Problems wth 7mgte.. how unusual

[Mantisboy]

Hey all!

Having some problems with the 7m in my soarer. I have just finished doin the head gasket and intalling arp head studs and reorquing etc. Also i have intalled new plugs and leads and some other bits and peices, as well as a new auto box. My car has a strange habit. After accelerating if you back off suddenly the engine tries to die, the revs drop right off and it tries to stall. Im not sure whatthe problem could be, i have had all the sensors checked by a mechanic with an oscilliscope and they are working (wether or not they are working properly is another matter). Also, and probably worse, the car has developed a big flat spot off idle. If i touch the throttle more than very gently it bogs down until the revs come up. Any help with this would be appreciated. At the moment im looking at the TPS, i drove it to a mates place on the weekend ad when i got there i noticed the plug had fallen off. It didnt seem to make any difference to how the car was running, so this may be an indication. One more thing, what is the standard boost cut on a 7m? At the moment im hitting it at about 10psi. Is there a cheap and easy way to raise this??

Cheers

[hamgatan]

are u venting to the atmosphere (bov?)

i had this problem on my supra before because the stock bov was vented to the atmosphere and u couldnt get enough pressure back into the 3000 pipe to maintain a good
consistency of airflow.. id say you have some sort of pressure leak there. i would change the stock bov if i was you because theyre unbelieveably weak as piss sometimes and open at quite low boost. go the bosch replacement! will cost you about 70 bucks plus piping

oh and standard boost cut is 11psi.

[Mantisboy]

Ok,
I have an aftermarket GFB BOV already. My pipework was all completely re-done in 2.5" mandrel bent stainless. The BOV dosent plumb back at the moment, it just vents to atmosphere, so u suggest i should plump it back into the 3" pipe?

[MR 1JZ]

that would most likely be the issue you are having on backing off...afm cars dont generally react too well with an atmospheric venting blow off valve...

I had similar issues on my 1GGTE powered soarer...

[CrUZida]

My 7M did this, never really worked it out.

I have a slight feeling the TPS wasn't going into IDL mode, and such the ISCV wasn't engaging quick enough.

Pulled the car off the road before I managed to find the time to fix it though.

[Mantisboy]

Yeah, sounds like a go. Fits in with the problem anyway. Ill give it a whirl. Any ideas on the flat spot?

[Mantisboy]

Ahhh. I have a sneaky feeling that the TPS is a bit ordinary too. You rekon a replacement would be exy? Be nice if i could find one to shove in and see if it makes a difference. Might give the wreckers a call. Cheers fella's!

[hamgatan]

Ok,
I have an aftermarket GFB BOV already. My pipework was all completely re-done in 2.5" mandrel bent stainless. The BOV dosent plumb back at the moment, it just vents to atmosphere, so u suggest i should plump it back into the 3" pipe?

correct.. plumb it back.

it ties in exactly with what CrUZsida says there about the ISCV.. no backpressure causes the ISCV to think theres no airflow.. and thus drops right down and out and stall.

[Mantisboy]

Hmm, my BOV has 2 outlets, one with a fitting to a pipe for the plumback, and one on the other side with a sort of trumpet arrangement. Will jsut fitting the plumback for the side with the coupling on it do any good? or should i try and adapt something for the trumpet outlet too?

[RyleyMA61]

i have a very similar problem with my 7m- when you put the clutch in (changing gears around town etc) if the revs drop enough, it goes right down to about 400rpm for a second, then comes back up to 650rpm.......

Had the ISCV checked over and over, no faults...

TPS you reckon? I've also had one extreme case of the opposite- put the clutch in and the revs go mad and shoot for the redline...

thanks, and sorry for hijack

[hamgatan]

Hmm, my BOV has 2 outlets, one with a fitting to a pipe for the plumback, and one on the other side with a sort of trumpet arrangement. Will jsut fitting the plumback for the side with the coupling on it do any good? or should i try and adapt something for the trumpet outlet too?

stocko keep in mind... feeds out from the 3000 pipe and there are two pipes coming off it as well... one is the plumb back into the pipe before the turbine wheel... the other is the smaller tube that connects into the metal piping that leads to the ISCV. if you have a big trumpet here instead... it aint getting to the ISCV...

[mullett]

I'm going to join the bandwagon and go with BOV too. It might be other things too, like a vacuum leak somewhere in the system. Make sure there's nothing leaking in your intake piping etc, or cracks in your cooler. I think you can check the voltages from a TPS with a multi-metre, anyone here got any info on this?

RM.

[thechuckster]

power steering idle up valve not working/removed?

i only suggest it as wilbo's iJZ sometimes stalls when going to closed throttle - as well as hard turning at low speed/rpm). He is fixing by installing the factory valve on the PS pump.

Doesn't explain the flatspot tho - sorry.

[EldarO]

My 7M does this too, boggy off idle, and when cold relucatant to stay running, and has the odd hissy fit where it drops its idle to some rediculous level..

Doesnt reallly bother me though, although if you find why its doing it, i wouldnt mind a fix

Eldar.O.

[Mantisboy]

Ok, i think i understand what your saying with the BOV, quick quiz though WTF is the ISCV??

As for the tps, i had it checked with an oscilliscope and it appears to be sending signals. However there was something i found confusing. The TPS its connected to the AFM by a wire as well as the ECU etc. The TPS sends a signal to the AFM. Now, in the case of my car it is a straight 4.5v feed that dosent fluctuate with revs. This seems very strange as why would you feed a voltage to it from the TPS and not straight from the battery or loom? Does anyone know what this signal is suppoed to be doing??