2.0 L petrol idle speed adjustment

[Andrewpridmore]

Hi All

Anyone know where the adjustment for idle speed is on the 2L petrol engine? (2003 model) All the photos & posts I've found are for either the diesel or V6 and don't match the 2L engine.

I'm assuming it's the same screw as the others with a locknut and is adjusted using a flat bladed screwdriver, i just cant find it. Photo would be great but just a pointer to where it is and how to reach it would be very helpful. At the moment the bongo sits at under 500 even with AC turned on & from a standing start it either bogs down or stalls or just goes so slow at first that it's almost a hazard.

Has had a new air filter & has same issue on petrol & when on LPG so seems independent of fuel. Next stop after idle speed is spark plugs & the belts are being done next week.

Ta muchly

Andy

[Bongolia]

Idle speed is controlled automatically to compensate for engine load AC etc.
I think what you are refering to is the base idle screw. That shouldnt need any adjusting and is factory set. There is an idle air screw on the plenum somewhere. I think its around the butterfly valve area where the plastic induction pipe fits.
It may be that the ISCV is coked up/failed.

[Northern Bongolow]

you could test the throttle pedal is set up correctly but i would go with dirty throttle body too, usually crappy fuel or lack of fuel system maintenance, or egr putting crap into the inlet manifold.
ive had this on 2 seperate cars recently and had to replace both throttle bodies as the adjuster screw for the butterfly is usually sealed up or tamper proof, one of them i freed it so i could adjust it but the throttle position sensor sensors this adjustment and alters everything else, as it should.
the carbon build up around the butterfly seems to strain the internals so that when the carbon is removed/cleaned it goes slightly out of adjustment.
make sure your sat down when you ring up for a price for one.

[Andrewpridmore]

Thanks for the info guys, i will look into it.
It has always been slightly slow from a standing start but i figured that's down to the 2L engine. This sluggishness first appeared when running on LPG (new system 3 months old) over the Easter weekend & is there regardless of LPG or petrol so even if it was the throttle body, why is LPG causing the same issue?

Last night i found i could improve the response by pumping the accelerator pedal at varying speeds. Pressing too far too quickly made the engine bog down, too little made it do nothing but somewhere in between it would actually respond. Once it gets over 1000rpm or so it all functions the same as ever. If i could keep over 20mph & 1000 there wouldn't be a problem. Curse those other drivers, junctions, lights etc.

A strange point - at idle, the engine revs just drop when a/c etc come on, it's as if the engine has no feedback to tell it to respond to the increased demand, same as when pulling away at low speeds, it goes straight for a rev drop to 300-400 or stalls.

I have tweaked the throttle cable to force it to idle at around 800rpm for now, not ideal but better than it stalling at every other stop. This is in P or N. However, as soon as i put it into drive it drops the revs down low again - whatever system is supposed to be keeping the engine going seems to not be working very well. Coming to a too rapid stop has also been known to stall it, not emergency braking by any means, that would guarantee a stall.

[Andrewpridmore]

Oh - also that statement "Idle speed is controlled automatically to compensate for engine load AC etc." - what part does that automatic control (ECU?) because it doesn't seem to be doing it & may need looking at too...

Thanks again

[Bongolia]

Oh - also that statement "Idle speed is controlled automatically to compensate for engine load AC etc." - what part does that automatic control (ECU?) because it doesn't seem to be doing it & may need looking at too...

Thanks again

The function of the Idle Speed Control Valve (ISCV) is, as the name implies, to control the engine's idle speed according to its temperature and different load conditions.

When the engine is first started from cold, the engine management Electronic Control Module (ECM) gives the engine cold start enrichment and increases the engine's idle speed to about 1200 rpm. It is the ISCV that is responsible for this increase. As the engine reaches operating temperature the enrichment is eliminated and the idle speed reduced to a predetermined speed. This speed is maintained regardless of electrical loads on the alternator and to a certain extent mechanical loads, for example, when an automatic gearbox has drive selected.

The ISCV is an electromechanical device that has a supply voltage either from the ECM or a control relay. It has 2 or 3 electrical connections, with the aforementioned voltage supply and either a single or a double switched earth path. The rate at which the earth path is switched is determined by the ECM to maintain a pre-programmed speed. An ISCV can be either a rotary or an electromagnetic type, both of which are popular with the rotary being the most common. The valve forms an air bypass around the throttle butterfly to deliver a controlled air bleed within the induction tract, and is therefore susceptible to dirt and carbon like deposits impeding its performance. It is recommended that they are cleaned at the manufacturer's service intervals with a spray solvent to maintain their efficiency.

If the engine has an adjustable air bypass and an ISCV, it may require a specific routine to balance the two air paths.
Cut from the PICO site.

The above is why you shouldn't touch the base idle screw. As N.B. says the ECU will just try to sort things to match its map.
You can make that adjustment (and igntion timing adjustments also) but you need to switch out the ECU while it is carried out through the diagnostic socket but at the end of the day the ECU will have the final say according to its map.

Generally these ISCV are "forgotten" when the vehicle is "serviced" so they can suffer from a build up of goop and that will impair their function.

You may have two likely problems here though. The first may be the the throttle pot and the second may be the ISCV, the idle circuit.
These two are where I would be looking, first the clean up then if required the pot.
The throttle pot is just a rotary resistor and a base idle switch in some cases. a bit like the volume control on the telly.
The first part of the track gets most use and wears and so does signal the ecu as to the throttle position and you get the flat spot you describe although there can be other causes for this. But you need to eliminate these two first.

If you have the vehicle booked in for work it may be easier to ask them to clean out the system for you first and then address the throttle pot later if at all.
In the meantime you could be checking all the tiny vacuum pipes you can see around the engine for splits and kinks and at the rear of the engine at the top you will see a large intake duct these can split around the securing clip also check this ducting right back to the air box for security or splits.

I am in work today so if I get a chance I will ID the components on Lush and put the links up on here unless anyone else can ID them first.
If you want to have a go at cleaning the system yourself you will need a couple of cans of carb cleaner spray a small paint brush and a bendy neck tooth brush.
Question.
That aside now you have adjusted the cable to take up the revs does it idle smoothly or is it hunting up and down?


I

[rita]

Andrewpridmore ,

Personally I would get the LPG fitter/engineer to retest and rest the system if required.

[Andrewpridmore]

With the throttle cable tightened the revs are fine until i put it into Drive, then they plummet to 500 or less.

It doesn't go to 1200rpm when started (am sure it did go higher before but no longer does) - without the throttle cable tightened it goes no higher than 500rpm and attempts to stall unless i keep my foot resting on the pedal to keep the revs up. Clogged ISCV sounds possible as the engine doesn't bother increasing at all when cold starting, doesn't seem to want to know until over 1000rpm. Can a clogged​ ISCV be overcome once I'm going fast enough or should i still see an issue at 2000rpm?

This has all come on since good Friday which has included about 400 miles of mostly motorway driving.

It's still useable just slow - am more worried about other drivers as i can see it agitates them taking so long getting going. It's worse starting on a hill too.

I will call the LPG engineer to have a look later. There's redex in the petrol which i will run through and fitting new spark plugs this weekend so we will see if that helps.

[Bongolia]

Andrewpridmore ,

Personally I would get the LPG fitter/engineer to retest and rest the system if required.

Good point that, although this would still be applicable.
But for clarity I gather the issue is the same both ways round OP?
I.E. same symptoms LPG or Petrol?
I have little to no experience with dealing with LPG so I am approaching this from a purely petrol pointy of view.
Let me know.

[Bongolia]

With the throttle cable tightened the revs are fine until i put it into Drive, then they plummet to 500 or less.

It doesn't go to 1200rpm when started (am sure it did go higher before but no longer does) - without the throttle cable tightened it goes no higher than 500rpm and attempts to stall unless i keep my foot resting on the pedal to keep the revs up. Clogged ISCV sounds possible as the engine doesn't bother increasing at all when cold starting, doesn't seem to want to know until over 1000rpm. Can a clogged​ ISCV be overcome once I'm going fast enough or should i still see an issue at 2000rpm?

This has all come on since good Friday which has included about 400 miles of mostly motorway driving.

It's still useable just slow - am more worried about other drivers as i can see it agitates them taking so long getting going. It's worse starting on a hill too.

I will call the LPG engineer to have a look later. There's redex in the petrol which i will run through and fitting new spark plugs this weekend so we will see if that helps.

No the ISCV will be out of the loop by then. ~But it would be prime suspect in the first instance, unless the LPG fitment takes control over that, does the LPG have another ECU piggybacked onto the standard system if yes does it run stand alone or intercept the OE somewhere along the line .. Rita?

[Andrewpridmore]

Yes, the same results on both petrol and LPG, the problem is exactly the same with no noticeable difference when running on either fuel. Both fuels share the plugs/HT leads, the throttle body/ISCV and the vacuum/air hoses.

Will check the hoses and clean the throttle body after work today and see how it goes.

[mikeonb4c]

I have a sort of cruise control on my Bongo. It works by having a cable that is attached to the throttle lever and that can be locked. It is handy also if i want to raise the tickover. Is the OP able to raise tickover by slightly depressing the throttle. If they are, is there any way the throttle lever can be persuaded to rest in this new position? I do agree that any underlying problem should be addressed but I'd be curious to hear views regardless.

[Bongolia]

Yes, the same results on both petrol and LPG, the problem is exactly the same with no noticeable difference when running on either fuel. Both fuels share the plugs/HT leads, the throttle body/ISCV and the vacuum/air hoses.

Will check the hoses and clean the throttle body after work today and see how it goes.

I will knock up a check list of some basic checks to carry out relating to the idle control and pot.

[Bongolia]

As you said this happened after a motorway drive I would check that the engine is breathing OK you have dealt with the air filter so that would leave the exhaust.
I have known for the matting inside the exhaust to become detached and restrict the outlet of gases.
If you have a vacuum gauge tee that into the inlet manifold some where and make sure your getting around 19 inches of mercury snapping the throttle should pull up around 25 or so. If you dont have one then start the engine and put your hand over the tailpipe blocking the outlet when you release it you should have a healthy PHUT with a good flow when revved!
Alternatively a dirty but foolproof method is to remove it some way down the system preferably as close to the front down pipe as you can thus allowing the gas to bypass the silencers completely.
This could be a mucky job so you may want to do the other checks first.

This is a 2001 and has no EGR I dont know if the later type had EGR fitted or not. If yours has this then treat that as a separate issue for now
Here are some images that may help and the basic checks to carry out.
This is of the butterfly (throttle body) at the rear of the engine. The hole you can see is where you would normally find the base idle screw or air bypass. Its not fitted so the ecu controls it. There may be an adjustment on the air valve. Will come to that later.

https://goo.gl/photos/uK593L63xxRMJwod9

You can see behind it the duct that splits and the fabulous repair made.
You would need to remove that pipe in order to get in to clean the butterfly they become brittle so take care.
Below it is an idle switch with a grey cap, This tells the ECU to switch to the idle circuit. a continuity check here will show if that is working ok its just on/off. Off when open. Adjusting your throttle cable m,ay have pulled this off the rest position you can just ignore that for now.

The large dark grey plug on the right is the throttle pot.
https://goo.gl/photos/qPFRBF6Eju5DXo5d8
To check the throttle pot disconnect the plug and place an ohmmeter across an outer pin and another to the centre pin on the pot. Resistance at rest should be around 1.2k rising to 4.50k on wide open throttle or vice versa depending on what terminal you are on.
What is more important is that the resistance rises and falls steadily with no drop outs or sudden rises in resistance.
The supply voltage to the pot should around 4.5- 5Vs at the plug ignition on.

These are of the air valve its at the front of the engine, as well as having air pipes attached it is also fed with coolant so would also act as cold start valve also.
https://goo.gl/photos/vKvYHhQhTLWoU5t88
If you place your finger on the top and turn on the ignition (not start) you should feel/hear a buzz of about 5 secs as it sets itself up.
If you want to clear this out you will need to remove it from the van to get to it properly. You will need to clamp off the water pipes.

Here are some images of the unit detached.
https://goo.gl/photos/nkZnGv4HEUXMXDrg8
At the end of this device is a cross head screw without taking the unit apart I cannot see for sure its purpose , it may well be the base idle screw as this would be the logical place to put it, anyhow I would leave that alone.
If you dont get the buzz then check the supply voltage should be around 5V igntion on.

This image is of the PCV valve that sits in the rocker box if you trace the tube coming from it it runs to a Y branch under the manifold just check that they are all connected with no splits or kinks. Its a one way valve so check it by sucking and blowing.
https://goo.gl/photos/SYZFdhDdgZivnQMF9

While you are under there check the degassing unit is operating OK by switching on the ignition while holding the valve you should feel it click.
https://goo.gl/photos/vYmhVFjaVhec1mHW6

Next on the list is the AF metering unit, this is in the ducting next to the air filter. Ensure it has a secure connection and look for any air leaks around this after the unit. This unit is a bit trickier to test so may be best to do after the others.

Those are your basic checks relating to this system.
Let us know how you get on.
Has your vehicle a separate ignition coil?

[Andrewpridmore]

I have a sort of cruise control on my Bongo. It works by having a cable that is attached to the throttle lever and that can be locked. It is handy also if i want to raise the tickover. Is the OP able to raise tickover by slightly depressing the throttle. If they are, is there any way the throttle lever can be persuaded to rest in this new position? I do agree that any underlying problem should be addressed but I'd be curious to hear views regardless.

I've manually set the throttle cable adjusters to force an idle rpm of around 1000 but as soon as i engage drive (or anything other than neutral or park) the revs dive to 500 or less, as if the engine can't handle any initial load. Put it back into park or neutral and the revs go back up.