Loss of power and loss of acceleration

[HomersCanyonero]

I went to Mammoth Lakes, California (altitude around 8K feet) for 4 days. It was very smoky in the late afternoons due to the Creek Fire. On the last day I decided to check my K&N air filter and it was pretty dirty. I banged it against my tire to let a lot of dirt and dust come off the filter.

After driving for 10 minutes, I got a loss of power that forced me to pull to the side of the road. The car stalled on me while trying to accelerate from a stop sign. After i turned the car back on, there were no problems. At the condo, I verified that I had put back the air filter correctly.

I was a little concerned since I was about to drive back to LA. The next 250 miles on the drive back everything seemed okay. I even filled up in Mojave at a Valero gas station.

Near Lancaster I started having problems keeping a steady speed of 70 mph. I had it on cruise control and it was revving up to over 3200 rpms even on flat stretches. I took it off cc and noticed it wouldn’t accelerate to keep speed at 65 mph when the rpms were around 2000.

This went on for an hour. Going uphill was fine because it was revved up. Flat or downhill I struggled to keep speed unless I gassed it.

There was a traffic jam and had to slow down to about 10 mph and when traffic cleared I could not accelerate to pick up speed.

I had the gas pedal pressed all the way and it did not accelerate at all. I then changed gears from D to 2nd and pressed the gas. This did something as I put it back in D and the problem went away.

I was able to drive another hour until I got home. No issues with acceleration. No codes. No lights.

The next day I go run an errand and the CEL comes on. Check the codes and it’s P0420 and P0430.

The pair of downstream O2 sensors were replaced with denso O2s about 35k miles ago in 2017. New denso iridium long life oem spark plugs in 2017. New gas cap in 2017. Rebuilt denso alternator in late 2017. Battery is 3.5 yearsI have 161k miles.

Can a bad cat or O2 sensor cause the acceleration problem I had? Is this what is known as limp mode? Any ideas?

I’m trying to figure out all the inexpensive things I can do to figure out how to solve the acceleration issue and now the codes.

My scangauge code reader doesn’t tell me which bank. Just says the two codes.

 

[captainva]

I would check your airflow sensor. K&N filters don't remove the vast majority of contaminants in the air and can coat the airflow sensor in oil or debris. I'd swap that out with a paper filter ASAP and toss the K&N especially with all of the smoke in your area. Then I'd clean the airflow sensor and see what happens. I'm sure there's been a ton of particulates going into your engine with that K&N. Project farm did a video comparing filters recently and it shows how much dirt lets though.

 

[Tanner H]

I'd start with the cheaper/simple route and replace air filter with anything new from the store...then I'd pull your maf and clean that with maf cleaner from autozone.

if you have a code reader i'd erase the codes and even disconnect the battery for a bit for the motor to do its factory re-learn.


my theory behind your 02 sensor codes:

- filter and maf were dirty and the air quality on the 395 just sent it over the edge. not enough air into the motor
-truck was probably running too rich since you were trying to keep up with traffic and it was just throwing off your ratio causing the 02 sensors to throw a code. so i wouldnt focus on your 02 sensors yet...In my opinion its your air/fuel ratio.

Hope this works and keep us posted.

 

[Arailt]

It's not limp mode. Limp mode won't let you go above ~10 mph. I've had it happen in my GX after the dealer did suspension work and forgot to plug in a brake sensor.

Sounds like a bad O2 sensor to me. Stalling, wild revs from the cruise control to keep the engine from stalling.

I also agree - check your MAF and dump the K&N for a Toyota filter. If it's dirty, clean the MAF and throttle body.

 

[HomersCanyonero]

Thanks for the advise. I just ordered a new oem air filter. I’ll clean the MAF with the CRC electric cleaner I bought last year.

The bad air was in mammoth, but the acceleration issues were in Lancaster so that’s a big delay.

However, it makes sense to start by replacing the air filter and clean the MAF.

Also, last year I cleaned the MAF twice because I was getting the other codes P0171 and P0174. Codes went away after the second back to back cleaning of the MAF, but come back every few thousand miles.

 

[Arailt]

Also, last year I cleaned the MAF twice because I was getting the other codes P0171 and P0174. Codes went away after the second back to back cleaning of the MAF, but come back every few thousand miles.

Is your K&N filter an oil or dry filter?

 

[HomersCanyonero]

When i bought the GX470, it came with the K&N filter that looks like this one.

it says it has an oil layer. I vacuumed it clean once before, but haven’t washed it. This last time it had a lot of dust and dirt, so I just banged it against the tire to clean it some.

i can’t tell if there are models without the oil layer, so I’m going to guess mine is oil based.

 

[captainva]

I believe that the MAF in the GX is the hot wire type. The hot wires really don't do well when they get any oil on them. I'd avoid K&N in the future as they're known to cause problems with these

 

[HomersCanyonero]

Good to know. I’m going back to an oem filter and cleaning the MAF and ride it out.

 

[Arailt]

Yeah, those types of filters are supposed to be cleaned and re-oiled on a periodic basis. The oil helps filter the dust/debris. I've run them in the past and never had good results. If you over oil or under oil, it can cause problems with the MAF and engine components themselves if enough dirt gets past.

Best to just use the stock Toyota filters.

 

[Max Nguyen]

i like AEM Dryflow filter.

 

[HomersCanyonero]

Well, cleaning the MAF with CRC electrical cleaner and installing a new oem air filter didn’t solve the problem. The P0420 and P0430 codes are back.

Also, my pair of downstream O2 sensors were replaced in 2017 when I got the gx470. Got new denso oem parts at that time. They have under 30k miles on them now.

i ordered a new Bluetooth odb2 scanner since my scangauge doesn’t display too much info.

 

[Arailt]

Well, cleaning the MAF with CRC electrical cleaner and installing a new oem air filter didn’t solve the problem. The P0420 and P0430 codes are back.

Also, my pair of downstream O2 sensors were replaced in 2017 when I got the gx470. Got new denso oem parts at that time. They have under 30k miles on them now.

i ordered a new Bluetooth odb2 scanner since my scangauge doesn’t display too much info.

I think the GX470 has two sets of down steam O2 sensors, one pair after the manifolds and one pair after the cats on the Y pipe. I could be wrong.

 

[SteveH]

P0420 can be fixed with spark plug anti-foulers. Oldest trick in the Toyota book - use YouTube to see how it's done.

 

[binaryaudax]

P0420 can be fixed with spark plug anti-foulers. Oldest trick in the Toyota book - use YouTube to see how it's done.

+1 to this. My buddy's 2008 GS350 had the same issue. We installed an extension on one of the O2 sensors (didn't even replace the sensor) and the codes went away.