maxey87

I have a 87 4runner 4wd 5spd it is missing really bad. At an idle it runs decent and in neutral and slowly rev it it revs up pretty smooth but if you rev it in neutral fast it misses and Boggs down and also in gear when trying to drive it misses extremely bad and takes forever to even go the speed limit I have replaced the dizzy rotor plugs wires o2 sensor and about 2000 miles ago I put a new fuel filter fuel pump and injectors and I cleaned all of the fuel lines the air filter is also new all of the fuel parts were replaced way before this problem started all of the cylinders are getting fire so I have come to a stand still any help would be greatly appreciated and yes I have searched and can not find a similar situation as what I have

My99

Go here and download the FSM if you don't have it already. http://ncttora.com/fsm/index.html

I'd be looking to the AFM and TPS (throttle position sensor). It's a simple process on how to test them and you'll only need a cheap multimeter and a feeler gauge tool to test them.

BTW, how's the fuel mileage?

92dlxman

tps. check tps, one easy way is to un-plug it and see if the condition gets better

maxey87

If I unplug the tps then it gets worse

My99

Check AFM next. Take it off the truck and test it with a volt meter. If that checks out, you need to check the timing. Also, goes without saying you need to ensure you don't have a massive hole somewhere in your intake, down stream from the AFM.

Any more background information would be helpful - such as - it drove great 2 weeks ago, or I just bought it and it was like this...

maxey87

Yes it drove perfectly fine went wheelin the weekend before the fourth and then on the fourth it started acting like this and I just replaced the afm today and is still missing but sometimes in neutral if I barely touch the throttle and slowly give it more it revs up smooth but if I just lay into it it misses and Boggs really bad and not increase in rpm and no matter what if I am trying to drive it it misses and Boggs like crazy

My99

Honestly it's very difficult to follow your thread without punctuation. I'd settle for just using periods. By the way, nobody advocates throwing money at the problem. That can get expensive.

When you say "miss" are you referring to the hesitation as you try to throttle up or is it missing at idle? How is the idle by the way?

Kinda scratching my head on this one now...
I'm starting to suspect something with your fuel pump / fuel filter. You replaced both? Was something wrong with your original one?

maxey87

It miss at an idle. Sorry about my punctuation I'm using my phone and is just a pita to put correct punctuation and I have bigger problems than my punctuation right now. It misses at an idle, it Boggs and misses when I give it throttle. Plus the pump and filter are brand new along with the injectors because I had to clogged injectors and clogged filter when I first bought it so I just replace all of it so that is that. But I think it may be the ecu because one minute I can pull the spark plug wires one at a time at an idle and each one will make the engine run worse. But then a few minutes later I can do it again and then two cylinders did not make any change and then when done again minutes later only one does not make any change on how it runs. So I am at a complete stand still right now

maxey87

And I'm not just throwing money I tested the afm and it was bad so I replaced it, it helped the idle a little bit but that was about it

beach_yota

same crap happened to mine and then the HG blew. does it ever smooth out with driving?

maxey87

No it doesn't smooth out at all while driving it, it just falls on its face.

beach_yota

whens the last time you had a valve job?

Nailit69

Did you time it correctly or recently? Sounds like it could be a timing issue.

Like Beach said too... head gasket could be on it's way out or gone. Hope you didn't crack a head!

^^AppfreaK^^

Any update on this? I'm going through the same issue. I just bought my '87 4runner. The previous owner had the motor rebuilt, tps adjusted, replaced fuel filter, and cold start injector timing switch. I gave it a good test drive and it felt strong and responsive. Two hours into my trip home, it started to "miss" or sputter if you will, under load. The smell of fuel in the exhaust is evident.

I've since replaced the plugs/wires/cap, cleaned the maf and TB, replaced tps and O2 sensor. I also seafoamed it (poured into the gas tank and brake booster vac line), then replaced the plugs again since they were black after the treatment. I also checked the o2 sensor that I just replaced and it too was black. I cleaned it and put it back in...

The CEL comes and goes. I checked the computer using the jump method and got a number 5: bad o2 or cpu.

I cant find any vac leaks or loose grounds.

Any help would be greatly appreciated. Thanks!

-Patrick

Teuf

mm subscribed.....

^^AppfreaK^^

Bump!

bjlambert

Have you checked the MAF? They get clogged and foul very quickly, especially in dusty conditions.

^^AppfreaK^^

Ok so a little update...

I replaced the afm and added some HEET to the gas tank and it seemed to get better over the next few days. It no longer ran rich, it was more responsive, and the missing disappeared. Fast forward to yesterday when I had to get on the highway for a bit (60-70 mph for thirty min) and the missing started again. The only coincidence that I can see is that I ran the gas tank a little low again....

Guess I'll try cleaning the tank this weekend and see what I find. Any tips would be greatly appreciated add I've never done it before.

Thanks!

^^AppfreaK^^

Update:

Drained the tank, blew out the fuel lines, replaced the fuel filter. I also went ahead and replaced the fuel pump and sock. To be honest, I was a little disappointed at the little to no sediment that I got out of the tank both when I drained it. I let it soak in seafoam and some ethanol remover, then filled it with chains and bolts and shook the crap out of it. The residual liquid that I got out was discolored, but still not much sediment.

We'll see how it acts once everything is hooked back up. I had a theory that the pump was old and heated up as the tank level dropped. It uses the gas to cool right? Plus, the pump and the sock looked pretty old. Then there's the whole cold start problem. I have to use the jumper trick, turn the key, then let the pump charge the system before I can crank it up.

More updates to follow (just in case someone besides myself has any comments or is following this).

-Patrick

^^AppfreaK^^

Arghh....

Still getting a sputter at highway speed.