my '90 celica 2.0 GT (jap import, 4ws, active suspension)has developed a serious misfire at 0-3000 rpm. I've checked the compression of each cylinder and I've got 14bar in the two cylinders on the drivers side, 14.5bar in the next one and 14.25 in the cylinder furthest from the driver. The coolent level has not decreased at all and the revs vary wildly at idle. Does anyone out there know what the compression figures should be and what the variation limits are? Does it sound like a head gasket to you? Any advice in curing the misfire would be appricated. If you are viewing this as a guest and have got some help then email at greenslugsix@...

any cream in the oil? The compression seems fairly the same across all 4 cylinders which is usually a reasonably good sign. Have you changed the dizzy/plugs/leads recently? How's your timing? Could be  a dripping injector flooding at low rpm?

The oil was changed not long before the fault occurred, and there are no signs of water gettin in to it (i.e. not creamy). My first thoughts were fuel filter or ignition, however, i am a pessimist and have to fear the worst! I really haven't had time this week to get under the bonnet and change the fuel filter, ht's, rotor arm and dissy cap. Shall do it saturday and hopefully that will be the end of it. Cheers for your help.

Good luck

hey,have u changed ur spark plugs lately? >

Yeah, changed plugs a few weeks back. They're a nice light brown colour at the electrodes.

i changed my plugs a week ago,and the car was not running well at all,the problems sounded like urs,people were sayin i might have damaged the ht leads,i was so scared about the miss-fireing and acceleration was lumpy,anyway i found out that the plugs were platinam(the ones i took out)the ones i bought from halfords at ?10.49 were copper i think...or none platinam,i had a feelin it was that but all these brainless people were tellin me"na na na there all the same,just that platinam last longer". The origanal price for platinams for our car is ?16.00 EACH!! lucky me found a shop that done some for ?30.00 a set of 4, so i had the same plugs in as before and my car thank god is ok now...sorry just wana know ur name and where u are? my name is peter and i hope this helps ya...c ya >

if you check the specs of the dodgy plugs perhaps they were a colder plug and hence not best suited? A set of NGK coppers should be less than a tenner and should work perfectly.

I'm with Alistair on this one. The plugs that were originlly in my Celica were platinum. It had a very slight, un-concerning miss fire in 4th and 5th gear around 2500 rpm but only when I slammed the throttle and when the motor was at max operating temp, so I changed for a set of ?20 Bosch quad elecrodes from Halfords. The car ran worse than it is now! The plugs were to cold a rating. Which I think generally means they start to break down at high temps, and if one thing is for sure it's that the 3sGE engine does have a high operating temp (Go for a 10 mile drive with a mate following you in his motor, then stop and pop the bonnets, put your face near each engine and you'll soon see what i mean!) Anyway, I chucked the Bosch and fitted NGK coppers and the car was back to as it was previous, slight miss when hot. If i could get hold of a set i'd experiment with an even hotter rated set just to see what happens. I've got a day off tomorrow, so I'll change what I think might be the offending items and I'll report back. Oh, me names Alan and I live in Aberdeen.

well, that didn't work! So we now know it's not the head gasket, dissy cap and rotor, leads, plugs or fuel filter. I'll get the timing checked. Is it likely there's a fault in the injectors/sensors? Any other suggestions?

hmmmmmmm bung a dose of injector cleaner through it and see if it makes any difference.

I put STP injector cleaner in the fuel every 4000 miles (I do 150 miles a day to work and back), but I'll try one that goes in every time i fill up. The STP stuff might be shite. I'm still having to use the car daily, and today I got a warning light come on for about 30 seconds that I don't recognise but it looks like something was overheating. It came on when I was trying to accelerate and the car was misfiring about as badly as it has ever done (still not enough of a misfire to prevent me driving it! But if I had two cars i would not be using the celica!) I've attached a picture of the light, do you know what it is? Attachment: (application/octet-stream) Warninglight.bmp [not stored]

Thats the cat overheat light, check the diagnostics for an error code. Having eliminated all the usual suspects i'm thinking you have either a duff oxygen sensor (should give a code 21) which might result in the car over fuelling or a duff knock sensor. What sort of mpg have you been getting sin ce this started?

I've been getting slightly less mpg since it started missing (although it has never been great!) It seems to be down to about 25 mpg. Am I supposed to have a 'check engine'  light on when i turn the ignition on, which disappears once the engine's started? I don't have one, but read on an american web site that I should. Hope you don't mind me picking your brains but I'm reasonably new to the 3S GE engine. I have a decent understanding of engine mechanics as I used to build engines for Cosworth but the electronics leave me behind.

Mpg should be 25-30 dependant on how you drive, and you should have a check engine light when you turn the ignition on.

Is the check engine light a picture type warning or does actually say 'check engine'? Also, what colour is it? Can you tell me where to locate the oxy sensor (I've ordered one and hope to fit it at the weekend)? And you mentioned the knock sensor, what is the purpose of this sensor and where can I locate it. cheers again for your continuing help.

have a look at http://www.imoc.co.uk/technical/faq/warninglights/warninglights.htm the engine warning light is halfway down the page. The oxygen sensor should be just below where the 4 branch of the exhaust manifold join into 1, the knock sensor is at the back of the engine screwed in near no.3 piston, it "listens" for detonation and the ecu then retards the ignition. As far as i can remember it only operates over 2500 rpm.

I've check the engine diag for a fault code. The check engine light flashed constantly without a break/gap. Does this mean it's not recorded any faults?