NCT Problem - high idle speed

cr17

hi,
Dont know too much about whats under the bonnet, but had nct last week on 96 corolla. Said they couldnt do the emissions test as i had a high idle speed, not me, the car. . Was up around 1250-1300 when it should have been 850 .
Drives grand, but just wont pass this test.Few other things like cv boot, but nothing that cant be fixed . This idle speed is the problem

Any ideas? One mechanic i brought it to said it could be a range of things and said it could cost a bit of money trying and testing different things, Said i,d get a second opinion.

bladespin

Get another mechanic and get him/her to check the air mixture on the carb, most likely cause or a crack in the air system.

cr17

Thanks, will be bringing it to my usual mechanic at weekend, just tried a new guy in dublin to see what the story was, he was sound in fairness and didnt charge.

DublinDilbert

bladespin wrote: »

Get another mechanic and get him/her to check the air mixture on the carb, most likely cause or a crack in the air system.

Surely a 1996 Corolla would be fuel injected?

To the OP, it sounds like the mechanic you brought it to didn't want to look at it or get involved. Get someone who's interested in fixing your problem and not someone who wants to just change oil and oil filters!

It could be something very simple, like the accelerator cable has shifted out of place...

bladespin

Correct, apols, they were injected.

As posted, cable is a poss culprit too. If not I'd be looking for an air leak though.

Darragh29

It's probably a manifold air leak. Check the usual suspects, pipe running from manifold up to brake servo assist unit, MAP sensor rubber pipe (check this very carefully as I've seen this been the culprit for this problem a few times on Corolla's). I think there is also a small rubber pipe on the top of the air filter housing for a cold start device, worth checking.

If it isn't an air leak, it could be a defective engine sensor, if a coolant temperature sensor was giving a wrong reading back to the ECU, this could in theory cause this issue, although it sounds more like a bad case of an air leak to me.

cr17

Thanks everyone, will try all of the above. got a mate in work who knows a bit more than me, so we'll try and solve it.

beachlife

cr17 wrote: »

Thanks everyone, will try all of the above. got a mate in work who knows a bit more than me, so we'll try and solve it.

It may not be directly related to the injection system,on some of the toyota's the ecu will increase idle speed to alert driver of other possible fault's, so don't forget to check things like the temp sensor and idle control valve etc...... cheers

garyegt

everyone jumping to air leak etc first. step back and first thing you do is look at the throttle positioning. there should be a screw or something to adjust it up or down. start with that. its a 2 minute job and could help with the idle problem:)

cr17

thanks everyone. something to go on now.

kermitpwee

It's more than likely your throttle body that is causing the problem. It's a regular problem on toyotas. A mechanic with a brain wiill be able to sort it. It might be ok with a clean. They are expensive new so you might have to get a used one of a scrappie for 50 -80 euro.

Muckie

I'd go with giving the trottle body a good clean first.

Theres Injector spray you can buy in any good motor factors.

Take off the air filter and spray it in as you gentle rev the engine.

Should help clean out any carbon or dirt build ups on the internal

sensor. She'll splutter a bit as you do this. Then come back to normal.

If that doest help a diagnosic check might be worth getting.