Cleaning Throttle Body

[BigMo82]

Does anyone know if a faulty intake manifold gasket can cause slightly low pressure in a cylinder?

Mo

[frankie406]

google toyota air intake manifold.there is some info on that. there same sort of issues as yours mo.

but its mainly the 03-08 corolla 1zzfe engines.but you could try that too mo?

[BigMo82]

Thanks for the reply Frank, I googled it last night and like you say the issues are mainly on the corolla which is much easier to work on as the manifold is on the front of the engine where as on the avensis it's on the rear so the access may be an issue.

I went with my dad earlier to his mechanic to pick up his car and the mechanic had a quick listen to mine. According to his info the idle should be 675 +50 and as is always the case it sat there for about 20 minutes and didn't really drop below 675. I drove off and 5 minutes later it was back down to just under 600.

I called Toyota who said they would charge £111 plus VAT for a diagnostics check but considering there are no fault codes I'm not sure what there going to find.

I also spoke to Derek at Tech One who is a Toyota specialist and he said he could give it a check over for an hour for around £60 which sounds reasonable.

Mo

[frankie406]

yeah mo sounds a bit steep at toyota! go with the specialist he might be a better choice and probally not fob u off with thousands in parts! good luck!

[Druid Boy]

Mo, go to Derek, ask him to do no more than an hour without asking for your permission. Bet he solves it pronto.

[BigMo82]

I hope so mate. If I could get the idle sorted it would be a major result.

Mo

[BigMo82]

Just dropped it off, lets hope for a positive outcome. Will know in a few hours..... hopefully!

[BigMo82]

Ok just got back from Sidcup. Derek was a friendly guy and very professional. He checked for a vacuum leak with a smoke machine and found 2 small leaks which he resolved with jubilee clips. He also checked the electrical input for the throttle body to be sure the signal from the ecu is constant and not fluctuating. He checked a few other things using the computer and said they all seemed fine. He finally said that the only other thing he can think is that there could be a problem with one of the ignition coils or the software for the ecu may need updating. Still at a loss as to what is causing this.... The search goes on. Thanks again guys for all your input.

[Druid Boy]

This is so weird. Remind me, did this start after the throttle body was cleaned? If so surely it has to be related to that work? Otherwise if its something else its one heck of a coincidence that it started after that.

[BigMo82]

It was always an issue but it was intermittent. It's become a lot more obvious since then. Saying that as the weather was still fairly cold it would remain on cold start a lot longer so maybe that was disguising the problem.

I will speak to Mr T tomorrow regarding a ecu software update. Thanks for the reply DB.

Mo

[Vlado P.]

i must admit i'm not very familiar with car electronics although i'm pretty savvy computer-wise.

what i don't understand is how a software which worked correctly when the car rolled out of the factory, can suddenly start to cause problems? it could happen because of some memory leaks, program errors etc, but this should be remedied by clearing the memory (i.e. Battery removal). once the memory is cleared, it is as if you have done a computer restart. there are no "car viruses" that could corrupt the software, there are no values that the ordinary user can alter, leading to erroneous behavior.

ecu software update might be required if you install some newer sensors or modules, which won't work properly with the ecu software because of version mismatch; because of functions not present in previous software versions etc. sometimes software updates eliminate bugs, but more often introduce new ones.

other than this, when a garage suggest that software update is required it is because they have no idea what is causing the problem and are looking for ways to rip you off. lets face it, how can anybody (without special diagnostic tools) tell if a software update has really been performed?

[BigMo82]

I agree Vlado but I calling Toyota isn't going to cost me anything. The mechanic did also mention the ignition coils can cause this problem too.

Mo

[+robster+]

in regards to vlados 2nd paragraph above

its the input sensors (tps etc.)that start to fail causing intermittent or poor feedback to the ecu. as a computer savvy guy you will understand GIGO .

as for certain folk not able to find thier icv

fully electronic throttle bodys have the ability to regulate thier own idle throttle angle

there are variations but imainly work with the Bosch type and it has a big plug on it that feeds the output from ecu side to move butterfly and other pins give an input to ecu of throttle angle etc.

the ecus i work on have thier own set maps and the throttle bodys are plug and play as there are no servicable parts or adjustments. i.e self calibrating by the ecu looking for rpm. coolant temp. air flow lambda alpha learn blah blah blah.

the cable type throttle needs a seperate icv as it would be daft ( and poor engine braking)for the idle to sit high to stop it stalling or you sitting with partial foot on the pedal to stop stalling at junctions etc this is where the wonderfull solenoid type discreet icv works very well at bleeding air past the shut butterfly to keep a nice setpoint idle not really noticable to the everyday motorist and doesnt get enough credit.

tps usually adjustable potentiometer with the 2 screws on slotted retainer on throttle type with that era of control software

values for setupin signal output voltage or resistance usually found in haynes or autodata etc

lastly

how is your temp gauge

id hate a stuck open or missing thermostat to be giving you the runaround.

on the theory it takes ages to warm up to proper temp .

then when it does the fuelling goes out of open to closed loop giving you an indication of lambda or similar problem.

or i hate to say it

when cooling fan kicks in the load on the alternator dips the revs a bit till it turns off again and the revs rise a bit

[Vlado P.]

"its the input sensors (tps etc.)that start to fail causing intermittent or poor feedback to the ecu. as a computer savvy guy you will understand GIGO."

agreed! but this is in no way software's fault. poor sensor input can only be corrected by replacing/repairing the sensor. software re-installation will not solve this problem.

regarding the new TBs that you mentioned. does this mean that we can remove and clean the TB without need for manual recalibration afterwards? i can't locate the TPS as well so it's probably fully electronic!

[BigMo82]

If only it had a TPS it would make things so much easier.

Mo

[BigMo82]

Hi Robster and thanks for the detailed reply mate. I was told that the mechanic checked the thermostat and temperature sensor. And in all fairness the car does warm up reasonably quickly.

Regarding the fan, yes when the fan kicks in the revs normally drop by about 50rpm. However even when it's not kicked in the car is usually around 620-650 rpm and the fan pulls it down to 580-600ish.

A part of me thinks it is still an issue with the throttle body itself but I am hesitant to buy yet another.

Mo

[+robster+]

"its the input sensors (tps etc.)that start to fail causing intermittent or poor feedback to the ecu. as a computer savvy guy you will understand GIGO."

agreed! but this is in no way software's fault. poor sensor input can only be corrected by replacing/repairing the sensor. software re-installation will not solve this problem.

regarding the new TBs that you mentioned. does this mean that we can remove and clean the TB without need for manual recalibration afterwards? i can't locate the TPS as well so it's probably fully electronic!

you kinda answered what i said sorry i skimmed over the post as it was a long 9 page read lol

cant speak for the denso ecu but bespoke control systems i work on you can remove and reinsert throttle body as they are set up without any adjustments available and the ecu is programmed to know how these values.

the ecu programming has a margin for error to allow wear and tear drift of sensors

this is a reason for software updates to lessen or largen this margin ( amongst other things)as the manufacturer sees fit if they have have had a spate of errors due to a "too sensitive trigger" or safety issues due to a not sensitive enough trigger.

other software updates can be due to recalls changing a part that usually fails with a part from another supplier and the parameters need to be changed to match the values of the new part.

all ecus are different and i suspect some to have a calibration mode in the vehicle software to dial in the setpoints

i have had parameters change (usually due to static or spikes) on my software systems but i can save .par files

manually go in and change parameters back to suit or default the whole system.

the parameters stay changed on the eeprom,s no matter haw long the Battery is disconnected.

probably due to backup batteries or capacitors in the pcbs to hold memory just like the clock Battery on a laptop motherboard.

i digress so back on topic.

i guess a lambda is failing as the symptoms sound familiar but its only a guess.

it would be good to have a look at vehicle manual

[BigMo82]

Bank 2 has had both its sensors replaced. I guess I could check bank 1.

Any ideas in the best way to check ignition coils?

Mo

[+robster+]

below is a copy and paste of a note i copied somewhere regarding ignition coils.

its just a general guide.

Test an ignition coil at home to narrow down the culprits behind its problems. Ignition coils have gone through a myriad of transitions over the years as to size, location, form and accessibility. They all have one thing in common: internal structure and function. They differ in resistance readings due to temperature and amount of coil windings relative to output voltage. For this reason, these methods will be for the determination of functionality in real time as to a failure of the unit.
For intermittent faults, a service manual will be needed for the particular engine. The service manual will give the maximum voltage output, ohm readings for internal resistance and the method and location of the proper terminals with which to access the positive and negative terminals for the coil.
There is one common factor in all coils: They all need to have power to the positive Battery terminal, a negative terminal and a coil tower or output terminal. The negative terminal can be controlled by a computer and ignition control module, an ignition igniter or a hall effect sensor and control module. These also have one thing in common: They must ground the system each time the coil is to be fired, causing oscillations which can be witnessed on a voltmeter or scope.
Disconnect one of the easiest spark plug wires to reach and push an extra spark plug in the wire end. Lay the plug on a good ground on the engine. If the engine uses a coil on plug arrangement, remove the two 10mm bolts securing the coil to the valve cover and pull the coil up and off the plug. Install a spark plug and lay it on a good ground.
Start the engine and observe the spark at the plug's electrode. If the spark is weak, inconsistent or nonexistent, shut the engine off.
Check the coil for power at the positive terminal. Turn the key on with the engine off. If the coil is exposed, check the positive terminal with a voltmeter. There should be Battery voltage on this terminal. If the coil has an electrical connector or sits on an ignition control module, disconnect the electrical connector and check the terminals for Battery voltage. If there is no voltage, check the fuse for the ignition. If there is battery voltage, shut the ignition key off.
Check the negative terminal for fluctuations on the voltmeter indicating that the computer, ignition control module or igniter is functioning. If the voltmeter shows a rapid rise and fall in voltage, the coil is faulty. If this is not observed, there is a problem elsewhere, either in one of the above control devices or connectors.
A good way to search for intermittent coil misfires is to connect an inline spark plug light. This is a tool that consists of a light that is connected between the spark plug wire or end and the spark plug. As the engine runs the light can be observed blinking with every spark plug firing. A miss can be easily seen by a break in the frequency. This way, the miss can be contributed to the coil or ignition. If all the plugs are checked and no break in frequency is observed, the misfire is other than ignition. These ignition tester lights can be purchased at any auto parts and are very inexpensive. They are a great tool for expediency.
To confirm the failure of the coil as opposed to a bad connector or wiring, a service manual will be needed to get the proper resistance factors for the particular coil voltage and temperature conversions.
Test the coil with an ohmmeter by connecting one lead to the battery+ and one to the negative terminal. There should be very little resistance. On standard coils, there should be about .02-.025 ohms. Remember these resistances are very close but approximate. These approximations are going to be close enough that if the readings are far distant from these, the service manual won't be needed--the coil is bad. Now take one of the leads from the ohmmeter and touch the primary terminal in the coil tower. The reading from either the positive or negative terminal to the coil tower should be from 7,500 ohms to 18,000 ohms.

[BigMo82]

Thanks again for the reply mate.

Mo

[BigMo82]

Tested the coils using a ignition coil tester and they all seem to be working. Not sure if the problem only occurs once they heat up.

Mo

[ulflun]

On 6/3/2013 at 1:11 PM, BigMo82 said:

Tested the coils using a ignition coil tester and they all seem to be working. Not sure if the problem only occurs once they heat up.

Mo

Sorry for waking the thread up after these years, but did you ever solve this issue and what was the culprit? Thanks