1ggte misfire when coming off gas

[86TT]

Hi all , my 1st post on the board ...I have a 1986 narrow bodied 1ggte supra , when coming of the gas the car seems to misfire/stumble breifly (more noticeable at speed ).
Its a stock motor except for the addition of an air filter and blitz bov , and the cat has been removed , so its almost stock lol ...Any ideas what could cause this ?

[BeRad]

the bov could be causing it, how old is the bov, have you checked its not leaking etc?

[86TT]

I,m not sure how old the bov is as it came with the car ( which i,ve had for a month).
All the connections are good tho .....is there any way to test the bov itself ?
Thanks for the reply
Mick

[BeRad]

take it off and see if the piston is jamming or if the piston is really soft to push in, while its off remove the sir clip and pull it apart and soak it in some cleaner of some kind for a while get rid of all the junk in there

[86TT]

Cheers dude i,ll give it a try

[oldcorollas]

misfire can either be too rich or too lean.... can you tap into the O2 sensor wire and see if it spikes high or low during the stumble??

[86TT]

misfire can either be too rich or too lean.... can you tap into the O2 sensor wire and see if it spikes high or low during the stumble??

Unfortunately i dont have the facilities for that , i,ll check out the bov this weekend and see where we go from there , The guy who owned it before me put platinum plugs in, although i,m not sure what make he used ( have heard lots of poor reports about bosch platinums and supras ), Thanks for the advice tho

[oldcorollas]

all ya need is a multimeter and tap into the O2 signal wire it should vary between 0 and 1V...

[86TT]

all ya need is a multimeter and tap into the O2 signal wire it should vary between 0 and 1V...

Cheers mate , looks like its time to buy a multimeter this weekend ...i didnt realise you could test them this way , Thanks for the good info
I take it you run the wires of the multimeter into the car or is there a place on the interior side of the loom to tap off from ?

[oldcorollas]

i have no idea about your car, but i would assume that there is a output for it in the diagnostic plug??

voltage comes from this pin (the O2 pin... or wire), and ground is ground, so you can use any.. but better to use ECU ground or nearby...

it's no good for testing mixtures in general, but is rather good for telling if you are way rich or lean on overrun (ie.. either side of stoich)

[wagonist]

Just to through in a theory which may just confuse things.
If the original BOV had a plumbed in return, & the Blitz one isn't, wouldn't the ECU be expecting more fuel (or is that air) on over-run?
I know Subaru's have this problem when a vent to air BOV is fitted.

[CrUZida]

Has it always done it, or has it just started?
Can you pin it down to a time when you changed sometihng?
Like the BOV as mentioned?

[Hydra]

The 1g didn't have a plumb back from factory, plus it's AFM. So the same rules apply if the blitz BOV is vent. Assuming it is venting, try work out a way to make it plumb back or get a plumb back BOV.

Or just get rid of the BOV and run it like it came from the factory

[Rattlehead]

This happened a lot to me (I got 1JZ) - until I changed to a colder range spark plug.

[Lambolica]

Yeah like Hydra said. 1G's do not have factory BOV's

Try disconnecting the BOV and see if that makes a difference. Also BOV's and AFM don't really mix well on 1g's ( and by that I mean BOV that vent air to the atmosphere)

As has been mentioned try running a pipe from the vent of the BOV to the piping between the AFM and the intake of the Turbo. or simply dissconnect the vacuum hose from the BOV and see if it makes a difference.

Think of it this way. you AFM has measured x amount of air. when you come off boost some of that air is lost, but the factory computer doesn't know this and keeps ramming the fuel in. until the system realises there is too much fuel and adjusts.