2007 Toyota Corolla 115,000miles Automatic
Bought the car from a friend of mine after he bought a new car. I bought it knowing it had an issue that the dealership couldn't figure out (MY BIG MISTAKE but to be fair, they didnt do anything really).
The car intermittently hesitates or doesn't respond at all to gas pedal being pressed. Sometimes I floor the gas pedal and it doesn't respond for 2-3 seconds. Seems to happen after initial car start or after sitting at a light for a minute. Happens more often after cold start but still happens after engine is warm. Happens more often under 30 mph and after sitting at a light for a minute.
Here is a list of things I've done already in the order I replaced them. I've been throwing parts at this issue and can't figure it out!
Changed all fluids. This was done by the Toyota dealership by the previous owner.
Car finally threw a code (P0121) so I replaced Throttle Body (Reman. Spectra). I later replaced this again used OEM part from LKQ (I didnt trust Mexico made Reman part)
Replaced air filter (OEM)
Replaced spark plugs (NGK Iridium)
Got another code (P2103) randomly and went into "Limp mode" Replaced Upper manifold gasket with newer OEM orange gasket. (Common issue with this model)
Got a another code (P0172) a few days later so I replaced MAF sensor (OEM) and upper O2 Sensor (OEM)
Replaced Fuel pump and assembly (not OEM). I ended up putting the original one back in after it didn't fix the issue.
I was worried about fuel injectors so I put fuel cleaner in a full tank of gas 4 times now. 1 seafoam bottle each time.
I took the car to my mechanic (at this point I had given up) and he check for vacuum leaks. None were found.
Mechanic told me it could be the ECU. I pulled a used one from LKQ, installed it, and did the key relearn. This didn't fix it either.
Its been several weeks, no codes and still same issue. I have no idea what to do next. Please help! Thank you.
P.S. Sorry for the long post!
What you've done is called "firing the parts cannon." That is, you went and changed half-a-car of parts without paying for a proper and guaranteed diagnosis first, from a good diagnostic mechanic. It's expensive, as you well know, and problems have multiplied, rather than reaching a positive resolution.
Of course, the danger is that you've likely replaced some perfectly good parts with less reliable aftermarket/rebuilt parts, thereby creating new problems. You were smart in reinstalling the original fuel pump and using used OEM parts.
I don't know why your vehicle hesitates, although it's curious that you haven't mentioned pulling up electrical diagrams and finding if the power/ground/relay from the pedal's electrical circuit itself is compromised. That's got to be checked, with a probe. Hey, maybe it's even a fuse that is no longer working at full capacity. I don't know.
The main point is to do some testing and diagnosis before swapping out parts wholesale. Or, alternatively, finding a diagnostic mechanic who will do the testing and guarantee a fix.
By way of example, videos from Ivan at Pine Hollow Auto Diagnostics or Eric O at South Main Auto will show you how they diagnose problems BEFORE they identify a fix. You have to find someone like Ivan or Eric O who will pull up a car's schematics and test, first and foremost. That's the main lesson to be learned here. Find a mechanic who will do better than "guess" on your dime.
Definitely learned a valuable lesson. Thanks for the reply!
Is your gas pedal assembly electronic? If so, these newer pedal assemblies have sensors that are basically variable resistors.
What you've described is similar to what I've seen on Ford Focus' with failing electronic pedal assemblies causing hesitation or flat out not throttle response.
I think it is! I will give this a shot. I can get a used part from LKQ for less than $50 probably. Thanks for the reply
Yes, 2005 was the year that Toyota switched the Corolla over to drive by wire.
2007 is an early type of electronic pedal assembly. I hope the LKQ works for ya.
It didnt fix it 🙁
Toyotagrl has the answer. You should have started with the drive by wire accelerator pedal. Why manufacturers replaced the throttle cable with an electronic accelerator is a mystery to me. I never broke a throttle cable in my life. I never had one fail. With an electronic accelerator, all you need is wet shoes to screw them up.
They did it for safety (traction + stability control), and better engine control. No need for an idle valve. Low maintenance (no cable adjustment needed). Also allows for drive tuning (eco mode etc.), better cruise control etc etc. It was an inevitable evolution.
I still think that having a simple cable makes more sense.
Sounds good in theory, Joe but I would never buy a vehicle with one.
@doc
good luck. cables are a thing of the past. If you travel by airline, it's all by wire too.
@billybob
that's probably what people said about fuel injection and distributors. Well then I guess you'll have to buy 20+ year old cars.
**Update****** (Should I update here or a comment on my orginal post, I'm not sure)
Replaced the pedal with a used Pedal sensor and that didnt work at all. I would press the pedal and car wouldnt go and threw some code that I dont remember.
Bought a brand new sensor from Toyota (came with the sensor and the physical pedal.) Sensor worked but didnt fix the issue 🙁
I did see Scotty's video on my issue so I ordered the BG fuel system cleaner. I was able to find it for about $16 plus shipping! I used 2 bottles on 3 tanks of gas, but it hasnt made a difference.
I gave up and took it to a mechanic that was recommended by my father in law. Mechanic said it was the ECU. (I'm not sure if he is a good mechanic honestly)
I bought a used ECU for about $40 and the problem got better actually. BUT it still has the same issue just less often now. I dont understand that!!!
I'm starting to think its a wiring, battery, or fuse issue kinda like @geriscan mentioned above. I am not quite sure how to go about checking that though. I barely passed my Intro to electrical engineering course in college (I am AWFUL with electrical things) so I am hesitant to do anything myself in regards to that.
Next steps? I want to stop my parts cannon but not sure what to do next! Should I buy a new ECU for about $360? Should I find a new mechanic? Should I do what my wife wants and get rid of it after putting all this $$ into it? Would Scotty be willing to check it out? I'm within 2 hours of his area in TN by the way.
you did it right
If you’d like Scotty to have a look at it in TN, set up a repair appointment with him by emailing scottykilmer@gmail.com
Early Toyota drive by wire systems did have issues with delayed responses from accelerator inputs, so what you are experiencing may actually be normal. I believe it was even worse in cars with the 5 speed automatic.
Update
Took the car to my local Toyota dealership yesterday. They gave me a call this afternoon and said they had there best technician on it for 4 hours and couldnt figure out whats wrong with it. They even called some Toyota help number to get advice from the manufacture. They told me to come pick it up and they werent gonna charge me anything since they have no clue whats wrong. Thankful for that at least.
Looks like I'm going to email Scotty and see if he wants to give it a shot; I have no idea what to do other than that.