Cut out

[SuperRedMR2]

Hi,

The car is timed up and actually producing around 32mpg since it’s been running properly so no problems there.

The car keeps cutting out randomly – more often when I’m changing down a gear or going into neutral. It happened last night on a roundabout but thankfully no one else was on it. Only when its up to temperature.

The idle is around 1k when it’s hot and that’s down the nature of the camshafts running on the standard ECU and if it goes any lower, it stalls constantly.

Any idea as to why it randomly cuts out?

Cheers

[pistol pete]

can you adjust the idle screw higher? (or air mixture screw i thinks it is) to stop it cutting out? its probably to do with cams if you have different ones in

[SuperRedMR2]

Yes Pete I can adjust the screw but if I'm at 2.5k rpm in 2nd press the clutch to go into 1st, sometimes it drops down to nothing n cuts out. .

Is it to do with the fact I have a lightened flywheel and have to adjust my driving habits?

[pistol pete]

Lightened flywheels can do that.. but not from 2.5k unless its silly light...

air leak somewhere?

[Lauren]

What cam specs are you running?

But really it sounds like something else if it won't idle from cold anyway.

[SuperRedMR2]

Cold idle is fine.

252/260 - 8.5/9.0mm cat cams

[pistol pete]

Yeah I'm handing this one to Lauren. I don't know much about fitting cams in age and what effect they have..

[Lauren]

Well, those cams are not extreme in terms of duration, but a huge amount of lift especially on the exhaust, which is odd.

You can try retarding them a little, 4 degrees may help, but normally that issue is caused by duration rather than lift per se.

I run 264 in, 256 ex with 8.3mm of lift. My at zero degrees on the cam timing does idle a little rough, but not a problem at 1200rpm. It doesn't ever stall. But, if I retard the timing around 4 deg in and 5 ex (I'd need to check) it idles much better. You must of course have an adjustable vernier.

If you increase your idle speed and it still stalls, the cams aren't the issue.

Aha, just checked here's my cam timing when I got my car:

Looks like 6deg on inlet and 10 deg on exhaust.

AE86 cam timing by Lauren Blighton, on Flickr

The 106 and 113 relate to maximum lift settings BTDC I would say.

[SuperRedMR2]

Hi Lauren, I recently sold my adjustable pulleys as I had reverted back to the OEM pulleys after the re-rebuild - had to source some money for wedding stuff, so they were sold!

In a few months i'll probably buy some more (better brand) and have a fiddle again.

I'll adjust the dizzy for now to see if that makes a difference.

Do you run with the TVIS on yours or does the corolla not have that as standard anyway?

[Lauren]

I have TVIS yes, it was disabled previously, but I renabled it, just for the sake of low down torque.

The AE86 has the earliest reiteration of 4AGE, so yes, does have TVIS. My engine, well the block is from Phil's MR2 mated with the head the car came with, which was a typical early large port head.

Certainly do your timing properly, it will help. But it should never stall even if it's off. If it keeps stalling, timing won't be your issue, more like TPS or idle up failing for whatever reason.

Just to get this right, did you put the cam with the greater duration on the inlet or exhaust?

[SuperRedMR2]

Hi Lauren,

Couldn't have put them round the wrong way as only one had the dizzy gear on.

[kaiowas]

I seem to recall that hot idle problems are reasonably common, I know I had an n/a that did it at one time and I'm sure I've seen a few other people report similar symptoms so I wouldn't get too hung up on blaming the cams.

Mine would often stall when stopping at lights or roundabouts after a hard run, it got to a point where I just learned where it was likely to do it and gave it a little throttle in neutral just to keep the revs up and stop it dieing. Often doing this would allow me to gradually come off the throttle again bringing the revs down in a more controlled way and prevent it dipping low enough to stall.

I can't recall the cause or whether I ever fixed it but I'd expect Paul has probably encountered similar and fixed it several times.

[SuperRedMR2]

That's exactly what it does! Much better description than what I gave!

Sounds like the ISCV may be the issue.

[Lauren]

Hi Lauren,

Couldn't have put them round the wrong way as only one had the dizzy gear on.

Yep fair enough, both of mine had the dizzy drive on. It seems to be the case that with fitting different duration cams the longer duration is generally on the inlet, though your's seems to be a longer duration on the exhaust.

[jimi]

That's exactly what it does! Much better description than what I gave!

Sounds like the ISCV may be the issue.

The MK1 4A-GE doesn't have a ISCV.
With engine at normal temperature what's your idle speed ? If it's around 900rpm, try this, with engine idling (at normal temps) take off the inlet hose, look for the round port about 4 o'clock and seal it with your finger, what happens to the idle rpm ?

[SuperRedMR2]

Hi Jimi,

Wrong abbreviation then for the waxstat if that's what it is...

I've put the car to bed in the garage now as the gearbox will be removed next week so I will try that before it comes off.

I've dodged the waxstat fault for almost 8 years so it did well.

[Lauren]

The SC has an idle control valve the NA doesn't. It does have idle ups for head lights and AC and all that if fitted. These are done on vacuum and the like so worth checking your vacuum hoses.

But if it's not turning on the headlights that's causing it to stall then that is not the problem. Also if it's still stalling at high idle ,then the waxstat is not the issue either.

Likely cause possible airleak somewhere.

[PW@Woodsport]

Likely cause possible airleak somewhere.

I agree, also as has been mentioned the Waxstat cold idle auxiliary air valve has nothing to do with maintaining the correct idle speed when hot, a Mk1 NA has no idle speed controller, just an air bleed screw to meter the necessary amount of air past the throttle, crude but effective.

It could be any number of things, basic settings count for a lot on the 4a-ge, cam timing, ignition timing, TPS, air leaks, EFI temp sensor, all play a massive role.... so you really do need to go through everything.

The favourite is an air leak though, if the ECU sees conflicting data from the TPS v MAP sensor it will induce fuel cut (you can hear injectors being switched off on infamous "bouncing idle" cars).

So it's highly likely the ECU is in conflict between the EFI,TPS and MAP readings.

Could literally be anything, I'm not a big fan of internet diagnosis, so it's all best guess, hands on I'd fix it in minutes.

Hope that helps.

[SuperRedMR2]

That's exactly what it does! Much better description than what I gave!

Sounds like the ISCV may be the issue.

The MK1 4A-GE doesn't have a ISCV.
With engine at normal temperature what's your idle speed ? If it's around 900rpm, try this, with engine idling (at normal temps) take off the inlet hose, look for the round port about 4 o'clock and seal it with your finger, what happens to the idle rpm ?

Hi Jimi,

When the engine up to normal temperature, it idles around 1000rpm, I took the inlet hose off and covered the hole and the revs dropped considerably. It was stuttering a bit.

So?

[PW@Woodsport]

It isn't the cold start valve to blame, that either works or it doesn't, so if you see a 2000rpm ish cold idle which drops to 900rpm ish then it is working as it should be.

That valve has nothing to do with cutting out when hot.

As above, you have an air leak or basic timing/sensor setup issue.

Check the TPS once cam timing and ignition timing have been checked, if it's not set correctly its idle switch may not be engaging when you let off the throttle, so the ECU isn't catching it.