So Close! yet so far! CIS A/F new issue

[MD540iT]

Well, I thought I had it running better. Took it out for a a test drive for a bit over an hour; and after about 45min. and a few WOT runs (but always limited due to the too rich on full boost, so WOT runs only last about 5sec)

the problem that popped up now, is going to rich on Tip in. SO it was running decently (never perfect but I come to expect that) and now all of a sudden, its dipping into the 9's A/F when cracking the throttle. So its bogging off the line, which makes accelerating from a stop sluggish.
Now once up to speed and I'm mostly out of the throttle, just cruising, when I open the throttle to accelerate, it briefly dips to about 10a/f before coming back to normal.

and yes I checked all the hoses/lines can not find anything.


If I had to say it analogously, its like something is "slipping" everytime I think I have it running right, I go drive it, and half way through, something goes out of whack and I have to fix it again!

[patina]

Have to tested your CIS pressures? Cold/warm/boost? If so, what are they? What mods done to the car?

[MD540iT]

Originally Posted by patina

Have to tested your CIS pressures? Cold/warm/boost? If so, what are they? What mods done to the car?

yes, inline Pressure gauge, not much aside from boost controller.
and double adjustable WUR

[RarlyL8]

You need to compare AFR and fuel pressure real time simultaneously when this phenomenon occurs. It could be that the fuel pressure is taking a dump. If so that would give you a good starting point.

[MD540iT]

Originally Posted by RarlyL8

You need to compare AFR and fuel pressure real time simultaneously when this phenomenon occurs. It could be that the fuel pressure is taking a dump. If so that would give you a good starting point.

thats a little hard to do while driving.
But wouldnt fuel pressure going down make it lean not rich?? Plus it has a new fuel pump.

it would be easier to figure out if it was going lean.

[Bucketlist]

Originally Posted by MD540iT

thats a little hard to do while driving.
But wouldnt fuel pressure going down make it lean not rich?? Plus it has a new fuel pump.

it would be easier to figure out if it was going lean.

Some of us have added a Control pressure gauge along with Air fuel in the dash so we can always be aware of what is going on.




Good Luck!

[mark houghton]

Originally Posted by MD540iT

thats a little hard to do while driving.
But wouldnt fuel pressure going down make it lean not rich?? Plus it has a new fuel pump.

it would be easier to figure out if it was going lean.

Surprised nobody has corrected you. CIS is in some ways counter to what you intuitively think. Fuel pressure is the counter force against the force of air flowing down on the metering arm. Reduce the fuel pressure and the arm will deflect further...opening up the fuel delivery ports further.

[MD540iT]

I half figured it out! I noticed the FV was just barely working, but when I opened the throttle slightly, It would come on more. SO, I disconnected the throttle "sensor" and immediately the RPM's went up about 500, (I turned the idle back down) got in the car and revved the engine, and NO A/F dip!! and the FV was running "normally" so that kind of fixed the problem.... but why? WTF???
and after a couple minutes of running with the TPS disconnected the RPM's settled down. Then I plugged the TPS back in and now things seem back to "normal" (for now)

Obviously the Closed throttle switch is working but what happens when you open the throttle, thats making it go way rich??

[MD540iT]

Originally Posted by mark houghton

Surprised nobody has corrected you. CIS is in some ways counter to what you intuitively think. Fuel pressure is the counter force against the force of air flowing down on the metering arm. Reduce the fuel pressure and the arm will deflect further...opening up the fuel delivery ports further.

YES< you're right, had a brain fart there. I was simply thinking "regular car" FP from pump to the system. not the "control pressure"

[mark houghton]

Originally Posted by MD540iT

YES< you're right, had a brain fart there. I was simply thinking "regular car" FP from pump to the system. not the "control pressure"

Brain farts happen to the best of us...me notwithstanding.

[MD540iT]

any thoughts on why disconnecting the throttle switch would seem to clear up the problem?