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[steve6367]

Well it still generally runs better that it had for some time, so hopeful I've done nothing too silly.

However:

Cold start (sat over night) perfect, but it does not hold first couple of gear changes to higher revs.

Hot start (off for less than an hour) perfect

Warm start (3 or 4 hours after switch off) - starts immediately and is using rich mixture and increased idle speed but very lumpy. If you hold revs at 2k smooths out and if you give it 20 seconds of that all seems well. After this it also holds the first couple of gear changes until higher revs as expected on cold start to warm cats.

Plugging in I have stored P0170 Fuel Trim Malfunction.

I've had a really good look over the engine and can't find anything out of order.

Any thoughts from the panel?

Many thanks

Steve

[TheBoy]

What engine?

Given the code, be suspicious of MAF, airleaks in intake/exhaust or front lamda(s).

[TheBoy]

LOL, its in title

The same applies though

[steve6367]

Thanks - inlet side I've been over and MAF is only 6 months old, will take a look at live data from it though to see it looks sensible, I m learning not to assume anything! Exhaust is blowing slightly beyond the CAT section so sounds like I should get that changed. Can it cause problems even if blow is beyond both lambda?

Steve

[SIR Philbutt]

......

Cold start (sat over night) perfect, but it does not hold first couple of gear changes to higher revs.

Assuming it's an auto that is normal, warming the ATF, thats why OK when warm

......

Warm start (3 or 4 hours after switch off) - starts immediately and is using rich mixture and increased idle speed but very lumpy. If you hold revs at 2k smooths out and if you give it 20 seconds of that all seems well. After this it also holds the first couple of gear changes until higher revs as expected on cold start to warm cats.

I would assume that is the same thing, like auto-choke was in older cars

...

Plugging in I have stored P0170 Fuel Trim Malfunction.

Mine does that and have concluded it is when switch on/off LPG. If not causing a permanent spanner light (only when ign on - not running) it is not something of great significance IMO

HTH
Phil

[steve6367]

......

Cold start (sat over night) perfect, but it does not hold first couple of gear changes to higher revs.

Assuming it's an auto that is normal, warming the ATF, thats why OK when warm

......

Warm start (3 or 4 hours after switch off) - starts immediately and is using rich mixture and increased idle speed but very lumpy. If you hold revs at 2k smooths out and if you give it 20 seconds of that all seems well. After this it also holds the first couple of gear changes until higher revs as expected on cold start to warm cats.

I would assume that is the same thing, like auto-choke was in older cars

...

Plugging in I have stored P0170 Fuel Trim Malfunction.

Mine does that and have concluded it is when switch on/off LPG. If not causing a permanent spanner light (only when ign on - not running) it is not something of great significance IMO

HTH
Phil

Thanks - can you clarify? I thought the auto box should allow higher revs before gear change on a cold start to warm the CAT's quicker?

[Gaffers]

Thanks - inlet side I've been over and MAF is only 6 months old

Genuine or pattern?

[steve6367]

Thanks - inlet side I've been over and MAF is only 6 months old

Genuine or pattern?

Bosch, but not new from a breaker....

[SIR Philbutt]

......

Cold start (sat over night) perfect, but it does not hold first couple of gear changes to higher revs.

Assuming it's an auto that is normal, warming the ATF, thats why OK when warm

......

Warm start (3 or 4 hours after switch off) - starts immediately and is using rich mixture and increased idle speed but very lumpy. If you hold revs at 2k smooths out and if you give it 20 seconds of that all seems well. After this it also holds the first couple of gear changes until higher revs as expected on cold start to warm cats.

I would assume that is the same thing, like auto-choke was in older cars

...

Plugging in I have stored P0170 Fuel Trim Malfunction.

Mine does that and have concluded it is when switch on/off LPG. If not causing a permanent spanner light (only when ign on - not running) it is not something of great significance IMO

HTH
Phil

Thanks - can you clarify? I thought the auto box should allow higher revs before gear change on a cold start to warm the CAT's quicker?

That as well 

[Kevin Wood]

...

Plugging in I have stored P0170 Fuel Trim Malfunction.

Mine does that and have concluded it is when switch on/off LPG. If not causing a permanent spanner light (only when ign on - not running) it is not something of great significance IMO

HTH
Phil

I would say it is significant. On an LPG car it usually indicates that the LPG system is poorly mapped. On a petrol car it's an indication that something is significantly degrading the accuracy of the fuelling. There is quite a wide margin of adjustment before this code is stored, so something has gone badly wrong if this code is being reported. As said, air leaks, MAF and lambda sensor issues are the usual suspects.

[Gaffers]

First port of call:

- Test the MAF by unplugging it, see if it runs better.
- Test for air leaks by blipping the throttle and listening for those unmistakable whistles

Then you are in to needing a reader to watch live data for the lambdas.  Double-check it is correctly plugged in though, it can be easy to forget or not quite push home

[steve6367]

Thank you both - I only have a very limited window to do any testing as it runs perfectly, except on a warm start for around 20 seconds.

I know if parked at work for the day it will play up when started, so can try unplugging the MAF before I do so and see what happens. When I do that does it assume a MAF value? Or just run open loop?

MAF and Lambda live data looks ok, but I don't have Tech 2 - also the freeze frame data attached to the code stored shows a MAF value 0.0gm/s which clearly can't be correct.

I wonder if I have 2 different issues here to be honest.

Could the Lambda sensors have been damaged by all the steam in the exhaust when the HG went?

Steve

[Kevin Wood]

Can you see the fuel trims in your live data?

[steve6367]

From the Freeze Frame if that helps, I can also see when in live data but don't have the car with me currently.

Freeze Frame data
Fault code   Sensor   Value
P0170   Sensor values:   
Calculated Load   55.29 %
Coolant Temperature   86. C
Short Term Fuel Trim Bank 1   12.5 %
Long Term Fuel Trim Bank 1   11.72 %
Short Term Fuel Trim Bank 2   -100. %
Engine Speed   2426 rpm
Vehicle Speed   42 mph
Ignition Timing Advance   63.50 º
Intake Air Temperature   32.00 ºC
Air Flow Rate (MAF)   0.00 g/s
Absolute Throttle Position   7.06 %
Oxygen Sensor 1 - Bank 1 voltage   0.42 V
Oxygen Sensor 2 - Bank 1 voltage   0.42 V
Fuel System 1 Status   Closed Loop

[Jimbob]

Maf reading 0 according to that.

Air temp also seems hot

What device are you using?