Blacktop 4AGE issues

[spectral]

Hi all,

To cut a very long story short...

Dyno'd my Westfield yesterday after it feeling *very* lacklustre on the track.

Pulled a screaming 28.4Hp at the wheels. Obviously something very wrong.

Got the quad throttles balanced checked, and its all OK. We did another couple of dyno pulls and the poor thing just can hardly rev out.

Spark is good and strong.

For some reason unknown, we decided to disconnect the VVT plug from the side of the head. Next dyno pull netted 59.9Hp .... just from disabling VVT.

Plugged it back in, back down to ~29Hp. The car idles beautifully. It only goes flat above the VVT line in this graph : http://www.club4ag.com/faq%20and%20t...VVT_SWITCH.gif It also goes absolutely pig rich up there

Thinking that the camshaft timing might be out I've pulled off the timing covers and its all perfect. All crankshaft timing pulley and camshaft pulleys line up with their respective "dots".

Any other suggestions? I'll check ignition timing this afternoon, but I've haven't moved the dizzy since I checked it last time.

Thanks in advance... I'm pulling my hair out a little here.

Cheers.


EDIT: More info:

* Std Blacktop ECU.
* Only mods are a set of alloy trumpets with Unifilters on them... plus a different exhaust system.
* Engine has always been very flat since installation, so its not a recent problem.
* Its a track car so I can't road test it

[Hydra]

Seen a similar issue with a silvertop... turned out to be the AFM signal wire was broken.

Maybe check the MAP sensor?

[RobertoX]

error codes on the ecu?
what was the afr on the dyno?

[spectral]

Hydra: Did it exhibit the same problem that the power dropped when the VVT was active? Sounds strange to do that with an AFM

RobertoX : Haven't checked the codes yet. My autoelectrican chopped the damn connector off.. so to do the ignition timing I have to jump the E1 and TE1 at the ECU with a paperclip ! I'll wire up an LED to the check engine light I guess and see what it gives me.

Thanks for the suggestions, +rep. Keep em coming

[spectral]

My other thought is a faulty mechanism in the VVT pulley on the intake camshaft itself? Are these common to fail?

Perhaps when it hits VVT operation the cam timing is going *way* too advanced and the overlap is just all wrong?

[tooch]

The actual whole VVT pulley can go bad if I'm not mistaken?
I think they normally start making funny sounds when they are dying, maybe yours has completely died in the arse?

[Hydra]

Hydra: Did it exhibit the same problem that the power dropped when the VVT was active? Sounds strange to do that with an AFM

Yeh man, exactly as you have described.. was really sluggish to drive.

Connected the magic AFM signal wire and BAM! skids!

[terryo]

the VVT pulley can internally fail. look for spray of oil around its outer edge near the gear part. its obvious where the inner/outer join is.
it does sound like a jumped belt. the only way to be certain is to remove the cam cover and check the cam timing from 1st principals.
did you phone me about poor perfoamnce of this car a few months back????

[spectral]

the VVT pulley can internally fail. look for spray of oil around its outer edge near the gear part. its obvious where the inner/outer join is.
it does sound like a jumped belt. the only way to be certain is to remove the cam cover and check the cam timing from 1st principals.
did you phone me about poor perfoamnce of this car a few months back????

Thanks Terry. Nah I didn't call you. Although you bought an old 3SGTE block and head off me when I lived at Shailer Park. Dunno if you remember or not.

You are right it does sound like a jumped belt and I was dead sure when I cracked open the timing covers I would find it at least a tooth out... however its perfect, all dots lining up where it should. I have the day off work tomorrow, so I'll check the ignition timing as well. I didn't have my Official Toyota SST with me (ie paperclip) to jump TE1 and E1... I doubt its ignition timing either though as I set it properly a while back and haven't moved the dizzy.

I'll check for oil leakage more throughly but certainly didn't notice any at a glance when checking the cam timing.

Its driving me around the twist... so all suggestions appreciated.

[spectral]

Also, could a faulty O2 sensor cause these issues? Some of the wires look a little, ummm, toasty when I didn't realise they were touching the exhaust.

I didn't think it could.... just thought the o2 sensor trims mixtures at cruise for economy and is ignored on WOT runs.

[30psi 4agte]

It may be worth checking the toothed crank pulley to make sure it lines up with the dimple on the oil pump as well the harmonic balancer lining u on the timing cover..

This will totally eliminate any possibility that a gear or balancer could have slipped on the crank.


I tend to agree it does sound like a timing issue....... but with out seeing or hearing it, it is hard to diag.

Being a 16v boy i am unfamilliar with the 20v VVT cam gear. Is it possible to try another gear on the camshaft of atleast veiw another ( good ) gear to see if you can reference any differences between the way the line up with the cam ???

[spectral]

I've checked the crankshaft timing pulley with the dimple on the crankshaft. Its also perfect.

Being a blacktop I don't like my chances of VVT pulley (or sprocket at Mr T calls it).. I wonder if a silvertop one is the same??? Heaps of ST heads around going pretty cheap.

If the ignition timing is correct when I check it this morning, I'm going to have to go down the path you suggest I think.

I'll also be checking MAP and TPS voltages this morning.

[Mr Revhead]

st pulley is different from bt
but thats not your problem, its not possible for the pulley to move far enough to cause your issue, same with the vvt solenoid.


checked fuel pressure?

[spectral]

Yeah.. heaps of fuel. Running very rich rich when its starting to go all flat.


I have a new cap and rotor on order. Ignition timing was pretty spot on... flicking from about 9.5 to about 10.5... very slight movement.

Had a track day today and the problem is just getting worse. -=Lance=- suggested a faultly CAS or dizzy. I'm going to investiage that further.

I can't rev past 5700rpm anymore and if I press 100% on the throttle, it just dies and actually goes faster with only 50% throttle.

Sigh...

I have a new dizzy cap and rotor on order with Mr T. The current ones look a little sad and certainly wouldn't be helping at all.

[psychofox]

have you checked your exhaust doesn't have anything blocking it? I had a blocked cat once and it exhibited similar characteristics...anything more than 50% throttle and it died in the ass.

compression check (I know it's unlikely to cause that much power loss...)