96 j spec stalling randomly

[alex h]

Hi all,

Posting this for a mate,

His Supra decided that it would stall, or at least try to stall, the engine every time he lifted off.

Symptoms are:
Lifting off the throttle causes the revs to drop below the idle point - engine has a fit and pinks a bit, ECU tries it's best to recover the situation.
The higher the revs when I lift off the more chance it will die despite the ECU's best endeavours.
If I crack the throttle open a miniscule amount, so that the throttle cam doesn't even seem to move, it has a struggle.

Tried:
Checking the hoses. Lots of them, several times.
Bypassing the stock BOV
Swapping the BOV out for another one
Cleaning the Idle Control Valve
Oiling the springy thing under the throttle position sensor that cushions the butterfly when it tries to slam shut
Unplugged the VSV on the pressure tank as it makes lots of clicky noises when you open the throttle
Reset the ECU

Other notes:
Turning on my lights still raises the idle correctly, which is handy as this means the car is less likely to stall.
He just had a service and got some NGK BKR7E plugs installed. I can't make the connection between liftoff to idle problems and spark plugs/coils yet.
The Idle Control Valve has been cleaned and a spare tested in its place.
The battery was discharged fully by accident and has since been fully recharged.
The O2 sensor and a spare tested along side both read 0.03v whilst the engine was cold.
Accelerating up the rev range on boost is faultless...just when you lift off it has problems.

Next step?
Could it be the plugs? Can't see how!
Could it be the intake air temp sensor?
Could it be a bad earth?
Could it be a throttle body issue? throttle bump stop stuck down? ICV not working properly?
Could it be a fuel issue at idle? Closed loop screwed by the battery drain?


Any ideas?

[Martin F]

Quote[/b] (alex h @ Feb. 10 2004,11:14)]He just had a service and got some NGK BKR7E plugs installed. I can't make the connection between liftoff to idle problems and spark plugs/coils yet.
You know this is weird, beacuse a guy called Ian C is having exactly the same problems on another forum. http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/shocked.gif

Anyway, the whole thing sounds like an air leak to me and a thought just occured to me. Has he checked the two little hoses that connect between the cam covers under the spark plug cover ? I wonder if one of them hasn't been put back properly or is damaged.

May also want to check spark plugs for any helpful indicators whilst under there and double check gaps.

[alex h]

Quote[/b] (Martin F @ Feb. 10 2004,13:35)]You know this is weird, beacuse a guy called Ian C is having exactly the same problems on another forum. ?http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/shocked.gif
Bizarrely he's the same Ian C that sits next to me at work too....I'll point him at the post...again http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif

[alex h]

Done some searches on Supraforums and Crank Ventilation is mentioned, Ian is going to check his PCV and all hoses related to it.

Cheers

[Chris Wilson]

The coil pack connectors haven't been butchered and the miniature spade connectors put on one or more coils with incorrect polarity, have they?

[alex h]

I would ask that if the problem hadn't been found last night! http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif
It looks like it was a burst pipe all along, but one of the most inaccessible.
http://www.ian.chisholm.clara.net/pix/burstpipe1.jpg

[Martin F]

Isn't that sods law !!

After taking the engine out of my breaker, i'm amazed people manage to get the stock twins off when in the car let alone some of them pipes near the bulkhead.

Good luck

[Chris Wilson]

Was it one of the blue silicone ones? I just wish people wouldn't fit that crap, they are far more likely to split than a decent "rubber" hose. They have no fabric layers in them, so a tiny nick develops into a full split for fun. Total crap, IMO. Gates rubber hose is king!

[Ian C]

Hi all - I didn't want my first post on here to be a cry for help for various reasons, but Alex charged in anyway. ?Thanks for your assistance all http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif

Chris - nope, stock rubber hose. You seriously think I'm gonna swap those ones for coloured hose?! ?You can't even see them without dismantling bits of the engine... ?I've plenty of spare stock rubber hoses that will be used to replace it as well.

Martin - I've taken the stock twins off twice without even taking out the exhaust system - madness ?http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/shocked.gif it's a nightmare job and one of the more difficult things I remember is... getting those pipes off at the back ?http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/cry.gif ? And that's with half the engine removed first ?http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/cry.gif

-Ian

[Nathan]

Blimey, Cool Hand Luke has turned up. Welcome fella.

I can echo CW's sentiments re silicone pipe as some will have seen in the 'Hose group Buy' thread. Theres nothing inherently wrong with using silicone vac pipes but the method of attachment can be a problem as can the routing of them to make sure nothing ever rubs against 'em. At least silicone doesn't go hard and brittle like rubber...

[Ian C]

Hiya http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif

I got some fairly rubbish blue hose from a local place in Norwich as it was cheap and, lord help me, looked nice http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif I figured if it gave me any hassle at all it would get binned but it's lasting suprisingly well! In fact, I've replaced two knackered bits of stock hose with it (although I won't be chancing it on this particular job!http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/wink.gif

Brittle rubber pipes, oh yes - I have a scar from Alex's old Soop when a pipe snapped straight in half and my hand went rocketing back over another pipe's clamp. Those buggers are sharp.

-Ian

[alex h]

My soop bit you for letting Paul's brother drop a beer bottle or can on it! http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/mad.gif

http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif

[Nathan]

BTW, did you ever get your 2nd PPK? I didn't, but still fancy the John Woo stylee..

[Ian C]

I went for a second PT Extreme paintball handgun instead http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/biggrin.gif Much more fun as you can legitimately shoot at other people John Woo stylee http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/biglaugh.gif

[Nathan]

Top!! Fair enough.

It's because of people like you that I stay away from hardcore paintball venues. I bet you got all the shades of Rambo-esque face paint as well http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/laugh.gif

Ooops..bit OT

[Ian C]

Nah, no face paint, it's hilarious seeing idiots put that on the first time they have ever been, and then you point out they will be wearing a mask that covers their face.... I go for practical stuff like tough trousers and a t-shirt so i don't overheat.

Back on-topic, fixing the hose made no difference to the porblem. Arse. Changed the FPR, that's not it. What are your thoughts on a coil being dicky?

-Ian

[Nathan]

Do you know what? I've never had to replace a faulty Mk4 coil.

Probably doesn't help though.

[Martin F]

Could be one of the coil connectors. Have been known to tire with age.

Wonder what the chances are of a dud couple of plugs.

[Ian C]

Not a lot, I swapped back my old plugs to test that theory.

The coil packs look spot on, no dodgy connections, craks, nothing. But I'm going to disconnect them in turn to see if anything *doesn't* change.

-Ian

[Chris Wilson]

On some engines a dead or disconnected cam position sensor will all but kill idle, but allow pretty much normal high speed running. Dunno about the 2JZ-GTE, worth a look?

[Ian C]

In a blatant copy-and-paste, here is some more info:
Right. Progress. I've swapped the idle speed control valve, and that didn't change a thing. I swapped the MAP sensor, that didn't change anything.

I unplugged the PAS hose from the intake manifold and the idle rose to 950rpm and sounded sweeeeeeet :eek: http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif The hose prong was sucking in air like a hoover.

So - it's not getting enough air. Going back to a shit idle, I took the big fat feed hose to the idle speed control valve and that didn't change anything, so there isn't a blockage intake-side of the idle control valve. I find it hard to believe that two different ISCV's have exactly the same problem so I don't think it's that at fault. The rearmost hose on the intake manifold feeds the BOV, so that's not gonna normally draw in air, the top one feeds the brake booster so that's not going normally draw in air either. The PCV hose isn't supposed to supply much in the way of air so I can rule that out.

This leaves the PAS line. Now, there is a hose coming from the intake, *before* the trac and throttle butterflys, which goes to the PAS pump, onto one prong of a dual-pronged attachment. The other prong goes off to the intake manifold, the very hose I removed to make the idle better. Both hoses are undamaged and are not blocked up, but I can't blow through either of them if they are both attached to the prongy thing on the PAS pump.

Questions - why does the PAs pump need two vac reference lines, one pre and one post throttle body? And should there be a path of air through this prongy thing, i.e. is it blocked? Because if it didn't stop air going through it, the idle would be correct...

The other area I need to look into is the internal channel for the air delivered by the ISCV. Could be a serious dismantlement http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/sad.gif

Thoughts please http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif

-Ian

[Martin F]

The hoses on the VSV attached to the PS pump are used to increaes the idle when you put the PS pump under load. The theory being that if you are putting a heavy load on the PS pump at idle the engine could possibly cut out, so you increase the idle slightly by means of a VSV operated by the PS fluid pressure.

Try blowing through the hoses whilst somebody turns the steering wheel, should find its possible.

As you've eliminated the ISC as best as possible by substitution, i can only assume its the control signal that drives the ISC. Going to be a bit of a chicken and egg situation here. How does the ECU determine how much to increase or decrese idle ?

Any chance the TPS could have been disturbed ?

[Martin F]

Just thinking aloud ..............

IIRC don't you have an AFC ? I'm sure they are hooked up the TPS line, if so it may be worth disconnecting it just temporarily and seeing if idle returns to normal ?

Does idle increase when your AC is under load ?

Could be barking up the wrong tree, but it is an odd one.

[Chris Wilson]

Quote[/b] (Martin F @ Feb. 13 2004,22:16)]Just thinking aloud ..............

IIRC don't you have an AFC ? I'm sure they are hooked up the TPS line, if so it may be worth disconnecting it just temporarily and seeing if idle returns to normal ?

Does idle increase when your AC is under load ?

Could be barking up the wrong tree, but it is an odd one.
I agree, I said to ian that the most likely cause is one of the gizmos or its wiring. If any gizmo is in this wire then I would consider it a prime candidate. Like i always suspect the alarm in cases of none starting cars...

[Ian C]

The AFC is wired in but no wires are actually cut and the AFC loom is unpluggable - I've unplugged it and nothing changes http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/sad.gif

Battery was flat again today, grr. Forgot about the bonnet switch again, and it wasn't exactly the best charge I did last time, so I've gotta wait. I've bared a bit of the coolant sensor signal wire and I'm gonna monitor it's voltage while the engine runs.

-Ian

[Ian C]

Coolant sensor read OK. I unplugged the FCD and to my suprise the idle went up and sounded healthy. The engine revved and dropped back to and idle. Still not spot on but interesting.

I didn't immediately blame the FCD and after more experimentation I found that I could change the idle characteristics by....

...prodding the mass of ECU loom wiring.

I'll get me soldering iron http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/biggrin.gif

-Ian

[Martin F]

Well bugger me!! (not)

As it seems to be linked to the FCD are we assuming its a dodgy connection on the MAP signal ? If thats the cure then its a strange sequence of events.