Unresponsive gas pedal; full throttle, then slow pickup and erratic hesitation

[crypticlineage]

2000 Corolla VE
156,000 miles
Codes set since a few months: P0420 and P0171

On our spring break 2000 mile trip this week, on the way back, with just 30 miles to go, I came to a stop sign. Hit the gas pedal and no go. Kept pressing all the way down, then slowly acceleration picked up, but around 40-50mph, car was shaking erratically as if engine was having trouble breathing. Somehow made it home. Had this trouble at every stop after the first incident.

Next day, the car would start up but would die immediately. So I cleaned up throttle body, MAF Sensor and put a Techron Chevron bottle in the gas tank. The car now starts ok, and there has been no further hesitation, but the power is low.

I have had P0420 and P0171 since almost a year, but haven't done much about it. More than likely my bank1 sensor is going bad, so is my MAF sensor (both are original). The cat should be okay, because it's only 3 years old and haven't had a problem accelerating up until now.

Basically, I am wondering what my course of action should be. Do I need all three of the following things, and in what order should I replace them?

1. O2 sensor (before cat: bank1) $106
2. MAF Sensor $135
3. Catalytic converter (guestimate: $300)

Any advice much appreciated.

[white_trix-e]

i have o2 sensors cheap. 30 shipped each upper and lower. working great
u shuldnt need a new cat.
maybe a fuel pump o clean the injectors.
send me a pm if you need the o2 sensor will have it shipped out within 24hours

[CorollaTRD99]

Originally Posted by white_trix-e

i have o2 sensors cheap. 30 shipped each upper and lower. working great
u shuldnt need a new cat.
maybe a fuel pump o clean the injectors.
send me a pm if you need the o2 sensor will have it shipped out within 24hours

maybe you should change yout cat. i changed mines yesturday actually, had a deal because my fatehr knew the guy (200) and my car has a much better throttle response and as far as gas comsuption, my needle has not moved since.

[azncapcom]

i had a similar problem before. But it only happens at higher speeds, when im at 45mph (slowed down cause of traffic) and try to accerlerate back up to speed, the car hesitates and accelerates VERY slowly, even though the pedal was on the floor. This only happend for a few times for about a week, and then the problem fixed itself...

[VanDave]

Always try to do easiest cheapest things first......sounds like may be a plugged cat to me so unbolt it,and run it to see.

Magnaflows are around $170 US...penetrating fluid all the fittings and have it out in 15 minutes.

Check on eBay

[lexter89]

I have a 2002 Corolla, and am having a very similar issue. Currently there is a check engine code p0171. I've cleaned and checked the MAF, cleaned the Throttle Body, Replaced spark plugs, checked fuel injectors (haven't cleaned them yet), cleaned and checked O2 sensors. Eventually I brought the car in to a garage, and they told me they were getting better readings when they removed the air filter, and advised me to replace the old air filter although it looked brand new to me. I was able to plug in some diagnostic equipment, and found that when accelerating I was seeing long term fuel trim above 30%. I was told this number should be under 10%.

Anybody have any ideas where to go from here? Even the garage had no idea where else to go.

Thanks

[lexter89]

I have a 2002 Corolla, and am having a very similar issue. Currently there is a check engine code p0171. I've cleaned and checked the MAF, cleaned the Throttle Body, Replaced spark plugs, checked fuel injectors (haven't cleaned them yet), cleaned and checked O2 sensors. Eventually I brought the car in to a garage, and they told me they were getting better readings when they removed the air filter, and advised me to replace the old air filter although it looked brand new to me. I was able to plug in some diagnostic equipment, and found that when accelerating I was seeing long term fuel trim above 30%. I was told this number should be under 10%.

Anybody have any ideas where to go from here? Even the garage had no idea where else to go.

Thanks

[sam333]

Check fuel pressure on both cars.

[lexter89]

At one point I did try to check the fuel pressure, but the directions that came with the fuel pressure guage kit, and my haynes manual told me to pull a master ground from beneath the dashboard to discharge the fuel rail. However, when I pulled this, it also killed the power to my starter, which defeats the purpose. How do I go about relieving the fuel pressure at the rail? Or can I get away with not relieving this pressure?

Thanks

[fishexpo101]

Not sure why the directions want you to disconnect a ground from beneath the dashboard - this kit is for an 8th generation Corolla?

Also assuming that you checked the other fuel system components - fuel pressure regulator, fuel pump, fuel filter, hard and soft lines, vacuum leaks, etc.

To check the fuel pressures (abbreviated writeup)
- disconnect the negative battery terminal
- remove fuel pipe clamp (by firewall)
- wrap fuel tube and fuel pipe with shop rag to catch fuel spray
- disconnect fuel tube from fuel pipe (by firewall)
- note: residual fuel pressure in the 10-20PSI range, prevent fuel from being sprayed around engine bay
- connect SST (special service tool and gauge to fuel pipe and fuel tube connection (basically adding a t-fitting and gauge)
- wipe up any spilled fuel
- reconnect negative terminal of battery
- start engine, measure pressure at idle (44-50PSI)
- stop engine, measure residual pressure after 5 minutes (at least 21PSI)
- removal is reverse of installation
- connect fuel tube

[lexter89]

I was finally able to check the fuel pressure, and we were getting very good readings. I honestly have no idea what else to check.

Does anybody have anything they've seen before that I could check?

Thanks

[CorollaTRD99]

Boss I had the same issue. It was my bank 1 o2 sensor. Try to see if it is the o2 sensor by disconnecting the o2 sensor and run it like that. The issue arouse when I thre on headers on my car. The headers heated up the o2 sensor a lot so I bought a o2 sensor adaptor the separates the o2 senor from the header by about 5 inches. Works fine since! My issue symptoms was when idle, rpms drop a lot and sometimes shut off. Off a stop, I would get a late response. Car would shake as if its going to shut off. This is a really bad o2 sensor. I also gutted my cats out but left the resonator so I wouldn't get such a loud noise. Hope that helps