One Bank Running Rough

[uza70]

Hey All,
Long time reader first time poster.

I need some help in working out what is wrong with my 1uz. I have a ma70 supra with a 1uz that my father and I made about two years ago.

Car has run brilliantly for the last two years but now its not going so well.
I did a timing belt change and a shim replacement.
There was an issue with putting the timing belt back on, i got it one tooth out on the passenger bank. But after realizing that I correctly aligned it. in replacing the shim i took the intake cam out.

After doing those two things it nows runs rough on the passenger bank, you can take a spark plug lead off and nothing changes, but take a lead off the other side and its noticeable.

First thing i assumed was incorrect timing on that bank. but i checked the marking and it all lines up. ignition timing is fine as well.
checking error codes on ecu, it said o2 sensor, i have replaced both with genuine ones, still problem, but ecu says its all fine.
i check resistance readings of all cam and speed sensors
swapped igniter's around
tested wire continuity and shield grounding.
changed plugs.

I am running out of ideas,
Please help me, i can usually fix things on my own but now i am really stuck.

thanks in advance for your responses.

 

[sideshow]

check compression on that cylinder
if u did shims
u either have low comp open valve
bad injector
or lead

so basics are check comp and fuel and spark

 

[uza70]

It was only one shim I did, I am borrowing a compression gauge to test that cylinder.
It is the entire bank that is causing the trouble, not just one cyclinder

 

[sideshow]

mmmm

make sure u havnt got a dead coil
this will have 2 cylinder out per bank

not sure how all 4 cylinders can fail all on one bank
unless 2 wires got cut which power the injecotrs on that bank
what is it missing
spark or injecotr pulse
if u have both then its prob mechanical

 

[uza70]

swapped coils over to see if there was a difference and there is no change. its not 2 on each side, its one bank. Im struggling to think of all the things that can effect only one bank.

Spark is fine, and spark timing is fine.
Injectors are fine, although it smells like its running rich on that bank

 

[sideshow]

did u make sure inlet and exhaust cams are timed correctly
timing belt might be ok
but if u had cams out u mgith have put in slightly out
id check compression

 

[Bushwhacker]

Cam sensor on that bank plugged in? Wires broken?

 

[Zuffen]

As it smells rich it means the engine is getting fuel through the injectors.

On that basis I would rule out a fuel problem.

Spark on one bank and not the other suggests a timing problem.

Have you checked each spark plug lead for spark at the plug. I know you checked for continuity but spark at the end of the wire is the real test. Put a spark plug in the leads and run the engine with the plugs earthed. They should all have spark.

The intake cam sounds like you have it right as your timing marks must line up for you to say it's correct.

I lean toward the timing marks being out when you put the exhaust cam in that head.

It sounds like the fuel is passing straight through that head and not igniting.

Easy fix.

Take off the cam cover and rotate the engine until the timing marks on the two camshafts line up, or don't line up, as may be your case.

 

[uza70]

I have checked the timing twice on the inlet and exhaust gears, if there is another way to check other than lining up the marks please tell me.
I have tested spark on every cylinder by pulling out a plug and visually checking. i have also checked spark timing using a timing light
i have replaced dissy rotors.
I checked the cam sensor wiring, it connects to the computer correctly, it has the right ohms across it, and its shielding is grounded. taking it out and starting the car will cause it to stall if it reads from another angle on the cam. i checked the engine speed sensor as well

 

[Zuffen]

OK,

Let's work through it logically.

You have spark on one bank so you know the distributors, caps, igniters & coils are functioning correctly.

From what you say there is no spark on one complete bank of the engine.

Have you checked for spark at the distributor for the leads that don't have any spark. I'd be inclined to try a different plug lead in one of the "dead" leads position and see if you have spark. If you do I would then test the other 3 and you may have an answer.

I note you said you tested the "leads" and "shielding" but I suspect this was for the cam and crank sensors.

Have you tested the spark plug leads?

My suspicion would be that somehow you've damaged all 4 leads on the one side of the engine (don't ask me how it could happen but happen it may) as I can't see any other answer for no spark on one side of the engine.

I have a few spare leads here in Sydney if they are any use to you.

 

[Bushwhacker]

Rotor arm missing/broken or contacts broken in the distributor cap on that side?

 

[uza70]

I have taken out the spark plugs and visually checked for spark, it looks fine. I did have to bend the leads around a fair bit to do engine work so it may be possible that I damaged them.

I will swap one over on the weekend.

My rotor caps look fine, and if it was a damaged rotor it would be two pistons on each side not an entire bank.

The problem really only exists at low revs and idle, I'm assuming that at a higher engine speed it just isn't as noticeable.

 

[gloverman]

Have you done a compression test yet? Cheers

 

[Cobber]

Just had a similar problem with a friends 1uz, one of the exhaust valves was stuck open.

 

[uza70]

Still waiting on a compression gauge so i havent done a comp test yet,

if it was only one valve stuck open wouldnt that only effect one cylinder?

 

[Supra967]

Possible to line the cams up on the wrong cycle with these engines?

 

[sideshow]

Cam belt only drives one cam per bank
Then that cam has gear in middle which drives
The cam next to it
These gears I think have a dot or maybe even three dots
So there is a special way to line em up
If problem is all four cylinders on one side then it can't be
Dizzy or rotors as each dizzy drives two cylinders per side

 

[Cobber]

a stuck valve will allow exhaust fumes to be sucked in to the plenum and cause un even firing. Do a comp test.

 

[uza70]

I swapped spark plug leads across to from the working bank to the rough bank.

Still the same problem, so that rules them out.

Compression gauge is on its way, so i will test that.

Just to ensure my timing is right, i will pull the rocker cover off and check again. Does anyone know how to check the exact positioning?

I put marks on the scissor gears and i put marks on the cam gear and the block. So when i put them back in it would all line up.

But if there is a fool proof manufacture way to test, I am keen to check it against that.


If one banks cam was a full revolution out that side wouldn't run at all, the rough side runs, just rich.

 

[Zuffen]

I think you'll find the problem is in the cam timing as you've eliminated any other possibilities.

Try this link.

http://www.lextreme.com/forums/showthread.php?t=6302

At the bottom of the page is another link to an article on setting the cams up.

If you use all the factory reference point it will go together easily.