Misfire!

Typical! just when i thought everything was going well:(

seem to have developed a miss, mostly apparent on idle and low throttle openings, not noticeable under load, but that doesn't say its not happening, checked coil pack plugs, lambda, and connections, i guess i have a long session with the meter etc, although i think i might just throw anew set of plugs in, just in case;) hope its not coil packs as I'm due to go away for a few days from the 2nd.

Typical! just when i thought everything was going well:(

seem to have developed a miss, mostly apparent on idle and low throttle openings, not noticeable under load, but that doesn't say its not happening, checked coil pack plugs, lambda, and connections, i guess i have a long session with the meter etc, although i think i might just throw anew set of plugs in, just in case;) hope its not coil packs as I'm due to go away for a few days from the 2nd.

Take the plugs off 1 at a time and replace them while the engine is running. Whichever one doesn't make a difference is the one ur having bother with. To rule out the coilpack switch it out with one of the known working ones.

Already checked that, its only intermittent, apart from switching coil packs, as i don't have any spares.

Was there a question or was it just a statement?

Already checked that, its only intermittent, apart from switching coil packs, as i don't have any spares.

I didn't mean use a spare, i meant if no.5 is missfiring and no.4 isn't, swop no 4 & 5 over. That way if 4 starts missfiring u know its the coil pack. Otherwise it could be the injectors or the connectors.

I had same on my import supra, missfire when accelerating "hard" from low rpm. Changed to iridium plugs, now working fine... and car also keeps idle better! Old denso plugs got around 1.1-1.3mm gap and were "quite" black.

I broke one black connector "plug", now terrible interference to stereos! :blink:

I didn't mean use a spare, i meant if no.5 is missfiring and no.4 isn't, swop no 4 & 5 over. That way if 4 starts missfiring u know its the coil pack. Otherwise it could be the injectors or the connectors.

I understand what your saying but as its only intermittent, once you have pulled a connector you have then created a misfire so its impossible to tell, so pointless changing the packs over, injector connectors have been checked, its definitely an ignition issue as you can see the AFRs go richer as it misses.

Hi

I had the same thing which then developed into a misfire under full boost and one day it just went "bang" - thought I had blown something or at least blown off an intercooler hose but I couldnt fine anything wrong. The problem got worse and worse until it wouldnt rev over 2k and then wouldnt start. I checked the coil pack connectors and only one looked dried out/crumbling. I changed that - no difference. The rest looked fine but when I changed them all - hey presto- it was sorted. So even if the connectors look OK it is worth a go changing them for the sake of £35 (Whifbitz) unless you know they have been done recently.

cheers

Paul

Already changed most of my connectors, and the others are fine, continuity checked.

I've been through this too with a misfire on one cylinder at idle and just above idle, pointless disconnecting a coil pack with the engine running you just end up with a constant misfire.

So far I've remade all the connector, replaced a coil pack one by one with a spare and noticed no difference. Next i'll change out the plugs, running fairly new IK22's at the moment.

Interestingly enough my missfire disappeared when the aircon kicked in raising the revs to 1k.

Next on plan is the Idle control valve.

I understand what your saying but as its only intermittent, once you have pulled a connector you have then created a misfire so its impossible to tell, so pointless changing the packs over, injector connectors have been checked, its definitely an ignition issue as you can see the AFRs go richer as it misses.

If the spark is defective on one cylinder the mixture reading on a wideband will almost certainly show lean, due to the unconsumed excess oxygen. I'd look at a sticky injector myself, or varying fuel pressure.

Sorry Chris i meant lean, even say left when i mean right sometimes:blush:

Although come to think of it I'm sure the AFRs went rich, as i deliberately switched the wide-band back to the STD lambda to eliminate that, and it was the same for both?

Anyway later i will sit with the EMU and Innovate software going and see if i can spot something, and i bung in a new set of plugs tomorrow just in case.

I would also hope that the injectors are fine as you flow tested and cleaned them about 8 to 10 months ago, also got an Aeromotive FPR to go in so I'll check pressures.

I have lots of issues with Aeromotive regulators, if it turns out to be a pressure issue you could look at the ones on the EFI Technology web site, they are bullet proof.

http://www.efitechnology.com/documents/2008%20PDFs/2008%20EFI%20Price%20Guide%20Rev%201.0.pdf

Well i bunged in a new set of plugs yesterday, and it appeared to cure it, spoke to soon:( thought i would install my adjustable FPR this evening, checked fuel pressure etc, started up all fine, but as the engine got warmed up, i started to get the miss back, in fact at times it was even worse, changed fuel pressure to see if it was related, but no! so then followed TPS, lambda again, it seemed to slightly improve when the engine was loaded up by switching on lights and air con, but not by much, but here is the strangest thing of all, i switched off the engine and then re started and the miss was gone:blink:

I'm now starting to wonder if i may have a problem with my EMU:(

hope not as I'm skint, will go through it all with the software running and the logging going and see if i can pinpoint a problem,

anyone else had this odd behaviour, and what was it?

What about crank sensor and/or its connector?

Do you have access to an oscilloscope?

Will also check that, but i don't have a scope, but surely if it was the sensor, wouldn't it show up more at higher RPM?

hopefully i might get an inkling when the EMU software is hooked up as that uses the crank sensor for the RPM source.

Spent another couple of hours on it but still no resolve, can't find anything as yet in the logs, and unfortunately i haven't checked the CAS yet as i wanted to start it from cold and log it as it started to miss as it only does it when warmed up, which keeps pushing me to think it may be coil pack related, sometimes i hate cars.

Hmmmm, is it a very very slight miss once every second or so?

I have a friend with an auto vvti who had something like this and it seemed to go away ig the revs were over 1500 or the aircon was on. No changes with sparkplugs but don't think he tried coilpacks.

No this isn't the slight one that most Supras seem to have, i think due to ECU over compensating for lambda switch over, it a bit more pronounced definite irregular pop, having said that after another session of trying to diagnose and making it worse, i then did a compression test just to be sure, and later i started it again and it seemed to be OK again? and no it wasn't that the ECU fuses where out so it was doing its little idle relearn, as i had tried this before, will see how it behaves tomorrow.

just take it out and give it a good spanking Mate

just take it out and give it a good spanking Mate

Will do in the morning , and if its not to bad I'll make it over to the Japbash, you going Matt?

Ya i see that thread earlier if the weather holds out i might pop over for a while

Took it out this morning but had to take things a bit easy due to rain, it seems to have settled down a bit, one thing i did do before compression testing it was to check the CAS plug, so i don't know if that had an influence, just have to run it a bit more and see.

Still doing it, but i now think its due to something i forgot to consider before, a small exhaust leak, can't hear it but its starting to pop a bit on overrun which is a sure sign.

This is really starting to get to me, been living with this, it seems to still be intermittent, in that some days its quite apparent, and others it hardly noticeable, and i have been kidding myself its a down pipe leak, as it will backfire on the over run, but having started it today and just let it idle its now popping/missing quite a bit, yet behaves OK on load.

So i now think it is electrical, but would appreciate input, especially on the CAS effects when breaking down?

Will also try coil packs, but can UK coil packs be used on J spec? I'm presuming that the only difference is in the igniter pack?