91 4runner bogs down at speed

[meistr]

I have a 91 4Runner SR5 V6 3.0L that has been a great truck (like all of them?) until just recently.

Symptoms are bogging at roughly 25 mph or 2500 rpm in second to third gear. It will also sometimes not take off from a stop at a slight incline. By hammering the throttle down and forcing a downshift, the truck will rev up and then accelerate, but then again sometimes bog down until the same "forced shift" is done. This seems prevalent when the engine is hot, however, that may be coincidental with the high temps here in So Texas lately. The truck does seem to run fine for a while after starting it.

Please help!! Mechanic hasn't isolated anything.

Mike

[OzzyO]

I would guess you tried the fuel filter and possible dirty injectors ?
I have a 94 4Runner, with the same engine I had a problem very similar to yours and it tured out to be a sensor at the rear of the engine next to the firewall, apparently when I had the head gasket fixed this sensor was partially damaged, but it took another 3 years for it to completly go on me, I wish I knew the name of the sensor but I don't, how it was found was by having a 4Runner with the same engine and they replaced the sensors one at a time and it lead them to that one at the rear and I haven't had a problem with it since. Check out the manuals at the beginning of each page, you might get some ideas there also with the FAQ, good luck.

[meistr]

Yep, done all that: plugs and wires, throttle body/injectors cleaned out, cut the exhaust to rule out(?) cat converter, the sensor you are mentioning I think is a CTS (coolant temp sensor), anyway they replaced a sensor at the back of the engine, fuel filter. Ran better for a short time, they thought they had it, now a day later, acting up again.

Ready to make the thing a boat anchor...

[OzzyO]

Are you getting gas from the same dealer, possible water in gas and also check out the Manuals at the beginning of each page there is alot of information that could help you, one more possibility is your ECU, I had one go on mine. There are alot of sensors that may be checked also and in those manuals I mentioned it shows you how to test your sensors. Did you check your O2 sensor ?
I know how you feel it took 6 months to finally fix mine, at a cost of over $3,000 and believe me those weren't easy months. Also ask Brian he's one of the moderaters here and has alot more experience with this than I do, Good Luck.

[meistr]

I don't have any manuals. How do I ask Brian?

Thanks for the tips. I am thinking about getting a used ECM and swap to see. Also considering either a transmission fluid change/flush. The systems esemble torque converter problems - things is that doesn't explain the idle problem I don't think.

[Brian R.]

Send me your e-mail address by PM and I can send you a manual for your truck.

[meistr]

Okay, since last post I have replaced the ECM with a used ECM. It ran fine for 100 miles then original symptoms returned. Now I have the TPS unplugged and it is running like a top - beautiful.

Will I damage anything by doing this long-term?

[Brian R.]

Check your plugs periodically to make sure you're not running lean.