Cold Weather Blues

[Highlander]

Pull the plugs to check and see which one is a different color first, also check gap, one may be shorted or gummed up keeping it from firing.

[danzo]

A non-sparking plug would not cause a knock, but like Highlander said it can help you diagnose a dead cylinder if that's the case. If the plugs look OK then with the engine running pull one plug wire at a time (again, wearing thick gloves). Each working cylinder will run worse when the wire is removed; when there is no change then you know what cylinder is not firing. This doesn't necessarily mean it's an ignition prob just for that cylinder, but ground the plug and test for spark as mentioned above. If you have spark then most likely you have a compression prob, most likely due to a stuck/burned valve. If you have a comp guage then it now earns it pay.

In the cylinder that shows no comp you can tell where the air is leaking out by forcing compressed air into the cylinder via the plug hole when it's at top dead center (when the valves are supposedly closed). Just listen for air rushing out. If it comes out the tailpipe then you have an exhaust valve burned/not closing (most likely). Air out the intake/carb means the intake valve is not sealing, and air oil the filler cap means bad piston rings (least likely). Ideally you use a compressor for this, but you can use an air tank pumped up as high as it can go.

You can also simply remove the valve cover with the offending cyclinder at TDC and see if there is a huge clearance between the rocker arm and the top of the valve. If so then most likely the head needs to be rebuilt, which fortunately is not very expensive on these cars. Good luck, keep us posted and sorry for the thread highjack earlier.

[Petros]

Do not drive it, or you will do even more damage.

unfortuantly it sounds like the head has to come off at least. No way to fix an internal hard knocking without pulling it apart. If you dropped a exhaust valve (the valve head breaks off) you have the valve head, or part of the valve, rattling around in the cylinder, this occurs most commonly on the number one cylinder. It could be a broken piston, or bearing (this occurs most commonly on the number 4 cyl.), and means you have to pull the whole engine.

Pull the spark plugs and with a flash light see if you can inspect the tops of the pistons for damage or loose parts,

Good luck.

[sebsi]

OK, I pulled the plugs .

1 and 3 are heavily corroded with light tan deposits. 2 and 4 looked okay. I switched them around (put 4 where 1 was moved the rest "up" a number) and of course it's still knockin' and bangin' like mad; worse than earlier today. I'm doing a compression check tomorrow.

Do I have to pull the motor to pull the head? I've never pulled a head before (but my trusty neighbor has).

Blake

[Petros]

the head comes off with the engine in the car, it is easier than most cars to pull off. Should only take about an hour and half if nothing hangs you up. Follow the procedure here:

viewtopic.php?f=7&t=6059

let us know what you find.

[sebsi]

Very informative and dense stuff, Petros. Thanks for putting in the typestrokes.

It's supposed to get down below zero again next week; we're shooting for the weekend to pull the head.

Blake

[danzo]

Did you do a compression check? Did you remove the valve cover? If it's a rod knock then pulling the head won't do any good; the whole engine would need to come out.

[Petros]

If you actually have a rod knock, sometimes the extra slop in the rod bearing will allow the piston to strike the head surface. So it will tell you something if you pull the head and see that there was contact between the piston and head surface.

[sebsi]

Too cold right now to do anything but...drive the other car!

We're doing the comp check and pulling the valve cover this weekend, followed (inevitably, I'm afraid) by pulling the head.

B.

[gatemaster]

I have always lived in cold climates. From my experience even a good working stock ignition is not up to that kind of cold except in the newer cars. I installed a jacob's 65k ultra coil and now my tercel jumps to life even in -20 degree temperature which we had last week.

[sebsi]

Update:

Compression check was:

Cylinder 1: 100
Cylinders 2-4: 120

Pulled the valve cover and we couldn't see anything amiss but it's still knockin' like a Jehovah's Witness. So this car starts right up, seems to have decent compression (unless the 100 on #1 is cause for concern; is it?), but knocks like mad and I'm out maybe 25% of my power. Oil, coolant, etc are normal. Timing belt looks okay, i.e. teeth seem to be well-placed and making good contact.

My newbie analysis: if compression is okay, can I rule out cylinder/piston/valve problems? Wouldn't the failure of any one of those give me low comp?

What's the story I've heard about fuel pumps causing a knock? How would I test it? If there's something wrong with the pump, it's sure not affecting the otherwise-stable running of the motor.

Thanks again for all the interest in my car, gents.

Blake

[sebsi]

Update #2:

For the record, I tried this:

"Try carefully pulling one plug wire at a time while the engine is running. If the knock mostly goes away when one is pulled, you've located a bad piston/rod/bearing. Engine pulling time..." - splatterdog

and the knock did not go away, "mostly" or otherwise. I'm not sure I understand how this method isolates a piston/rod issue, because even if that particular cylinder isn't firing, the piston and rod are still banging away thanks to the efforts of the other 3, right?

Regards,

Blake

[rer233]

i got a t2wd wagon from a former girlfriend (long story- not going into it now) a few years back- same story- no power, loud knocking noise (i SWORE it was a rod knock.) turned out to be a loose crankshaft pulley.. put a new/used pulley and key in and gooped everything up with loctite (the crank was somewhat boogered- up.) the engine's run fine for the last 30,000 miles. just a thought- maybe you'll get as lucky as i did!!

[rer233]

addenum- i also replaced the crankshaft gear that drives the timing belt- it was wasted too- made setting the ingition timing impossible.

[sebsi]

i got a t2wd wagon from a former girlfriend (long story- not going into it now) a few years back- same story- no power, loud knocking noise (i SWORE it was a rod knock.) turned out to be a loose crankshaft pulley.. put a new/used pulley and key in and gooped everything up with loctite (the crank was somewhat boogered- up.) the engine's run fine for the last 30,000 miles. just a thought- maybe you'll get as lucky as i did!!

Interesting! How do I check for this? Pull the belt and wiggle? Ahem.

:^)

Blake