Help!!, with engine prob all out of ideas

[d-_-b]

At the moment my car has developed a problem which has 2 effects:

 

1 when driving at lower revs, such as driving around a carpark or slowly in traffic, the engine becomes very "lumpy" for better use of words, the exhaust note goes very low and there is a distinct limitation in power when this happens.

(The engine will enter in and out of this state when this happens)

 

2. if the car is stationary sat on idle, the idle will drop down below 1k (to the first line below the 1k mark) then drop a slight bit more so sounds "burbly" and sounds as though its going to stall, then the car searches back up and down in and out of this.

 

3. above seem to happen intermittently, also when car has warmed up sounds as though with slightly miss when normally idling (when not doing the above other 2 points)

 

 

I have read through numerous posts on here looking for idea's but a lot of people who seem to experience problems with idle seem to have it sorted when the engine warms up, mine seems the opposite and it occurs when the engine is warm..

 

I have replaced the spark plugs with brand new iridium plugs, new dizzy cap and a new rotor arm.

The car is filled up with coolant and has had the oil changed recently.

 

I am kind of at a loss as to what can be causing this now. Can anyone help or suggest what this could be??

Any help would be really appreciated.

[AlanM]

Is the AC switched on when the revs are fluctuating?

[d-_-b]

Hi Alan, nope the AC & blowers are all off mate.

[gaz1]

ldle control valve maybe

[legendswraith]

Is it a MAP or MAF based engine?

If its MAF it may be worth giving the sensor a clean with electric contact cleaner. Does it normally idle at 1000rpm? Both 2jz's i have had (N/A and vvti) idle at around 650rpm and only went up to nearly 1000rpm at idle when the aircon was on.

[d-_-b]

ldle control valve maybe

 

What would be the best way to diagnose if it is this Gaz?

[Terminator]

O2 sensor?

[d-_-b]

Is it a MAP or MAF based engine?

If its MAF it may be worth giving the sensor a clean with electric contact cleaner. Does it normally idle at 1000rpm? Both 2jz's i have had (N/A and vvti) idle at around 650rpm and only went up to nearly 1000rpm at idle when the aircon was on.

 

It normally idles just below 1000, so guess 650 would be about right, however at the moment it seems to drop down below that which is when it almost stalls itself.

Where would i find the MAF sensor (if my engine is a model that has one)

[d-_-b]

O2 sensor?

 

Would that be the one that sits in the air intake pipe? or is that the air flow sensor? (still trying to learn all the positions of the sensors around the engine :S so sorry for sounding a bit of an idiot atm.

[bondango]

Have you checked for any fault codes?

 

Could be a lot of things, over fueling due to bad o2 sensor, vac leak, timing, bad/worn faulty miss adjusted TPS sensor, Idle control valve etc etc

[d-_-b]

Have you checked for any fault codes?

 

There are no lights or anything on the dash to indicate a fault code? Is there another way of checking for fault codes?

[bondango]

Click the word fault codes

[d-_-b]

Could be a lot of things, over fueling due to bad o2 sensor, vac leak, timing, bad/worn faulty miss adjusted TPS sensor, Idle control valve etc etc

 

So check O2 sensor for wear, dmg, dirty

Check for vac leaks in any of the pipes

Timing - if this was out woudlnt it always be apparent as apposed to intermittent?

 

 

 

TPS sensor & idle control valve, how would i check these?

 

Thanks for all that have helped so far, is really appreciated.

 

Is the cleaning procedure for the ICV the same on the NA as it is on the turbo models?

Edited April 15, 2009 by d-_-b (see edit history)

[d-_-b]

Disconnected the ICV from the loom connector that runs to it to see if it made any difference, didnt seem to do anything? Should i notice something if it is disconnected?

[Terminator]

b;2345692']Would that be the one that sits in the air intake pipe? or is that the air flow sensor? (still trying to learn all the positions of the sensors around the engine :S so sorry for sounding a bit of an idiot atm.

 

It is in the exhaust, it feeds back info to the ECU about content of exhaust gasses. When they pack up they feed garbage to the ECU. [Remember the TESCO fiasco, when some silicone got in with a batch of fuel and loads of O2 sensors got killed.]

 

When you have fault codes you will be able to narrow down the search.

[d-_-b]

OK, i checked the diagnostics port to see if there were any error codes, and there are none. Have the throttle body off the car at the moment, but cant really see anything to clean?

Anyone have any ideas?

[Ian C]

O2 sensor, then the O2 sensor, and after that the O2 sensor.