The intermittent cranking no start Yaris VVTi mystery continues. FASTTEC used.

[YarisVVTi2002]

This intermittent Cranking No Start problem has been going on for years in my 2002 Toyota Yaris 1.3 VVTi Auto. The cause of the problem was never identified. You can read up on the history here:

The Yaris has been laid up not working since last year unused. About a month ago it started on the first attempt this year and was running fine. I took it for an MOT and it passed without problems. I was using it every day on short journeys and it started easily. The Yaris was parked up for a week fully working and when I got back to it and tried to start it the old Cranking No Start problem returned. 

I have already previously done lots of checks on the Yaris which failed to find the cause of the problem. So I thought a new approach would be more successful. The most comprehensive method of testing I've found is FASTTEC, which is described here: https://www.youtube.com/watch?v=LuRI8bjjNho&t=106s

So I thought I would work through each system below systematically and get your opinions on the results and what to do next. The details are here:

Fuel 
Air
Spark
Timing (Ignition / electronic)
Timing (Crank / Cam shaft)
Exhaust
Compression

1. Fuel
I don't have a fuel pressure gauge. I had previously checked out the fuel pump which seemed OK. I loosened off the 4 fuel injectors out of the inlet manifold but still connected to the fuel rail and turned over the engine, all the injectors produced a noticeable spray. Removing an injector from the rail produced a noticeable release pressure as fuel jetted out. 
I connected an injector wire to an oscilloscope and the injector pulse width was about 33ms over a 0.4 sec cold cranking cycle (cranking speed was about 150 rpm). From what I can see online this may be a bit long and means the car could be running rich (please see photo 1).
I tried disconnecting the injectors and spraying quick start spray into the air inlet but there was no sign of the car starting in this case. 

2. Air
It has a new air filter and the MAF sensor was cleaned. The 5 pin MAF sensor has 2 resistors and a ground. The resistors seem to have normal resistance. The 5 pin connector to the ECU had a correct +12V and +5V signal and some grounds. 
I removed all the vacuum lines to the inlet manifold and air supply and blocked up the holes. 
I replaced the throttle body (complete with a TPS sensor and Idle Control Valve (ICV)) with a known working one- the car still didn't start. I tried starting with no air inlet pipe to the throttle body – still no start

3. Spark
The 4 coil packs were removed and inline spark testers were added. On cranking all 4 sparks testers lit up in sequence. Previously the coil packs were changed and it didn't make any difference. 

4. Timing (ignition / electronic)
I connected an oscilloscope to both the Crankshaft and camshaft sensors (please see photo 2) and they both produced cranking signals that seem reasonable. I disconnected the temperature sensor and it still didn't start – I saw some report that if it produces a faulty low temperature reading it can trick the ECU into making the fuel mixture too rich as a cold start situation. I've taken the ECU out and looked inside, it all looks clean with no corroded contacts etc. I've checked and cleaned many earth wires on to the block and fuses. 

5. Timing (Crank / Cam shaft / mechanical)
I took the rocker cover off and checked the timing chain by rotating it around with the starter. There was no sign of any excessive wear or damage and the chain seems to get lubricated as the engine is turned over. When the white timing mark on the crankshaft pulley is lined up with the TDC mark then the marks on the camshaft cogs are at the top (after second rotation of the camshafts). This would suggest that the timing chain hasn't jumped any cogs (please see photo 3).

6. Exhaust
The Catalytic convertor was removed and I inspected it internally with an endoscopic camera (please see photo 4). There is no sign of the honeycomb structure breaking up or showing signs of damage. I could see some light coming through the honeycomb at some angles. 
I checked the O2 sensors in a gas flame and they produced voltages between about 0 to 0.9V. 
The car still didn't start with the exhaust and Cat removed.

7. Compression
The readings from the compression tester were:
Cylinder 1: 7 Bar / 100 psi
Cylinder 2: 2.25 Bar / 35 psi
Cylinder 3: 2 Bar / 25 psi
Cylinder 4: 2.25 Bar / 35 psi
I added a cap full of engine oil to each cylinder and retested the compression:
Cylinder 1: 8.5 Bar / 125 psi
Cylinder 2: 11.25 Bar / 165 psi
Cylinder 3: 10.25 Bar / 155 psi
Cylinder 4: 11 Bar / 160 psi
These reading seem to be more in line with what they should be and I put the spark plugs back in and it started straight away but it cut out after a few seconds. Lots of smoke was produced.
I checked the compression again and the first few compression reading were 
Cylinder 1: 5 Bar / 85 psi
Cylinder 2: 2.5 Bar / 35 psi
Having burnt off the oil which was sealing the piston rings or valves, the low compression has returned. 

I also noticed that when the engine was turning over but not starting that exhaust gases were venting out of the top of the rocket cover vent hole (with pipe removed). Quite often the cranking revs would increase after about 5 seconds of cranking. Maybe fuel is being burnt but the combustion is not fully contained in the cylinders?
Many people thought that the Cat was blocked as the Yaris was giving a DTC Catalyst System Efficiency Below Threshold error. Since removing the Cat and checking that nothing is breaking up inside, that possibility can be eliminated. 

I had considered whether the engine was running rich and even flooding during starting. This could cause low compression if excess petrol washes away the oil seal around the piston rings. I'm guessing that an engine running too rich could cause the Cat error? There are also signs that the top of the engine has got hot in the past as there is sticky baked on oil and carbon deposits under the rocker cover. One idea is if the fuel injectors leak when the car is not used and flood the cylinders. I never noticed any fuel sitting on top of the pistons when I have checked in the past. 

Another idea was if the VVT unit was stuck in an advanced position, could this cause the low compression? I heard that the maximum advance is 15%? The VVT solenoid was changed before and it had no effect. The VVT unit uses oil pressure to operate, so if an oil way was blocked or a moving part was stuck in the advanced position, I could see how this could be intermittent. If adding oil to the cylinders restored compression could we eliminate this option?

The only clear fault I have found is the low compression. This is an intermittent problem and sometimes the Yaris works fine and has good compression. This would eliminate worn piston rings. If the valves or piston rings are intermittently stuck by sticky oil deposits, that would have to occur on all cylinders together, could this happen or produce the observed compression problem?

I have another engine ready to swap out if needed, if the problem is not an easy fix. 

I'm open to any ideas and comments.

[bathtub tom]

What's the mileage and service history? Those low compression readings are worrying and only a complete strip down may find the problem.

[YarisVVTi2002]

11 minutes ago, bathtub tom said:

What's the mileage and service history? Those low compression readings are worrying and only a complete strip down may find the problem.

Currently about 63,000 miles, the full service history goes back to 36,000 miles (2011). I have no reason to doubt it was fully serviced before that. 

I'm tempted to unbolt the inlet camshaft and see if I can get the whole camshaft (with the VVT unit) off without removing the timing chain. Has anyone tried this? 

Has anyone had a no start problem due a faulty VVT? I'm guessing that if a 15 degree advance would never cause a cranking no start condition, checking the VVT would waste time?

[furtula]

You can get detailed repair manual from https://www.toyota-tech.eu/Menu/Repair

Granted, 1 hour costs 3 euros since it's payable content, but you can save or print it for later use.

Guess it's worth spending a few euros than to spend few hours under the bonnet.

[YarisVVTi2002]

22 minutes ago, furtula said:

You can get detailed repair manual from https://www.toyota-tech.eu/Menu/Repair

Granted, 1 hour costs 3 euros since it's payable content, but you can save or print it for later use.

Guess it's worth spending a few euros than to spend few hours under the bonnet.

Thanks for that Furtula. I just registered and it says 19 correction bulletins are available. The only one that relates to the 2NZ-FE engine is repair manual RM749. It doesn't say what they contain - are these comprehensive repair manuals or just field remedy bulletins? I already have the Haynes manual for this car which has quite a lot of detail on removal and re-fitment of parts. 

[Gerg]

You mention several times about your sticky oil deposits under the cam cover etc.

Back in the early days of the Ford Puma, Vauxhall Tigra etc, (so, 16v small petrol engines), I seem to remember that both those manufacturers changed their oil recommendations for their respective engines to a thinner grade than was first specified.  The reason for this was to cure 'sticking valve problems', they said.  I don't know what the symptoms were, but that such a fault could exist on a 'modern' engine surprised me, as did the fix.

I wonder if, given your demanding use (short journeys) and visible, sticky deposits inside the engine, that you have some 'sticky valves'? 

I would go for ring/bore wear as more likely, but given that the fix for that is so involved, I thought I'd chuck the above idea in for discussion.

[furtula]

They should be detailed repair manuals, which i guess even Toyota dealers use, but as i said, it's in payable section.

I havent used the payable section so far, as i found a Russian copy for my car,which has served me well so far.

Here's an example for the Avensis https://www.toyota-tech.eu/td/template/index.aspx?file_reference=fi94Y3ZydHkzL1BaNDcxWkEwMDFDQV92NC9jb250ZW50cy9pbmRleC5odG1s

 

 

[YarisVVTi2002]

6 minutes ago, Gerg said:

You mention several times about your sticky oil deposits under the cam cover etc.

Back in the early days of the Ford Puma, Vauxhall Tigra etc, (so 16v small petrol engines), I seem to remember that both those manufacturers changed their oil recommendations for their respective engines to a thinner grade than was first specified.  The reason for this was to cure 'sticking valve problems', they said. 

I wonder if, given your demanding use (short journeys) and visible, sticky deposits inside the engine, that you have some 'sticky valves'? 

I would go for ring/bore wear as more likely, but given that the fix for that is so involved, I thought I'd chuck the above idea in for discussion.

Another 2NZ-FE engine which I have which has done similar mileage is completely clean under the rocker / cam cover. So sticky baked on oil is highly suspected somewhere. 

The problem I have with the idea of sticky valves or piston rings is that it would have to switch from a sticky state causing low compression to a non sticky state with normal compression on an intermittent basis and it would have to happen across all 4 cylinders together. Maybe there is a threshold temperature at which this occurs? What is the chance of that?

[furtula]

I think i found the Yaris manual on that website too

The left column is in Russian, but the rest when opened is in English

You can use the link below, just FYI ДВИГАТЕЛЬ is the engine part.

It should have all the detailed manuals you need, the manuals are pretty in depth.

https://www.autocats.ws/manual/toyota/Yaris_90/rm.htm

[bathtub tom]

I'm leaning towards sticky rings now they've been mentioned, particularly those compression readings. There's something in the back of my mind about pouring diesel fuel (or Redex) into the combustion chambers and leaving overnight. Be fun getting it out again. I've done it once with Redex and had to drive for miles before it stopped smoking.

[Gerg]

48 minutes ago, YarisVVTi2002 said:

The problem I have with the idea of sticky valves or piston rings is that it would have to switch from a sticky state causing low compression to a non sticky state with normal compression on an intermittent basis and it would have to happen across all 4 cylinders together. Maybe there is a threshold temperature at which this occurs? What is the chance of that?

I agree with your comment above.  My reference to the Ford/Vauxhall problem was partly to highlight  that something that sounds so serious could be fixed with just an oil viscosity change.

An engine flush (Wynns, perhaps?) is not very feasible as the engine doesn't run properly.  But, I have tried this brand of flush in our 120,000 mile 1.4 vvti Corolla, it definitely dissolved quite a lot of crud, as suggested by the following fresh oil going off-colour very quickly.  The oil consumption halved as well (was a poor 1200 miles/litre), but only for 1500 miles or so.  I have done this a second time a year later with the same results.

Bathtub tom's suggestion sounds worth a try, but just as background - Redex petrol treatment was reformulated about 10 years ago and is now a fuel system cleaner, not an upper-cylinder lubricant etc. as it used to be.  I rang them a few years ago just to check this.  I guess it's the catalyst and O2 sensors that might not much like that procedure, though.  I'm sure there is a modern product that does this and is stated as catalyst-safe.  Just as an aside, what oil do you use?

[bathtub tom]

1 hour ago, Gerg said:

Bathtub tom's suggestion sounds worth a try, but just as background - Redex petrol treatment was reformulated about 10 years ago and is now a fuel system cleaner, not an upper-cylinder lubricant etc. as it used to be.  I rang them a few years ago just to check this.  I guess it's the catalyst and O2 sensors that might not much like that procedure, though.  I'm sure there is a modern product that does this and is stated as catalyst-safe.  Just as an aside, what oil do you use?

I did consider the damage to cat and sensor my suggestion might cause, but as the op has already done a wet compression test I thought a little more gloop wouldn't matter.

[YarisVVTi2002]

On 6/6/2019 at 12:35 PM, furtula said:

I think i found the Yaris manual on that website too

The left column is in Russian, but the rest when opened is in English

You can use the link below, just FYI ДВИГАТЕЛЬ is the engine part.

It should have all the detailed manuals you need, the manuals are pretty in depth.

https://www.autocats.ws/manual/toyota/Yaris_90/rm.htm

Thanks for that Furtula. It's proving to be very useful, especially in planning the next steps.

[YarisVVTi2002]

@ bathtub tom & Gerg

I used 10W40 semi-synthetic oil. I noticed the previous oil had turned quite red and the new oil I used is starting to go a bit red too - maybe the colour is leaching out of the baked on deposits?

I've started by spraying carb cleaner (I don't have any Redex left) into the cylinders and leaving it overnight - there little improvement in the compression. 

I've been cleaning around the camshafts and VVT unit but still no compression improvement.

I'm thinking the next step is to take the head off to look at the valves. It would be nice to open the VVT unit up but it has pentagon shaped nuts holding the cover on. . 

[Madasafish]

Re: non starting: you don't mention checking sensors.. Crankshaft sensors fail. They work OK when cool.. And then break down when hot.  Try a s/h one..

Is the timing chain noisy?

Have you checked the PCV valve?  

Flushed the engine?

Eliminate everything else before stripping anything..Reassembly will be fun if you still find it does not start...

My guess is poor maintenance and lumps of crud moving round oilways..or a combination of issues..

[Gerg]

I'm not an expert, but:-

I don't think the VVti has anything to do with it, and those five-sided bolts suggest removal/dismantling that unit is a real no-no.  And it might even be impossible to reassemble without factory tools/gauges etc.  

As I'm sure you know, the crud under the valve cover is not in itself a reason not to start, but an possible tell-tale of other more problematic crud elsewhere  e.g. piston rings.

The compression readings are pretty grim, but with a little oil into the bores, the engine starts.  So, I think the dilemma is what technique do you use to unstick the rings without damaging the catalyst.  After reading through this post again, I'd put my money on your problem being low compression through sticking rings.

If the engine was running, then that might be an engine flush and an extended 'Italian tune-up'.  With a follow-on of shorter oil change intervals with a synthetic oil, which is very widely regarded as having a much better detergent performance.  I don't think semi-synthetic is a big step up from regular mineral oil, as was suggested by an automotive engineer who did regular engine oil analysis as part of his job. 

With the engine not running at the present, I think a cheap improvement (enough compression to get it running) might be through bathtub tom's 'diesel down the spark plug holes' suggestion.  Most of it will end up in the sump after leaving it overnight.  Diesel is underrated as a dismantling fluid.

I am very happy for someone to disagree with any of the above.

This is an interesting puzzle when it is someone else who is getting their hands dirty.  My sympathies! 

Did you improvise when connecting the scope leads to the car's connectors?  Or did you have dedicated leads?  I've never done this, my old scope sits in the garage unused!

For what it's worth, the latest instructions for Wynns engine flush tell you to add the whole tin as normal oil, then let the engine tick over for 20 minutes.  Stop the engine, then drain the oil, replace the filter and refill with your regular oil.

[stantheman1]

Wow! What a great thread, lots of great suggestions. Yarisvvti2002 you have the patience of a saint, if it was me I would have said 'sod it' the second I took the top off to reveal that 'unloved' engine (far too much crud in there for my liking) I would have had that spare engine in by now. 🙂

[YarisVVTi2002]

On 6/8/2019 at 11:50 AM, Madasafish said:

Re: non starting: you don't mention checking sensors.. Crankshaft sensors fail. They work OK when cool.. And then break down when hot.  Try a s/h one..

Under 4. Timing (ignition / electronic) above I've checked the output (cold only as non starting) of both the crankshaft and camshaft sensors and they seem to be OK. I swapped the sensors over from the new engine as well, still no start. 

 

On 6/8/2019 at 11:50 AM, Madasafish said:

Is the timing chain noisy?

When the engine was working I didn't notice any excessive noise from the timing chain. 

On 6/8/2019 at 11:50 AM, Madasafish said:

Have you checked the PCV valve?  

I took off and cleaned the original PCV valve. 

On 6/8/2019 at 11:50 AM, Madasafish said:

Flushed the engine?

I changed the oil last year during the time when it wasn't running. It didn't have any effect. I recently dropped the sump and discovered a load of thick rubbery sludge at the bottom. Details to follow. 

On 6/8/2019 at 11:50 AM, Madasafish said:

Eliminate everything else before stripping anything..Reassembly will be fun if you still find it does not start...

 

My guess is poor maintenance and lumps of crud moving round oilways..or a combination of issues..

Yes that's right

[YarisVVTi2002]

On 6/8/2019 at 2:17 PM, Gerg said:

I don't think the VVti has anything to do with it, and those five-sided bolts suggest removal/dismantling that unit is a real no-no.  And it might even be impossible to reassemble without factory tools/gauges etc.  

Yes I think we are all agreed that the non starting is due to clogged piston rings and that a non working VVT unit wouldn't cause it not to start. So there is no point in taking it apart at this stage. 

On 6/8/2019 at 2:17 PM, Gerg said:

As I'm sure you know, the crud under the valve cover is not in itself a reason not to start, but an possible tell-tale of other more problematic crud elsewhere  e.g. piston rings.

The compression readings are pretty grim, but with a little oil into the bores, the engine starts.  So, I think the dilemma is what technique do you use to unstick the rings without damaging the catalyst.  After reading through this post again, I'd put my money on your problem being low compression through sticking rings.

If the engine was running, then that might be an engine flush and an extended 'Italian tune-up'.  With a follow-on of shorter oil change intervals with a synthetic oil, which is very widely regarded as having a much better detergent performance.  I don't think semi-synthetic is a big step up from regular mineral oil, as was suggested by an automotive engineer who did regular engine oil analysis as part of his job. 

With the engine not running at the present, I think a cheap improvement (enough compression to get it running) might be through bathtub tom's 'diesel down the spark plug holes' suggestion.  Most of it will end up in the sump after leaving it overnight.  Diesel is underrated as a dismantling fluid.

I am very happy for someone to disagree with any of the above.

 I recently drained the engine oil and dropped the sump and discovered a load of thick rubbery sludge at the bottom (please see photos below), the oil strainer was clogged with rubbery sludge too.  This together with the baked on deposits under the rocker cover and carbon on the tops of the pistons would support the idea of clogged piston rings. 

I tried to unstick the piston rings with different solvents, starting with diesel down the spark plug holes. I did this about 10 times, collecting the used diesel coming out of the sump and reusing it after filtering through paper. I did the same thing with petrol and carb cleaner. I turned the engine over sometimes to try to break up the deposits. The Cat was disconnected. The sludge was removed and the engine cleaned as far as possible. After this process which took about a week, I checked the compression again. 

The new readings from the compression tester were:
Cylinder 1: 10 Bar (up from 7)
Cylinder 2: 4.5 Bar (up from 2.25)
Cylinder 3: 4 Bar (up from 2)
Cylinder 4: 4 Bar (up from 2.25).

The car still wouldn't start after reassembly and putting oil in. I decided to call it a day on the old engine and fit the replacement engine I had. 

[YarisVVTi2002]

On 6/8/2019 at 2:17 PM, Gerg said:

Did you improvise when connecting the scope leads to the car's connectors?  Or did you have dedicated leads?  I've never done this, my old scope sits in the garage unused!

No special connectors. The scope came with a lead with crocodile clips on, which I used to connect to the pins on the crankshaft sensor etc. My little scope was a DIY assemble one from China I bought on eBay for well under £20. 

[YarisVVTi2002]

On 6/8/2019 at 11:17 PM, stantheman1 said:

Wow! What a great thread, lots of great suggestions. Yarisvvti2002 you have the patience of a saint, if it was me I would have said 'sod it' the second I took the top off to reveal that 'unloved' engine (far too much crud in there for my liking) I would have had that spare engine in by now. 🙂

Yes I really appreciate the great contributions made here and on the previous thread, many thanks. I hope the ideas discussed here might inspire others to adopt a methodical approach and help them get to the bottom of their car problems. My car has been taken to numerous garages and been looked at by many professionals including break down services. Nobody came up with the solution and the cost in terms of time and money doing this was probably more than me doing it myself. I've certainly learned a few lessons along the way.

The amount of sludge and other crud in the engine is surprising for an engine that's only done about 58,000 miles. I have my doubts it was due to a lack of servicing. 

I've taken your advice and put the replacement engine in now. The new engine started first time and runs well. 🙂

[Madasafish]

Well done. A tribute to perseverance..

[YarisVVTi2002]

Update:

The replacement engine has been in for nearly a month and it's still running OK. The only problem is that the check engine light has come back on after a few days with an OBD error P0420 (Catalyst System Efficiency Below Threshold) like before. I suspect that this error and the crud build up in the previous engine are related. 

I can't see anything wrong inside the Cat when you look through an endoscopic camera (see photos below). I can see light coming through it and it's not breaking up. 

Both O2 sensors produce voltages which change in the range 0.01 - 0.9V 

I took out the O2 sensors separately and put a compression tester in the holes, there was no noticeable pressure reading when the engine was running which would indicate that there is no blockage in the exhaust system. I understand it should be less than 1.5 psi. 

I used one of the laser type temperature measuring guns to check the temperature at the front and back of the Cat - the downstream temp was slightly lower and they were in the range 160-180c. 

Maybe the active surfaces of the Cat have been contaminated by the old engine?

 

[bathtub tom]

1 hour ago, YarisVVTi2002 said:

I've taken your advice and put the replacement engine in now. The new engine started first time and runs well. 🙂

What about the ECU, isn't it coded to the engine?

[YarisVVTi2002]

3 hours ago, bathtub tom said:

What about the ECU, isn't it coded to the engine?

I didn't change the ECU. I thought the ECU can vary all the operating parameters, air / fuel ratio, timing etc from the sensor information? I assumed that as long as the sensors are the same and that the engine has the mechanical spec, that the ECU code would cope with adjusting the outputs correctly from the input data. 

What do other people think about this?