Troubleshooting low power in '85 Toyota 22R engine

toyota
pickup

#1

To help a friend of a friend, I’ve offered to do a basic compression check on a 22R engine, '85 Toyota pickup, which is apparently low on power, won’t go above 50 mph. Yes it could be a multitude of things. Chances are it’s several of them.

I have not yet heard it run. I’ll consider myself lucky if I hear the uneven cadence of running on three cylinders.

My job Tuesday is to screen it for the most obvious things like a clogged air intake or air filter, choke stuck closed, worn spark plugs, etc, and do a simple compression test. I will again try to persuade the owner to take it to the skilled mechanic I’ve recommended, which he has resisted thus far, even though he’s about to set off on a long trip through desolate terrain.

I already suspect low compression based on what the owner has implied, but also wondering about ignition timing and vacuum advance. This is a carbureted engine, so does that mean that it also has a distributor and needs to have the timing set? I have a timing light, but only vaguely remember the procedure…disconnect vacuum line from carb and plug hose leading to distributor? Anyone know if there are marks on the harmonic balancer to align?

Evidently it has a bogus exhaust system too - no cat - making me wonder if there’s a problem there.

I’m not going to get too deep into this, but if I can at least spot the problem I want to be able to convince the owner that there’s a clear explanation, so he’ll get it resolved.

Thanks all.


#2

A vacuum gauge may give the quickest answer to the problem. And if it isn’t a plugged exhaust it could be the secondary on the carburetor. Of course a plugged exhaust would prevent the secondary from opening I believe. While the secondary has a mechanical linkage there is likely a vacuum lock out.


#3

Be warned, you have a good chance here of experiencing the example of " No good deed goes unpunished “. I would in this case raise hood , listen , and then say " You need to have this thing checked by an experienced mechanic.”


#4

I have a 20R engine in a 1979 Celica.

The timing should be set at 8 degrees BTC. Connect timing light to no. 1 cylinder. BE SURE to use inductive light ONLY!

Yes, disconnect the distributor advance vac line.

How is the AAP diaphragm on the carburetor? When these puncture, you will find gas in the vacuum line leading up to the diaphragm.


#5

Thanks Tom418. My light is not an inductive, so I guess I can’t check that.

Rod_Knox: I do have a vacuum gauge, and just found a good youtube video on how to interpret the readings, I appreciate your advice.

Volvo_V70: I had already tried twice to get him to a pro, no luck, so I had to raise the stakes slightly, but I’ll be mindful of your perspective.


#6

Update…

Engine sounded good, smooth and even, confirmed by compression: 165-170. Vacuum looked ok, steady at about 17 inches, with the predictable response when blipping the throttle. Apparently the engine is very good on oil, less than a quart in 1000 miles, more good news.

I took a chance and used my timing light, although not an induction type, and found the mark set at zero. When I set it to 8 btc, the engine seemed to come to life. The owner thanked me profusely and drove away to pick up our mutual friend. I’ve yet to hear back to know if there was an actual performance increase.


#7

@gmroadtripper-This might be a good day to buy a Lottery Ticket .You did good and dodged a bullet.


#8

The weakest link on a well maintained 85 Toyota 22R engine is the timing chain guides. If the chain gets noisy the guides can be replaced with the valve cover removed. If left noisy it will jump time and likely do some serious damage.


#9

Glad that worked out. Toyota cautions against using a non-inductive light as it can damage the electronic ignition.

@Rod_Knox: I could never figure why Toyota switched from the double timing chain on the 20R to the single one (and plastic chain guide on the 22R. Oh well…


#10

When checking timing w/a timing light , also verify the timing advances with increasing rpm. Easy enough to do once the timing light is hooked up. If you have the specs on the advance vs rpm curve the manufacture intends, you can check that too.

I think tho the low power was caused or mostly caused by the 8 degree retarded timing. On my truck the timing changes as the distributor points wear. But if this truck uses an electronic ignition system, probably they were just set wrong at some point. Good for you for getting the problem resolved.


#11

Absolutely @tom418. Even the early 22Rs had the metal backed guides that lasted 300,000+ miles but the solid plastic guides never lasted 200,000 and I replaced several at about 100,000. It’s a tedious job to remove and reinstall one of the bolts reaching into the timing cover but with a little care I seem to recall swapping them out in less than an hour and using the old metal parts that were still available.


#12

I had a 22R engine in my '89 Toyota pickup for 338,000 miles.
Definitely start with a compression check. If the compression is low and/or uneven, there’s not much point in proceeding unless your friend is willing to invest some real cash.

One issue I’ve found with that engine is the acceleration pump. .It operates off of a mechanical lever on the side of the carburetor, and that linkage gets gummed up and prevents the return spring from drawing the lever and thus the accelerator pump to its “start” position. Once the gas pedal is pushed once, the problem renders the accelerator pump unusable, resulting in terrible acceleration. I’ve corrected a few by flushing the pump linkage well with carb cleaner (any good solvent will work). It’s something to check.

Yeah, a vacuum gage can tell you wonders. And there are good primers on the internet on how to interpret the readings.

There are lots of possibilities here. I’ve mention a few that I think are good places to start.


#13

That 8 degree retard certainly wasn’t doing anything good for the engine power.

I read somewhere there’s a rule of thumb that says the idle timing should be about 1 degree advanced for each cylinder. I’ve never understood why though. It seems like the number of degrees of advance needed wouldn’t have anything to do with the number of cylinders.


#14

Thanks all, I appreciate the input.

I finally got some feedback on results: owner says it’s probably better, but he couldn’t be sure. So evidently there are other issues yet to be identified. For reasons I don’t understand, he seems unwilling to pursue those with a pro, even though I’ve suggested that the problem might be easy to identify, and likewise relatively inexpensive. With good compression, good vacuum, and very low oil consumption, some major and expensive issues are not a factor. I guess he’d rather just accept status quo, and continue to complain about the poor power. But he willingly says he “loves this truck”. Go figure.


#15

About the timing, spark advance may not be functioning. Both mechanical and vacuum advance can fail and if they do fail the engine will be gutless.


#16

Not sure if anyone has already mentioned it, but if the valve aren’t opening the full amount they should , that will result in a noticeable loss of power. So w/this problem it would be good idea to check for overly wide valve clearances. On my 4 banger Corolla anyway that’s like a 30 minute job to check, and doesn’t require any special tools besides feeler gauges. If the clearances measure too wide, then some special equipment is needed to put them back into spec, but still not that big of a job. Nothing more than any routine maintenance job.


#17

When you borrow a vacuum tester, you pull the distributor cap and apply vacuum to the advance diaphragm. When you see the pickup (breaker) plate move and stay moved you will know that the advance unit is OK. If you want to do it with the engine running, the engine will speed up. If it speeds up and slows right down, the advance unit is leaking. Usually though, it’s an all or nothing deal. Sometimes, the advance unit holds vacuum but is stuck.


#18

If this was your truck, it would be worthwhile to continue this discussion. Because the owner is happy to be cheap and complain, it’s best to wish him all the best, and find something else to talk about.


#19

@wentwest: Yep, you’re right, there is more to do, suspicion now is a bad vacuum advance. But he procrastinated long enough that he ran out of time to have the recommended mechanic help him before he leaves town (tomorrow). He lives in a remote location, but was visiting my friend here with plenty of time to address this. He made his own choice - might be a lesson learned.

With gratitude for the helpful replies,
Roadtripper


#20

And don’t forget the centrifugal advance, it can easily freeze up after this many years.