edeslaur

'87 4Runner, turbo
10K miles on new motor, new fuel filter
223K on the chassis, trans, etc.
It just started, out of the blue, to surge when it was cold.
Gutless, and I was in a hurry, but I recorded about 11mpg on the last tank with 4.88s. It was getting 13.5mpg (corrected) with 4.10s.

Start it up
Put it in Drive (yeah, I know)
push the gas
varoo-skip-ooo-skip-oooo-skip---mmmm

Putting it to the floor makes it a little better, not worse.

When it warms up, it's much better, but still does it a little bit from time to time. The skipping is much less noticeable, and shorter duration.

It started acting like this a couple days after the gears/lockers were installed, leaving work.

It doesn't seem to do it at cruising speeds, including highway speeds. But it does seem more gutless than when it had 4.10s vs the new 4.88s. Tires didn't change, still 285/75R16s (33s)... Just now I can, sorta, use OD where I couldn't before. But not like when it had 245/16s or 225/15s (stockers). I could do brake stands with the 245s. Granted, these are a little wider, and I did install new rear brakes...

Speedo went back to being dead on with the gear change, so it should be a LOT zippier. I could go faster on the highway with 4.10s and 33s than I can with 4.88s and 33s since this problem started. That should say a lot.

I broke the gears in for about 200 miles before running them over 60, so didn't get to try it at higher speeds before this behaviour started.

Suggestion welcome.

I'm guessing fuel pump or filter, except that doesn't explain the miserable MPG.
I found the filter this evening, looks like a real PITA to pull. Well done, Toyota.
A Delphi fuel pump runs about $150-170 with the sock, so I'd rather replace it only if I'm sure that it. Tips on testing it welcome!

Thanks for looking and any help!

edeslaur

Ok, the keyword google was looking for was "hesitation."

And the fact mine did not have an issue while it was just sitting there running, all the other links I found didn't seem to apply since few of them talked about problems when driving down the road (purposefully avoiding the i-word we use to describe this since my search accidentally eliminated those).

BZZZT!

Turns out this was the TPS. Measurements between IDL and E2 showed it had a problem, as did the ECU, throwing a code 7. And, because it's a turbo, it also blinked 14 times, which is very different than how it provides other codes (1 flash, pause, 4 flash is what I would have expected). Blinking 14 times is... Turbo overboost. Yep, I know all about that. >

So... for those of you googling for "surging -<word for when the engine is sitting there running>", hopefully this will come up for you.

Some quick comparisons
1. It's back to being as powerful as I expected
2. It goes up steep hills in OD again, doesn't need me to shift it down to 3rd
3. The sproingy shifts into 3 and OD went away
4. Gas MPG is... well, that verdict is out still.

My last tank was 13.5, so I'm REALLY hoping to see 17 on this one. Or more is good!

thook

Nice troubleshooting, dude. <<<thumbs up!!>>>