[Diy_efi] Lumpy engine in closed loop cruise

[Mike]

At 12:19 AM 10/21/05, you wrote:
>Why to you say it is heavy load ?  they is almost no boost.  0.3 bar max  which is nothing really.
>Throttle is about 5-10% so the turbo is just ticking over.

huh ? Did I miss-read when you said:-

"In 5th gear,  trying to hold steady 85 mph,  3500 rpm, MAP about 100-130 kPa"

Am I correct in seeing that as absolute manifold pressure at that cruise ?

To me that says you are at close to atmos pressure in your manifold to
keep it at 85mph, thats a fairly high pressure for cruise - isnt it ?

>How do I richen it up,  that is one of my problems.  If you can the VE tabels will the BLM not pull it back.

Dont know anything about your ECU, maybe aftermarket performance
people can help. However, I have occasionally had similar problems,
came down to electrical connections on air flow meter, the ECU interpreted
this as faulty and switched in and out of limp mode.

If the car is more than 5 yrs old really worth checking connectors, often
just cycling them (plugging in and out a few times) can help diagnose.

Other thing that occurs, make sure all your low voltage leads
are well away from your high tension (EHT) . A common problem on the Nissan
engine used here in the commodore is the cyl 1 ignition lead being really
close to the crank angle sensor leads and the tags breaking so there
isnt the normal separation, this allows high tension voltage noise to
get imposed on low voltage signals this can cause ECU to misread
crank signals, in your case make sure the MAP is not being misread
because any high voltage leads cannot corona discharge influencing
the main sensors. On one forum in Australia we had one guy who went
through 4 crank angle sensors - suffice it to say - he didnt know having
good EHT leads right next to low voltage leads would or could be an issue 
ie. Even  brand new good leads allow some corona effect...!

Fortunately its not as if its plasma ignition, that would be far worse

<chuckle>

Rgds

Mike



>Dermot
>
>
>
>>Bit of a heavy load for cruise,
>>
>>And yes does sound a bit lean, can you richen it up by
>>20% and observe the effect ?
>>
>>Rgds
>>
>>Mike
>
>
>Regards from
>
>
>Mike
>Perth, Western Australia
>VL Commodore Fuse Rail that wont warp or melt !
>Twin tyres for most sedans, trikes and motorcycle sidecars
>http://niche.iinet.net.au