90 Laser 2.0 NT

I've been having bad idle problems for close to 6 months. Changed to obvious things, plugs, wires. Cleaned the thottle body and injectors. And it helped but Idle was still bad.

Had compression test done. Reading were (from belt side to left). 180,180,150,107.
Had leak-down test done: Results: 16,16,45,40.

Decided to remove the head and have new lifters, valve stem seals and depending...new valves.

Now I'm looking at the block and noticed a dent in piston #4. Right around the right exhaust valve along the cylinder wall. Maybe a half-inch long in two spots, side-by-side. From the compression reading above that was the suspect cylinder.

Now I'm confused. Does the piston need to be changed? I will find out what the resulting valve damage was to the valve in that area. So I would expect that if the valve is damaged, the piston would need to be replaced so it doesn't happen again.

And what could have caused it? Its a non-turbo car. It ran great for the first 6 months, then over the course of 6 months went from bad to worse. Am I missing something obvious here? I should mention that I had the timing belt changed at the end of last year. Could that be it? But only in one cylinder?

Anyway, I jwant it fixed. So I'm willing the remove the block if need be. Anybody have any advice???

Frustrated.....

Take a picture of the pistons and post them.

A dent on the top of the piston wont hurt anything as long as the piston is not cracked or the sides of the pistons are undamaged.

Sounds like you just need a re-ring and a valve job.

How many miles on the engine.?

Len, an update: I took out the block to get it re-ringed and honed and brought it to an autio rebuilder (dynamic auto - in TO). I was told the piston is fried and cyl wall is scorched beyond honing. so only thing left to do is bore it out and rebuild block. unfortunately, already had the head rebuilt so block rebuild would be $1400. the block has about 130k kms on it.

I've been trying to decide on rebuild or buy a used block and get it honed and replace pistons if need be or just re-ring and go from there. Any suggestions?

There's lots you can do.

1) get another block, stock bore, hone it and re-ring it. replace bearings and gaskets. This way is not that expensive. You could get a block for probly 100 bucks (no rods or pistons). I have a set of turbo pistons in good condition I could sell and they are mounted on 1g big rods already.

2) over-bore your block and go with 2g pistons. This would substancially be more expensive....Its about $300 bucks to re-bush the 1g rods to fit the 2g wrist pin...(others people will tell you $100 bucks, you get what you pay for!)

3) Ross 9:1 pistons, Eagle Rods, balance the engine and remove BS shafts. **** about $2500 bucks ***

Yo Len.

Good ideas but Derek got a 1G NT so going to either 1 or 2G Turbo Pistons would not be required...

Ghilain.

Ya, I quess your right....anyway, I have a set of nt pistons wasting away in the garage. Not sure what condition they are in though as they have 300,000 kms on them.

Or you could buy a set of NEW NT pistons for about 140 bucks complete set with wrist pins.

Derek, I've got a 6bolt block in good condition I'm willing to get rid of.

If you want, you can take it with you to the engine shop and have them check it out before you buy it (if you're interested)

darko@rogers.com

err...why didn't anyone suggest to buy a JDM N/T (or any used 4G63) for about $700?