Engine fault (not 350z)

[Jetpilot]

Maybe some engine gurus might be able to add some thought.

 

I have a daily Toyota Bb, its basically a 1.5vvti Yaris engine.

 

When pulling away its flat as a pancake mostly until the revs rise, on occasion its fine on other occasions its somewhere in between. I am guessing or presuming the timing is being retarded. It is not running rough or hesitating, just varying degrees of flatness, on brief occasions its fine.

 

I have checked and swapped the obvious maf sensor, no change, fuelling via lamda checked, all fine, plugs changed, even ran without an exhaust to check for blocked cat/ehaust, no change.

 

Apart from ecu, what sensors on a car would send a signal of varying degrees to the ecu to retard the ignition?

 

Or could it be vvti at fault.

 

P.s No engine light and no codes.

[Tricky-Ricky]

Most sensor faults will throw a CEL, if timing is being retarded I would expect a crank or cam sensor to be faulty, are you sure its ignition timing, and not the VVTI solenoid playing up?

could also be worth checking the fuel pump.

[Jetpilot]

Sorry should have added, swapped the vvti solenoid for a new one and fuel pressure checked out fine.

 

I have pretty much gone through everything at my mates garage.

 

Bar just swapping sensors i am lost. The only reason i made the assumption of timing is the varying degrees to which it does or doesnt want to perform, i.e its not just good or bad, it can be anything in between.

Edited October 26, 2014 by Jetpilot

[350zedd]

A knock sensor would retard the ignition if it senses detonation

[Jetpilot]

A knock sensor would retard the ignition if it senses detonation

 

I did think of this, would it send a varying signal though, if it detected knocking (which the car isnt), would it say, ah its not so bad retard the ignition by x amount or simply just send a signal to the ecu to say its detecting knock, retard the ignition?

[Tricky-Ricky]

The reason I didn't mention knock being detected is that this does throw a CEL on most modern engines, its not usually a full time condition, IE if you put a low grade petrol (although it should run on it fine as the ECU uses live monitoring unlike older ECUs so it can adjust timing to suite, rather than retard it and leave it there until no further knock is detected, if the sensor is duff it should retard the timing full time and throw a CEL.

[Jetpilot]

This is the pain of it all, no cel light so no fault code, so just trying to put myself in the right ballpark to start the process of elimination.

 

The only thing that throws a spanner in the works for me is the vvti as i presume if this isnt functioning correctly it could give these symptoms?

 

It does also appear worse under load, i.e i am climbing a hill from slow speeds or pull out onto a gradient, or the lack of power is just amplified because of the gradient.

 

Thanks for your thoughts gents, where would you start if you were in my position, sadly cant test the timing as its integrated coil/plugs.

[Tricky-Ricky]

 

Thanks for your thoughts gents, where would you start if you were in my position, sadly cant test the timing as its integrated coil/plugs.

 

This was my next input, no familiar with these engines in particular, but how is the timing controlled via the coil packs, surly the ECU timing map does this? I was going to suggest a coil pack breaking down under load, although it should result in a misfire,

I would still test or substitute cam and crank angle sensors as this could have a big impact, and effect the function of the VVTI system.

[Jetpilot]

Thanks for your thoughts gents, where would you start if you were in my position, sadly cant test the timing as its integrated coil/plugs.

 

This was my next input, no familiar with these engines in particular, but how is the timing controlled via the coil packs, surly the ECU timing map does this? I was going to suggest a coil pack breaking down under load, although it should result in a misfire,

I would still test or substitute cam and crank angle sensors as this could have a big impact, and effect the function of the VVTI system.

 

Ok thanks, going to try and source an ecu from a breaker just to eliminate that, wont hurt to have a spare. Then move onto your suggestion and start eliminating sensors, if its none of these, guess its the vvti itself and sadly the most costly, it may just be gummed up as by all accounts this can happen and restrict the movement.

 

Problem is i cant even get any live data as its just too old to test.

[350zedd]

I was thinking coil packs breaking down myself ....might be worth a check in the dark for any tracking to earth.

Link for checking crank & cam sensors ...http://easyautodiagnostics.com/misc-index/ckp-cmp-sensor-basics-1

[Jetpilot]

I was thinking coil packs breaking down myself ....might be worth a check in the dark for any tracking to earth.

Link for checking crank & cam sensors ...http://easyautodiagnostics.com/misc-index/ckp-cmp-sensor-basics-1

 

Thanks for the link, i really dont think its coils as in essence its as smooth as, no misfire, no hesitation, just flat, like its stuffed full of cotton wool and cant breathe, when it does occasionally work it runs the same, but feels crisp and responsive, as much as 1.5 can be

[Ricey]

It's got a failing sensor of some description written all over it.

[Ekona]

Is the CEL actually working?

[Jetpilot]

Yes, I have pulled a couple of items, maf being one and threw a cel and appropriate code straight away.

[Tim BW]

Hope you can get it sorted.

[a2orry]

Readings between cam and crank sensors outwith specified limits .timing chain wear causes this.