Hot engine, sluggish acceleration

Hesitant to post this, I know 4Runner's aren't fast.

Been noticing first thing in the morning on a stone cold engine the truck is fast off the line, lots of pep, smooth acceleration on the freeway. Once she is up to operating temp the engine feels sluggish, exhaust is louder and the transmission has to drop a gear or 2 (usually 2) to accelerate at most speeds. Truck hasn't always been like this seems like a newly surfacing issue.

Thought the issue might be maintenance but I have worked through that laundry list which helped. Truck is low mileage but has seen what I would describe as severe driving conditions for the last 20k miles and lots of idling this summer running the AC. Thought maybe something was going on with the EGR system but after some digging it turns out there is no EGR system, only secondary air injection.

I just replaced the front & rear brake pads/ rotors and made sure the calipers were not seized and that the pads slide freely (the rear calipers did seem more difficult to compress than they should have but they did compress). Just replaced the driver's side engine ventilation hose, made a significant difference engine feels much more consistent other than this hot/ cold issue. Plugs were replaced ~10k miles ago. Fresh oil change & air filter less than 1k miles ago. MAF sensor was replaced about this time last year for a similar but worse issue.

2020 TRD Offroad @ ~75k miles

Let me know what you guys think. Might just live with it and chalk it up to bad maintenance over the last year she had a rough winter at high elevation and I feel like that aged her. There's not much else I can think of that would be wrong with such low miles.

Thanks in advance.

 

Did you check the air pump to see if the foam filter is intact?
Why did you replace the driver's side engine ventilation hose?
Why did you replace the plugs at 60K miles?
What plugs did you use and where did they come from? ie: Amazon, eBay or dealer?
Reason behind you replacing the MAF sensor ? OEM toyota or other brand?

 

I wonder why you started throwing parts at it? No way plugs were bad, same for MAF sensor. What parts did you put back? OEM?

Get a infrared thermometer. Drive it up to speed-so it becomes sluggish to you. While idling, crawl under and shoot front, middle and back of cat. Are the temps similar? Huge difference? Shoot wheels-stuck caliper?

 

Haven't been throwing parts at it, replaced the spark plugs as preventative maintenance before leaving on a 6 month trip through the mountains living in the 4runner. In hindsight the plugs looked ok and could have lasted longer but I prefer to replace items like spark plugs early, they were replaced with Denso with the recommended part #, probably from autozone but I verified the part number independently. I've pulled plugs on previous 1gr-fe engines with less miles that looked worse I guess with the updates Toyota has made to the modern 1gr-fe they run much cleaner. The more you know.

MAF was replaced with an OEM part due to intermittent complete lack of throttle response, vehicle was nearly undriveable and would leave me stranded in intersections, replacing the MAF completely fixed the problem at the time. Like I said the last 20k miles have been mostly severe driving conditions, the MAF sensor kept getting contaminated with dirt after spending 6 months straight going from one dirt road to the next. I cleaned it a couple times which helped up until it didn't. Finally figured out the carbon filter in the air box was full of dirt I ended up removing the carbon filter and then replaced the sensor. I've been telling myself that if gets contaminated again I'm going to get a snorkel but so far so good.

The ventilation hose was not sealing properly causing a vacuum leak & drivability concerns. I've had these crack and leak on previous 1gr-fe engines I've owned so it was forefront of my mind. Immediate improvement when it was replaced.

Brakes were severely warped and thus replaced.

When I get a chance I will buy an infrared temp gun and check the cats & brakes thanks!

 

Did you check the air pump to see if the foam filter is intact?

Spark plugs!
Hope the plugs came from local autozone or dealer, because counterfeit plugs are know to have come from Amazon, eBay!

 

Carbon air filter for the airbox? Do you mean it’s carbon impregnated, like cabin air filters? I thought the carbon was only used to remove odors. Any chance that airbox filter is the problem?

I have a fair bit of severe driving miles on dusty roads. I should probably clean out my MAF too.

Edit: it sounds like you’re givin’er the the beans while the engine is still cold. That hurts reading that. I don’t think that’s very good for engines or automatic transmissions.

Any chance that it’s at higher altitude when it’s warm? (Giving you the impression a warm engine is causing the lower power). When I was out in Colorado this summer, the drop in performance was notable in the higher towns. Interstate driving happened in 4th, sometimes third for long stretches.

 

Yeah the carbon filter element that is affixed to the intake air box just after the paper filter. Best guess at one point there was a low quality intake filter installed that didn't seal properly and let dust past it into that carbon element. I replaced that low quality filter and remember how crappy the filter seemed and then it was year long issue of the MAF sensor being contaminated every couple months. I cut out the carbon filter and haven't had any more issues with the mAF

 

Looks like you have done a pretty good amount of troubleshooting here.
Just additional ideas in no particular order:

• Did you clean the throttle body and inspected the whole are up to there - needs to be pressure tight. No holes.
• Throw in a can of this techron...stuff..some swear by it...I'm skeptical at times.
• Switch to 93 for a little while if you can. Feel the difference there.
• Some have already given opinions on the spark plugs....you know best there.
• If you can connect her to a scangauge or device that might give you codes or any pointers there.
• Check your feet? Has it gone bigger and heavier?

 

I have not checked the foam filter in the air pump, I can hear the pump running when the truck is started so I'm not super worried about it but I will add the filter upgrade to my list of mods. Spark plugs were probably from autozone, maybe oreillys but I did buy them in store and not online.

 

Oh, I understand now, it’s “permanent” filter. I don’t think it’s meant for heavy duty filtering, but more as a last resort kind of thing. Did you replace it with an OE part?

Maybe your throttle body needs a good cleaning given the dusty conditions and leaks past the air filter. This video is a good one that discusses the whys and hows. https://m.youtube.com/watch?v=3B-a8WJtd8w&pp=ygUaQ2FyIGNhcmUgbnV0IHRocm90dGxlIGJvZHk=

 

Personally, I’d be careful about introducing a modded secondary air injection filter until this is well and truly solved. Just check to make sure it hasn’t fallen apart and ingested into the exhaust/cats.

 

I pulled the intake tubing off earlier today and glanced inside the throttle body, pushed the plate open and it looked very clean imo, I've never cleaned it. I inspected the lines going into the intake tubing but not the intake tubing itself I will take another look. I drove around a bit more after I posted this and it very much feels like a vacuum leak.

I love techron I've had it clean up rough idles and quiet down noisy injectors on older vehicles. I run it every couple oil changes and just I burned through a bottle with premium on my last fill up.

I've never seen any codes stored and my code scanner was stolen last month

Haha I have been driving a bit more aggressively lately but only because everyone else in this area does. What I'm describing is very consistent now though, cold start great performance, once up to operating temp poor performance. Smooth idle regardless.

 

I pulled the cover on the air injection pump just now and the filter is still intact

 

Nah I'm saving the beans for when they're warm If anything I'm slightly lower in altitude when I start noticing it I live at a slightly higher elevation than the rest of town but not by much

 

75k miles is a lot without cleaning the TB. They often don't look terrible visually when their performance starts degrading.

 

Try to also do a bit of pressure test if possible just to see if you have any cracks or anything from the intake all the way to where the metal starts. Also, when you start the vehicle see if you can smell gas near the engine bay area. Looking for the gas line and see if there are any cracks or things that are lose around it. If nothing else works and you really want to keep her and it is a for life kind of thing...then add a supercharger. That should take care of the sluggishness until your foot grows again.

 

I just cleaned mine at 55k, so yes, he’s due!

 

Have you installed any equipment that draws too much power like an aftermarket amp, lights, etc?

 

Just curious- are you consistently running non-ethanol gas? Or going back and forth ethanol and ethanol free?

 

It may just be the nature of these engines. They seem to do better the colder they are. Colder air-better throttle response. As things heat soak a little pep loss is expected. I have had that on all my Toyota engines, heck all engines. Most don't notice, you may be sensitive to it.

 

The engine is in open loop when cold (the ECM adjusts fuel based on MAF reading). When it warms up, it runs mostly in closed loop (the ECM adjusts fuel based on A/F sensor aka upstream O2 sensor on each bank). Get a scan tool (Bluetooth OBD2 dongles are convenient). Verify the performance issues are happening indeed under closed loop. When the engine is warm, check the short term and long term fuel trim values for anything unusual. Normally fuel trims are 100% +/- 10%.

 

I took everything into consideration last night and was planning on buying throttle body & mass air flow cleaner today to give those a shot.

Last night though on a whim I decided to leave the battery unhooked overnight, reconnected it this morning, let the engine idle for 15 minutes and so far the issue seems to be resolved. Smooth acceleration, lower/ smoother idle and just all around feels like she's back to her full glory. Will need to do some more driving to know for sure but so far so good after just leaving the battery unhooked overnight.

 

Can you elaborate on your 'severe' driving conditions?

 

Dusty conditions, extreme temperatures (sub freezing to 100+ degrees), sustained driving in freezing temperatures, stop and go, long distance driving, excessive idling, high altitude (8k-11k). Not just short spurts either, months at a time in each condition.

 

What spark plugs did you use (model or part #?) where did you get them?
I´ve seen strange things when wrong plugs are used. They seem fine at first but have a huge impact on the short or long run

 

Easy to hit the ignore button.

 

I've always noticed the opposite, anything approaching freezing and below the engine feels very detuned until it is warmed up almost like self preservation. Agree with the comment on cold air though I always notice in warmer weather 90-100+ degrees the engine feels sluggish which is just the nature of engines, hot air means less fuel.

After unhooking the battery and clearing the learned values the truck is back to its normal less power when cold and strong when warm like it should be. It's finally got that classic Toyota truck pep back and reminds me of my 2nd gen tacoma, gets up to speed and holds speed easily. Fun to drive again.

 

Glad you sorted this one out.

 

Nice that you got it fixed. It makes sense after you changed the MAF sensor, totally missed that, is the best to clear PCM tables by disconnecting the battery

 

I'm not 100% certain but I'm pretty sure I disconnected the battery when I installed the new MAF sensor last year. But a month or 2 after that I spent 6 months around 8k-11k elevation in sub freezing temps then down to 6k elevation in 90-100 degree temps the last couple months. The issue started happening when I came back down to 6k elevation and compounded over the summer months.

These are the kind of problems that make me miss my 2015 Tacoma, truck was consistent regardless of elevation and temperature and didn't learn bad habits like this.

Regardless glad it is fixed.