3.4L Stumble...

[Doric]

So, back in December of last year, I had my '96 SR5 poo out on me when a small leaf got burned onto the MAF wire. Don't ask me how this happened. I have no idea.

The sensor was cleaned, and the truck ran again, so I didn't pay it any more mind. I'm commuting 100 miles a day with this thing now, and gas mileage is right around 19mpg. Abysmal, but what can you expect, right? It's still an SUV.

This week, it's picked up a nasty stumble when I put my foot in it beyond about 25% throttle. It chugs like it isn't getting fuel, or it's run out of MAF. Or bad wires...? I spoke with a mechanic friend of mine who mentioned that he's worked on a Land Cruiser of similar vintage with a similar problem, and that plugs, wires, ignition coils, etc. had no effect.

Could this be the MAF that I didn't replace in December? What else should I be checking? It's not completely consistent, so I'd be hesitant to think it's anything mechanical.

Any thoughts and/or advice are obviously greatly appreciated.

 

[druuu88]

clogged fuel filter? really bad air filter? basically anything that restricts air/fuel getting to the engine since its only happening at open throttle. is it throwing a check engine light??? if so, take it to any auto parts store and they will usually read obdII for free....

 

[Doric]

The fuel filter is new as of last summer (which doesn't mean that it isn't bad, necessarily - just less likely), but the air filter might be in need of some TLC, I guess. It's a K&N, but I don't think I've recharged it in the last 30K miles or so.

Thanks for the reply.

No CEL, BTW. I have an OBDII scanner, and nothing worthwhile has popped up yet.

 

[druuu88]

well the air filter would only be doing that if there is stuff actually clogging it up... like large leaves or whatnot. recharging it restores its effectiveness at catching dirt/grime but it wouldnt increase airflow THAT much (at least i dont think). although you are in denver... so altitude could play a role. umm lets see what else.... maybe carbon buildup in the engine. try a product called Seafoam (http://www.seafoamsales.com/motorTuneUpConsumer.htm). i loved it when i did it... you even get to see alllll the rich white smoke blow out your tailpipe.

 

[Doric]

Can't hurt, I suppose. I'll give it a try.

Thanks.

 

[brad6841]

Even though the fuel filter was changed as of last year....most recommend changing external filters on a 15,000 mile basis. And at 100 miles a day you've probably hit 15,000 by now.

I would also check into Seafom like druuu88 said....that stuff is supposed to be really good. Just find and available vacuum line into the intake and suck about half a can into the top end, then let sit for about 20 min and then start her up, lots of white smoke to burn everything off. You can also add it to you gas tank to clean the injectors and the combustion chamber.

 

[Doric]

Even though the fuel filter was changed as of last year....most recommend changing external filters on a 15,000 mile basis. And at 100 miles a day you've probably hit 15,000 by now.

>sheepish grin< More like 20K.

I'll add that to the list.

 

[druuu88]

yeah i used seafoam last year and wow what a difference it made. You can pick it up at most autoparts stores... or online at like amazon.com ($5.99). id give it a try for sure. vaccum lines work better/quicker than just putting it into gas tank. but both wont hurt either....

 

[brad6841]

From what I understand you want to use and upper vacuum line to clean the top end of the engine, you want to put it in the tank to clean the injectors and combustion chamber, and you can even add it to you oil (for short periods of time) to clean the bottom end.

It is basically the complete engine cleaner. :biggrin2:

 

[Doric]

Is there a particular line I'm better off using? Most times, I go for the brake booster line.

 

[brad6841]

Is there a particular line I'm better off using? Most times, I go for the brake booster line.

That's the winner on most vehicles....never used Seafoam on my 4Runner....but on my Silvy the brake booster or the PCV valve vacuum lines are the 2 favorites...

 

[Her4Runner]

I had a similar stumble that turned out to be the TPS sensor. You didn't mention whether or not your truck threw a code, but FWIW, mine didn't either when I 1st started experiencing the problem.

Just something else to be on the lookout for...

Her4Runner

 

[Doric]

I had a similar stumble that turned out to be the TPS sensor. You didn't mention whether or not your truck threw a code, but FWIW, mine didn't either when I 1st started experiencing the problem.

Just something else to be on the lookout for...

Her4Runner

Really? I ruled out the TPS based on the fact that there was no code set.

Methinks it's just time to sell the bleedin' thing and move on.

 

[Doric]

OK, so here's an update for the archives.

Dunno why I did things in the order that I did them, but this it:

• Replaced the TPS and test-drove the truck. No change.
• Ran 1/2 pint of Seafoam through the brake booster line and fumigated my entire town. No change.
• Replaced the fuel filter - oops, the old one was installed backwards (hey, it happens). No change.
• Ran STP fuel injector cleaner through the tank. No change.
• FINALLY, a CEL. Misfire on Cylinder 6.
• Replaced the plugs and wires. Stumble's gone. A little sluggish starting out, but I attribute that more to resetting the ECU than anything else.

Thanks for all the help, everyone. I really appreciate it.