ECU prob

[Gran]

Hi
I am trying to source an ECU to try & eliminate an erratic tickover, the ECU has been tested & appears to be the culprit...but I can only find ECU's with numbers that match except for the last 3, does anybody know what these refer to ? could I have fitted an ECU with 480 or 550 and got away with it ? mine is 500 ?
I have put a "wanted" in the sales section & am waiting on find-a-part to see if they come up with anything.

any input appreciated.

Cheers

Gran.

[JJ]

gran,

is your car a normally aspirated or turbo ???

erratic idling usually cause by an air leak into the inlet manifold... this can be the throttle body gasket not sealing properly or perhaps a vacuum pipe being accidently removed and not refitted.

Have a nosy about, I dont' beleiv eit ecu related !

[Gran]

Hi JJ

It's an n/a & I have been told before that it sounds like a air leak on the induction side but have been through it & the garage it's at now have also had a check. He had a guy he uses check the ECU (don't know how or what with) & he says it's 100% ECU related.

I had several breakers phone this afternoon but none had an exact number match,usually the last 3 digits were different & wondered if anyone knew what they equated to.
Eventually sourced one & it should be here tomorrow, will let you know how it turns out.If it doesn't sort it we'll have to go back to the air leak.

Cheers
Gran

[JJ]

Bizzare how you've got an odd ball ecu part number... wonder whats different about yours ??

what year is it again ??? i know the rev 3/4's power dropped in 96/97 - probably necessitating to an ecu part number change... this was a more efficient ecu as there was quite a few MR2's failing emission tests - leaned out a little.

[Gran]

The car is a 95', N plate. the complete number is 89661/17500/S3GMT.
It arrived this afternoon & hopefully we can try it tomorrow (Thurs).

Its just the 500 that was the problem to match but eventually got one. I had offers of 480 & 550 but the garage wanted a complete match to be safe.

Gran.

[Gran]

JJ, you were right... the new ECU has not corrected the problem, they checked for a leak by using a spray to check the joints on gaskets etc.. apparently the aerosol is sucked into the air stream & causes the revs to rise sharply.

The only thing I can think of now is taking it to a auto electrical specialist to go through the sensors to see if there is a dodgy signal being sent to the ECU...after that I ain't the foggiest.

Cheers

Gran,

[JJ]

Gran,

can you detail your erratic idling a little more ??

People cannot test ecus unless your bolting it to another car... so for someone saying the ecu is faulty and the cars starts, they're talking outta their butt.

Gimme more information and I can direct you what to check for.

[Gran]

When I start from cold everything is OK, when the temp starts to rise the tickover then "hunts" from say 500 revs to 1800 revs & sometimes drops off altogether. the idle contol valve has been changed & no air leaks have been found. I am going to check for air in the coolant system today because a search on this site & google has thrown up that has a possibility.
The garage didn't charge for the work done so far so I am only out of pocket for the ECU (£65).
If the air leak was the cause surely it would still be there on cold start which is stable at about 1600 revs.

Thanks for the input.

Gran.

[JJ]

Air leak gran !

Reason why its not there on a cold start up is due to the enrichment on the efi... basically, theres a shed load of fuel entering and the idle control valve when its wide open... the engines is expecting an extra flow of air and fuels.

When the engine gets hot, the fuelling is majorly reduced... when an air leak occurs, its draws it in from there instead of the throttle body ... so the engine rises in rpm... but theres not enough fuel and confusion occurs as the throttle is closed ( throttle position sensor ) and hence your surging engine idle.

Suggest replacing the gasket for the idle control valve for a start ( as its been off ), then throttle body, then the intake manifolds !!

Basically all the gaskets on the inlet manifold.

Its difficult to tell if theres a leak ( mechanical view ) - where air is being pulled through. It only needs to be a little bit of grit on the surface when bolting up to draw the air in to upset the idling.

Hence - change all the intake manifold gaskets - check / inspect surfaces / casing for cracks etc.

That should resolve the problem.

the idle contol valve has been changed

Was this changed for a new one or for a used one that may have been caked up ??? I've cleaned a few up where they've been stuck open, so cold idling is good as the valves wide open, but then when warmed up, the valves still jarred open = excessive air being drawn in which will give you that erratic idling.

So recap :

Inspect idle control valve first ( strip off throttle body and inspect valve actually moves and not seized )

Change throttle body gasket whilst your there, or thin coating of instant gasket will seal it up.

All the above and still no resolution, budget for changing all the intake manifold gaskets.

Have you ever unbolted that top flange ( curiosity ? ) which is part of the plenum on the intake manifold.. the bit with the bolts ??? ( just in front of the engine lid anchor point !! you could try doing that one yourself, unbolt all the nuts and bolts, get some instant gasket, thin coating around the gasket and bolt it back down !

I'm 99% sure its an intake drawing too much air issue... all mechanical, not electronic.

The engines generally don't have a problem like that unless its been disturbed - like idle control valve removal etc.

Keep smiling.

[Gran]

Hi JJ
The idle control valve that came off was OK, I had a look at it in the workshop. The gasket was replaced when it went in for an MOT at a dealership. They said it was probably the idle valve but I didn't fancy paying their prices.
If the coolant drain doesn't cure it it's booked into Protune on Tues so I will pass on your advice to check the air intake gaskets.

You know what it's like when they act up...it's probably not that big a deal on a scale of one to ten but it gets you wound up trying to figure what the bl**dy hell is going on.
I'll try to keep smiling but it may take a quantity of alcohol tonight to kickstart the process

Later

Gran.

[Gran]

Coolant drain didn't do bu88er all, so it looks like a gasket.
I am going to get Protune to look there first on Tues morning.

So it looks like Wed pm for the next instalment....

Thanks again JJ

Gran.

[JJ]

Coolant drain didn't do bu88er all, so it looks like a gasket.
I am going to get Protune to look there first on Tues morning.

So it looks like Wed pm for the next instalment....

Thanks again JJ

Gran.

Better stick your ecu up for sale... recoup some money !!

[Gran]

The next instalment....
Protune have checked for air leaks & are sure there are none,rechecked the idle valve for sticking again, not stuck. put a map sensor off another car on,not that. I am picking the car up again Fri a.m. because they don't know where to go next.
Even though they say no air is leaking into the intake ....wait for it.......the intake vacuum pressure is not high enough, they were expecting 20 ? whatever scale they were looking for psi,bar etc.. & only got 15 but it is constant. Also it is over fueling like mad, what should be a reading of 0.5% is showing 10% (scale of what I don't know)
Just who exactly do I take it to next, Toyota dealer in Nottingham or is there somebody else who specialises in MR2's ?
JJ does this low pressure & over fueling still look like dodgy gaskets to you ?
Be kind..

Fed up !!

Gran.

[JJ]

Hey gran,

Chin up chap - go get a paper clip and bridge TE and E1 in the diagnostic port.... see if it throws any error codes now ??

Idle control valves not off a turbo model is it ?? turbos normally have to dra in a little more air as they're a lower compression engine = valve slightly more open than normal.

Okay - try this, take the intake pipe off so your in view of the throttle housing.. there should be a hole in there where the car draws air from ( before the main throttle butterfly - for the idlling..... stick your finger over halve of it and see if the revs settles.

See if you can control the the idle with your finger.. !! That will tell you straightaway if you have additional air being drawn in wether its the idle control valve in need of adjustment or there is a air being drawn in from a flange somewhere.

Theres a breather to the right of it, it pull the gases from the internals of the engine ... check to see if the hoses arn't split - if the hose is split there, then air can be drawn in and the idle speed will go up - causing the eraticness.

You don't need an MR2 specialist to diagnose the problem you have - its fri88ing basic mechanics !

As for all those values ... lol !! Ever heard about bull$h1t baffles brains ?? You will have a lower vacuum pressure ( closer to zero ) if there is a leak !! Duh !! Hes stating the obvious !

Report back chap !

[Gran]

I have taken off the intake pipe & looking into the butterflies there is a small hole in the sidewall of the casing about 4 mm in diameter on the right hand side. This is letting air into the airstream into the butterlfies.
The pipe on top of the throttle body that goes down under the body is OK & not leaking.
There is a air pipe that emerges from the intake pipe about 4 inches from the butterflies that is drawing air (Idle?) which if I partially cover starts to make the revs drop & if I cover it all the engine dies.
Make any sense ? the throttle body also has a tube coming from the top that is blocked off (turbo body ?) I did not notice this on my original one.

Has for the paper clip trick I don't know how to check error codes but will search this site, it will be here somewhere.

One thing that I have noticed over the last few days is that it is relatively stabler since Protune had a look at it but if I rev the engine to 2000 revs & release the throttle it will always drop the revs right off & die.

The plot thickens...

Regards

Gran.

No error codes showing.

[JJ]

There is a air pipe that emerges from the intake pipe about 4 inches from the butterflies that is drawing air (Idle?) which if I partially cover starts to make the revs drop & if I cover it all the engine dies.

Okay - concentrate on this area ... you want to reduce the engine speed by limiting the air going into the manifold. This is where the idle control valve controls the speed of the engine. Its possible that the valve is out of position... I know its a ball ache.. but if you remove the throttle body in a position where you can get access to the idle control valve - remove it and partially strip it... you'll see the main valve area where it opens and closes - this is linked to an heated coil - basically the coil windings depending on temperature adjusts its position - this coil winding mechanism is behind the 2 little screws in the idle control valve - if you remove that - you can see if its broken or not. ensure everything moves fine.

What you can then so is adjust the maximum closing of the valve on the idle control valve too... there should be a very small allen key grub screw at the base of the valve - this stops the valve from fully closing - you need to reduce the opening of the valve by closing the gap with use of adjustment !

Unfortuntely, you'll have to go with a guess and gradually adjust it - I understand its location for further adjustment once bolted up may be an issue... but its one of those things

If you look at the coil winding / mechanism of the valve too, you'll see thats adjustable - make note of the direction of closing the valve and opening of it... then you can use this as a bit of a float afterwards for adjustment as you should be able to just get into it.

Try that !

[Gran]

Will do as you suggest but it will be a weekend project.
thanks for being so patient with an amateur.

What is the spare blanked off pipe on top of the throttle body ? does this suggets it's off a turbo ?

Regards

Gran.

[JJ]

Will do as you suggest but it will be a weekend project.
thanks for being so patient with an amateur.

What is the spare blanked off pipe on top of the throttle body ? does this suggets it's off a turbo ?

Regards

Gran.

Plenty of patients for a chap banging his head against the wall !

Throttle bodies for the turbo won't interchange with the normally aspirated ! If there is a pipe coming from the top, plug it ! small vac pipe, then stick a small bolt into it.

That pipe would normally go to a charcoal canister... black thing about 8 inches by 4 inches - cylinder shaped - just an emmisions thing drawing gases from the fuel tank !

[Gran]

Hi JJ

I have retrieved my original throttle body from the first garage & had it to bits as you suggested. The metal spring that operates the idle valve is OK & I cleaned the idle valve & lubricated it so now its like new. slapped it back on this afternoon but it is still dropping the revs off & dying if I blip the throttle. The revs now are only bouncing twice before it settles at around 1000 rpm. When it has settled it is stable & not bouncing at all.
If it was like this when it started I would not have been too bothered but now I am on a mission & wont rest until its sorted.
The car is booked in at Rogue on the 17th to hopefully get it sorted once & for all.
If you have got any other ideas I would still like to hear them because it will give me great satisfaction to sort this bu88er out.

Thanks for the help so far.

Regards

Keith.

[JJ]

Hey keith,

getting somewhere now !!

Look into pulling your plugs out and generally giving the ignition system an inspection.

Check / change spark plugs ( for the price of them change them out ) and inspect the distributer cap. Remove it, check all the points where the spark arcs - usually there a build up or corrosion to the surface - scrap it with a screw driver and further cleaning with a bit of sand paper / wet & drys is a stronger then household stuff.

Does the car generally perform well ?? rev to the redline good ?

Although the engine relys on the air going to the intake manifold via the idle control valve - the ecu works far too quickly to catch it out... meaning the ecu can control / adjust the idle control valve faster than the engine can react.

If the engines dieing on a blip of the throttle, this usually relates to the ignition system in need of a bit of replenishing - perhaps a ignition timing check too.

Your getting there ..... the lads at rogue are good, failing that, next door is thor ( unless they havent moved yet ! ) so either way the problem will be sorted - but changing / inspecting what I've suggested may also form a resolution to your problems.

Over and out !