Why is my Toyota Corolla bogging down?

Sounds like a job for the Car Talk guys.

Have you checked the mixture at the carb? Maybe it’s running too rich.

Start by checking the Distributor, make sure the Diaphragm is working!

my wifes car did something like that. the catalytic converter was plugged up, causing significant restriction in the exhaust. That would only alow a small amount of air in, ant thus, no ppower at all. Even healthy it had not much power, so it was really bad

@majorrich The last clogged cat I dealt with made little power at low RPM and could not even reach high RPM so I doubt that is it. Once I hit about 2100RPM< it pulls pretty good.

@phil196662 I’ll have to check that out.

@pdworkin No, but given that it happens only at one particular RPM, I figured it was something else. I guess I’ll have to see about that too.

One other thing I forgot to mention is that if I am engine-braking with my foot off the gas, it will surge a bit around 2000RPM and the engine-braking will be uneven, varying in-time with the RPM wavering. Again, it won’t do this above ~2100 or below ~1900

And check the catalytic converter too, restricted would do that too.

@phil196662 Just at that one specific RPM though? I mean, I’ll check but it’s counter-intuitive to me considering how it acts everywhere else in the rev-range.

Ahhh- thought of some other things to check! does it have Points/ Condenser? check/ change both if so- condenser could cut out, you could need to have the carb cleaned/ overhauled because at that RPM your transitioning from a low speed jet to a high speed jet and if the low is clogged it will run lean from 1,600 to 2,200 and stutter BUT will run WHITE HOT burn up from there! Check the distributor and then make sure ALL the vac lines are attached and have no holes (vac leaks)- this can cause it too! be detailed, it will be worth it!

@phil196662 Hmm… 25 years old, 305K miles… maybe it is time to rebuild the carb even if that isn’t the problem :D

True, has it been starting hard in the morning? that could help.

@phil196662 Actually, not really. If the engine is cold, I just stomp the gas pedal before cranking to squirt some fuel in (same as I’ve had to do with every other carburated vehicle I’ve owned or borrowed) and it fires right up, idles smooth, and drives good if I’m either gentle on the gas or keep it above 2K. Even forcing a downshift that takes it >2K avoids issues.

Still, it is an older car and needs some TLC. I just got it a couple of months ago and I’m not sure how well the previous owners took care of it, so I’m still tryingto find/fix it’s quirks.

After this, I’m going to try stopping the leaky sunroof again. Two tubes of rubber sealant around the edges hasn’t done the trick :(

Sounds like the Carb is a good start!

what fuel octane are you using? Is it as recommended?

92, the highest I can get. Seems to ping a bit otherwise, even with the ignition timing retarded. However, my ‘87 Corolla also pinged on anything 89 or lower anyways but it didn’t have this particular issue, so I’m writing that off as a quirk of high-mileage 4A-C engines.

Now for an update: I adjusted the hot idle (it was about 400RPM too high) and that seems to have lessened the problem considerably. Unfortunately, if I turn it much lower I won’t be able to have the thing idle smoothly when it’s in-gear since it really hates going below 700RPM.
A little more carb-tuning and borrowing a timing light might do the trick.I remember my ‘87 needed non-stock settings to run right though, so I may just do the timing by ear… if we get a dry day warm enough that I can feel my fingers after more than a few minutes :D

Always use a Timing Light, there are several settings on the crankshaft to reference for proper performance.

@phil196662 I am aware of that, but if the ignition timing on this car is anything like the 4A-LC in my ‘87 then 5 degrees BTDC (factory specs) won’t be correct unless I plan to run CAM2 racing fuel. Timing lights are essential if you know what the correct timing value is, but if you don’t then it’s still guesswork whether you use the light or not.
Then again, that ‘87 wasn’t totally stock either so maybe it’s different timing specs reflected that.

Going back to the struggling at 2,000 rpm, If the timing os in the range then the Carb might be a good place to start. even if it starts good cold with the choke closed the problem is when it’s at operating temp, the lean time and the chambers need to be optimal. on piece of dirt in the low speed jet can cause this problem. If you put new spark plugs in it and ran it for a short time at the hungery rpm you would likely find White Plugs telling you there is a lean condition.