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Throttle response while cruising

5K views 15 replies 5 participants last post by  kode3020 
#1 ·
I'm having some throttle response issues on my 1994 2dr 4wd manual RAV4.
While cruising on low RPMs, lifting the throttle pedal just ever so slightly seems to cut the throttle entirely. This creates a bumpy ride while trying to keep constant speed.
The throttle seems to go from 20% instantly to 0%. Reapplying throttle produces a similar bump.

Things I've checked:

  • All rear differential bushings have been swapped to new
  • Front engine mount has been changed, rear mount in near future
  • All shocks, springs and suspensions bushings are also new
  • Throttle pedal and cable seem fine


Things Im about to check:
  • Cleaning the throttle body
  • Measuring the TPS -values

Anything else I should look into?
Otherwise the car works great, even after 230k miles on the clock. What a great little clunker!
 
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#2 ·
Hey, I don't know where in the world you are posting from but if you have an OBDII port, read the codes and see what's there if anything. If you don't have an OBDII port, the OBDI diagnostic port under the hood can be used, search the forums and you will find how to read the codes.

It could be on of the following:

Throttle Position Sensor (TPS)
The throttle position sensor (TPS) is linked from the accelerator pedal to the throttle body.
The TPS tells the ECM that the driver is pressing the accelerator pedal. The ECM can also verify this information with the MAP or MAF sensor readings, thus increasing the injector pulse width and spark (ignition) timing.
The TPS is located on the throttle body. Honda has an adjustable TPS sensor and if the initial if your RPM is high and cannot be controlled through the IACV, then the voltage readings of the TPS should be checked. The normal reading for a Honda is close to 0.6V at idle.
I remember playing with the TPS in my friend's car and adjusting his TPS to about 2.5 volts at idle. The result: The became a gas guzzler, consuming about 30 litres of petrol (about 7 gallons) in 30 km (about 18 miles). I guess we learned the hard way.
A newer system for the throttle control came in 2003-2005 and newer models of vehicles, in which a throttle cable is no longer used. A sensor has been placed in the accelerator pedal and the TPS sensor has been replaced with a throttle position motor.
This sensor never requires cleaning. If you do want to clean something on it then just clean the connector points with electrical contact cleaner and a toothbrush. That goes for all the sensors.
Symptoms of a Faulty Throttle Position Sensor
An unexplainable bucking and jerking in the vehicle
Sudden idle surges
Sudden engine stalling without any apparent reason
Hesitation while accelerating
Sudden surges in speed while driving on the highway
Intermittently flashing of check engine light for no apparent reason
Difficulties in changing gears
A drastic drop in fuel economy

BARO/Manifold Absolute Pressure Sensor (MAP) RAV4.1
The baro sensor measures the ambient air pressure, which tells the ECM the current altitude of the vehicle. If you're driving in the mountains you'll need less fuel, because there is less oxygen in the atmosphere and therefore less oxygen in the engine cylinder. The ECM will adjust the fuel injectors "throwing time" or pulse width accordingly.
The map sensor detects the vacuum pressure created inside the intake manifold of the vehicle and sends the engine load information to the ECM. The ECM will adjust the fuel injectors pulse width accordingly.
Note: Baro and MAP sensors look and work in a similar fashion, therefore only one of the two sensors will be found in one engine.
Usually found either bolted on the intake manifold or linked with a vacuum pipe from the intake manifold.
If mounted on intake manifold then should be cleaned every 6 months to 1 year, using carb cleaner (depends on fuel quality where you live; the lower the quality of fuel, the more carbon deposits found). I've had to clean some every three months.
Symptoms of a Faulty Manifold Pressure Sensor
A faulty manifold pressure sensor has symptoms that closely resemble a vehicle with injector problems or low compression problems. Here are some of the most common symptoms associated with a faulty manifold pressure sensor:
A rich or lean fuel mixture. You may notice a gas smell after the engine has warmed up. The engine will knock or ping at times for no apparent reason
Excessive fuel consumption
A rough idle
Hesitation or slight jerking during acceleration, or when putting the vehicle into drive
The vehicle stalls or dies immediately after you try to give the engine gas to start the car moving

Camshaft Position Sensor (CMP)
The camshaft position sensor (CMP) is electromagnetic and produces a voltage when a metal object moves past. This sensor is responsible for telling the ECM the current position of the camshaft. With this information the ECM can calculate which valve is open and throw fuel through the injector into that cylinder.
This sensor is found on one end of the camshaft, usually on the right side in a front wheel drive car. It's normally not very difficult to access.
Cleaning can be done with a simple dry cloth, but if the oil has been used for too long, a golden-brown stain is left on metal portion of the sensor. In some cases it even comes out black and gooey, which is basically old engine oil turned into sludge. if it's stained then you can use a wire-brush or very fine sandpaper to remove the stain. Make sure no metal bits remain on the sensor. If you need some liquid type material to get some stains off, try WD-40.
Failing camshaft position sensor (CMP sensor) can produce a confusing range of problems, depending on the way it fails and the model of the car:
On some vehicles, a failing camshaft sensor may lock the transmission in a single gear until you turn off and restart the engine. This cycle may repeat intermittently.
If the sensor begins to fail while your car is moving, you may feel the car jerking while losing power.
You may experience a noticeable loss of engine power. For example, the engine can't accelerate above 35mph.
The engine may stall intermittently.
You may notice poor engine performance including irregular acceleration, misfiring, hard starting, or surging.
On some car models, a failed CMP sensor will prevent the ignition from making a spark, so that the engine won't start at all, not usually applicable to the RAV4.1.

See this thread for more information on diagnostics for each sensor, Camshaft Position Sensor (CMP)
The camshaft position sensor (CMP) is electromagnetic and produces a voltage when a metal object moves past. This sensor is responsible for telling the ECM the current position of the camshaft. With this information the ECM can calculate which valve is open and throw fuel through the injector into that cylinder.
This sensor is found on one end of the camshaft, usually on the right side in a front wheel drive car. It's normally not very difficult to access.
Cleaning can be done with a simple dry cloth, but if the oil has been used for too long, a golden-brown stain is left on metal portion of the sensor. In some cases it even comes out black and gooey, which is basically old engine oil turned into sludge. if it's stained then you can use a wire-brush or very fine sandpaper to remove the stain. Make sure no metal bits remain on the sensor. If you need some liquid type material to get some stains off, try WD-40.
Failing camshaft position sensor (CMP sensor) can produce a confusing range of problems, depending on the way it fails and the model of the car:
On some vehicles, a failing camshaft sensor may lock the transmission in a single gear until you turn off and restart the engine. This cycle may repeat intermittently.
If the sensor begins to fail while your car is moving, you may feel the car jerking while losing power.
You may experience a noticeable loss of engine power. For example, the engine can't accelerate above 35mph.
The engine may stall intermittently.
You may notice poor engine performance including irregular acceleration, misfiring, hard starting, or surging.
On some car models, a failed CMP sensor will prevent the ignition from making a spark, so that the engine won't start at all, not usually applicable to the RAV4.1.

See this thread for more information on diagnostics for each sensor, https://www.rav4world.com/forums/83-4-1-general/291247-sensors-their-descriptions-symptoms.html
 
#4 ·
Hey, I don't know where in the world you are posting from but if you have an OBDII port, read the codes and see what's there if anything. If you don't have an OBDII port, the OBDI diagnostic port under the hood can be used, search the forums and you will find how to read the codes.
Thank you for great RAV4 specific info! These symptoms would point out mostly to TPS, so this is the first thing I'm going to focus.
Went through the whole sensor description list as well, good stuff for the future.

I'm in Finland, so no OBD II in these year models yet. I will check the OBD I and report back here for future reference.



How in the world do you have a "1994" RAV4!? Perhaps a way of asking "Where are you?" Spotted my first RAV4 at its debut in Panama, while I was in Panama, 1995.
Thanks for the additional info on throttle body cleaning. That's definitely something I should do, even disregarding the issue.

You got me on the year model. Rechecked and the car is registered 03/1995, so most likely a 95 year model as well.
The shorties were never sold here in Finland, so most of them are imports from Germany. This one was most likely brought from Russia in 2004, as the import-company was near eastern border.
2-door RAV4.1s and Pajero Pinins are in great demand here especially among hunters and reindeer herders. Usually these go for $4000 and above because of the rarity.

This is how I got mine. Almost completely repaired now. Will do a proper writeup once it's done!
 
#3 ·
How in the world do you have a "1994" RAV4!? Perhaps a way of asking "Where are you?" Spotted my first RAV4 at its debut in Panama, while I was in Panama, 1995.

Your idea to clean Throttle Body, spot on. Excellent results for quick 15-min. investment. Old toothbrush & rags. Also clean PVC Valve-- remove & shake it up & down, it should "rattle." If not, it's clogged. Clean or buy new OEM. They're cheap. Do both, expect wonderful results. Eliminated my '98 RAV4 "hesitation" & improved (i.e., cut down) cranking/starting time. (Correct me if I'm wrong-- I don't believe you have a MAF Sensor):

 
#6 ·
The driver hit a laying moose on the road (that had been crashed into a moment before) around 80km/h. The RAV fell down on its side and slid for 100 meters.
Everyone was unharmed, except the moose of course. :(

Had to change all the panels and the front right steering knuckle. Lucked out on the parts as those are very rare here as well.
It now has a complete rally spec roll cage, so strength vice the body should be better than ever.
 
#7 ·
If your RAV4 has O2 sensors, the upstream one (the one on the exhaust manifold) quit working and my RAV4 was "stumbling" and running rough as you described and it ran fine once the sensor was replaced. I forgot about it until tonight.
 
#8 ·
Hello. I was just wondering if you found a solution? I followed the info from eodgator and believe it's my TPS. How do I know what position it should be adjusted to? Since the weather changed from cool dryish to hot and humid, it has those symptoms. It's temporary relieved if I run it without the sensor plugged in.
 
#11 ·
OBDII was required for 1995 on. Does this ''1994'' RAV4 have an OBDII diagnostic port?
 
#12 ·
Don't forget that OBDII ports are mostly on cars made or sold in America, however for whatever reason most cars sold in other countries don't have OBDII ports.

The 1994 RAV4 was not sold in America, so that and the date made would probably preclude them from have an OBDII port.

Fun to know tidbits.
 
#14 ·
Good to know I didn't know that the OBDII port is a required standard in the UK from 2000 on.

I found this information about the implementation of OBDII:

OBD-II
OBD-II is an improvement over OBD-I in both capability and standardization. The OBD-II standard specifies the type of diagnostic connector and its pinout, the electrical signalling protocols available, and the messaging format. It also provides a candidate list of vehicle parameters to monitor along with how to encode the data for each. There is a pin in the connector that provides power for the scan tool from the vehicle battery, which eliminates the need to connect a scan tool to a power source separately. However, some technicians might still connect the scan tool to an auxiliary power source to protect data in the unusual event that a vehicle experiences a loss of electrical power due to a malfunction. Finally, the OBD-II standard provides list of standardized DTCs. As a result of this standardization, a single device can query the on-board computer(s) for these parameters in any vehicle. OBD-II standardization was prompted to simplify diagnosis of increasingly complicated emissions equipment, and though only emission-related codes and data are required to be transmitted through it according to U.S. legislation, most manufacturers have made the OBD-II Data Link Connector the main connector in the vehicle through which all systems are diagnosed and reprogrammed. OBD-II Diagnostic Trouble Codes are 4-digit, preceded by a letter: P for engine and transmission (powertrain), B for body, C for chassis, and U for network. Manufacturers may also add custom data parameters to their specific OBD-II implementation, including real-time data requests as well as trouble codes.

EOBD
The EOBD (European on board diagnostics) regulations are the European equivalent of OBD-II, and apply to all passenger cars of category M1 (with no more than 8 passenger seats and a Gross Vehicle Weight rating of 2500 kg or less) first registered within EU member states since 1 January 2001 for petrol (gasoline) engined cars and since 1 January 2004 for diesel engined cars.[22]

For newly introduced models, the regulation dates applied a year earlier – 1 January 2000 for petrol and 1 January 2003 for diesel. For passenger cars with a Gross Vehicle Weight rating of greater than 2500 kg and for light commercial vehicles, the regulation dates applied from 1 January 2002 for petrol models, and 1 January 2007 for diesel models.

The technical implementation of EOBD is essentially the same as OBD-II, with the same SAE J1962 diagnostic link connector and signal protocols being used.

In 2017, all previous standards were revoked because there were more than 24 standards produced over 35 years. The new document supplanted all previous versions.

JOBD
JOBD is a version of OBD-II for vehicles sold in Japan. (This all I can find on it, no other information like dates implemented, etc. I did find that you need a scan tool designed to work with the JOBD protocols.)

ADR 79/01 & 79/02 (Australian OBD standard)
The ADR 79/01 vehicle standard (Australian Design Rule 79/01 – Emission Control for Light Vehicles, 2005) is the Australian equivalent of OBD-II. It applies to all vehicles of category M1 and N1 with a gross Vehicle Weight rating of 3500 kg or less, registered from new within Australia and produced since 1 January 2006 for petrol (gasoline) engined cars and since 1 January 2007 for diesel engined cars.[25] For newly introduced models, the regulation dates applied a year earlier – 1 January 2005 for petrol and January 2006 for diesel. The ADR 79/01 standard was supplemented by the ADR 79/02 standard which imposed tighter emissions restrictions, applicable to all vehicles of class M1 and N1 with a gross vehicle weight rating of 3500 kg or less, from 1 July 2008 for new models, 1 July 2010 for all models.[26] The technical implementation of this standard is essentially the same as OBD-II, with the same SAE J1962 diagnostic link connector and signal protocols being used.

Ref: https://en.wikipedia.org/wiki/On-board_diagnostics#OBD-II

I thought this might be helpful for all of when discussing diagnostics with people from all over the world.
 
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