misfire and clunking from under valve cover

[bukkow]

My car is a 1990 ggsx

Went for a drive with my daughter and when I came back the car was misfiring and there was a somewhat loud clunking coming from the head. Anyone know what this could be? I did a Google search and I'm leaning towards valve keepers.

Any help would be appreciated!

Thanks, Ben

 

[EfiniX]

Could be a bunch of things. Sadly, you might not know just what until you pull the head.

What do the plugs look like?

 

[holeshotmoe]

Pop the timing belt cover off and inspect the belt for missing teeth or other indications of failure, e.g., shredding. I don't know how many teeth need to slip before the piston-valve clearance goes away, but it can't be many more than a couple. If you find clues of that or suspect it, I wouldn't try to run or even crank the car over until you rule that out.
Also pulling the cover might be a good idea. I've seen the rockers get knocked out when the belt broke with the engine at idle. If yours slipped a couple teeth, the pistons started slapping the valves, and a few of the rockers got knocked loose, the car would run terrible and the loose rockers getting tossed about by the still-operating valve action would make for some nasty sounds.

 

[EfiniX]

To add to Holeshot's recommendations, when you pull the plugs, shine a flashlight into the hole. If you've been banging your valves into your pistons, you can typically see the impacts. If you don't see anything, it doesn't mean everything is ok, but if you do see impacts, well...

... hope it's not that...

 

[bukkow]

thank you for the replies fellas. I'm going to leave work a little early and start diving into it.

i just bought this car... frustating!

Thanks!

 

[holeshotmoe]

Quoting EfiniX:
To add to Holeshot's recommendations, when you pull the plugs, shine a flashlight into the hole.



Yeah, that's a better idea to do before pulling the cover.

 

[bukkow]

took the timing cover off and immediately noticed the cams are off time.

The belt seems loose too. Looks like i'm going to have to time this thing first and possibly order a tensioner. (even though the PO told me he replaced all of this)

maybe i just have to adjust the preload on the pulley?

Does anyone know how much belt deflection is ok if i'm pulling up/pushind down on the belt in between the cams?

Thanks, Ben

 

[EfiniX]

If he replaced the tensioner with a non-OEM part, it could have easily failed in short order. aftermarket tensioners are notorious on the 4g63.

When you pull the belt, you really are going to want to pull the head and inspect the valves, guides, piston heads, etc... for damage. Good luck!

 

[thomcasey]

As you turn the crank by the crank bolt, the belt should tighten. The real area to check for slack is between the crank sprocket and the Exhaust cam sprocket when it is in time. But, you can also remove the 14 bolts that hold down the valve cover and see if anything is laying around. May give a prelude to possible valve damage

 

[bukkow]

I did remove the valve cover yesterday and everything looked in order and very clean might i say!!

I'm going to place an order with Jays racing soon to get the 3 piece timing belt install tool kit.

Then I'm probably going to order an OEM tensioner as well.

whats the best site to order OEM parts?

Thanks, Ben

 

[prove_it]

JNZtuning.com

Better than most places.

 

[bukkow]

Thanks man, I appreciate it!