Fuel Trim Codes

[rmoconnor41]

Afternoon
The vehicle is a 2.8 99 with 96K.
The miles were clocked up early in its life. It the last 5 years it has done about 6K

It idles a little unevenly and displays the codes I have attached.

It has a new MAF and a smoke test showed no air leaks.

I would be grateful to know in what order you would replace item to resolve this issue.

Would you continue to drive with these codes?

Thank you

 

[AntStark]

Check the wiring to the MAF is connected properly Rich..they may have taken it off or disconnected it to do the smoke test. Other thing it may be is a faulty O2 sensor on the exhaust

 

[Oddly Godly]

Also check for air leaks in the rubber pipes between the maff and the throttle body. The small corrugated off shot is a prime area to fail. But they can fail anywhere. Did you get the maff because of these codes? After market ones are notoriously un reliable and genuine oem ones pricey. You can disconnect the maff and see if it improves the idle

 

[rmoconnor41]

Also check for air leaks in the rubber pipes between the maff and the throttle body. The small corrugated off shot is a prime area to fail. But they can fail anywhere. Did you get the maff because of these codes? After market ones are notoriously un reliable and genuine oem ones pricey. You can disconnect the maff and see if it improves the idle

The MAF was replaced when the car wouldn’t start.
All hoses are fine. The one after the MAF had a big split but has been replaced.
Vehicle didn’t show any leaks with a smoke test. Thanks

 

[Zephyr]

Whats the fuel trim values?
Positive short term fuel trim equals vacuum leak (the DME has to inject more fuel to counteract).

Negative equals too rich; there may be a leaky injector, or other cause.

have you tested the “smooth running values”? What are the readings?

 

[rmoconnor41]

Thanks. Let me look at those and maybe you will help interpret them.

 

[colb]

@Zephyr describes the interpretation of fuel trims very well.
High is indeed usually down to air leaks that get picked up by the exhaust sensors when they see unmetered air in the exhaust that dosn't match what the Maf has reported as passing through it. I note that you smoke tested it and couldn't find any leaks, dont just look at the intake side, look all over the engine from Maf to Exhaust and all rubber and plastic vaccum pipes/hoses. In the case of a 2.2 I dealt with I found the plastic cam cover had a leak around No4 plug well was the cause of elevated fuel trims. The plastic had degraded around No4 and was starting to crumble, that let air into the engine and oil would have eventually filled the plug well if it had been left. A good used cam cover was fitted with new gaskets and restored the engines vaccum system. A smoke test revealed the leak in that case but that was after other leaks on the intake side of the engine were fixed, that side included a leaking sucking jet valve just below the throttle body intake. The cam cover leak only showed up as a very feint smoke trail but was the root of the problem.
Always go for oem brand Maf's Bosch or Seimens, cheaper brands are a waste of money they don't work or last long, been there done that, lesson learned.
Worth looking at live data from the exhaust sensors to see if they are working, in live data you should see pre cat sensors ranging up and down their voltage range, if viewed in graph form they should be producing a regular wave pattern. Post Cat sensors when viewed remain preety static unless they are picking up abnormal exhaust.

 

[rmoconnor41]

Thanks. When weather improves I will run the car up and get some values. Regards

 

[rmoconnor41]

@Zephyr describes the interpretation of fuel trims very well.
High is indeed usually down to air leaks that get picked up by the exhaust sensors when they see unmetered air in the exhaust that dosn't match what the Maf has reported as passing through it. I note that you smoke tested it and couldn't find any leaks, dont just look at the intake side, look all over the engine from Maf to Exhaust and all rubber and plastic vaccum pipes/hoses. In the case of a 2.2 I dealt with I found the plastic cam cover had a leak around No4 plug well was the cause of elevated fuel trims. The plastic had degraded around No4 and was starting to crumble, that let air into the engine and oil would have eventually filled the plug well if it had been left. A good used cam cover was fitted with new gaskets and restored the engines vaccum system. A smoke test revealed the leak in that case but that was after other leaks on the intake side of the engine were fixed, that side included a leaking sucking jet valve just below the throttle body intake. The cam cover leak only showed up as a very feint smoke trail but was the root of the problem.
Always go for oem brand Maf's Bosch or Seimens, cheaper brands are a waste of money they don't work or last long, been there done that, lesson learned.
Worth looking at live data from the exhaust sensors to see if they are working, in live data you should see pre cat sensors ranging up and down their voltage range, if viewed in graph form they should be producing a regular wave pattern. Post Cat sensors when viewed remain preety static unless they are picking up abnormal exhaust.

The MAF went in a couple of years ago. The make is NTK
Went through my menus but couldn’t find fuel trim values in there.
Smooth running values. From cold start seemed to be all over the place
1=0
5=0.15-0.37
3=0
6=0
2=0-0.27
4=0
I attach a file showing what I thought might be sensor numbers.
Regards
Richard

 

[rmoconnor41]

Whats the fuel trim values?
Positive short term fuel trim equals vacuum leak (the DME has to inject more fuel to counteract).

Negative equals too rich; there may be a leaky injector, or other cause.

have you tested the “smooth running values”? What are the readings?

The MAF went in a couple of years ago. The make is NTK
Went through my menus but couldn’t find fuel trim values in there.
Smooth running values. From cold start seemed to be all over the place
1=0
5=0.15-0.37
3=0
6=0
2=0-0.27
4=0
I attach a file showing what I thought might be sensor numbers.
Regards
Richard

 

[colb]

The adaption menu on your scanner is in fact looking at the fuel trims, I see they are reporting minus figs which would indicate the car is running rich. Now we know its running rich turn attention to the Maf for mis reporting what it is seeing passing through it and the exhaust Lambda sensors pre and post Cat. See if the pre cat are ranging up and down their voltage range, in graph form you should see them cycling up and down the scale. The post Cat sensors usually look static unless they are picking up abnormality in the exhaust gas. Good explanation of fuel trims here worth a read. Previous response about leaking injectors might be a factor as well.

Fuel Trim Adaptation | Technical Focus | Snap-on

Thats my take on the situation with your car, I may be wrong, be interested in views from other members.
Never heard of the Maf brand you have best to use Bosch or Seimens oem brands, expensive but quality assured, they work out of the box.

 

[Zephyr]

What @colb said.
and something more, cylinder 5 is playing up. Try swapping coils with No1 and read again.
if it remains off compared to the others then try swapping injectors.
then measure on a warm engine (108 celsius on the temp reader).

 

[rmoconnor41]

What @colb said.
and something more, cylinder 5 is playing up. Try swapping coils with No1 and read again.
if it remains off compared to the others then try swapping injectors.
then measure on a warm engine (108 celsius on the temp reader).

Thank you.

 

[rmoconnor41]

The adaption menu on your scanner is in fact looking at the fuel trims, I see they are reporting minus figs which would indicate the car is running rich. Now we know its running rich turn attention to the Maf for mis reporting what it is seeing passing through it and the exhaust Lambda sensors pre and post Cat. See if the pre cat are ranging up and down their voltage range, in graph form you should see them cycling up and down the scale. The post Cat sensors usually look static unless they are picking up abnormality in the exhaust gas. Good explanation of fuel trims here worth a read. Previous response about leaking injectors might be a factor as well.

Fuel Trim Adaptation | Technical Focus | Snap-on

Thats my take on the situation with your car, I may be wrong, be interested in views from other members.
Never heard of the Maf brand you have best to use Bosch or Seimens oem brands, expensive but quality assured, they work out of the box.

Thanks

 

[rmoconnor41]

The adaption menu on your scanner is in fact looking at the fuel trims, I see they are reporting minus figs which would indicate the car is running rich. Now we know its running rich turn attention to the Maf for mis reporting what it is seeing passing through it and the exhaust Lambda sensors pre and post Cat. See if the pre cat are ranging up and down their voltage range, in graph form you should see them cycling up and down the scale. The post Cat sensors usually look static unless they are picking up abnormality in the exhaust gas. Good explanation of fuel trims here worth a read. Previous response about leaking injectors might be a factor as well.

Fuel Trim Adaptation | Technical Focus | Snap-on

Thats my take on the situation with your car, I may be wrong, be interested in views from other members.
Never heard of the Maf brand you have best to use Bosch or Seimens oem brands, expensive but quality assured, they work out of the box.

What I do notice with this Z apart from the slightly uneven idle at cold is quite a sweet smell from exhaust when cold.

 

[Z3inter]

Hi, did you ever get to the bottom of this and what was the fix?