emich

While driving I got check engine light flashing, code P0302, but also P0301-4, 300
Coils, injectors, spark plugs are less than 10 000 mi. P0302 appears few minutes after I start driving, if I clear it P0302 doesn't appear until I start the engine the next time. The only thing done recently was modifying downstream O2 sensor. I have bad catalytic converter.
Could that be the reason?
Thanks

Slumpertcivic

emich

The catalytic converter is not clogged it is just bellow threshold.

ezone

Valve adjustment
Compression test

Slumpertcivic

emich

Here is the results of the compression test
1-90 2-65 3-81 4-85 psi
Next step is valve adjustment

Slumpertcivic

ezone

Those numbers are quite low. Is the tester okay?

Adjust valve clearances, then recheck compression

Make sure you do the compression test right. Good hot battery, all plugs out, throttle wide open, and keep on cranking the engine until the tester needle quits climbing, plus a few more hits to be certain its maxed out

emich

That was my first thought. I checked the tester with the tire pressure. It is accurate. I am doing the compression test exactly as you describe it. I’ll check the valve lash and I’ll do adjustment. Should I check the timing as Slumpertcivic suggested above?

NDNV

Are you using OEM NGK spark plugs?
Yes check timing belt if skipped teeth. When was timing belt and tensioner replaced last? What is mileage now? Valve adjustment?

emich

Yes OEM NGK spark plugs. I changed the timing belt 18000 mi. ago at 175 000 mi. at the same time did valve adjustment,

ezone

Does this engine actually run? I would not expect numbers that low on an engine that still runs.
No-start/flooded might give numbers that low
I expect 180 psi or above when I do the compression test.

Can you feel it misfire at idle?
Does it only set misfire code at road speed? (egr passage clog)

emich

Yes I can feel and hear the misfire at idle. I did clean the EGR passage last time I did major work 18 000 mi. ago.
I did compression test today with new tester. The old one was defective. The numbers are 1-122 2-85 3-112 4-122. Still #2 is low. I am afraid it could be bend valve. Verified the timing mark on the harmonic balancer aligned with the notch and piston #1 is at the highest position. Trying to dedicate some time for valve adjustment.

ezone

It's not a bent valve unless it happened during your timing belt service (or head was pulled off?), and if so it should have been an immediate problem at the time it became bent....

It would not suddenly happen to become a misfire problem 18k miles after getting bent.


This does not yet confirm the cam is still correctly timed to the crank.

emich

This does not yet confirm the cam is still correctly timed to the crank.
You are right. Thanks. How a timing belt can jump a tooth?

ezone

but is it?

You're going to take off the valve cover. Remove upper timing cover at that time and verify cam timing is, in fact, correct.

BrotatoChip

Not installed correctly, debris getting caught between the belt and a pulley, failed/failing tensioner, etc.

emich

I'll check I hope on Saturday and I'll report

ezone

It can happen
But......If the belt had jumped time, it will never correct itself on its own.

emich

Still this doesn't explain the lower compression on cyl. # 2

ezone

Tight valve clearances can. That's why check valves is a step in the diag

emich

tomorrow. thanks

emich

Did valve adjustment with maximum allowed 0.009 in. and 0.011 exh. The timing is perfect. It seams to run better. No misfire so far. The new compression is: 1-130 2-90 3-112 4-122 Versus the old reading 1-122 2-85 3-112 4-122. Still #2 is low. What could be the reason besides bend valve?

ezone

You figure out where the leak is.
Read up on how to perform a cylinder leakage or cylinder leakdown test.
Carbon buildup or chunk on valve seat
Burned valve
Piston rings
Gasket breach
Failing tester or methods (remember I expect 180+ on these engines....I wonder why your results are so low?)