Maintenance continued; low power when warm

[jross20]

Maybe you have tranny issues. Maybe it runs out good with cool thick fluid, but then slips when heated up.
Maybe driving spirited helps it lock up the TC and Driving miss Daisy has the TC slipping?

I’m stretching here.

What’s the service history on the tranny?

Transmission was flushed about... 6 months ago I think. We used the blue bottled Valvoline dex merc. Replaced the filter and bypassed the radiator with a standalone cooler.

It doesn't feel like she slips, I don't think so at least. How would you personally describe a slip? All of the shifts are very quick, first gear is a firm snap but the rest are almost butter smooth. If I really gun it the shifts are more pronounced but I think this is normal. She's never blipped or jerked.

On a side note though, what do you call it when you almost come to a stop but then accelerate and the engine seems confused for a second?

 

[Dieselchessy]

I’m not sure what to think. Sounds like the tranny may be fine.

I’d start with general maintenance, conform no rear axle seal leak, plugs, wires, TP sensor, throttle body cleaned, injector cleaner, cv valve, air filter, fuel filter. Test for vacuum leaks.
If that did nothing, then a compression check, maybe a leak down test, drop the tank and replace fuel pump and strainer.

With no engine codes and no clear description of a repeatable symptom it’s hard to say where to throw the parts money.

Have you replaced the timing belt, pulled the timing cover and confirmed cam timing is good?

Test the cat, might be your exhaust is clogged like others have mentioned.

 

[gamefreakgc]

See that's what I don't get. I'm hoping to test it this weekend and find rule the cat out.

I went ahead and ordered a TPS as I had some Amazon points, was one of those "ah what the hell why not" moments.

I replaced the MAF with an oem from Mcgeorge totoya.

See mileage...is odd. If I drive "normally/conservatively" I average 16-17. If I drive spirited, accelerate pretty quickly all the time, I average high 18-19s. My weekly commute is identical and rarely deviations. I never use drive thru's or do any other idling unless it is at a stop light. These averages are from 6 months of doing the math at the pump.

The wide variance and the increased in economy from driving faster just make no sense to me. That is one of the reasons why I thought the engine was bogging, like maybe when I give her more gas she doesn't bog and thus works more efficiently.

I've noticed that on some hills on my commute that sometimes she struggles and has to drop to what feels like 2nd and the rpm's get close to 4,000 or so, but other times it just feels like a gentle drop to 3rd and she powers right up without the slightest hint of issue. I recall the power from test driving other 3rd gens as being exceptional when you just convinced the transmission to unlock or drop to 3rd, never did I need to revv past like 3500 to speed up or go up a hill. I mean unless I was going nuts haha.

I specifically remember being impressed and really enjoying driving them during the test drives.
And I'm pretty sure that not a single one of them were supercharged or something lol.

Anyway. I'm going to run some seafoam as well to see if that helps. Also going to get a vacuum gauge for testing, I had no idea how useful they could be and I feel like I should just have one regardless.

Hmm, you do have a loss of power. You are right about the downshift behavior, it should be consistent. There's a sensor that's not playing nice, now the hard part is to figure out which one. Are you good with a multimeter? The FSM has voltage and resistance checks you can do.

 

[jross20]

Hmm, you do have a loss of power. You are right about the downshift behavior, it should be consistent. There's a sensor that's not playing nice, now the hard part is to figure out which one. Are you good with a multimeter? The FSM has voltage and resistance checks you can do.

I have a .... Questionable quality meter, but yeah I have one haha.
Is there a specific section in the FSM? I have the PDF files so I'll have to look

-UPDATE-

I swapped the throttle position sensor and unplugged the battery for a while. After doing some test driving I concluded that things seem smoother and the response seems quicker, but the power issue still remains.

On to 02 sensor testing

 

[jross20]

UPDATE

Now that it has been a few days since I changed the throttle position sensor I can officially say that the new part has made a huge difference. I guess the computer had to relearn with the new sensor or something.

Power and acceleration has greatly improved, if anything it feels extremely smooth now. It doesn't take much throttle for her to give you a nice push into the seat from a stop now
The other biggest change is that cruise control is now butter smooth. It used to always jerk the throttle a little bit when I turned it on, I had tried adjusting the cable to no avail. But now I can't even feel it engage when I set it. It also doesn't wildly speed up or down anymore.

Awesome.

I'm still going to change out the O2 sensors and also do that test with the catalytic converter just to be sure, but I think she's really close to where she should be.
:zoom:

 

[jross20]

Another update for anyone who was following or for anyone who may have a similar issue.

Saturday I replaced the accelerator cable and wow what a difference. The old one was tightened all the way but still had slack and the little grommet was wasted. Pedal was also a bit stiff compared to the new cable.

Still waiting on the new 02 sensors. I will also update the original post.