temp sensor can cause problems with the truck running properly. My thermostat has gone bad before, and it caused the truck to idle rough. It all went back to normal after i replaced the bad thermostat.
 

derrickalda

Well-known member
Lutzgaterr said:
Your description says 97, yet you have mentioned distributor parts being replaced.
That is rather odd to say the least... anyways, I had the same issues, however the hoses were good, TPI good, blah blah blah... it was the VSS for my issues.
She acted fine one moment and the next I prayed to get home.


sorry im a little dumb sometimes....what does VSS stand for?
 

derrickalda

Well-known member
alex3324 said:
vehicle speed sensor

oh yeah....yeah i knew id feel dumb on that one.....mine went out on me on a road trip to moab and got it replaced at a rover dealership in denver (great guys). the truck kept just shuting off and speeding up at highway speeds....finally the speedometer stopped working and then i knew it was time to fix something.