Help! My Celica Revs Itself!

[wiltems]

:ffs: My 1989 2.0l GTi Celica has recently taken to revving itself between 1500 & 2000 revs whenever its at a standstill, or I have the clutch down.

It can't seem to tick over normally and I have no idea why. Took it to a local garage who are equally mystified why its doing that.

It makes the ride very jerky, it revs too high the whole time and drags you along faster than you want to go!

Has anybody else experienced a similar problem or can anyone shed any light on what the problem might be please?!

My last resort will be taking the car to Toyota to run a diagnostic but I can't really afford that at the moment. :(

Any help will be very much appreciated!

[GT4 BOOSTER]

there should be a tick over screw somewhere on the throttle body , near where the throttle cable sits.try that.

its most probably the cold start sensor is knackered

try resetting the ecu by taking the earth lead off the Battery for a minute .

[wiltems]

Thanks for the suggestion I tried disconnecting the Battery and no change. I believe your right about the tempeture sensor playing up can you tell me where abouts its located so I might disconnect it for a while see if that makes any difference.

Thanks

[GT4 BOOSTER]

its 1 of 2 sensors on the exit for the water , near to the throttle body.

[mikeb]

I would not mess with the idle speed adjuster screw until you have checked everything else, as it is least likely to be this. Especially if this happened suddenly, rather than gruadually getting faster over a long period of time.

It could also be the idle speed control (ISC) valve sticking. When it opens it will allow extra air to bypass the main throttle butterfly to get the engine to fast idle, i.e. it should only open when the engine is cold. Of course, if the temp sensor is faulty and telling the ECU that the engine is cold, then the ECU will be holding the ISC valve open, so check the sensor out first.

If the temp sensor is faulty then I would have thought you would be using loads of more petrol than usual. If not, then it could just be the ISC valve giving a fast idle but without any extra fuel.

My manual describes the test procedure for checking the ISC valve on the 3S-FE engine, it is probably the same for the 3S-GE? Let me know if you want it posting on here.

As for checking the temp sensor, I can't see it in book (I might be missing it), but simply unplugging it is unlikely to cure the problem (but it should give you an error code on the dash). The other sensor near the temp sensor is the cold start injector time switch, but I don't know which is which. I doubt that the cold start injector time switch, if faulty alone, would cause a fast idle (not 2k anyway), but you would definitely be guzzling the gas.

I am assuming you have checked for error codes already?

[GT4 BOOSTER]

the cold start is next door to the temp sensor, on the throttle body ,the tick over is controlled by hot water passing over it and closing a gate inside the throttle body,you could try taking the throttle body apart and giving it a good clean as they do get gunked up.a vaccuum pipe could also be the reason for high revs ie - fallen off or holed. with reguards to adjusting the tick over screw ,that was sugested as a make shift option to get his revs down until he can get it sorted at a garage.

[mikeb]

I'm confused about the ISC valve myself now. I have looked at mine, and you are right about a couple of water pipes passing through it. But mine also has an electrical connector, and the diagram in my manual shows it wired to the ECU. But it also shows another bypass to the main butterfly described simply as 'air valve'.

The cold start and temp sensor are on the water outlet from the end of the head.

Wiltems, when you find out what is causing your problem, let us know.

[GT4 BOOSTER]

its 1 of the 2 sensors you can see here. the number 1 sensor is the 1 that sends the message to lower the revs as the engine gets hotter , i think via the right hand sensor number 2,unplug this ( number 1 ) and the revs should die down, the left hand sensor is the needle on the dash for temperature.if the gate(where number 1 sensor plugs into ) inside the throttle body is sticking it will not let the revs die down.

[wiltems]

Thanks alot guys for all your help on this matter :D

I think your right about the ISB could you post the testing procedure of this valve and I will give it a go.

Thanks alot I will keep you all posted on the outcome

Cheers

Wiltems

[mikeb]

First thing is to check out any diagnostic codes if you haven't tried already. With ignition off bridge terminals T and E1 in the diagnotic connector (LHS rear of engine bay) using a paper clip or similar. Turn on the ignition and count any flashes of the engine symbol on the dash. If the ECU detects a fault it will flash a fault code (2 lots of flashes for the 2 digit code). There are places on the internet that list the fault code descriptions (or post it back on here for someone to lookup).

Right, the procedure for checking the ISC that I have is for the 3s-fe and 5s-fe engines, it might well be the same for the 3s-ge but I've never tried it myself.

Ah, just read it and it won't help for your situation anyway (it only checks that the idle speed rises, so it's no use if it never falls). What you can do though is measure the resistance of the ISC. You will need a multimeter. Unplug the connector to the ISC. The middle pin should be +B and the outer ones ISC1 and ISC2. I don't know if they are labelled on the connector. Set the meter to measure resistance and measure from +B to ISC1. Then measure from +B to ISC2. 1989 and earlier should measure between 16 and 17 ohms, 1990 onwards should be 19.3 to 22.3 ohms. If it reads 0 or infinity then it is at fault. If it reads OK then it is likely to be the temp sensor at fault.

Just a thought, before you do all that try wiggling the connectors to the ISC and temperature sensors while the engine is running. If this make the idle speed change then it is simply a faulty/corroded connection. Try removing and replacing the connectors (with the ignition turned off otherwise you will cause a fault code).

[Wibble]

mine is doing the same thing, however, if I remove the ECU temp plug the engine idles properly & runs great.

I do need to replace the thermostat as it is stuck open & the engine temp never gets higher than a quarter.

do u think I have another fault?

[mikeb]

mine is doing the same thing, however, if I remove the ECU temp plug the engine idles properly & runs great.

I do need to replace the thermostat as it is stuck open & the engine temp never gets higher than a quarter.

do u think I have another fault?

That does sound like your thermostat. There are always differences between temp guages and sensors, but I would expect it to read higher than a quarter (mine gets to half way when fully warmed up). How warm does the heater blow when on set to full heat?

I looked for a new thermostat for mine a while ago. I couldn't find any motor factor who listed one for a gen 5 celica . I daren't ask toyota for a price as all their spares seem ridiculously expensive. Fensport list TRD ones for £47 + VAT :!Removed!: .

[GT4 BOOSTER]

if your thermostat is jammed open , the revs will always be high because the water just isnt getting hot enough to close the gate inside the throttle body , which controls cold start - auto choke, the minute you pull away the wind will knock the temp back down to quater thus kicking the cold start back into action. get it sorted for the winter comming.

a thermostat for a gen 6 at toyota is only £ 17 not expensive at all.

[wiltems]

This does sound familiar to wats going on with mine, except I now think my thermostats not opening enough. I replaced this a couple of weeks back with a none genuine one and no change.

Is there such a difference between the original Toyota one and the cheap one if so I think this could solve all the problems.

[GT4 BOOSTER]

the guy in my local motor shop wouldn't even sell me a thermostat , saying that toyota water works are oh so sensitive and that i should put OME in , never copied parts to do with the water works.if the revs dont die down with the car ticking over and temperature guage reads half way i wont think changing it will make any difference to be honest.

best bet is to take off the throttle body and examine the gate i speak of that controls the cold start signal , clean it up oil it or wd40 it , polish the throttle body whilst its off , get rid of any excess oils and reassemble. toyota thermostats are around £ 17 , not really worth skimping on one.

[Wibble]

on full heat its not that warm & takes a while to warm up too..

I'm changing the thermostat this weekend so fingers crossed.

I'll take the throttle body off too & give it a going over with some brake cleaner, that should sort it..

[Hou]

idle control valve needs cleaning if they have them on the celicas