Changed timing belt - idle now rough
 

I recently changed the timing belt, cam & crank seals, water pump and thermostat in my GC8. I made sure I followed the instructions to the letter, and the crank and timing marks were perfectly lined up. Since then the car has had a rough idle. Shakes quite a bit in the car when sitting idling. It has not stalled in the 50kms I have put on it since the belt change. Just a rough idle. When I did the timing belt, I noticed that the belt was out one cog (thanks to the dealer servicing) on the exhaust on the drivers side. I corrected this and made sure they were perfectly lined up.

The car revs fine and has no strange knocking noises. A bit of belt noise. It is slightly sluggish, and seems to have a tiny miss before boosting.

The car is stock as a rock. No modifications at all.

Any ideas what is causing and how to fix my lumpy idle?

What ecu are you running ?

So issue is only after timing belt was done?

Post a video with audio if you can
What does it sound like to drive?

My money is on timing belt out a tooth.

I had by the sounds of it the exact same issue, which appeared after a timing belt change.

The motec timing had been thrown out by the change so the crank and cam angle sensors were trying to read at the same time causing a miss at x rpm. It also caused the car to very rough on cold idle.

If this sounds like your issue go speak to Cash and Sean at Allstar Garage and they'll know the fix

I believe the car is running the stock ECU.

Just a slight miss on idle, makes it lumpy, shakes the car a little. Enough to be an irritation.

I tried to reset the ECU but for some reason I do not think it reset. Connected the green to green, black to black, under the steering column. Accelerator flat to floor, then half throttle. Fan was on and off, clicking sound, but "Check Engine" and a couple of other lights stayed on. No flashes, no nothing. Took it for a drive, no flashing "Check Engine". So bugger it if I know what is up.

Could have knocked the cam or crank angle sensors.

I just connected the black to black and I get a constant "Check Engine" flashing light. No code, just constantly slowly flashes.

Any ideas as to where to next?

I would revisit the camshaft timing.
Disregard the white lines on the belt, especially if it's a Dayco belt.
Rotate the engine backwards by enough that you can slowly bring the crank into position in the correct direction and there's no slack in the belt. Then double check the marks.
Is there a chance you damaged a valve when you removed the old belt? Did the cams all spring off in every direction? Did you rotate the crank at all while the belt was off or was the belt removed at TDC rather than the halfway down the bores position? The valves can easily touch each other if you rotate the cams in the wrong dirrection and they have very small stems that bend easily. If they have bent valves they often have a characteristic valve train noise at certain R/min.

[QUOTE=dtrally;783622]I would revisit the camshaft timing.
Disregard the white lines on the belt, especially if it's a Dayco belt.
Rotate the engine backwards by enough that you can slowly bring the crank into position in the correct direction and there's no slack in the belt. Then double check the marks. [/QUOTE]
I checked the belt a ton of times before I bolted it back together. Turned it over by hand a bunch. Figured how to get it exactly lined up when the tensioner is on. Took me the best part of 2 full days to get it all done. Rotated the crank a ton of times and the marks always lined up perfectly. Even had the better half eyeball it.

[QUOTE=dtrally;783622]
Is there a chance you damaged a valve when you removed the old belt? Did the cams all spring off in every direction?
[/QUOTE]
Sure. There is a chance that a valve is bent. The cams sprung when I took the first belt off. I did however set the crank pulley to the service position before taking the belt off. The crank never moved. I only turned the cams the direction indicated. I am hoping it is not a bent valve as that would be slightly unfair given I painstakingly went through all the steps to the letter, minus not having the tool to stop the cams turning when the belt was first removed. Took me by surprise!

[QUOTE=dtrally;783622]
Did you rotate the crank at all while the belt was off or was the belt removed at TDC rather than the halfway down the bores position?
[/QUOTE]
I made sure it was in the service position prior to removing the belt.

[QUOTE=dtrally;783622]
The valves can easily touch each other if you rotate the cams in the wrong dirrection and they have very small stems that bend easily. If they have bent valves they often have a characteristic valve train noise at certain R/min.[/QUOTE]
I do not have any significant valve train noise. It runs reasonably smoothly. Just that slight miss and shake on idle. It is a bit quieter than before I changed the belt. My better half thinks it is smoother now.

The idle is the thing that is killing me. Just that lump, miss, slightly off. Gives the car a bit of a shake. The engine mounts are mushy as anything so that probably does not help. That said the car has done a cheery 230,000... was hoping to get it to 330,000

Edit: I should also note that it had a slight miss and shake on idle before doing the timing belt. It is now just a bunch worse. I wonder if the retarding of the left side exhaust cam by a tooth (as it was set previously) was deliberate to reduce this miss?

Retarding the cam timing to reduce a miss is not a procedure I'm familiar with, it may be a technique used though??

It sounds like you covered all bases with the belt change. When the cams spring around they only ever close the valves, there's no chance of damage then, only when re-opening them to set the cams in the right position can they clash with each other. It sounds like you were careful in regard to that.

Did you use the upper engine cleaner at the same time? Clean the throttle body and/or change fuel filter?

If you are confident that the cam timing is correct & you have a rough idle, you may possibly have a fouled plug / dodgy coil pack?

pulled the pin?

[QUOTE=dtrally;783647]
It sounds like you covered all bases with the belt change. When the cams spring around they only ever close the valves, there's no chance of damage then, only when re-opening them to set the cams in the right position can they clash with each other. It sounds like you were careful in regard to that.
[/QUOTE]
That is good to know. It makes infinite sense when I think about it. Good to see someone was thinking when they conceived the little makers.

[QUOTE=dtrally;783647]
Did you use the upper engine cleaner at the same time? Clean the throttle body and/or change fuel filter?[/QUOTE]
No, I did not touch the throttle body or fuel filter (* minus knocking one hose off it by accident - the one without the clamp).

[QUOTE=RoughStilin]fouled plug / dodgy coil pack? [/QUOTE]
I really don't like coincidences. It seems likely that something is amiss with the stuff I touched or inadvertently touched. I knocked one of the hoses off the fuel filter (one of the hoses without a clamp). I must have done this when ripping at the radiator hoses. Putting it back on achieved next to zero from what I could tell.

[QUOTE=magic1]pulled the pin? [/QUOTE]
On the tensioner: Yes. On fixing the issue: No.

Given the amount of time I have spent on this already I know each nut and bolt (on the stuff I touched) like the back of my hand. I am thinking I might rip out the radiator fans again, drop the alternator and A/C belts, pop the crank pulley, pull the covers and check the timing once again. I know in my own mind it can't be out as I took photos. But who knows now the belt has stretched a bit it could conceivably be off ever so slightly.

The only other thing is that I never drive my car down to the low fuel level. Given it was out of action, when I started the job it was down under 1/4 and I neglected to fill it up. Running it and pissing about I sucked a bit of fuel. I might have sucked a bit of bad fuel/dirt from the bottom of my tank. I guess I could always change out the filter and see if that makes any difference.

With that all said, I really want to reset the ECU. It will not reset and the "Check Engine" light just stays on when I connect the black/black, green/green connectors. Any ideas why this might be so?

Upon second thoughts, maybe the idle is bad given that the battery was disconnected for a few days. When I disconnect the battery I get a siren for a minute or two. I used the brakes to roll the car back, so I assume that would have reset the ECU after the power was all drained from the system?

If the CEL is on/flashing, you should be able to get the code from it.

I have attached the guide for reading the codes. I am fairly sure this is the GC8 one, though I also have a liberty one so here's hoping they aren't mixed up or something.

Once you plug the read connectors (black) together, the CEL should flash, short and long flashes in a sequence. If you read the guide it should determine what code/problem it is detecting.

You shouldn't be using the green connectors unless you want to clear codes completely.

Given these idle issues never seem to get resolved, I thought I should post the outcome.

As mentioned previously, I went ahead and pulled the crank pulley and checked the timing. The timing looked OK, but not perfect. It seemed like it was close, but possibly out 1/2 a tooth if I squinted hard enough. On that basis I ended up pulling the belt and setting the timing so that the mark on the pulley (passenger side / or US drivers!) was before the mark on the cover, not slightly after. This made the timing look not as correct as it is meant to, but it made the car run like a dream. The [B]idle is now perfect[/B]. No misses or hesitations, it is running better than it ever has. On to boost, off boost, it just purrs and is rather [I]sprightly[/I]. Red lining the puppy and it is alive! It is so quiet at idle, although the Dayco belt makes a lot more noise than the OEM belt. With this change, there is no miss like there was before I did the belt.

So the moral to the story is, if you do a belt, and it idles poorly, then you have to pull the covers and play with it. Retarding it ever so slightly may well fix the issue for you.. I spent about 8 hours fiddling (after initially changing the belt) to get it perfect.. I would hate to do that for my day job!

Good news is that no cam or crank seal leaks (replaced them all) and the water pump and thermostat are all flawless. Now I can go back to enjoying my WRX'y :lurk:

make sure you have sufficient clearance to belt guides too ;)

[QUOTE=Strubaru;785195]make sure you have sufficient clearance to belt guides too ;)[/QUOTE]
I was a bit anal on the clearance. I had the dayco "clearance plastic" slipping in between the guide and belt nicely.

Bumping an old thread...

Recently swapped my near new (3,000km) EJ257 for a forged bottom end EJ257.

Only thing that changed was the internals but now I have a really rough idle and it tries to stall when coming to a stop, and hunts really bad when unloading yhe AC compressor.

I pulled the motor and checked over everything and played with the timing change discussed here, but didnt test it out on the car running.

I took some photos and just wanted to see if Ive lined it up correctly as per the above (1 tooth counterclockwise) and if this might be a solution to my problems?

Not a vac leak, tried new plugs, etc etc. Been there done that for all the usual so resorting to new things :)

1 tooth retarded
[IMG]http://i58.tinypic.com/116ryo1.jpg[/IMG]


After rotating the crank a few times
[IMG]http://i57.tinypic.com/102ko0g.jpg[/IMG]