bob9801

Hello,
I am having a really tough time sorting out my 22r. I have never been stumped by one of my vehicles before.


Short story.
Between 2000 and 3000 RPMs, during partial throttle and engine braking, the engine shudders. As I have been going through the engine it has been getting less but I can't get it to go away.


Specs
22r, stock exhaust, 20r head (stock), 20r intake, Weber 32/36 DGAV, 2 Redline piece adapter (no vacuum leaks), stock 1990 distributor (matched the '84 as best I could tell), W50 transmission, desmogged engine bay, double roller timing set.


Long story
I rebuilt my engine after my Fram oil filter (I stick to Wix every filter before and since) disfigured and gummed up internally and prevented oil from flowing. I was at about 3500 miles on that oil change running Mobile 1.

I started running out of money partway through the build so I ended up with a rebuilt stock ~'80 20r head on my rebuilt 84 22r block with original pistons, rods, covers, and oil pump. I grabbed a '77 20r crank that was mint and had it go through the machine shop. I also got a double roller timing set because I figured double the chain is double the reliability. (My original chain and tensioner had almost 200k miles and looked almost new. I could hardly measure any stretch and the pad on the tensioner was great. I did replace my guides once before already though.) I put everything together in the garage with Rock brand gaskets. At several recomendations I used Gasgacinch and followed the instructions to the letter. Within two months I had to replace every gasket on the entire engine, I went back to my personal favorite Permatex RTV Ultra Black and haven't had a leak for ~30k miles and counting.

Like I said, I had 30k miles with no leaks. I also had only two items of none standard maintenance, a starter and a single outer wheel bearing both of which were original with ~210k miles.

Now after all of this great performance since the rebuild I started having issues. I was starting to get valve noise and rough running so I decided I should adjust them a little early this year. I took off the valve cover and was in the process of adjusting them when I discovered that my timing chain tensioner had popped completely out and my chain was loose. It had wedged in a position to keep the chain tensioned for quite a while until it wore through the metal shaft. I replaced the full timing set and my original oil pump. Once I got everything together I had the same rough running as before, and described above. It was so violent at some points my steering wheel bounced ~1.5 inches. It had a great harmonic resonance.

Since then I have rechecked the valve adjustments, checked multiple time in multiple ways for vacuum leaks (didn't find any), measured vacuum (well within toyota spec) adjusted ignition timing (0 to ~20 degrees. It is now at 8 degrees and seems to like it best), rechecked that the timing chain is staying tight, inspected the spark plugs (tan/brown, not black or chalky. I did regap them to stock), inspected the plug wires (great shape NGK brand ~80k miles), checked compression (185, 182, 185, 180 yes I have to run premium), installed a Holley FPR (as recomended all over the YT forums), cleaned my reusable air filter, inspected the fuel filter, replaced the oil (it smelled like gas. Biggest red flag I can think of), inspected my fuel pump (as thoroughly as I could), swapped the distributor (the original one had one of the electronic ignition wires wear through on the cover), replaced the cap and rotor, tuned the carb (per the YT thread), and checked everything again for fun.


My exhaust is cleaner than it has been for a long time. The truck was running great while generating soot and smelling a bit rich. Now it is very clean and smells well tuned. It is dang hot though. I have been around my propane Celica quite a bit recently and the muffler stays cold to the tough. I can easily burn myself on the truck's muffler.

The truck will idle all the way down at 400rpm with only a slightly rougher feel. It idles real smooth at 700rpm. It accelerates well at full or nearly full throttle. It is really close to daily drivable, but with that shudder there is just no way I can put the engine through that commuting every day.


I understand some of my ways and parts my not be the best practice or the optimum for performance or reliability but it was working great for a long time. I cannot figure out what changed around the time of my timing chain that I haven't accounted for.

During all of the work I have put into it no one thing made a huge difference in the shudder. Fixed the ignition wire, 10% better. Adjusted the valves, 10% better. adjusted the ignition timing, 10% better. Cleaned the air filter 10% better. Adjusted the carb, 10% better. I am down to the last few percent but I just don't know. I have never had a consistent symptom persist over so many different parts and adjustments.


I hope I got enough details for someone to say "have you tried _____" or "you missed the ______". That would be great.

Thanks

AKHeathen

as far as i know, the 1990 should not have the same vaccum advance system as the 84, but be otherwise similar. that would certainly cause many problems, including decel timing. it should be fed from a mid-venturi passage, iirc.

AKHeathen

also, put an oil gauge on it. look for low or jumping around/bouncing.

bob9801

Should I attempt to put my '84 vacuum diaphragm on the '90 distributor body?

Where can I get an oil gauge for this test? I attempted to use a 0-100psi air gauge and it broke it; I am assuming from oil contamination, not over pressurization.

Is it possible that the timing got so far off when the tensioner broke that the 20r valves can hit the 22r pistons? I don't recall if the build would result in an interference motor, I didn't think so.