Won't stay running - help me figure this out!

[takza]

I once moved the t-belt on my car off by one tooth (9*?)...it idled OK...but had no power to speak of.

[4wdchico]

The way to correctly diagnose a vac leak is to use raw propane. Unscrew the burner/mixer off a propane torch and put a chunk of hose on it. Turn it on so it is flowing a small amount of volume and then apply it to the intake of the engine. If it runs better at low engine speed while propane is being introduced you are running lean. While the engine is warmed up and at idle, take the hose and apply the propane flow to every possible point where an air leak could happen. Check the underside of the EGR valve. The car's idle will change when you have found a vac leak.

Yes, I know that the ghetto version is to squirt carb cleaner around. I don't do that as carb cleaner can mess up rubber vac lines & diaphragms and is much harder to meter accurately than the simple propane rig as described above.

[Snax]

After letting the car sit in the garage for more than a month, it still won't run. Go figure.

Ok, perhaps it has not been a priority . . anyway, I think we have it figured out as being a blown head gasket. The rings may be in dire shape as well with over 200,000 miles on the original motor, as the compression #s shake down as this:

#1 - 128
#2 - 128
#3 - 100
#4 - 146

The FSM states 128psi as the minimum with good compression being over 170.

So gasket or not, it looks like it's time to take the head off and check things out more closely. Not what I was wanting to do, but apparently 27 year old cars have their problems.

[Snax]

Ok, the head is off and stripped of everything but the valves at this point. It doesn't look too bad, but there is significantly more carbon buildup on the valve of #3, a little less on #2, and virtually none on the other two sets.

I have not noticed anything obvious with the bottom side of the head or the top side of the gasket to suggest a problem, but the head bolt that came out of the middle hole on the port side of the head has an obvious coating of carbon on it right about where it would go through the gasket. Another one of the bolts was damp and a bit rusty at the threads, and most obvious of all, one of the middle two spark plug ceramics broke apart as I was removing them all from the head. I have to wonder if it was already damaged or if I was just careless in removing it. If it were already bad, that would certainly explain the erratic behavior.

The pistons themselves look good and the bores are in terrific shape with no scarring. I'm thinking a simple re-ringing is all I need there. With the low compression numbers, I'm reluctant to leave it alone. Anyone know if this is easy or possible without removing the block?

I'm going to get the valves done and mill the head while it is off. Any ideas how much compression I can pick up by milling it down?

[Petros]

I am not sure it is practical to replace the rings with the engine in the car. If you lower the front cross member (requires temp support of the engine) you might be able to get the pan off, and you can remove the connecting rod caps to remove the pistons. I hear it has been done, but the access looks like a PIA.

If you replace the rings lightly hone the boars (stuff news paper to the bottom of the boars to protect the crank journals from the honing debris). If the bearings look worn just replace the connecting rod bearings, they are only about $20 or so.

Removing about 0.020" from the head will raise the CR about 0.25 points (to about 9.75 to 1 CR), that will still allow you to use regular unleaded gas, and improve the power the bit. Taking off .040 will raise it to about 10:1, marginal with regular gas, you would have to buy the more costly mid grade or premium gas.

You should take the head to a machine shop to have the valves reground (consider having the exhaust valves replaced, well worth the small extra cost). They can check the valve guilds for wear, replace if necessary, and install all new stem seals. the valve stem seals and wear in the guild is why you get the carbon build-up, oil leaks past the seal and down the stem.

With those things done it should run like new, and you should have compression about 175 to 180 psi.

good luck

[Snax]

$88 for a complete head gasket set with valve seals as well as all new valves and guides from RockAuto.

Napa wants another $100 for the same parts!

[Toys4US]

Hi,

I read you can get a deal on parts at Advanced Auto parts. Spend $100 dollars get back a $50.00 dollar coupon for your next purchase. Do it soon as the promotion ends soon! Good luck.

[Snax]

Thanks for the tip. I've already ordered everything that I KNOW I will need including new rings for another $65. I may end up doing the whole bottom end as well, but I'm going to hold off until I get a look at it.

[keith]

I know when I thought that the converter might be plugged, I never did get the front bolts off, but I got the rest of the exhaust system off and ran a long screwdriver thru the converter to make sure it would not restrict the exhaust.

I don't think this is your problem. A plugged converter usually allows a good idle, but no power at higher rpms. I was thinking that maybe the shaft bushings in the distributor might be worn out. It will cause a bad idle but smoothes out at higher rpm as the shaft stabilizes. However, when I've encountered this, the engine just wouldn't start.

I would look at the idle fuel air mixture screw. Take it all the way out and clean the tip. Also spray some carb cleaner into the hole until is flows freely. then put the screw back in. Screw down all the way, finger tight only, and then a very loose finger tight. You can damage the tip easily.. Once the screw touches bottom, back out 1.5 turns and start the engine.

If that doesn't work, pull the top off the weber and lower the float by at least a 1/4". They come too high anyway. Also check for any debris in the fuel bowl. I once had a similar problem when a piece of the gasket broke off and stuck in the main jet. Messed up low end, but did not affect idle or max throttle.

[Snax]

I've pretty much decided from the compression numbers that a rebuild is warranted anyway, even if it is just the head gasket that has failed, the rings are likely nearly done at 200k miles. The up side is that the bores look silky smooth, so no overbore required. I just need to get the head cleaned up and revalved while I pull the pistons out for a re-ring, then I'll see where things go once it's back together.

[splatterdog]

If the bores are silky smooth that is a problem. There should be crosshatch scratches on the cylinder walls. This is critical for holding oil. It not only lubricates but helps to seal the rings. This engine sounds like it had a hard life before you got a hold of it and may be officially worn out.

I would go the whole way and rebuild at this point with all the effort you are putting forth. If you don't get acceptable compression after or spin a rod bearing down the road you will be mighty frustrated. These engines pull pretty easy, easier than most. Good time to check/replace the clutch at the same time.

A good running used engine might be the quickest and cheapest way to go.