Idles fast when i crank my truck up it runs wide open and then it will idle down what causes this and sometimes when i push the clutch in it will be idling fast

wow no year car stated nor a country x10 worse.
welcome to our USA forum!
the country with ZERO, carry cars. not a one. here
and due to that , no books here nor coverage at mitchells. either.
That is a G13 engine, (not m13) is my 1st guess.
Most Suzuki's with tiny engine and run a map sensors, not MAF
so is called SPeed Density system.

if yes, the that means ALL vacuum leaks cause fast idle.,
armed with that juicy fact, we know why it races.
you never said and actual RPM so no Tachometer?
only 2 causes. a huge vacuum leak
or unlikely the ISC stuck wide open with gunk inside, (clean it?)
ISC is idle speed control.
old suzuki's had man killler ISC software, my 91 did it.
and all others like it........
it would hunt idle like mad with any vacuum leak.(of any kind)
today this is very *******, this mode. (hunt)
toyata cost them $1billion in fines for this same deal.

but Clutch drivers have no problems with idle hunt, "skills"
what year/country.?
please showa photo of engine. ?
and win. a win/win
you win and I win not guessing all that.

fact 2 , is that that hunt tells me the ISC is moving fast.
so is not stuck. (99% says R3PO)
unplug ISC see the hunt end? sure.
the ECU has lost its wits. from..... this....
it sees a massive air leak (vacuum map readings ) and then (dumbblly ) hunts it like mad, (bad Firmware code) but real.
i can demo this is seconds hood up.
causes?
1: vacuum hose fell off.
2: same hose cracked.
3: brake booster diaphragm cracked, sucking air big time)
4: lots more,. even gunk under throttle plate blocking it open.
and more. lots more. can cause lots of vacuum leaks.

you need to check all sensor connections as the crank shaft sensor also will mess up your idle....try slightly unscrewing the tps and push it up or down slightly to see if this fixes the problem.

Fast idle is often caused by a faulty TPS. Throttle Position Sensor. The computer is not able to determine exactly where the throttle is so it compensates by applying too much throttle automatically to avoid stalling the engine. Just went through this with a delivery truck at work that would run at 40 without touching the gas. Scary ride in a 2 ton truck.

check the setting for the auto choke and adjust the linkage with it.. Adjusting screw on the throttle butterfly that runs on the fast idle cam of the auto choke.

difficult one this ,its a manual so this obviously not a american version ,To be honest here this is one of them questions where i would need a road test i think to see first hand the problem,Their is a multitude of things that could cause this ,the idle with foot off the clutch could be the crank thrust bearing are worn causing a resistance ,to check this get someone to push the clutch down and you check the front pulley to see if it moves forewards when clutch is pushed down ,now as for the missing at 1500rpm this may just need the plugs regapping to 25 th but it could also be a mass air flow sensor even a coil pack and without head under bonnet i have no idea

HAVE YOU TRIED REPLACING THE FUEL FILTER SOMETIMES WHEN A FUEL FILTER IS FULL OF TRASH YOU WILL GET THIS OUTCOME.

check and make sure air filter is ok, and there are no restrictions in hose to throttle body, check iac (idle air control.

It is the harmonic balancer, ie. pulley. It is a two piece--with rubber between the two. It will, especially if belt dressing or other lubricant has penetrated it, slip. I just ordered a new one online for $70. It is a fairly common problem.

Sounds like a vaccum leak at the throttle body or the intake. check for loose lines hissing with the motor running. Had a brake booster line come loose on my 92 and it ran at about 3000 rpms.

When I crank my truck it runs wide open for a minute of so and then it starts to idle down. What causes this? It is a 1992 Chevy S10 v6 pickup. How can I fix this problem? I have no manuel on this vehicle for a diagram of the engine at all.

Thank you. Dave