Erratic/low idle on E10 Corolla 1.6 4A-FE

[NeilMH]

Hello All. I've just bought a '97 CDX Auto with 1.6 4A-FE engine. It runs beautifully when moving along. It has a perfect Toyota dealer history and virtually perfect MOT history from new. However, it's done hardly any mileage since it was last serviced 9 months ago - less than 100 miles.

The one issue it does have is, when hot, an erratic idle - in fact a couple of times the revs dropped enough for it to stall. It re-started easily but with revs immediately down at about 200 or lower.

I am aware that there could be a number of explanations but I'm guessing that, given the service history it's unlikely to be things like Timing belt incorrectly tensioned or incorrect valves clearances etc. I suspect there may be a more simple explanation.

My question is, where would you start looking for the answer - maybe it just needs a good run at motorway speed, or vacuum pipe issue/leak or MAF issue? The air filter is new and clear.

Thanks in advance for any thoughts.

 

 

 

[oldcodger]

Hi,

Looking a the web pages for such a problem seems it could be one simple thing or a series of worn parts.

Might be worth getting a computer diagnostic to isolate the problem rather than lots of expensive parts on a whim ..?

If you have a carb? my first thoughts would be to check  it out.

[NeilMH]

Thanks - it’s fuel injection with EMU but without a normal OBD port to use a standard modern code reader. Having said that I’m also thinking either stale old fuel that’s been in there for months or simply suffering from a lack of use  - I’m going to try a good fuel system cleaner and a decent blast first, and fill with V-Power which has more detergents in.

[furtula]

I think it should have some diagnostic port in the engine bay, but it should also might be possible to get some codes using certain combinations inside the car, so i would like into that if i were you.

[NeilMH]

Thank you furtula. I think the port in the engine bay is something the garage can use but I’ll look into the other procedures you mention if my clean and blast doesn’t solve the problem.

[oldcodger]

Hi,

The first  vid shows where the diagnostic socket is, and the second one on how to "flash" out the error codes onto the dashboard lights.

Its the same way that was used on the old Avensis we used to have, it seems a crude way, but it does work ok.

Of course you do not mention seeing the dashboard Engine Check light being illuminated, so there may not be any error codes in there, or the ones that are could be from a very long time ago,

You can clear / reset its Error memory by disconnecting the Battery for 20 mins or so, or by linking the socket in a certain way, if you search the web you will find full details and error code lists.

Of course your tickover problem might not be bad enough to flag an error code ..?.

 

https://www.youtube.com/watch?v=RE6EZYJAOHE

https://www.youtube.com/watch?v=l_YhNmIVcbA

 

 

[NeilMH]

Thank you oldcodger, that’s very helpful. I don’t have any warning lights, however I’m going to proceed as follows, seeing what the situation is after each step

Fuel system cleaner and Motorway blast - if still issue then 

Remove Battery for time you suggest to allow a full reset then drive again, if still issue then

Follow the procedures in the videos.

Already the limited running I’ve done has made a little bit of difference with the revs dropping rather too much but not stalling. I still suspect the problem is that’s it’s been sitting for about a year (with just 100 miles done) albeit it was garaged.

[oldcodger]

Hi,

Would suggest thats the wrong way,  better to read out any existing codes stored in the ECU before disconnecting the Battery as that will show any you may have.

There might not be any in there, or if there is , nothing to do with idling, but worth finding out either way, then Clear its memory so that if any New error codes appear you know they relate to a time after that Clear.

As well as a fuel cleaner you could try a can of  Carb cleaner spray in and around the butterfly valve as if that flap is dirty and not closing fully it could cause the problem ?

There are Ytubes about doing so, but they remove the whole lot a more diy complicated job ,but for starters it easy enough to unscrew the air intake to expose the valve and spray in there and clean with a toothbrush etc.

That will not get everything, but if it makes a noticable difference to the hot tickover, you know thats the likey area that needs a full clean.

See this vid at 3min 45s where he releases the ducting and e xposes the flap.       Carb cleaner  from most places typically £5

https://www.youtube.com/watch?v=sAANEIR5QOE

 

[NeilMH]

Good point - I should have thought of that logic - that was very nearly a stupid thing I did there. I have quite a bit of carb cleaner left over from my Caterham 7 days! Thank you for the other stuff as well - very helpful. I’m just trying to get this solved before Monday. I bought this car cheaply with a very short MOT but it all looks good bar this problem. I’ve never had a running problem with either of my other 4A-FE cars so this is a novelty! Thanks for the help oldcodger.

[NeilMH]

As I had 30 mins to spare today, I've just cleaned up all the bits of the throttle body/butterfly valve that I could get at. I decided to have a go at this as I had also noticed a little stickiness in the throttle operation which is another symptom of carbon build up. It was full of black crud which took some time to remove with toothbrush, carb cleaner and appropriate cloth. The throttle stickiness has gone away and the tickover has improved a bit more. I'm not quite there yet but I'm getting there. Thank you oldcodger.

As a aside I'd hoped the car might have an OBDll port as it's post '96 but it's got the old one, so bridging with a paper clip and counting flashes is going to be the order of the day.

[oldcodger]

Glad to help

The method of flashing out the error codes is quiet easy, once you get used to its way of working,  if you do have any, you should easily find the meaning by a web search or post here.

As you can see from that video, once you have read all the codes out, if any, just pull the EFI fuse for a minute to clear them all.

Do you mean you have the MOT on Monday ?  would not have thought an erratic-ish tickover would be a problem , the exhaust tests are usually done at higher revs.

You could check the actual throttle cable, they can partially seize up / become stiff or some strands can break internally and catch on the outer casing. You really need to disconnect it both ends so the only resistance you can feel must be within the cable.

Would think your problem is there all the time, though you do not notice it when cold, probably because the choke is overriding things ..?

The Caterham sounds good, for those with a thick skin in this weather !

[NeilMH]

It's MOT on Monday but I think I'm ok now - it was actually stalling before but isn't now. The codes and what they mean are in the Haynes Manual. When I was doing the throttle body I checked the cable and did some lubrication - it was definitely a sticking butterfly valve - it was grating on built up carbon deposits.

The ECU probably enriches the mixture and increases revs when it's cold - but that it still revs lower than it would normally. So the problem is noticeable when cold but it just isn't enough to stop the engine.

I think I'm well on the way now - I'll find out tomorrow when I'm on a longer run.

The Caterham (X2) and Elise are sadly now in the past. I'm just pleased I did it when I could. Then graduated to a 350Z and then an XK8 but they were all weekend toys which it got harder to justify when I retired. All gone now - sob, sob.

 

 

[NeilMH]

Job done! The throttle body cleaning recommended by oldcodger, a full bottle of fuel system cleaner and a long run out has solved the issue. Thank you.