Intermittent problems with acceleration..

[Andrew162]

I don't know how else to term this problem, but last time this kind of thing happened, the MAP sensor was stuffing up. I've checked it this time and there's no problem with it.

I give the accelerator a stab up to about 4000RPM and sometimes I'll get a popping or a backfire from the exhaust, which initially I thought might be a fuel, fuel supply or even inlet air temp problem. After this happens, the idle becomes erratic, but only temporarily. Then I start thinking either dizzy or rotor button, leads, spark plugs, etc. or even idle vacuum.

There's a range of different symptoms from idle-hunting, to mis-firing, and there was even a case today where I tried to get up a hill, and the harder I pushed the accelerator, the less response I got... and the ECU is trying to compensate for all of the symptoms. Eventually it re-stabilises and becomes driveable again. It first started happening on a hot day which made me thing the air intake temp was too high. Today it did it again and the air intake temp was only 29°C.

Has anyone else had this happen to their 3S-GTE as well? Any fixes?

[-==L=a=N=c=E==-]

Have you had a read of the Toyota BGB at there trouble shooting guide. It is very useful when determining a problem.

Have a look over this. It covers the basic problems that you may encounter. It is for a 2nd gen, but some of it still applies for you in this situation.

http://ugbox.net/~lance/GT4/Technica...leshooting.pdf

[Andrew162]

Thanks heaps for that Lance... I'm almost betting that it's a vacuum problem, somewhere..... today it was idling at 2 in-Hg (vacuum) instead of around 18-20, and it was idle-hunting in a big way.

I'll suss-out the vacuum system when I get home.

[RWDboy]

Sounds big time like some kind of leak in the intake system! It's interesting that it can be so bad on a MAP sensored car... where is the MAP sensor on your 3S-GTE?

[oldcorollas]

Sounds big time like some kind of leak in the intake system! It's interesting that it can be so bad on a MAP sensored car... where is the MAP sensor on your 3S-GTE?

not so strange really, the manifold pressure must be very close to what the ECU thinks it is, or else it will be in a completely different part of the table.. is a serious downside to MAP sensors

MAP is typically on the manifold? the later 3SGTE have the actual sensor ont he manifold.. no tubes..

yah, no vacuum = no good at least you know that the prob will be between the TB and the engine..(or associated stupid vac lines )

good luck!!!

[Andrew162]

Sounds big time like some kind of leak in the intake system! It's interesting that it can be so bad on a MAP sensored car... where is the MAP sensor on your 3S-GTE?

Well, actually my MAP sensor is mounted on the firewall, and the boost gauge line T-pieces into it from the TB.

not so strange really, the manifold pressure must be very close to what the ECU thinks it is, or else it will be in a completely different part of the table.. is a serious downside to MAP sensors

MAP is typically on the manifold? the later 3SGTE have the actual sensor ont he manifold.. no tubes..

yah, no vacuum = no good at least you know that the prob will be between the TB and the engine..(or associated stupid vac lines )

good luck!!!

Well mine is a bit of a strange bastard in that case, because I never knew it was supposed to be mounted on teh manifold.

Not to worry, I got 1.5m of bling silicone vacuum tube, and I sourced a connector (was a T-piece, now a straight-thru with a bit of modification). Anyways I spoke to one of the tech guys at GFB, and they said that the way the vacuum lines were joined up was all wrong, because I was getting bugger-all vacuum from teh BOV.

So far I've managed to manufacture a bit of a fix, which I'm hoping will be an effective remedy for the BOV's "fluttering" (read: non-functional state!), based on the advise of the GFB tech. I just have to plumb-up the pipes to the specs given, and apparently all should be sweet vacuum-wise.

We'll see....

[RWDboy]

not so strange really, the manifold pressure must be very close to what the ECU thinks it is, or else it will be in a completely different part of the table.. is a serious downside to MAP sensors

MAP is typically on the manifold? the later 3SGTE have the actual sensor ont he manifold.. no tubes..

I think you'll find it's equally bad on AFM cars If the MAP sensor is after the leak then i imagine it wouldn't be totally disastrous - but at least in this case, the MAP sensor must be before the leak.

[Andrew162]

Ok guys, success!! ... so far.

Not 100% sure what the deal was with the vacuum earlier, but I fashioned some vacuum piping up to the stock connectors with a little re-routing having to be done. Basically I took out a T-piece that wasn't needed and put a straight-thru in instead, and managed to get the BOV some decent vacuum by tapping it into the line just before the TB.

Regarding the MAP sensor, the piping to that was all ok... in fact there wasn't a split hose or anything to be found, out of all the rubber bits that I pulled off it. Makes me wonder what was wrong with it before I re-routed the vacuum lines, as it seems to have vanished all by itself.

Now the BOV actually works! I gave my bitch a flogging around Rydalmere this afternoon, including a bit of a thrash down James Ruse Dr. Up around 5500 RPM, and no sign of any idling hiccups or farts at all. I loved the sound of the BOV but I had to turn it around to plumb-back instead... a bit much attention for me. I think I'll adjust it somewhere between atmo and p-b. A lot more pick-up off gearshifts now, and the response is fantastic!

So that seems to have fixed up most of the problems for now, although I think the re-routing of the vacuum lines has made the idle vac around 18in-Hg instead of flat on 20, which doesn't seem like much... the idle seems a bit "poppy" from time to time, nothing major or obvious.. but something that I notice.

[Toobs]

Sometimes a flogged out ignitor or buggered coil can cause this sort of hesitation under load... but then normally your ECU would spit at you.
But then again you have a PowerFC which may not spit codes the same way the factory ECU would.

[Andrew162]

Yeah well it hasn't done it again so far, so I'm happy with that. I also realised that one of the spark plug leads has a stuffed connector to the dizzy, and looks like it's about to fall off. What do you recommend when changing over these leads? Bosch, Top Gun, Eagle, etc.? And what size do they come in?

BTW I had the CDI / coil / etc. all tested out when I first had issues with idle when the engine was first installed. All came back good.

[hi-ace]

On mine I run 10mm Top Gun leads and have never had any problems from them.

[Andrew162]

I'm making an enquiry into some Top Gun leads which are 8mm dia. I still can't believe the stock 3S-series engines only have 5mm.

[JustCallMeOrlando]

Use your Toymods membership and grab yourself a discount on some Magnecor ones

[Andrew162]

I called Magnecor earlier, and apparently they have no stock of the boots required. They do an ElectroSports 70 (7mm lead), and they also said they weren't sure if the had the proper retainers/clips for the leads to the dizzy cap.

Sounds like they don't have too much call for the 3S-GTE's.

[JustCallMeOrlando]

Damn willis, you'd think they'd have even less call for a 1G, but they had mine