Technical Jerkiness at lower speeds

[rmjbn1]

Did the poor starting and stalling occur after the cleaning operation, or was the cleaning an attempt to address this issue?
If the issue occurred before, were the symptoms the same, or are they now different or similar?

Thanks pb. Cleaning was an attempt to cure the issue, symptoms are the same now.

Some background:
Car bought October 2018 92k miles, no faults.
Spring 2019: new spark plugs (Champion RA7YC), throttle body removed and cleaned with brake cleaner & toothbrush as part of routine service
Now at 106k miles, been running fine ever since (apart from occasional low-speed kangarooing) until...

Friday: warm start after a short run turned over 5sec or so before firing. Engine stalled twice and started running again on journey home. Check engine light came on when stalled and off again when running.

Saturday: disconnected battery, removed TB, MAP, plugs and leads.
Cleaned TB with rag sprayed with brake cleaner. Tried & failed to prise IACV from TB. MAP was clean, sprayed with brake cleaner.
Plugs were clean, gaps slightly wide on plugs 1&3, regapped to 0.9mm (35thou).
Reassembled, connected battery, fired straight away but idled fast @2000rpm and unevenly for 1min. Engine check light stayed on.
Turned off, unplugged & reconnected MAP, IACV and TPS. Started fine and idled smoothly @800rpm, engine check light still on and has been on since.

Sunday: turned over without firing from cold, 2 attempts for 10+secs. Unplugged and reconnected MAP, car fired and ran normally. Set off on journey, runs fine when not intermittent stalling, usually off-throttle or trailing throttle. Sometimes engine fires up again, sometimes coasts to a halt. Often turns without firing, hot or cold.

The poor little thing is clearly unwell but got us home last night I've found a source for an OBD connector, will try and get codes read on MES.

 

[koalar]

was there originally mayo under the throttle body ?

 

[rmjbn1]

was there originally mayo under the throttle body ?

No, mostly clean, just a bit of sooty residue on the throat and butterfly and around the IACV housing that I was trying to clean. The green gasket under the TB is clean in good condition, a light coating of soot inside the intake manifold over by the MAP, but that was it.

I've got as far as checking the throttle position sensor with a multimeter, I get voltage and resistance at the plug, resistance on the sensor which increases as the throttle is opened, so I'd guess the TPS is reading OK? Again, reluctant to start, then mostly running fine but occasionally stalls, so maybe any error is intermittent.

I'll report back once I've got some error codes. Thank you for your help.

 

[portland_bill]

You have aimed straight for the intake/fuelling system, and are now focussed on that. Time to step back, clear all assumptions, and diagnose fresh.

Poor starting and stalling, are often associated with head gasket issues. On older FIRE engines, the head gaskets used to just get old and fail, any time after about 80k. Later ones are pre-coated with a lacquer adhesive and seem to last better. (IF changing the gasket, the new one should come sealed in a bag, and must not be opened until ready to fit, as the lacquer starts to cure immediately.)

First, we need to read the codes, to see if that points us anywhere useful. Of course, codes report out of parameter readings, and may show cause, or just the effect.

A simple compression test would also be useful, if you can do that too.

These engines do seem to eat their plug leads. Ideally they should be considered a service item, maybe every second big service, although mine have helpfully self-destructed on removal, so have set their own change interval. Poor plug lead usually show as poor starting and poor low speed running, but should also give misfires at higher speeds, although this may not be easily felt. MES should show if there's a misfire history. In some cases, poor plug leads have led to failed coils, so they become a cheap preventative replacement.

 

[koalar]

You have aimed straight for the intake/fuelling system, and are now focussed on that. Time to step back, clear all assumptions, and diagnose fresh.

Poor starting and stalling, are often associated with head gasket issues. On older FIRE engines, the head gaskets used to just get old and fail, any time after about 80k. Later ones are pre-coated with a lacquer adhesive and seem to last better. (IF changing the gasket, the new one should come sealed in a bag, and must not be opened until ready to fit, as the lacquer starts to cure immediately.)

First, we need to read the codes, to see if that points us anywhere useful. Of course, codes report out of parameter readings, and may show cause, or just the effect.

A simple compression test would also be useful, if you can do that too.

These engines do seem to eat their plug leads. Ideally they should be considered a service item, maybe every second big service, although mine have helpfully self-destructed on removal, so have set their own change interval. Poor plug lead usually show as poor starting and poor low speed running, but should also give misfires at higher speeds, although this may not be easily felt. MES should show if there's a misfire history. In some cases, poor plug leads have led to failed coils, so they become a cheap preventative replacement.

All correct

I have never had the original HT leads fail even at 200K however replacement cables even Same brand tend not to last.

 

[rmjbn1]

I haven't changed the plug leads or given her a compression test yet, so will do, thanks for the advice.

I hadn't considered the head gasket, there's no sign of mayo anywhere, not losing coolant or oil.

Similarly with HT leads or coils as she's not misfiring or running rough. She either runs fine or abruptly stalls.

For the same reason I'd guess fuel supply is ok, surely it would cough and splutter before dying if the pump was playing up.

I'll happily admit I have no idea what the issue is. I just have a habit of starting with the basics when a car's not running right.

Checking plugs, cleaning throttle body and attached sensors at least eliminates those factors and in my experience often fixes or identifies the issue.

With IACV unplugged she idles fast at 1800rpm and unevenly, which does make me wonder if it's stuck open? Still waiting on error codes though...

 

[rmjbn1]

My Bluetooth ELM327 arrived today, but all I could get at short notice here in Ireland was one of these cheap ones and I can't get it to connect to MES or any OBD scanner application I've tried:

I've installed different drivers at ftdichip.com, adjusted the COM5 bit rate and buffer settings.

It's discoverable as a bluetooth device on my Win10 laptop and android phone, but won't connect to ECU As well as MES I've tried the Car Scanner and Torque (Lite) apps.

After leaving the battery disconnected overnight the engine check light has gone off, and she starts OK now, so there's some good news...

...but still stalls abruptly. So, not much further on after a frustrating morning.

Need a proper OBDII interface I guess. Can anyone recommend a reliable one please?

 

[koalar]

Force you software into KWP fast if you can. Torque has an option in settings.

I Take it you got as far as imputing the PIN to pair
I don’t use ELM so can’t help much

 

[rmjbn1]

The cheapo ELM327 paired fine via bluetooth with both laptop and phone by entering PIN 1234. Driver installed on Win10 laptop OK.
It just won't establish a connection with MES/Car Scanner/Torque to read the ECU.

 

[rmjbn1]

Now have error code! P0335 rpm sensor.
Which seems a fairly typical error code for my symptoms, lots of threads on here.

Ended up taking the car to two places today.

First place carried out a health check scan, loads of old codes came up: power steering, airbag, abs, alternator etc. Codes cleared but most came back. He thought it was stalling as the fuel pump was not getting power, probably fault in ECU due to all the error codes being thrown up.

Bumped into second chap when stalled at a junction trying to get home! He thought that diagnosis was rubbish, had a code reader with him, quickly pulled up P0335.

So I guess next step would be new crankshaft sensor and cross fingers?

 

[koalar]

fails only at junctions, low revs

before changing the sensor

check the alternator belt

and clean the battery terminals and leave the battery on charge overnight.

Crank sensors normally fail when hot or High revs

I suspect the supply voltage or ground isnt correct throwing up the error rather than the sensor itself.

 

[rmjbn1]

Thank you koalar. I was just reading your post about that here: https://www.fiatforum.com/panda/484311-dreaded-p0335-crank-sensor-fault-code.html?p=4568190

I'll charge the battery, run a temporary earth with a jump lead from battery negative to gearbox, check the alternator is charging and test again before changing anything.

The symptoms do seem worse / more frequent when slowing / off throttle, but we have had a sudden stall when hot at speed as well.

I think this issue is way out of the scope of this thread though - I'll continue it with a brief summary over on that P0335 thread.

 

[DaveMcT]

Crank sensors get changed as a matter of course because no CS signal is regarded by the ECU as the engine is not running so it cuts everything.