Vitara idle surge on backoff

[kimclive]

Hi Guys,

I have flushed out the cooling system on my 91 Vitara and ever since the engine surges when I take my foot off the gas. It wont idle slow either.

I have checked all the mechanical linkages and they are fine. When I accellerate by hand and watch the cable on the throttle body there is no movement but the engine revs surge.

Any ideas?

Cheers

Clive

[Beastmavster]

hmmm..... alternator maybe? Try with headlights on on high and see if it does it.

My wife's audi does the same thing. EFI can cause this sort of stuff for a lot of reasons - sometimes it's better to find someone who can read the codes off the EFI than stuff around.

[kimclive]

Thanks BM,

I forgot to mention its a 91, 16v MPEFI G16B.

I'm thinking it could be in the emission stuff.

I'm trying to work out how to read the codes and will try again in the morning.

If it works I'll post up the instructions.

Cheers

Clive

[DamTriton]

General comments only

Leaving the aircon on can also give similar results (normal condition).


Sounds like the idle air bypass valve sticking, or dislodged hose in/around that area. It is usually mounted on the throttle body as a dangly bit off the side (seperately or physically cast onto the side of the TB.) If a hose is dislodged or off altogether on the IAC it allows air into the inlet, the mass airflow sensor interprets this as more air into the engine and the ECU says more fuel please. Net effect is a higher idle speed. May/may not throw a code, depending on the ECU.


Another remote possibility is the engine temperature sender (to the ECU) not functioning correctly (electrical connection, or actual function), effectively telling the ECU to stay in "warm up" mode with a higher idle speed and generally richer running. It should also throw a code of some description, as a test of all the sensors is usually done by the ECU on start-up. Usually will not let you into overdrive in an automatic.

Who says I can't do tech??

[kimclive]

Awesome! I'll try all that.

It wont go into overdrive until it's warm. Is that normal?

Cheers

Clive

[DamTriton]

Awesome! I'll try all that.

It wont go into overdrive until it's warm. Is that normal?

Cheers

Clive

That is normal. Also means you can eliminate the temp sender.

[Beastmavster]

Im thinking maybe oxygen sensor or possibly map sensor? Incorrect/intermittent airflow readings.

Oxygen sensors do this a bit.

[christover1]

If its happened after a cooling system flush, then maybe you got an air lock in the cooling system, and it needs a bleed.
ecu can be triggered by water temp, so maybe its sticking on the choke, thinking its still cold.
just a wild guess, but werth a thought.

christover

[kimclive]

Thank you all for your replies.

And the winner is: christover.

I replaced the thermostat while I was flushing the system and the new one didnt open until the engine was too hot. I saw it was throwing the fluid out so I flushed the system, changed back to the old thermostat and carefully refilled the system.

I checked the ECM code and it showed code 12 - normal state.

I went for a long drive this morning - perfect!

Bloody electromagic gizmos! I loved my 1975 Corolla. You could strip and rebuild it with a Leatherman and basic mechanical knowledge.

I will post up how to get the ECM codes on the EFI Vitara on a separate thread.

Cheers

Clive

[SiKiD_01]

I will post up how to get the ECM codes on the EFI Vitara on a separate thread.

yay, another for the bible.

[kimclive]

Another problem with this today. A cold day in Sydney and after running down a long hill the engine was so cold that it wouldnt engage 4th gear (auto).

I dropped the coolant (3rd time) and replaced the thermostat (2nd time). Very carefully refilled the system, ran till warm and filled again. Bled last of the air, went for a drive. 100% perfect and running the right temperature for the first time ever

The moral: Be very careful to bleed all the air out of the cooling system as it will effect all the sensors and upset the EFI.

Thanks for your help guys.

Cheers

Clive