Avensis Problem With Revs

[bobinog]

Hope someone can help. I have a 1.8 vvti petrol engine avensis. Recently while on the motorway, I noticed, i couldnt go any faster than about 70 mph, i had my foot to the floor in 4th gear, but the revs wouldn't go more than 3000 rpm. This is now a permanent problem, in neutral the revs will easily go to 5000 rpm, but in gear, it struggles to top 3000.

2 months ago i cleaned the MAF and the EGR , so they aren't the problem.

Any ideas ?

Bob

[fastbob72]

I'm. not sure what year yoy have but the 1.8 vvti doesn't have EGR because of it's ability to alter the valve overlap in response to engine speed/load/throttle pos etc. It allows exhaust gases to enter the comb chamber by the valve timing rather than feeding it back from the exhaust system into the inlet as with EGR.

Has it thrown up an error code as I would expect something as dramatic as that to have triggered a fault code of some kind. Perhaps it's only pending ao far, without any more information it's hard to suggest anything right now.

It's almost as if the knock sensor is retarding the ignition but I can't imagine why.

Are you sure the engine check light isn't coming on, sounds strange thatbit wouldn't??

[bobinog]

^{There is no engine fault code, but the fault has developed. Firstly the engine has been burning oil for months which i put down to worn piston rings.}

^{In the space of a week the performance has steadily deteriorated. the revs have been getting lower, and so has the speed. It really struggled uphill, then picked up a little on the flat. Yesterday, it was so bad i couldn't do more than 5mph. Needless to say it's now off road, and I suspect compression loss problem.}

^{I'm not losing coolant so I don't think the head gasket has gone. I am now contemplating an engine strip down.}

[fastbob72]

That's a serious loss of compression for sure.... if the rings are that worn you would expect to hear some piston slap when the engine id running........ an engine strip. down and rebuild would certainly tell you if that is the cause of the problem or another symptom.

[alan333]

If the compression is that low surely it wouldn't start?

[Konrad C]

^{There is no engine fault code, but the fault has developed. Firstly the engine has been burning oil for months which i put down to worn piston rings.}

^{In the space of a week the performance has steadily deteriorated. the revs have been getting lower, and so has the speed. It really struggled uphill, then picked up a little on the flat. Yesterday, it was so bad i couldn't do more than 5mph. Needless to say it's now off road, and I suspect compression loss problem.}

^{I'm not losing coolant so I don't think the head gasket has gone. I am now contemplating an engine strip down.}

That's a serious loss of compression for sure.... if the rings are that worn you would expect to hear some piston slap when the engine id running........ an engine strip. down and rebuild would certainly tell you if that is the cause of the problem or another symptom.

If the compression is that low surely it wouldn't start?

Bob, FastBob and Alan have a point about the compression.

You suspect compression, so will you do a compression test before stripping the engine?

There could be another issue like a blocked or collapsed pre-cat, failed vvti actuator, fuel starvation under load, maf sensor.

I thought that if the piston rings are worn, what about the cylinder bores? I thought that the bores are lined in a special material that cannot be machined!

Lets hope it is something not to difficult or expensive.

[bobinog]

So I have carried out the compression test and it seems ok. I got 185 psi on cylinders 1 and 4, and 165 psi on cylinders 2 and 3. All within the Toyota spec of between 145 and 190 psi . I did notice oil on the spark plugs as I took them out, so that probably accounts for burning excessive oil. Still no engine fault codes apart from what you would expect after a compression test. The engine still won't rev above 3000 rpm so I'm looking at other faults. It's been suggested a blocked cat, or a faulty crankshaft sensor,so I'll check them next. Any thoughts welcome.

Thanks Bob