AFR varying between banks - A problem?

[Ian C]

Hi,



I am currently fitting and early (1992) 1UZ-Fe into a kit car to replace a Rover V8 and have found that the AFR is different between the two banks when carrying out the initial fuel set up. The engine is out of a Soarer and has had a COP upgrade using Honda K20 coils and is controlled by a Link Storm ECU. I have an Innovate DLG-1, coupled to an LC-2, to provide AFR readings from both banks to the ECU.



The initial engine runs showed a variation of approx. 13% between the AFRs measured on the nearside & offside exhaust collectors (Nearside 15.0 and Offside 13.5). I swapped the sensors and wiring side to side to eliminate the potential of errors in the Innovate or Link ECU but the difference in AFR was unchanged. I then performed a flow test on the injectors (standard 240 cc/s injectors) and found the variation between the injectors to be less than 2%. The variation in the AFR, between the two sides, is most notable at idle and decreases to between 2% & 4% at 3,000 rpm.



So the question is: Does a variation of 15% between the nearside and offside exhausts at idle constitute a problem or is it within tolerance. Any suggestions or advice would be gratefully received.



Regards,

Ian

 

[ivan129]

Hi,



I am currently fitting and early (1992) 1UZ-Fe into a kit car to replace a Rover V8 and have found that the AFR is different between the two banks when carrying out the initial fuel set up. The engine is out of a Soarer and has had a COP upgrade using Honda K20 coils and is controlled by a Link Storm ECU. I have an Innovate DLG-1, coupled to an LC-2, to provide AFR readings from both banks to the ECU.



The initial engine runs showed a variation of approx. 13% between the AFRs measured on the nearside & offside exhaust collectors (Nearside 15.0 and Offside 13.5). I swapped the sensors and wiring side to side to eliminate the potential of errors in the Innovate or Link ECU but the difference in AFR was unchanged. I then performed a flow test on the injectors (standard 240 cc/s injectors) and found the variation between the injectors to be less than 2%. The variation in the AFR, between the two sides, is most notable at idle and decreases to between 2% & 4% at 3,000 rpm.



So the question is: Does a variation of 15% between the nearside and offside exhausts at idle constitute a problem or is it within tolerance. Any suggestions or advice would be gratefully received.



Regards,

Ian

Hi Ian, 13% variation between banks possibly wont show up in plug color but no harm in comparing them. Have you tried the soapy water trick (spray bottle with soapy water) over the intake manifold? You may have a vaccum leak. Also do a comp test and a leak down test while the plugs are out. No harm in checking valve timing too.

 

[Ian C]

Hi Ian, 13% variation between banks possibly wont show up in plug color but no harm in comparing them. Have you tried the soapy water trick (spray bottle with soapy water) over the intake manifold? You may have a vaccum leak. Also do a comp test and a leak down test while the plugs are out. No harm in checking valve timing too.

Ivan,



Thank you for the response. I did check the plugs when the problem first arose but not exhaustively so might be worth revisiting.



Since the original post I have refitted the injectors, in different positions to equalize the fuel delivery between the two sides of the engine, and performed another engine run. The problem has now swapped sides!! sides - the nearside now shows an AFR of 12.6 and the offside shows 14.7 (at 1,440 rpm).



Given that the problem swapped sides when I refitted the injectors it would seem to indicate that one (or more?) of the injectors may be sticking or slow. This would explain the fact that the difference decreases at higher rpm where the injector pulses would be longer?



Any further help / suggestions would be appreciated.



Regards,

Ian

 

[ivan129]

Sounds like you're on the track.

 

[Ian C]

Sounds like you're on the track.

Ivan,

I would dearly like to think so but I am afraid not!

Since the previous reply I have swapped all the injectors back to their original sides but the problem did not swap back with them. The nearside is still showing as running richer than the offside which is the opposite of what it was before the injectors were tested and repositioned.

I am now totally confused after being confident that, as the problem had changed when the injectors were moved, it must be a sticking or sluggish injector!

Any further suggestions would be welcome.

Take care,
Ian

 

[ivan129]

Vacuum leak from an Injector grommet?

 

[Ian C]

Now that's a thought!!! At least it is something to investigate, thank you

 

[Ian C]

Ivan - spot on, thank you!


Update

Following the last post I decided to try and check for a leak by squirting differential oil around the seals between the injectors & intake manifold (as suggested on another forum). Started an engine run but stopped it quickly when I had a strong smell of petrol to find fuel mixing with the diff oil round the nearside injector seals. Deciding enough was enough I removed both fuel rails and stripped them for inspection.

The rubber seals, fitted new when the engine was checked over before fitting, looked decidedly secondhand. Some of the O-rings were deformed and were not resilient - they stayed deformed when squeezed out of shape and just felt and looked wrong. I ordered new seals from the company I had bought the Link ECU and other upgrades from (Brands Hatch Performance) and when they arrived I was surprised to discover that the bottom seal (called the insulator in the Toyota 1UZ manual) was very different to the seals I had fitted. The new seals were like a flattened donut whereas the original seals were more like a cup. The O-rings were not noticeably different but felt more resilient. However the proof is in the pudding and with the new seals fitted I had no leaks and the difference in the lambda reading side to side is under 3% (previously 15%). Whilst not prefect I have decided that it is something I can live with and it is time to move on.

So a very big thank you to all those who have responded to my plea for help and for all the suggestions & tips.


Best regards,
Ian

 

[gloverman]

Chances are the seals you removed started their life the same as the replacements, they had just deformed with age.

 

[alwill]

Just to follow up on this, the bhp seals are totally different to the correct toyota seals. Bhp are solid whilst toyota seals are more of an outer collar effect. The bhp is more like the top shoulder seal. Toyota injector seals do split around the edge and will cause vacuum leaks