TS86

I have done some searching on this issue and found some posts but I cant seem to find the answer to my problems. Has anyone actually solved this problem.

My 86' 4Runner is stumbling when driving at all speeds. More so when the rev's are higher but it really happens across the board. This stumbling happens constantly sometimes every few seconds. Basically feels like the fuel is being turned off and on. The other key to this puzzle is that it will drive fine for the first 5 minutes or so. Plenty of power, no stumbling at all and then all of a sudden it starts and doesn't stop until I turn the truck off.

I have cleaned the small filter on the bottom of the fuel pump. That used to solve the problem but not so anymore. I have cleaned my air filter and checked my MAF and thats seems good. Next step is to replace the fuel filter and figure out how to check my TPS. The check engine light comes on sometime but not all the time. I will try to figure out how to check that as well. Am I missing anything? Has anyone experienced this before and actually fixed it?

The mystery to me is that it runs great for the first 5 minutes.

Any help is appreciated.
Thanks.

callmej75

Check timing.

BajaRunner

EFI right? Mgiht be the injectors?

The first 5 minutes the truck will run extra rich because its cold. When it warms up, the idle will drop.

Try fuel filter, I had problems like that with my buddies VW bus, and we changed the filter every year since and its been all good.

Im no mechanic ....

dragon564

You note the little filter at the bottom of the fuel pump pick up tube ...what about the main fule filter.....and the fuel pump is almost 20 years old now could it be time for a new one????

TS86

Yup its EFI.

The fuel pump has been replaced in the past few years so I am pretty sure that isn't the issue.
I will be replacing the fuel filter this weekend. Anything else to check/try while I am working?

TS86

Well.. A new fuel filter is in but my problem is still the same. The new filter didn't appear to help at all. I checked the code of the check engine light today and it read 5. From what I can tell that refers to the oxygen sensor. Does this seem right?
I guess I will have to find out how to replace that now.
Any tips?

TS86

So I now have the new fuel filter in, I replaced all spark plugs and added some fuel injector cleaner in a new tank of gas. The truck was running great and I thought my problems were over. However, today my gas level is just above half a tank and the truck started stumbling/hesitating again. Almost constantly when rpm's are high. So I stopped and filled up and It runs great again!!!!
What could possibly happen from a full tank to just over half a tank of gas. The truck goes from running like a champ to constantly hesitating and stumbling.
Can anyone help?

Snorkeldepth

I had a rough idle and stumbling acceleration problem in my 3.0. I put on a new air filter, distributor cap/rotor, spark plugs and wires, fuel filter, adjusted the timing, checked for vacum leaks, cleared the egr code . . . . . and finally checked the compression. I got 0 psi. in my #4. I guess that explains it. Lesson learned: A compression test is a cheap way to eliminate a possible cause!

Snorkeldepth

Is the fuel system in a 22re pressurized? I also put a new fuel tank cap on thinking that I might have a pressure leak. I had noticed that my tank didn't hiss at me as much at fill ups. The FSM recommended changing the cap gasket as part of regular maintenance. I think mine was original (1990). Isn't it harder to presurize a greater volume of gas than a smaller volume. At half a tank there's a lot more gas to pressurize that would be affected by a leak. I'm not exactly sure how the system in my truck works. But, it seems like the fuel pump pressurizes the tank which forces the fuel through the filter to the engine compartment. Long story short . . . . the new cap didn't help me at all. But, you already know why!

TS86

Thanks for the reply Snorkeldepth... I would assume my compression is ok as it was running great with a full tank of gas.
That is a good point about the pressure in the fuel system. How can I check to see if I that is the issue?

Dr.Feelgood

If the tank being either full or half full is the only common factor, it sounds like a problem with pressure. If you haven't yet, replace your cap and see if that helps. Do you have any fuel leaks that you're aware of or do you smell fumes? If so, you could trace it and they could very well be the problem. I've read something about the charcoal canister possibly being the culprit of a pressure leak too.

RuffRider

I had the exact problem and it turned to be the fuel pump relay. As it started to fail the contacts would "bounce" open and shut and the pressure would fluctuate all over the place. It wasn't until it failed completely did I figure it out.

TS86

Was it related to the amount of fuel in the tank? Or would it happen at all fuel levels? Where is the fuel pump relay located?

4-RUNNIN' FREAK

I'll be following this thread.

Can you or anyone explain how timing can make it stumble?

(I tried a few of the things mentioned, and I am leaning towards the FTC timing map being off a little. Seems to happen a lot around 2,500 RPM's. With cruise control on it's perfectly fine.)

jjcale

Dude the same thing is happening to me also. I have replaced the tb, tb sensor, had all adjustments made to the tb, mass air flow sensor, all vacume lines, cleaned the plenum and tb twice, motor was just recently rebuilt and has 1,500 miles on it, I ran all the test on the ecu to see if it was good and it was. I went to a shop and he thought I was nuts and still raped me for 117.00 for no fix at all. I have spent hrs trying to figure this out and not a damn thing. I dont want to goto a dealer and i know you dont either for the price. I talked to a guy that new of a person the works on just toyotas and I am taking it to him tommarow. It only happens after driving it just for a bit and then when you hit the gas it acts like it is getting shut off but then you let off the peddle and it seems to run just fine. I did notice that when I fill the tank it seems to act like it is running a little better. It might be me just thinking with the price gas is. The gas should fix it for 3.01 a gallon. When I shut it off and then start it it runs just fine for a little bit like 5min. I have not clue and when I get back from the shop tommarow I will get back to you. I Hope what that guy was saying with the fuel relay on this forum is right. It seems like it very well could be something to look at which I will today.

TS86

Keep me posted!!
Thanks.

jjcale

I took it to the shop and belive it or not it would not produce the problem for them. I have no clue what this could be but he stated to replace the distributer. he stated that their is a bushing on the shaft that will wear down and touch the contacts to make it stumble. I am going to buy one tomarrow and we will see what happens. Im going nuts

84sr5yoty

Try ohming out the signal generator on the distributor. On the 22re, the spec is 140-180 ohms. Test it with the motor both cold and hot. I've seen these ohm out correctly cold and then go bonkers when the motor reaches normal operating temperature.

AxleIke

So did you replace the O2 sensor or no? That will make your truck run really poorly if it's not functioning properly...However, i agree that this sounds like a pressure problem, with it having issues when it's only half full..

TS86

I haven't had a chance to replace the O2 sensor yet. I thought it was located on the exaust upstream of the muffler but there is nothing there. Is it located somewhere else?