My engine is Jealous

[Zuffen]

Well since I decided to use a different brand of engine in my new build my 1UZ has had a little dummy spit.

I run Autronic SM4 and Opcon supercharger at 21spi.

It's now running rich and spits and coughs until it is up around 2,500rpm at which point it gets up and goes.

Usually it goes very well from an idle.

All I can think of is either the water temp sensor or IATsensor have either failed or I have a wiring failure.

Before I start pulling it apart what are other peoples thoughts?

 

[cribbj]

Rod, how do the plugs look?

 

[JustenGT8]

I think you should lend it to me....i'll get it running in my car, tune it and give it back to you with 400rwkw

It does sound like a sensor issue? It could also be the TPS. Try a TPS reset first up and check it's not loose or getting bumped.

Another possibility is the bypass valve, no leaking vac lines or diaphram? I know you have had issues with this before?

 

[XR8tt]

Cold weather ?? I suspect tune or coolant / inlet temp sensor ??
Esp if it sounds like it's rich..
Does it clear when warm??
Yes check plugs ...

 

[Zuffen]

The problem has been around for a couple of weeks but I keep finding excuses to not fix it.

When starting it is very slow to fire and I suspect it is flodding pretty badly.

When it was on the dyno a wire failed in the loom that took out the coolant temp but I simply bypassed the faulty earth and I've checked that one and its fine.

I swapped plugs yesterday and they're black as.

Definitely running rich. You can smell it when it idles.

I'll accept any sensor is faulty except the IAT as that's fitted in the middle of the bottom of the manifold and it's 4 hours work to swap or check it!

I'll start by doing some continuity tests on the sensors and double checked they're all plugged in still.

No vac leak as the idle is low so that's one out of the way, and after my machining efforts it better be good.

I was looking at it today thinking I should fix it (or burn it) and the TPS crossed my mind.

I'm looking forward to a factory ECU that drives like a normal car.

 

[Cobber]

Does the SM4 have data logging?

If yes do a data log, this will give you feedback on all the sensors, TPS, MAP etc and AFR.

Or bolt the Opcon on the LS3.

 

[JustenGT8]

Or bolt the Opcon on the LS3.

Now there's some thinking

 

[cribbj]

If they're all sooty and the problem appears to be common to all cylinders, then I'd be looking at the CLT sensor and/or perhaps the fuel pressure is out of whack. A restriction in the return line can do that.

Of course it could always be that pesky IAT sensor too I know most ECU's start dumping fuel if the IAT gets too high.

 

[Zuffen]

Fuel pressure is spot on by the gauge so I can rule it out. Not that it's all that hard to check. Eaier than the IAT.

Thinking about it if the IAT is faulty I may just buy another and install it in the last air duct before it enters the manifold.

I could probably plug a laptop into the SM4 and see what it isn't seeing. Good thought. When my TPS failed onthe dyno the computer sent up an error message telling us it was out of whack.

I'm not allowed to FI the LS3 as the RTA calculatons put my max capacity at 6.35 litres and I'm at 6.15 at the moment. If I went FI I'd have drop to a maximum of 4.40 which would open up an opportunity to run a 1UZ!

Besides which the auto is at full stretch with 550nm of torque and I think it could become very expensive beefing up one of these.

I'll get into it today and see what happens.

 

[rms]

Rod,
Check the pressure/vac line from the plenum to the ecu,
That is normally the problem from the symptoms you describe.

Erol

 

[Zuffen]

Errol,

Checked that one today. As it runs so much boost I would have expected it to run lean when it got up to 15 or more psi wihout any coreresponding increase in fuel load.

I checked the continuity to earth for the IAT and Coolant temp sensors and the reading for the IAT was a bit iffy. After cleaning a connector all is as it should be.

The car still ran like a dog so I checked the TPS and its plugged in, the CAS is in but I may remove it and check if it's covered in grung.

I re-arranged al the spark plug wires in case one or more was shorting out.

The fuel pressure is 43psi at idle which is spot on. If it had a blocked return line I would be expect it to read much higher.

On one drive it was just like it used to be. Went like the clappers)) then when I went to start it next time it wouldn't crank over.

Battery voltage was fine and when I pulled the fuse that protects the crank circuit and reinstalled it it fired right up. This fuse could be feeding the ignition coils (I didn't check today) and may be intermittent. I've had the problem before with this fuse and as the holder is 15 years old I'll just replace it.

The miss is intermittent but comes in under load as you crack the throttle open.

I'm suspecting TPS but this is the 3rd unit in the car in the last 12 months. I use a F.A.S.T. billet throttle body and I'm starting to think it may have some runnout in the shaft that's killing off the TPS units. At $250.00 each I don't want to keep throwing them at the car.

I may try and borrow an LS1 t/b and try it out and see if it reduces the problem. Unfortunately my LS3 one is FBW so I can't use it.

The car's getting like an old girlfriend; still looks the goods and deliver's the goods but the girl down the road is starting to look a little too interesting and needs my attention more!

Even my wife has commented on my lack of enthusiasm for the car at the moment.

I better keep my wife I can't afford to replace her.

 

[samsdad]

Zuffen are we talking a manual box or auto behind?

Let's not go there about wives... Somehow I ended up with a Pinoy one

 

[cribbj]

So if all plugs are sooty, but your fuel pressure and MAP sensor are OK, and you've checked out the IAT and CLT sensors, then something else is telling the ECU to dump fuel in the motor. And it sounds like a connection or contact problem if you say that one time it ran like it used to. So I'd be looking at the following:

WB AFR controller: (sometimes we see big discrepancies between what the WBAFR unit is showing on its local display, vs what it's sending to the ECU. Usually an earthing issue, but it can cause the readings to be wildly different, and the engine to do some very strange things.)

TPS: You should be able to measure its output without the car running and see if it's smooth, or if it jumps around, indicating problems with the wiper in the potentiometer.

Maybe your fuel map got corrupted? (but it should stay corrupted, and not run fine sometimes, and most of the time not run fine.)

Stray injector earths causing them to stay open? (highly unlikely they'd be on "all" injector circuits, but.....)

 

[Zuffen]

TPS is what I think the most likely. But why is it eating them??

A bad earth is on the cards as the wire that failed when on the dyno was the earth return on the CLT and there was no good reason for it to fail.

All earths on the motor return to a bolt on the back of one of the heads.

The CLT now earths to the inlet manifold and is working fine.

I'll have another play and see what I can find.

 

[XR8tt]

Make sure all ECU wires are away from ignition to prevent interference..
Is the TPS operating in 5v range ??

 

[Zuffen]

Nothing happened today.

My 22nd Wedding aniversary.

Thought it a good idea to leave "1UZ" out of all conversation.

 

[cribbj]

Rod, we had our 22nd just last year.

The wives are definitely jealous of the attention (and $$$) we give these mechanical objects, but I keep trying to convince mine that the cars and engines demand less time and money than a 25 year old mistress would.

I've told her on several occasions that anytime she's ready for me to give up the car hobby and take up chasing young women and hanging out in bars, she can let me know. That usually shuts her up and buys me six months or so of peace & quiet......

She has no lost love for that "red-headed bi*ch" as she affectionately refers to the Fcar.

 

[XR8tt]

Is there possibly an exhaust leak ?? Before 02 sensor ???

 

[Zuffen]

I motivated myself enough to remove the throttle body and do some checking.

Looks like the TPS has died. No continuity between any of the 3 pins.

That's the 3rd TPS!

I checked the butterfly shaft in the throttle body with a dial gauge and it has around .001" run out in the 90dgrees of shaft rotation. I don't see that's the problem.

Closer inspection shows the TPS may be hitting the firewall. The throttle body sits very close to the firewall and it could be distorting the TPS body when the engine moves under torque. There aren't nay signs of the TPS being damaged but there is a slightly polised spot on the firewall.

The TPS appears to have excessive movement in the rotating assembly.

What are your thoughts?

 

[JustenGT8]

Picked it like a nose Could be the contact is distorting the TPS housing enough to fatigue the wires or contacts or cause some type of internal short?