Lumpy idle when warm…live data shows -20% long term fuel trim - running rich?

[electricfurnace]

Anyone good at reading/diagnosing from Live data? LONG TERM (-20%) and SHORT TERM (flutcuates betwen -8 and -18%) fuel trims are quite hefty minus figures - does this mean it’s running rich, which in turn can cause a lumpy idle?

So far its had:

- new MAP sensor
- new coolant temperature sensor
- new injectors (all of them)
- new VVT solenoid seal
- new inlet manifold gasket seals
- spark plugs are fairly new, about a year or so old
- new coil pack
- new pre cat lamba September last year
- cleaned throttle body

Car driveway excellent through the rev range. No driving issues.

I’m confident it’s NOT the timing as the owner before last had the belts done (by someone who knows these cars very well and knows what they are doing) and said the idle wasn’t lumpy for him.

Idle is only lumpy when WARM (not cold).

Any idea what else it could be?

 

[hopgop1]

Sounds like you've already fired the parts cannon, but HT leads?
Also genuine plugs and injectors? As in NGK PFR6E-10 plugs and genuine magneti injectors?

 

[SharpyClio]

Negative trims suggest the car thinks it’s running rich and is trying to lower the trim to compensate.

The main thing that manages that is the upstream O2 sensor which suggests that could be at fault as it might be lowering the trim in error and causing the lumpy idle.

 

[electricfurnace]

Ok so it had a new bosch lambda sensor last Sept and live data indicates its switching correctly so I doubt it would be that?

Injectors are the magneti injectors yes.

It had new correct NGK spark plugs Jan 2022 but done less than 1500 miles since.

Only thing I haven’t done is HT leads but can they cause rich running?

 

[electricfurnace]

Live data video here:

 

[electricfurnace]

 

[SharpyClio]

There are 2 O2 sensor, just checking you have definitely replaced the one pre cat? Seen a few people say the O2 sensor has been replaced only for it to be the downstream one as that's easier to see and access but has no impact on the trims.

 

[electricfurnace]

i think it was the pre cat as it failed on emmisions at laat mot last sept

can I just check where the upstream one is located?

 

[electricfurnace]

Also the live data seems to show the o2 sensor is switching correctly as the voltage is varying?

 

[SharpyClio]

Also the live data seems to show the o2 sensor is switching correctly as the voltage is varying?

There are two data streams for the o2, one is up stream one is down stream.

The upstream is in the manifold just before the joint.

You can see it in this thread

Lambda sensors

Are the pre and post cat lambda sensors the same, ie same part number? Thanks.

www.cliosport.net

This is from my project thread,

“Charlotte” The 182 FF

No paint on the throttle body?

www.cliosport.net

You can see the two banks being shown on data screens there.

 

[electricfurnace]

2nd bank on my data shows 0. 410v constant. Bank 1 varies between 0 and 0.09. isn’t this correct though as bank 1 is pre cat which should be switching like it is? Or are the readings too far apart?

 

[JamesBryan]

View attachment 1682052

If that's with the engine running your battery voltage is only 12.5v

Should be more like 14

 

[electricfurnace]

If that's with the engine running your battery voltage is only 12.5v

Should be more like 14

Yes engine running - would a slightly low battery cause it to run rich though?

 

[SharpyClio]

Just been out and checked mine,

This is what I get

So I’m getting static 0.41v downstream and fluctuating on upstream between 0.06v and 0.77v

 

[SharpyClio]

I think your upstream sensor is dead. Although it'd be good to see some more data, eh graph data is a bit easier to see what is going on.

 

[JamesBryan]

Yes engine running - would a slightly low battery cause it to run rich though?

I'm not sure really, but it can't help...

I would sort that and see how it is after.

 

[electricfurnace]

I think your upstream sensor is dead. Although it'd be good to see some more data, eh graph data is a bit easier to see what is going on.

Thats really helpful you checking thanks very much mate

I’ve got 0.41v static downstream

And fluctuating 0.740v to 0.09v upstream - which is almost the same as yours isn’t it?

 

[JamesBryan]

Thats really helpful you checking thanks very much mate

I’ve got 0.41v static downstream

And fluctuating 0.740v to 0.09v upstream - which is almost the same as yours isn’t it?

If it's flicking from 0.1v to 0.9v fairly quick, then yeah it's working.

What MPG are you seeing?

 

[electricfurnace]

Dont think the mpg is great, maybe 25mpg mixed?

 

[electricfurnace]

Ran the data again last night, still running rich. At a bit of a loss now!!

 

[SharpyClio]

I wonder if its worth just swapping the two O2 sensors around and seeing if that does anything. Its an easy way to check the upstream sensor. It still feels like an O2 sensor issue to me.

When my upstream o2 sensor was dead I was getting low 20's mpg and lumpy idle.

 

[JamesBryan]

Ran the data again last night, still running rich. At a bit of a loss now!!

Can you graph the O2 reading like Sharpy has.

 

[electricfurnace]

I do actually have a new lambda sensor here to swap in if it ever stops raining! I’d be aurpised if it was that though as the one on the car was new last September for the mot and also the live data seems ro show it switching correctly. Unfortuantely my scanner doesn’t do graphs!

 

[JamesBryan]

I do actually have a new lambda sensor here to swap in if it ever stops raining! I’d be aurpised if it was that though as the one on the car was new last September for the mot and also the live data seems ro show it switching correctly. Unfortuantely my scanner doesn’t do graphs!

It looks like a Launch scanner.

The blue wavy graph looking symbol on the right, if you press that it will show in graph form.

 

[SharpyClio]

Mine looked like it was switching but on the graph it was super erratic. Worth noting that cheap sensors either don’t work at all or fail quickly, even Bosch ones sometimes only last a few months, it’s a common complaint.

Might not be that but it’s the most common thing for over fuelling so needs to be 100% eliminated.

 

[electricfurnace]

Ok so here’s my graph data how does it look?

 

[JamesBryan]

Ok so here’s my graph data how does it look?
View attachment 1682317

Yeah looks to be switching fast enough.

 

[Alex82]

sorry if you already checked, have you fully charged and checked the battery? My trophy recently failed on fast idle lambda readings were high, thought it may have been an exhaust blow replaced both cat exhaust clamps as was a slight blow under engine load, still failed charged the battery and readings were considerably lower and it idled like a dream.

 

[electricfurnace]

Yeah battery all ok now showing 14.5v and still lumpy

 

[electricfurnace]

Intake manifold prrssure at idle says 410mbar (410kpa) some one on one if the facebook groups aaid it should be 360mbar so my timing might be out?

Be suprised if timing out as owner before last didnt have idle issues and belts not done since.

Is that correct as I thought around 400mbar was normal?

 

[JamesBryan]

Yeah generally around the mid 300's.

Your reading I would expect the timing to be out slightly or for it to have some sort of aftermarket cams.

 

[electricfurnace]

Ok, sounds like we’re getting somewhere. No idea if it has aftermarket cams unfortunately, assume the only way of knowing is for a specialist to take it apart and take a look? it was an ex track car so it migjht have been messed with, but the thing that is throwing me is that the owner before last said he didn’t have a lumpy idle when warm (dave120 on here). I don’t think timing can shift itself and it hasn’t had new belts since?!

 

[JamesBryan]

How long since the belt was last done?

 

[R3k1355]

the thing that is throwing me is that the owner before last said he didn’t have a lumpy idle when warm (dave120 on here). I don’t think timing can shift itself and it hasn’t had new belts since?!

Yea but you've replaced a load of stuff since then, so maybe it's made the issue more noticeable?

 

[electricfurnace]

How long since the belt was last done?

Nov 2020 - 6k miles ago

 

[electricfurnace]

Yea but you've replaced a load of stuff since then, so maybe it's made the issue more noticeable?

Yeah quite possibly I suppose! 🙈

 

[kaban]

I've got same problem here with my 172. My ignition is all OE new. When I bought it, it has problems with lumpy idle and gas pedal reaction. Then I have my timing belt change and it was set incorrectly. After work engine runs smoothly. Not like Honda but much better. In the meantime, the injector failed - it flashes CE. Today - after ~10t miles and 4 years it works on -20% fuel trim and lumpy idling again but while driving - throttle response is fine. This car is starting to annoy me. Sounds like a tractor.