GT-S hesitation issue

[stah]

Hi I am newbie on the forum and I do hope judging by the knowledge and experience level on the forum to find a solution for my problem. My GT-S 1.8 vvtli 2001 160k miles is hesitating when accelerating. It happens everytime at 3,5-5,5k revs. Feels like lagging...like all of the sudden you have started to tow someone behind till 6k revs when all goes smooth again and once the lift kicks in madess began I scanned her OBDII and got P0420, P0171, P1693 and first o2 sensor error (forgot the code). I have replaced CAT so P0420 is gone, cleaned the MAF ruling out P0171 and P1693 was probably triggered by erratic work of engine in higher revs as lift kicks in each time no problem (6400-8200).
I have replaced fuel filter, air filter, used injector cleaner, checked spark plugs(one of them). Car drives on 95 octane fuel, OBDII gives me no faults now, CEL is off and car still hesitates taking all the fun away from me. I am out of ideas, please help. Cat has new oil filter and 05w30 recommended oil, not burning or leaking a drop.

[stah]

also tried 7 different o2 sensors, swapping and checking with OBDII scan with no luck, idle is very good, when cold 1400 and 800-900 when hot, idling is smooth. I can hear a hiss noise when turn on cold after 15 sec idling ( short hiss, int light go dimm for sec like when you switch on AC, electric power drop) Sprayed around with carb cleaner with no affection on revs which rules out vacuum leak. Car is stock, no CAI, only bfly valve removed

[Muirner]

Did you ever figure out or fix the front (before cat/upstream) o2 sensor? This is the o2 sensor responsible for fuel trims.

[stah]

I did. I had few of them. I was swapping them and had them read with OBDII, sensor is going 01/09 V second one stays at 0,56/080 V so it looks they do the job.

[vegeta4ss]

i've had a few issues like this over the years.

My MAF went bad and the result was a surge when at a constant speed. By that I mean the car sort of jerked/lurched for a split second then it stopped. Then it did it again, then it stopped. Repeat cycle. But it only did this when you maintained a constant speed. Highway driving with cruise control was easy to trigger it. Even though I cleaned the MAF the problem only went away when I swapped MAF's with a friend for a half day.

My coilpack went bad and the result was a stumbling idle and acceleration. You could put your foot to the floor but the car would only limp along and accelerate slowly. In the beginning it just felt a little weak on power and then when the coilpack completely went it had trouble even idling. However I threw numerous cylinder misfire codes and when I swapped around coilpacks and reset the computer the misfire moved to a different cylinder. This whole time though you could hear the motor was not running at its normal tone.

My celica has never given me a vacuum leak issue however in my experience helping my friends fix their cars a vacuum leak would mean higher idle and the engine would sound mostly normal (not misfiring at least) but when you accelerated there would be a delay between your foot moving and the car reacting.

Do any of those three sound like what you are experiencing?

One thing to check is that your spark plugs are not fouled out. 95 octane is a bit rich for the celica to completely combust in bone stock form. Once the plugs degraded the o2 sensor (and the cat) would get worked a lot more than usual which might explain your having to replace it. You also have to make sure you are using the correct sensor. Check the part numbers against the factory manual. I do not know if USA pt #'s for o2 sensors are the same as yours but these may help:


Oxygen Sensor 89465-20700 front sensor 00-02 2ZZ
Oxygen Sensor 89465-20830 front sensor 03-05 2ZZ
Oxygen Sensor 89465-20710 rear sensor 00-02 2ZZ
Oxygen Sensor 89465-20851 rear sensor 03-05 2ZZ
Oxygen Sensor 89645-20680 rear sensor 00-02 1ZZ

hope this helps you narrow down your issue.

[navypilot041288]

I had this issue to and all i did was remove the maf sensor and spray it with maf sensor cleaner and let it dry then put it back it. Worked like a charm

[govenader]

When you clean the MAF, make sure you actually get to the platinum wires inside.
Be careful though, break one of these wires and you're screwed.

[mad.mdx]

If you have a scanner that can read current data, check to make sure the MAF voltage goes linear up/down as you increase/decrease throttle. It works better if you have a scope view but if its bad enough you can tell that way.

Also, oil change? Been done?

And 95 octane in ireland is 91 in north america i think, so i dont think hes running higher octane than recommended

[stah]

Thank you for response. I dont feel abandoned with this anymore. So...
I have cleaned MAF several times, 2 strings are intact, I ahve checked with scanner MAF test and could see how it is working along with the throtlle so it is not MAF. I dont have any problems idling or accellerating. Car does not stall or hickup or die on me never but I have noticed that there is a delay with gas pedal reaction. This is my first celica so I dont know how big the delay should be. To make you understand the issue better. It feels like you have someone on tow (from 3,5k-6k revs), then it let you go again aroung 6k revs and goes like crazy. Feels like no fuel/no air issue, poor combustion. Scan gives no error now, no CEL.

[2KGTS]

In a 2001 you have an accelerator cable. It runs to that black box near the front on the passenger side and then to the throttle itself. Check your throttle cable and make sure it's taut, not being interfered with, and clean. I know it's old, but I'm sure there's a thread here about how to get it all tightened up and how it runs.

And I don't mean to be this way, but I'd find a MAF to swap for a bit. I don't know what you mean by "scan". And I don't know that I'd trust a generic "scanner" for a Toyota part.

[stah]

Cable is good. Bu scan I mean OBDII where I have toyota software with several tests for each thing. I got it tested for everything believe me and it is good quality tool for over 3 grand USD

[jeetee-ess]

hey Stah, believe it or not, i have had the same EXACT problem as you. i have been keeping up with this thread until today, since i had some free time to work on the car. my dilemma was the same as yours. i've had my CEL on for about 2 years, and my mechanic said it was my custom intake (BB modded), which i have had since Blue Bomber made a thread on how to make the 'perfect intake' for our celicas (in 2008?), and it worked very well with no problems until i had my CEL about 2 years ago (2010). so i suspected that it had to be my MAFS, but i didn't want to think that it was the problem because i didn't want to blow $200 for a brand new MAFS just yet. i tried cleaning my MAFS numerous times, thinking i was doing it correctly, and my car ran just as sluggish as it did before i cleaned it. my car felt like its peak power was at 1/2 throttle, then when i take the peddle to the floor, my car struggled to feel faster, and the rpms just bogged lower. i read this thread about last week hoping for some solution from the guys on the forum, and the next thing i thought was wrong with the car was the coil packs. went to toyota today and asked how much is it for a coil pack for our celicas, and it was about $2oo EACH! $2oo x 4 = death, so i said f* that, and just bought the last MAFS in stock to just give it a shot. came straight home, disconnected my battery, installed the new MAFS, plugged that battery back in and test drove the car. This was probably the best thing i've bought for the car, because not only my CEL is out, but ALL my power is back in business! NO bogging, FULL throttle does feel like full throttle, and when LIFT hit, it felt like the first time hitting lift when i first got the car. So just like the above guys who gave you some input on checking for faulty coil packs FIRST before buying the MAFS, that would be your best bet. honestly, after installing the MAFS, it really does bring back the feeling of the first day of owning this car. i hope this helps, and i hope you get your car fixed. i've been almost 2 years of driving the car with a CEL and that 'sluggish' feeling, and it feels great having the car running back to normal again. also, i even read somewhere on this forum that it should be a MUST to change the MAFS around the 100k mark, because they are prone to wear out. i believe it was 2way or Blue bomber who said that in one of the stickies. i can't remember, but they're right! if you can find another celica buddy and switch out MAFS for a few hours, that can also help you in finding out if it's a bad. again, i hope this helps breh.

[2way]

Originally Posted by jeetee-ess

it should be a MUST to change the MAFS around the 100k mark, because they are prone to wear out. i believe it was 2way or Blue bomber who said that in one of the stickies.

Not I & I think the one you're thinking of is in reference to the Oxygen sensors.

What did you use to clean the MAF with?

[jeetee-ess]

Originally Posted by 2way

Not I & I think the one you're thinking of is in reference to the Oxygen sensors.

What did you use to clean the MAF with?

hmmm, my fault. it was so long ago, but i do remember someone mentioning about changing the MAF because the sensor wears out. and yes, i do believe it was your guidance that helped me out with my O2 sensors awhile back. thanks again man

[stah]

thx jeetee-ess, now I am pretty sure it is MAF. I bought one last week being sure it is denso but it was some aftermarket shite...it did not work at all so I sent it back to the shop. Now awaiting new OEM MAF. I ll have it by Wednesday. So far I replaced cat, lambdas, fuel filter, cleaned injectors, replaced oil with filter and air filter Funny is MAF was my first thought but my mechanic misleaded me big time. He just wanted to make some money on replacing everything else. Good thing is cat was dead anyway so was upstream lambda so it is not that I throw the money away. At last car got propper service and if it is MAF...on Wednesday night Dublin will listen to the scream of my baby when she Lifts thanks once again...I will update on Wed.

[celicalove3]

Were yall's hesitation issues there when the car was cold, or only after it warmed up a little bit?

[GrimIndustries]

I'm having a similar problem as well. Since around April, my car has been down on power and under acceleration, it'll hesitate so severely, it's even dangerous to pull out onto a busy road.

I did a tune up, new plugs, filter, MAF cleaning etc. but the problem kept getting worse.
I've been running the PFC for years, so no CELS. A recently switched back to my stock ECU to try and diagnose the issue. The factory ECU seems to adjusting the some variables, attempting to make up for the problem, whatever it may be. It's running a bit better, but still not right.

I unplugged the MAFS and it ran worse, so I know the MAFS is at least doing something and isn't completely dead.

With the stock ECU in, the hesitation isn't as severe, and is really only severe starting from a stop or at lower speeds. It's noticeably up on power, but when I enter lift, it'll backfire.

I've got 3 drive cycles in since I switched the ECU, so I intend to scan after another 2 cycles and see what codes I'm getting.

[vegeta4ss]

Originally Posted by GrimIndustries

I'm having a similar problem as well. Since around April, my car has been down on power and under acceleration, it'll hesitate so severely, it's even dangerous to pull out onto a busy road.

I did a tune up, new plugs, filter, MAF cleaning etc. but the problem kept getting worse.
I've been running the PFC for years, so no CELS. A recently switched back to my stock ECU to try and diagnose the issue. The factory ECU seems to adjusting the some variables, attempting to make up for the problem, whatever it may be. It's running a bit better, but still not right.

I unplugged the MAFS and it ran worse, so I know the MAFS is at least doing something and isn't completely dead.

With the stock ECU in, the hesitation isn't as severe, and is really only severe starting from a stop or at lower speeds. It's noticeably up on power, but when I enter lift, it'll backfire.

I've got 3 drive cycles in since I switched the ECU, so I intend to scan after another 2 cycles and see what codes I'm getting.

sounds like a bad coilpack or two. Pull the codes and play musical chairs with your coilpack order and see if the problem jumps cylinders. If it does then there's your issue.

[celicalove3]

Originally Posted by GrimIndustries

I'm having a similar problem as well. Since around April, my car has been down on power and under acceleration, it'll hesitate so severely, it's even dangerous to pull out onto a busy road.

I did a tune up, new plugs, filter, MAF cleaning etc. but the problem kept getting worse.
I've been running the PFC for years, so no CELS. A recently switched back to my stock ECU to try and diagnose the issue. The factory ECU seems to adjusting the some variables, attempting to make up for the problem, whatever it may be. It's running a bit better, but still not right.

I unplugged the MAFS and it ran worse, so I know the MAFS is at least doing something and isn't completely dead.

With the stock ECU in, the hesitation isn't as severe, and is really only severe starting from a stop or at lower speeds. It's noticeably up on power, but when I enter lift, it'll backfire.

I've got 3 drive cycles in since I switched the ECU, so I intend to scan after another 2 cycles and see what codes I'm getting.

I have the same problem, but no CEL. I switched out coil packs with another car, and the problem was still there. I'm thinking that it might just be the oil rings in my car though since mine is a GT. Does your problem occur when the engine is cold, warm, or both?

[celicalove3]

Did you decide not to answer my question before or after your engine was warmed up lol?

[stah]

It was MAF in my case. Cleaning was not enough. Brand new fixed the issue.

[silver_Streak]

I was unable to drive(stop and go) replaced my maf sensor with oem new.And now i can drive...However the po171 code is still on and my car hesitates if i mash on the gas pedal (2002 automatic celica)