car running lean

[mattsil80wis]

I just got done upgrading my motor...it is an s13 with an s13 sr20det with an enthalpy tune with 72lb injectors (resistors installed) and z32 maf. ALso upgraded cams.

The car runs and starts fine, however it does idle a bit ont he low side (approx 750/800 verified with Conzult), and is pulling 10 inches of vacuum (low) When raising idle through conzult to 1100, vacuum is in the normal 16-18inches range.

Now my main concern is that the car (when idleing) is showing completly lean ont he display (which should translate to 18+afr PLX wideband)

When the car is held at 2-3000 rpm the wideband reads 17/18.xx on the wideband...however when the car is quoickly revved, it goes into the 10-11 AFR range...

When driving the car, there is a slight (but noticable) miss in the rev range. This is not when beating ont he car, just casually driving the car around.

-The plugs are gapped to .022, the plugs look good but you can tell they are running on the lean side when checking them after driving around.

-Timing is at 15 degrees, checked with timing gun and conzult as well.

-I'm running JWT s3 cams, and im not completely sure if the ecu is tuned for them

-I did not pressure test the system yet (will be done tomorrow), but i my experience that should make it run rich, and stumble when revving...not super lean.

-I have sprayed starting fluid around vacuum lines, intake manifold and couplers (all from ATP, all Consta-Torque clamps) and notice no jump in rpm.


Any help/suggestions would be great, i have searched and research but it is hard to navigate through all the threads trying to solve my particular issue.

[SoguRacing]

perhaps there's a vacuum leak in the system or a leak before the air flow metering device. your cam will also lower your vacuum as there as valve overlap is more prevalent at lower rpms.

[4x4le]

like said earlier, its probably something mechanical or a leak, especially since you have low vaccume. I would say the leak is after the throttle body. Your vaccume shouldnt be that low unless your rpms are barely registering. Then when you rev the car it goes rich which should mean that metered air is being wasted (most likely out of the same hole).

If your confident that there are no leaks then this is probably just another reason that pre tuned ecus are not good.

[mattsil80wis]

perhaps there's a vacuum leak in the system or a leak before the air flow metering device. your cam will also lower your vacuum as there as valve overlap is more prevalent at lower rpms.

like said earlier, its probably something mechanical or a leak, especially since you have low vaccume. I would say the leak is after the throttle body. Your vaccume shouldnt be that low unless your rpms are barely registering. Then when you rev the car it goes rich which should mean that metered air is being wasted (most likely out of the same hole).

If your confident that there are no leaks then this is probably just another reason that pre tuned ecus are not good.


good points, but if there was a leak wouldn't it make the car rich not lean? that is what ive always experienced

[4x4le]

Well its idling lean but rich under boost and has low vaccume. That sounds like an intake manifold leak to me.

[steve shadows]

Where is your Wideband mounted?

Your Wideband should always be mounted about 3 feet from the back of your turbine wheel

otherwise you will get all kinds of screwy readings on them

ACOMS RAZOR

[mattsil80wis]

Where is your Wideband mounted?

Your Wideband should always be mounted about 3 feet from the back of your turbine wheel

otherwise you will get all kinds of screwy readings on them

ACOMS RAZOR


its mounted where the downpipe starts going under the car i would say its atleast 2 feet from the turbine wheel

[aziankingz]

usually people would mount their widebands to their testpipes..

[mattsil80wis]

usually people would mount their widebands to their testpipes..

i would say its about 8 inches away from the test pipe if that