7MGTE miss. >update, all fixed

[boxh34d]

Ok, i need help tracking a slight misfire in my 7MGTE.

There is a noticable misfire when on boost, with full ( or over say 80% at a guess ) throttle around the 2500 to 3500 rpm range. The car is dead stock save for an exhaust, and has no troubles starting, idling, running or boosting when the throttle is fed, rather than reletively quickly opened.
The misfire feels like a cylinder is not sparking properly, and can be felt, enough to chug slightly. It does this a little bit, but once over that rev range, I cant feel it anymore, and it revs cleanly.
Engine does not use oil or coolant, has no bubbles in radiator, and has no milkiness in oil or water, and radiator cap has no residue.
Also, the car does not fluctuate in temperature at all.
Any ideas anyone???

I had a search, but could not really find anything that sounds simmilar to this.

[SilverGhost]

It sounds like you have ruled out most mechanical issues with the engine, so I would be looking to electrical components. Check the condition of your plugs, leads, cap & rotor button (if using a distributor) If not, check the condition of your coil packs.

If your plugs arent fouled or bridged with deposits, then it could be an injector not spraying as well as it should. But generally if you have a problem with a particular cylinder it will show up on that plug.

Failing that, if you have an aftermarket ECU you might be able to check its log to see if it recorded anything out of the ordinary.

[ma61turbo]

7mgte doesn't use a dizzy, but check all the electrical stuff. Coil pack, leads, ignitor. You might want to check the CAS position to make sure it's correct as well. Good fuel? Replaced fuel filter? Maybe put some injector cleaner in and see if that makes a difference, or take the injectors out and get them cleaned properly. Maybe check FPR as well?

[boxh34d]

Yeah, it has brand new platinum plugs, but i will be invesigating the ignition side of things shortly.
It just seems strange that it is only at full boost, at that rpm band.

[ma61turbo]

Might want to check the plugs and see if anythings fouled them anyway, could give you an idea of what is going on. Do you know what the AFRs are doing when it misses? If it's going lean you've probably got a fueling issue.

[JustCallMeOrlando]

There is a noticable misfire when on boost, with full ( or over say 80% at a guess ) throttle around the 2500 to 3500 rpm range.

Wouldn't that most likely correspond to peak torque?

[ma61turbo]

I'd say you could be right there

[boxh34d]

Wouldn't that most likely correspond to peak torque?

Yeah, i thought about this, which is why i thought it was likely to be either fueling or spark related, rather than mechanical problems. . .
Hopefully i might knock off on time tomorrow so i can have a look at the plugs, and see if one is particularly fouled.

[QUOTE=Good fuel? Replaced fuel filter?[/QUOTE]
I always use optimax from the one servo, as they have a very good turn over, and the fuel filter is brand new.

[QUOTE=Do you know what the AFRs are doing when it misses? If it's going lean you've probably got a fueling issue.[/QUOTE]
No, i don't know what the AFR's are doing, as i dont know have a meter, or know anyone with one for that matter.

Thanks for the replies so far everyone.

[Blackmk3]

id pop ur old plugs in and try that.....i bought new platinums for my 7mgte and it ran bad like you described, talked to a mecanic friend he said sometimes the coil packs dont like the platinums....neways i took the $20 each platinums back and bought simple $7 coppers and problem solved]

mind you i tried my 17ur old denso's first and thats how i new it was the plugs

Nick

[CrUZida]

What are the plugs gapped at?

[JustCallMeOrlando]

talked to a mecanic friend he said sometimes the coil packs dont like the platinums....

What is with all the know-it-all but don't know anything mechanics? They come from the factory with platinums, why do they make stuff up?

[EldarO]

cowboys Nathan, cowboys!

i replaced bog stock 1991 plugs earlier this year from my import engine , doesnt say much for jap mechanics

have a look inside the plug wells, common leak in the 7M is the cam covers, and they can leak a butt load of oil down into the plug wells and cause all sorts of mayhem...

other than that, i dont have a clue, because i had something similar happen, and thats what it turned out to be!

Eldar.O.

[oldcorollas]

platinums are meant to last 100,000kms or so, so there is no need to change them within the japanese lifetime of the motor

also just means your engine could have been treated badly

yah, check plug gap, chuck in cheapy plugs gapped smaller.. see what happens, but sounds like spark issue

[EldarO]

the funny thing is Stu, my engine was brought in with 111k on it.

i love shutting you down, since you constantly seek out ways to prove me wrong, fix that massive chip on your shoulder and you'll be right.

the rest of your info is top notch though.

Eldar.O.

[hamgatan]

platinums or iridiums?

ngk iridiums are shit and keep failing for a lot of S13 drivers ive spoken to.. not sure how theyd go in a 7M. i got told to go the platinums myself but never got a chance to put them in. ask RA65_Sleeka if hes had any issues with them coz i sold them to him brand new..

keep in mind that the plugs have a heat rating...and if ur 7M is getting too hot, then the plugs you choose might not like it as well. maybe try plugs that are 1 step colder or something as well..