Cascade Crew

83Z28BlackBetty · Posted: Wed Apr 28, 2010 8:38 am Post subject: Surging feeling while cruising

Hey all, So my TBI setup is awesome. Have finally got it tuned pretty well. I still have lots of fine tuning to do but for the most part it is going well.

But now i have a strange surging feeling while cruising. it happens while there is relatively low load on the engine, such as going downhill on the freeway or exiting. it surges or has a feeling of stumbling. Also while idling in gear it seems to idle rougher than it did when i first did the swap.

So far i don't think it is in the tune because i burned one of the first tunes i did and it was still doing it. I've checked the ICM, replaced plugs and wires not too long ago, and flow tested my injectors. Its not throwing any codes or knocking so i'm at a loss here.

thoughts? The coil, MAP sensor, O2 sensor, coolant, air temp are all new. Knock, TPS, and pickup coil are all not new, but i don't want to just start replacing parts till i know whats wrong.

~JAKE

Alphius · Posted: Wed Apr 28, 2010 9:14 am Post subject:

Mine surged on the freeway and idled rough when I had it too lean at those points. Likes to run 15:1 on the freeway and 12:1 at idle, any leaner and it surges pretty badly.

Maybe you have a vacuum leak developing? Your situations where it's surging are high vacuum situations. Knock, TPS and pickup coil shouldn't cause those problems.

Kind of related but unrelated, but if I was you I'd pick up a wideband for tuning and diagnosing problems like this. Could help out.

Spikeophant · Posted: Wed Apr 28, 2010 11:12 am Post subject:

I'd say vacuum too, my car does this, it's carbbed, though, and I located a massive vacuum leak in a line going to the charcoal cannister. Turns out, when the 350 was dropped in, and they didn't put anything in there to hold lines up off the engine, one of them melted a 3" section out of the line.

aaron_sK · Posted: Wed Apr 28, 2010 5:34 pm Post subject:

What does the O2 see at that point?

kurfbird · Posted: Wed Apr 28, 2010 5:36 pm Post subject: surging

Check egr or egr soylnoid. that what the problem with my 92 tpi surging while crusing

Twilightoptics · Posted: Wed Apr 28, 2010 5:53 pm Post subject:

Is it a surge or a is it sharper?

If you've got too much timing and too lean for the timing it will missfire and jerk a little. It wont be a crazy "MISSFIRE" but enough to studder a little bit off and on.

83Z28BlackBetty · Posted: Fri May 07, 2010 9:31 pm Post subject:

O you all were right. Vacuum leaks from the front of the TB Smile

fixed and now i'm almost done with the tune! of course there are always little things to tweak as we go, but for the most part it is done.

I just got my AC serviced for the summer today by a buddy and its ready to be blowing ice chunks at me! which is a good thing since it is already 93 degrees out.

PS any good tips from you TBI tuners out there? this is all very new territory to me and any input would be a BIG help. THanks

~JAKE

Dewey316 · Posted: Fri May 07, 2010 9:40 pm Post subject:

83Z28BlackBetty · Posted: Fri May 07, 2010 9:48 pm Post subject:

I like that line of progression, its pretty much what i've been doing so far.

also, I've heard that i'm supposed to turn off power enrichment mode while tuning as well as a few other features. Is this true? if so how is this done?

~JAKE

Dewey316 · Posted: Fri May 07, 2010 9:56 pm Post subject:

Yes and no. You want to stay out of PE when you are doing part throttle, you do this by setting the PE enable TPS % value closer to 100%. Beyond 90%, you are basicly WOT, you don't really "part throttle" drive at above 3/4 throttle.

The thing to remeber though, is with PE disabled, the AFR you are shooting for is stoich. The PE enable is what richens the mixture. So you want to work your way up in the RPM and throttle openings, because you are goign to be running leaner than you should be with PE disabled.

--John

blue89 · Posted: Sat May 08, 2010 11:10 am Post subject:

How did you get the air pump o2 offset disabled? I've been meaning to call you but then I see something shiney or wanna go ride bikes.

Dewey316 · Posted: Sat May 08, 2010 6:49 pm Post subject:

Travis, it has been a long time since I have done it. There is a air-pump o2 sensor voltage offset, you basicly zero that out, so that regardless of if the computer thinks the air-pump is on or off, the target o2 voltage is always the same.

I would have to dig through the 747 tables and constants to find where it is though.

I was able to find it when I did the chip for my 8746, but when I talked to Jake, I couldn't remeber exactly where it was, and am not sure where it is in the 747 computer.