I know I never post here, but I could really use your help. The problem is my '86 4Runner (22re, 5 speed). If anyone in Denver wants to look at it, PLEASE let me know. I've had 3 mechanics look at it, and they are all stumped.

The problem is that the engine stumbles. Some times you can barely feel it, other times it feels like you are riding in a car with someone driving a stick for the first time (bucking so hard you get whiplash).

I've replaced:
plugs
wires
cap
rotor
tps (junk yard piece)
fuel filter
air filter

I've pulled the codes, and they seem to have no correlation (although all of them include the ECU). I've gapped the plugs, set the TPS using a multimeter, and adjusted the idle speed using a tach on a timing light.

For some reason, when I short out the plug on the drivers fender well (the same one to check the codes, right?) and I set the timing, the truck barely moves. I'm taking slower than my 50cc scooter. But it doesn't seem to stutter.

When I set the timing without the plug shorted, the truck runs much better, but it still stumbles. The stumbling increases with engine load, especially when accelerating, driving up a hill, or driving faster than 50 miles per hour.


This is my wife's DD, and I really need to get it fixed before the snow starts flying.


Thanks x 1,000

 

Id be checking 2 things. Take a vacuum guage, hook it up to direct manifold vacuum, rev it up to 2000 rpm and watch to see if you have a drop in vacuum, which would point towards a exhaust restriction(cat most likely). If ok, check your fuel pressure and be sure thats ok. My 2 cents.

 

Sorry im just guessing.

But you can try unplugging the tps and see if it runs better unpluged. If so you found your problem, if not, idk.

I had a plugged up cat, but it didn't do that, just absolutely no power. fixed now!

 

I forgot to mention that it has a new muffler and cat (well, new 1.5 years ago). I don't think that would cause a stumbling problem though. Could it?

 

i don't think so, but then again i don't really know.

I feel this is going to be one of those issues that is a pain to figure out.

let me ask a question that might help others.

is it doing this at idle or when moving? under load, no load? etc. The more information the better, it might be able to narrow down the possibilities of the problem.

possible motor mount????

 

it could be another thing your afm is crap

 

mine is doin the same thing....idles low, stumbles in gear, and when it shifts going around 50 if starts to stumble....any help would be good. The cat my be my problem. Could it be an o2 sensor?

 

Um, i thought i was told it is not needed to change the 02 sensor unless there was a check engine light(idk about this), but i changed mine recently just so i know it has been changed. (plus the previous owner used bosche )

My problem with my cat at least was it had absolutely no power, i was on a two lane highway and could not get above 45 miles per hour uphill, hill isn't even that steep. But it idled fine, and no stumbling.

i had a bad tps which would cause the truck to lurch really badly at a certain rpm.

 

It could possibly be the fuel pump, how many miles on it ?.

 

How long has it been doing the stumbling?

List what codes are thown? List them.

 

The AFM moves freely. (Not sure if that means its good or not though)
Happens under load.
New O2 sensor.
It's not motor mounts.
247k miles.
It's been stumbling the last 500 miles or so.

I don' t have the codes with me, so I'll post a complete list later, but I remeber it was RPM signal, switch signal, knock signal, TPS signal, and a few more that are escaping me at the moment

 

Subscribing... I have the same problem with mine. It fires right up and seems to run fine when cold (maybe I just don't notice it as bad) but seems to be that the more its run throughout the day the worse it gets. Mine seems worse at part-throttle though and I think clears up as I increase the load. It also idles really low. I've replaced cap, rotor, plugs, wires, O2, and am fixin to change the timing chain as some preventive maintenance and clean out my TB really good while I'm in there and then check/adjust my TPS.

 

The codes are 3, 6, 7, 10, 11 and sometimes 12. I believe these translate into (in order):

Ignition signal
No RPM circuit
Open or shorted TPS signal
No starter switch signal
IDL position in TPS is off during diagnosis check
Knock control sensor signal

 

codes-
3- no signal from ignitor 4 times in succession
6- no engine revolution sensor (NE) signat to ECU, or NE value over 1000 rpm in spite of no NE signal to ECU
7- open or shorted TPS circuit
10- No starter switch signal to ECU with vehicle speed at 0 and engine speed over 800 RPM
11- No TPS IDL signal to ECU during diagnostic check
12- knock sensor signal has not reached judgement level in succesion

codes 3,6,10 all point at the ignitor as a possible cause
codes 7 and 11 point at the TPS
code 12 points at the knock sensor
all the sensors in question are wired through the harness above the plenum runners, so I might lean towards a wiring issue in that area.

 

So replaced the fuel pump (hell, it still had the original pump with 247k mi. on it), and I'm pretty sure it didn't fix it. It was late, so I didn't take too long of a test drive, but it got up to 65 miles per hour decently fast, and without a single sputter. I turned around to come home, and I could feel a small sputter (typical behavior, sometimes it would get worse before).

BTW, $131 for a fuel pump??? $21 for a sock??? WTF, I payed $95 shipped for my performance fuel pump (with sock) for my Typhoon. I though Yota's were supposed to be cheap to repair




abecedarian: Do you have to pull the upper intake to check the wires in that area?

 

No toyotas are not cheap to reapair, its cheap cause you don't have to repair them that often!




Let us know if that solved your problem

 

I'd check the knock sensor, as they can come loose and give false readings thus retarding the timing till issue result. If the TPS is failing on diagnostic then you should test it, I had to pull it off to test mine (I had a diferent issue). Test continuity of your wiring harnes to each pin for each sensor, sensor end and ECU end, your checking for a short. Get a vacuum diaghram and replace lines they can leak and look fine. You can throw all the money you want at this problem and replace every part under the sun and still have the same problem. Diagnostic codes assist in narroming it down but the is relationship to how the different systems relate and how one failure causes a cascade of others.

 

Funny story about that. So the day after I replaced the fuel pump, I was taking a longer test drive. It was still sputtering. CEL came on. Knock sensor code was the only code stored. Unplugged the knock sensor, but it was still running the same way.



After that, I decided to do a complete tune up again (just in case). I replaced the plug wires in the Autozone parking lot (gotta love life time warranty). Since then, it has driven ~50 miles without a single sputter. So apparenty I had a bad wire, recieved a second set with a bad wire. What are the odds?

But for now, it seems to be working perfectly *knock on wood*. Now it's time to add some timing so it isn't so damn slow anymore

 

Anytime I've had a stumbling issue it's been either vacuum or spark. Once I was messing with the vacuum lines and forgot to hook 2 up. Ran like crap at low speeds but seemed to get better on the highway. Another time I had a spark plug boot that wasn't pushed snug onto the distributer cap. Ran like crap at all speeds. Bucking bronco lol.

Rob

 

150 miles and no problem *knock on wood*

Finished doing the tune up, and added timing yesterday. Highways are possible again