Odd 7M-GTE surging/stagger problem

[RyleyMA61]

Ok I have a strange phenomenon occuring in the ol' supra.

If the weather is very cold (maybe 5deg C) and often drizzling rain, and the engine is under heavy load (booting it in 3rd or 4th gear) the car will surge momentarily and cut out... sometimes it is just once and sometimes, if it's very cold and wet it will do it throughout the rev range and make fuck all power. It will do this despite the amount of petrol in the tank.

Now initially i thought it was fuel cut (when boost control was set to 13psi) but having since put it back to 11 (12 on cold nights) it still does it.

It has only ever done it to me in the daytime once, and I had like 2 bars of fuel left (on the digidash), and it was cold still (ballarat, so probably about 14deg. C)

topping up solved the problem in this case. The car is good as gold in warmer weather as well...

Now, I'm thinking it's either of the two things:

Fuel Pump? Are these symptoms of the fuel pump reaching the end of it's tether? (It's the stock 5M one ) Should I just get off my arse and get a walbro? I've got a VL turbo pump sitting there, would that be suitable?

With the 1UZ afm and CAI combo, the car was leaning out with the 550cc and apexi on the dyno at around 4500rpm. Putting the standard 7MGTE AFM back in solved this problem.

Could the extra air density be blowing out the spark in the cylinder? I've gapped the spark plugs to 0.5mm as well. If this were the case, would new coils and leads help?

And finally, if it was blowing out the spark, would this result in the car leaning out??? I fucking hope not.

This is the last thing I want happening when I'm off to Winton on the weekend...

Any opinions are very much appreciated.

[ONCE-NA]

Maybe it is running a bit lean? Cold air = denser air requiring more fuel, does your ecu (whatever it is, have air-temp compensation enabled) though being that its AFM i would have thought it could compensate for that!
Without checking I vaugly remember the VL pumps are good for about 300 hp (depending on fuel pressure of course) So you would be getting pretty much on its limit at my guess.
And 0.5mm is tight! If your coils don't have enough energy to jump that gap with the boost you are running you may have to consider something better (Capacitive discharge or the like)
In saying that maybe it can arc that distance in that density but the spark being small prehaps it cant fully ignite the mixture evenly...

[boxh34d]

I had a simmilar problem on two occasions. The first was there was some oil accululated in the plug wells and this would cause a momentary miss when running cold. Once it warmed up it was fine. If you've pulled the plugs out though, I guess you would have noticed this.
The second was when my coolent temp sensor was rooted, so it was running rich all the time. This was enough to give the symptoms you describe. I could only make it stutter in 3rd gear or higher, and only between about 3500 to 4200 rpm (peak torque range). With the rich mixture, crappy old spark plugs, a sticky wastegate actuator that was causing boost to spike a bit, and cold whether, it was just enough to blow the spark out.
Any of that make sense??

[wilbo666]

0.5mm spark plug gap is really small :S

Cheers
Wilbo

[doobs]

Strange, my Soarer has been suffering similar symptoms...

How come your running such a small gap? stock is .8mm for a 7M-GTE

Since my car was running original platinum plugs, leads, fuel pump and filter, I put it down to either one if those.
I've replaced the plugs, leads, fuel filter, and I'm going to change the fuel pump and pressure regulator soon, along with getting the injectors cleaned.

If this solves my problems ill let you know.

Sorry to hijack the thread but on the topic of 7M's, has anyone solved the problem of oil leaking into the "valley" between the cam covers? I have put hex head bolts on their and tightened them up well, and still she leaks... this time I'm going gasket goo all round it...

Cheers boys

[EldarO]

mine misses and carrys on like no tomorrow until its warmed up.

its the plug gap/coilpacks.

you might need to replace ya plugs too.

Elmo.

[CrUZida]

Sorry to hijack the thread but on the topic of 7M's, has anyone solved the problem of oil leaking into the "valley" between the cam covers? I have put hex head bolts on their and tightened them up well, and still she leaks... this time I'm going gasket goo all round it...

New seals + loctite on bolts = done.

[RyleyMA61]

thanks for the replies guys.

i have thought the whole colder air = leaning out thing, but it was properly dyno tuned in february (it was still cold). ecu is a mere apexi safcII, as im saving for an autronic at the moment. it was a fairly "safe" tune though, so i would hope the difference in air densities wouldn't have that much of an effect!

when the car was having leaning out issues on the dyno the spark plugs were replaced and gapped to 0.5mm... so yeah.

could something like a spark amplifier do the trick if this is the case??

could it be the 5m pump shitting itself??

[doobs]

New seals + loctite on bolts = done.

Cheers dude

[CrUZida]

The 7MGTE coilpacks put out WAY MORE spark you need.
I'd regap the plugs to at least 0.7mm, 0.5mm is just ridiculous.

I'd also get a new pump regardless.
If the pump starts to die, the motor will be dead within minutes, if not seconds.

[EldarO]

as CrUZ said, its your gap.

mine worked fine before (0.8mm gap) on the 1J while cold, and warm, but missed at anything over 1 BAR.

i regapped it to 0.7 and it misses while its still cold, but once its warm, i have had it up to 1.3BAR without a single miss.

Elmo.

[RyleyMA61]

alright thanks. initally the gap was closed to 0.5 to stop the car leaning out on the dyno, so its a fair assumption to say this would be affecting it in the extreme cold weather...

thanks guys. ill get a walbro too.

[CrUZida]

I'm failing to understand how a smaller gap will stop a car from running leaner...

[RyleyMA61]

the car was blowing out the spark once the airfilter had been relocated into the front guard... and the boost was on 13psi.... new plugs and gapping them smaller, combined with using the 7mgte afm fixed it....

[whatthe?]

Youve been running 227rwkw with a 5M pump and you think the AFM was causing it to lean out?

Methinks not...

Oh yeah, and check voltage at the pump plug when you change it, even a walbro wont work that well at 10 volts (that's what mine had in the silver car before I ran new wiring)