2.7 stumbles and bucks under load (solved)

The distributor timing can't be adjusted like on older cars. It is bolted in a fixed position. You just need to make sure the gears mesh correctly. It will probably throw a code for bad camshaft sensor reading if it's installed wrong. The sensor is built into the distributor on 96 models. It will not start or it will run poorly if the gears are off by a tooth.

I would suggest trying to get a Denso distributor from a junkyard if possible. The same coil is used on many models, so you could try a used Denso coil from the junkyard if you can't find the whole distributor.

The after market distributors/coils can sometimes have problems right out of the box. I'm not sure why, but the specs aren't exactly the same or something.

 

I agree with everything DrZ said. Additionally, I'd replace the entire thing. You can mess with the cap and rotor but if you pick up a used one it will have all those parts anyways.

When I replaced mine it was a pretty quick operation. I marked with a paint pen where the rotor was pointed. Then I removed it and made sure it was basically painting at the same spot on the new one after I replaced it.

Your symptoms sound very similar to mine. I recommend replacing the distributor next and hopefully saving yourself a lot of headache.

 

So i recently purchased a 96 tacoma with the 2.7L engine with 187K miles and I'm having these exact symptoms. The previous owner replaced from what i can tell by looking at newer parts under the hood:
Fuel Filter
Injectors
MAF
Plugs
Wires

I took it to an independent mechanic and they said they were 95% sure it needed a valve adjustment or possibly new valves. I took it to the dealer and they were 95% sure it was the fuel pump giving it a weak signal and wanted $1000 to replace it. They claimed the ltft was running lean so it was starving for fuel. I went ahead and replaced it myself with a Bosch unit for $150 and nothing changed. My truck skips/hesitates once it is warmed up and gone into closed loop between 2-3K in any of the gears. It is usually under load but can also happen going downhill if the rpms are up or on the freeway. I did unplug the MAF sensor and it ran just fine with no skips although it was in limp mode as it wouldn't go above 2k-2.5K rpm. The question that I have is my long term fuel trim is around 20 and short term is hovering around zero. That is reason the dealer gave me for a weak fuel pump, but after having that replaced it still has a lean condition. For those that this distributor replacement has fixed were you running a lean condition on your long term fuel trim before replacement? It seems odd that a distributor not firing correctly would cause a lean condition but i suppose it could be possible? I've gone ahead and ordered a junkyard denso distributor off of ebay that will be here later this week to give it a try but i figured I'd ask on the LTFT as I haven't seen that mentioned on this thread.

 

If it does it under a heavy load... Such as in a high gear at low rpms whole hitting the gas it could be a cylinder isn't getting enough spark. I had this happen with an Oldsmobile back in the day and new coil packs fixed it.

 

This has a distributor and the plugs/wires have been replaced from the previous owner. Wondering if a bad distributor would cause a lean condition on long term fuel trim.

 

Yes. And that has been discussed some, but it's kind of a secondary symptem after a misfire condition. You could really chase your tail following fuel trim information. But basically with a bad distributor you are not getting a spark, so just like with having bad or fouled spark plugs, fuel is being shot into the cylinder without being ignited, and then dumped out the exhaust valves and through the exhaust system. The excess fuel in the exhaust is picked up but the 02 sensors and will show a rich condition.

Just get that distributor installed. I have a feeling your going to be very happy. With these distributor system you are actually hitting 2 very major birds with one stone. You are replacing the distributor as well as the dizzys internal Cam position sensor. The cam position sensor is a major component in engine timing and spark management and often the fix for guys on newer coil pack systems with the sensor on the driverside of the engine just below the valve cover.

 

So i received my ebay/junkyard denso distributor yesterday and threw it in using the rotor/cap that was from my old distributor as it was almost new. The truck fired right up and absolutely has no hesitation it has totally disappeared while driving Thanks for this thread as I wasn't about to just start throwing parts left and right on this. The previous owner replaced a ton of stuff related to ignition/air/fuel so on the positive side I have a lot of new parts. I also have the new fuel pump that i put in so I guess that doesn't hurt. By the way if you need to put in a fuel pump on one of these trucks lifting the bed up and back makes it easy work. It always amazes me that professional mechanics even the dealer can't diagnose something like this. There were at least 3 different shops that looked at this prior to this fix and with all the parts that were replaced by the previous owner I'm sure he was done with the truck. Thanks Again for writing this fix up!

 

That's great news! I know it's the best feeling once the hesitation is gone. And I replaced my fuel pump the same way. Time to have some fun with the truck!

 

Im running into these issues again it seems. Does anyone have a copy of the FSM so I can test my distributor?

 

I'm hoping to just replace the coil in the distributor. $360 for a new distributor assembly hurts.

 

Just PMd it to you.

 

Thanks @SOMDTACO

 

Just goes to show that 30k in SnapOn tools doesn’t mean they necessarily know what to do with them. I trust only myself and knowledge acquired here touching my truck...

 

Son of a bitch.
This is the one on my truck at the moment.



And this is the spare that Green Tree Fab loaned me to use while troubleshooting...


The really bad one was what I took in to GTF 1.5 years ago and my truck wouldn't run hardly at all. They had swapped entire distributors with one of their old race truck motors and my really bad one.

This resulted in my truck running maybe 75% overall, but about 50% power from 1900 RPM to 3500 RPM with seemingly random sputtering and almost lack of total power. Also, my truck has run rich for years... also causing a P0420 condition, probably because I wasn't getting excellent spark all along! I recently just did the O2 sensor mod on my rear O2 sensor so I won't see that no matter now.

So I leave for hunting in the middle of no where Friday, just ordered a new NGK coil from RockAuto for $45 shipped, and to be sure I'll have one before I leave I'll be buying a used one from Ice Monkey Garage here in town too. So annoyed I didnt find this like 3 years ago when this started acting up. Thanks a ton for this thread and @SOMDTACO for sending me the needed docs.

 

Did you actually do any ohm testing on the coils to see if/how out of spec they are? At least you had a genuine toyota distributor. When I pulled mine out it was clearly aftermarket crap.

 

Yup. I tested it and it was out of spec on a couple of the tests.

 

Well that's actually good news then haha. Looks like you found the problem. Interested to see how that new coil works out.

 

Runs like a raped ape again!

 

not doubting your observations... was the LTFT + or - 20%

 

I really would have like to have an opportunity to actually test that distributor live and compare it to a know good.

https://www.picoauto.com/library/automotive-guided-tests/secondary-distributor-plug-lead/