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Loss of power; hesitation on tip-in - SOLVED

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3.7K views 19 replies 10 participants last post by  ill_mannered  
#1 · (Edited)
TL;DR: Car had a pronounced hesitation when getting into the throttle. Would noticeably surge a bit under full throttle above about 3000rpm and kinda felt a bit down on power. No codes. Totally solved the issue simply by cleaning the MAF.

Haven't driven my 145k mile, daily-driver, 2002, manual trans IS300 in about 6 months. Decided to rotate it back into service this past weekend.

Did NOT want to start. Cranked quite a while, wasn't firing at ALL
Sprayed starting fluid into the airbox - fired, tried to start. Now I'm thinking fuel pump is bad
Pull #1 spark plug to verify it's got good spark before moving onto the fuel pump
It STARTS (albeit sluggishly) with #1 plug out! However, idles at about 250rpm, barely running
Put plug back in, restart. Again, it struggles to start and again, only idling at about 250rpm.
Give it some throttle and it dies
Restart - starts easier, idling at 400-500rpm now
Let it warm up - idling at 650-700, seems smooth, will take throttle but there's a pronounced hesitation
Drive it - drives like crap. Heavy hesitation and bog when getting into the throttle. Low power when pulling through the revs. Can feel surging, particularly at wide-open throttle
Now restarts easily and idles smoothly
Get fresh fuel, it takes about 3/4 tank
Burned through that tank, definitely running better but not great
Re-fuel again (another 3/4 tank)
Drove 50-60 miles, no more improvement

The car starts and idles great. When I tip into the throttle, there is a pronounced hesitation. Driving below about 3000rpm, power/torque feels fine at both part throttle and full throttle. It feels fine above 3000rpm so long as I'm only at part throttle. If I floor it above 3000rpm, it feels low on power and I can feel some surging.

Only trouble code is bank 1 sensor 1 heater circuit.
I have a small exhaust leak between the exhaust manifold and the tailpipe (the dual-pipe flange connection)
When I watch live data of the upstream O2 sensors, they're all switching nicely between 0.2 and 0.8V
3 years ago, I installed an xcessive "throttle lock" (don't think this is related, but wanted to mention), otherwise engine totally stock
Checked VVTi oil filter/screen - looks perfect
Definitely needs valve cover gaskets - intend to do plugs, wires and coil connectors while I'm in there

After searching, I've found a bunch of old threads with similar symptoms - but no solutions.

Any ideas?
 
#5 ·
Did not check injectors. How is that done; aside from removing and sending to an injector shop to clean and test?

Also, don't my normal and good O2 sensor readings suggest the injectors are doing what they should?

theraflu said:
Off the top of my head, igniter and APPS would be the first things I would check.
Click to expand...
My issue does not feel like misfire; wouldn't a bad igniter cause a miss? Wouldnt a bad APPS cause a check engine light?

reklipz said:
something crawl up into your intake? how's the air filter look?
Click to expand...
Actually, I checked these. All good.
 
#7 · (Edited)
Really?

I thought the heater circuit was only there to warm the sensor up to operating temperature more quickly to make the Nernst cell functional. For years and years, switching O2 sensors didn't have a heater at all.

Also, part of my issue is some power loss and surging at WOT above ~3000rpm. Isn't the ECU in open loop at WOT, and ignoring O2 sensor feedback?
 
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