Hesitation and pulsing throttle

2001 TOYOTA COROLLA
134,000 MILES • 4 CYL • FWD • AUTOMATIC
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HADENUFAGIN
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Experiencing severe hesitation when starting up from a stop and when accelerating while at lower speed. When engine is cold hesitation is minimal but as soon as engine reaches normal operating temperature. hesitation is always so bad that I have to be careful pulling into traffic to avoid getting rear-ended. Engine never stalls completely and will eventually get going as long as you are patient and feather the throttle. Once hesitation is overcome and car begins to accelerate, acceleration is always in pulses. Even going up-hill with a steady foot on throttle just to maintain speed, acceleration is pulsing.

Have checked or recently replaced the following:
new MAF, new TPS, new fuel injectors, fuel pressure checked,good, new PCV. Engine new temperature sensor. Fuel rail was just replaced because of leaking pulsation dampener. New plugs, Denso OEM, throttle body cleaned.

No MIL or codes present.

Just recently noticed that if I stop and turn off car for short time (five to ten minutes), that when I start going again car runs like new (no hesitation or pulses) for a few miles but then symptoms quickly return.

Any thoughts as to what is causing these problems would be greatly appreciated!
Apr 28, 2010 at 3:27 PM
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HADENUFAGIN
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Hello,

I usually do not post on forums, but I saw this problem and wanted to tell you I had the same problem and it ended up being the PCM. I got a used one and plugged it in cost me $120.00 all fixed.
Apr 28, 2010 at 7:23 PM
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RASMATAZ
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I have seen this issue as well and I had to replace the the camshaft actuator valve. Here is the location.
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Apr 29, 2010 at 12:11 AM
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ROBBON60
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Auto appears to be fuel starved at takeoff. Had several mechanics look at it but none has come up with remedy. Replaced plugs and oxygen sensor, no help. Auto now seems to stumble when accelerator is pressed at higher speeds and does not seem to shift correctly. Car runs great at highway speeds and does not use oil and still gets terrific mileage. Problem seems to be getting worse and it is hard to start at times.
Jun 13, 2018 at 4:52 PM (Merged)
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RASMATAZ
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Possible Causes of Engine Hesitation or Stumble:

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor.
Bad TPS (throttle position) sensor.
Bad or dirty MAF (mass airflow) sensor.
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump).
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve).
Bad gasoline (fuel contaminated with water or too much alcohol).

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Jun 13, 2018 at 4:52 PM (Merged)
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CCROSS
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Rough idle on initial start up in the morning, then clears up, then hesitates slightly on acceleration from a complete stop after that.

I have changed coil packs, spark plugs, MAF and O2 (upstream) sensors, and added a fuel injector cleaner.

Still have idle and hesitation problems. Help!
Jun 13, 2018 at 4:52 PM (Merged)
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ASEMASTER6371
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I think you are on the right track with injectors. You need them professionally clean, not by an additive. clean the throttle body as well.

Another issue with Toyota's was carbon build up on the intake valves. A top engine cleaner done by a shop can be done to see if it helps. In a lot of cases, removal of the head and a valve job was the answer as carbon absorbs fuel cold and after it warms up, it will run okay.

Get a shop to verify this for you.

Roy
Jun 13, 2018 at 4:52 PM (Merged)
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KHLOW2008
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Any trouble codes?
Jun 13, 2018 at 4:52 PM (Merged)
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CCROSS
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P0300.

And it "consumes" oil (no leaks that I could find).

Thanks for the help!
Jun 13, 2018 at 4:52 PM (Merged)
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KHLOW2008
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Multiple misfires. Check the engine compression and valve clearances apart from what Roy had recommended.

Oil consumption would often create a lot of carbon deposits if the intake valve seals are bad.
Jun 13, 2018 at 4:52 PM (Merged)
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WILLNSUSIE
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My car hesitates when I accelerate. Sometimes it will even shut off. What would cause this?
Jun 13, 2018 at 4:52 PM (Merged)
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KHLOW2008
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Hi willnsusie,

Basics are the spark plugs and wires.
Jun 13, 2018 at 4:52 PM (Merged)
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CCROSS
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Will do. Thanks again!
Jun 13, 2018 at 4:52 PM (Merged)
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JIM MADDALON
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My car was stumbling on acceleration to the point it was dangerous to pull into traffic from a stop. I replaced numerous things after looking for answers on computer, almost by accident I discovered the cure, it turns out Toyota's have a positive cable battery mount with wires connected via a wingnut. It turned out there was so much rust and corrosion on the terminal ends that it was affecting the ECM's ability to function properly. After cleaning thoroughly and sanding contacts I have driven four hundred miles this month with not one time the car stumbling or missing it runs like a new car. So check you positive and negative battery connections before spending any money on things that most likely will not solve your problem. Hope this helps some people.
Jun 13, 2018 at 4:53 PM (Merged)
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STRAILER
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Great fix! Please feel free to help out whenever you are on the site. :)

Cheers, Ken
Jun 13, 2018 at 4:53 PM (Merged)
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COURTAU
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About three months ago I noticed my car having a harder time getting up steep inclines. Now the car will crank then shake and cut off. It has done the same thing when idling at a red light for an extended time twice. It hesitates the worst when I am going less than thirty mph and then accelerating, ie; merging onto a street. Not as bad on highway going fifty five mph or more, still feels like driving in quicksand. Check engine light has been on. Codes said running too lean and random cylinder misfire. I have used octane booster, fuel injection cleaner, replaced spark plugs and cleaned maf sensor. Two mechanics have said "I do not know" what is wrong. Help! (138,000 miles four cylinder automatic)
Jun 13, 2018 at 4:53 PM (Merged)
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RASMATAZ
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It sounds like you are experiencing a major false air leakage and bad fuel.

Could also have the exhaust system check for restriction.
Jun 13, 2018 at 4:53 PM (Merged)
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LEPERCHRON
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Hello, whenever my car comes from stop or parked position it starts to cut out or chug along at times that I have to stomp on the pedal for it to move. I scanned it and it threw a code for p0125a and p0135b. Could this be my problem or is it completely different? I appreciate this a lot.
Jun 13, 2018 at 4:53 PM (Merged)
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MMPRINCE4000
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I do not see the "A" on these codes in my library, but a p0125 indicates the coolant is not reaching operating temperature for closed loop control.

In other words, if coolant does not get hot enough (usually thermostat), then PCM will not take control of fuel air mixture, and car will run rich.
Jun 13, 2018 at 4:53 PM (Merged)
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MMPRINCE4000
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So, I would change thermostat.

You could also have PCM scanned in live data and look at coolant temperature. PCM is seeing, If low, it is either thermostat or temperature sensor.
Jun 13, 2018 at 4:53 PM (Merged)
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LEPERCHRON
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What about it cutting out or chugging along and the other code?
Jun 13, 2018 at 4:53 PM (Merged)
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MMPRINCE4000
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Other code is O2 sensor, but if not going into closed loop control, it will run rich and chug.

If this has been going on for a long time, the catalytic converter may be clogged or partially clogged.
Jun 13, 2018 at 4:53 PM (Merged)
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LEPERCHRON
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It starts to stumble more after I have replaced the o2, also replaced the MAF sensor with refurbished one. Also, went down a street going sixty mph let off the pedal and it felt like about max twenty km when it said about forty to fifty km. Thanks.
Jun 13, 2018 at 4:53 PM (Merged)