Looking for advice
 

I have been trying to figure out why I get this stumble around 2800k. I have replaced my wires, plugs, and added a Crane hi-6 for spark. I went through 3 cans of carb fluid with no leaks to find. My timing at idle is dead on. Mods are in my sig. Notice the area I outlined in red. Also, my inj duty cycle. Any help is appreciated.
Chris

I'm thinking this is not the same as the secondary stumble...Every single other report says it happens right at zero PSI while you say it's at high vaccuum. I'm guessing this is another problem. What's your staging RPM set to?

3584 staging rpm

mines the highest it will go.

well sounds like me and you have a similar issue. and now that turbo2ltr is on i think now would be a perfect time to get everything out in the open about issues and things to check/test?

also with this rtek do i need a wideband o2 guage or the display or can i just get the wb o2 and use the pda for now as the display?

Can you post a log like mine to view?

i dont know how to post it like that unless you tell me? im retarded when it comes to this crap.

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but what idont understand is ifits 100kb thats tiny willyou be able toveiw it?

lets see

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Heres some logs of my problems.. happens from anywhere from 2400 to 2800 rpm

the zip file has the .pdb log where it happens a lot. just look at the spots where the wideband shows 16-18 and the tps is not "24" (not decel fuel cut)

this could be totally retarded to ask but this could a have nothing to do with twin scroll could it since its around 2400-2800 rpms even though its removed and gone could the ecu not know this or something? im really prying into all aspects need to get this fixed.

Looks similar to mine.

how can this be so hard to figure out... hey wankler have you checkd your fuel pump? im going to tommorrow and im changing plugs and wires and fuel filter and o2 and then ill see if its still the same.

I will check my fuel pump. It is a carter, and I did do the FUle Pump Relay mod a while back. I have put new:
Injectors, Clips, Plugs, wires, Crane Hi-6, Checked my grounds, but I am re-dooing them again. Some guy I talked to mention that if you put a volt meters black straight to the battery, and then go check your ground with the positive side. You should see no more then .2v. If there is a greater voltage, then you have a ground issue. Well three of my four grounds read higher then .2v when the ignition is on. I am investigating. Still waiting for injectors so I can swap back to stock for testing purposes.

This is an old GM Technical Service Bulletin, but it should help anyone wanting to verify that their amp has a good ground:

METHOD OF VERIFYING ' GOOD ELECTRICAL SYSTEM GROUND ' #87-8-139 - (04/07/1987)
VEHICLES AFFECTED: ALL MODELS

When diagnosing electronic systems for incorrect operation, it is often necessary to verify that ground circuits are good. This article is intended to clarify what is meant by the term "good ground" and the preferred tools and methods for verifying it.

A "good ground" is a ground circuit that has a resistance of zero OHMS.

Ground circuit resistance can be measured in OHMS using a digital volt OHM meter (DVOM). When using a DVOM, it must be set on the 200 OHM scale to obtain an accurate measure of the circuit resistance. Many meters have both a 200 OHM scale and a 200 K scale. The 200 K scale will not measure zero OHMS accurately. If you are not sure how the meter is to be set for the 200 OHM scale, refer to the meter operating instructions for proper settings. If the meter is an autoranging or self-scaling meter, read the meter carefully to be sure which scale it is setting itself to.

Before measuring resistance in any circuit, the resistance of the meter should be measured by touching the leads together. A meter with a good battery and leads in good condition will read less than .2 OHMS usually zero. If the leads measure anything more, an accurate measure of the circuit resistance may not be possible.

Always remember - resistance cannot be measured accurately on a "live" circuit, All current flow through a circuit must be stopped by disconnecting its power source before measuring resistance.

Ground circuit resistance can also be checked by measuring the voltage drop across the circuit with a DVOM set on, the 2 volt scale. The voltage drop will be zero across a "good ground" circuit.
Remember, fully understand a meter's functions before using it!

To add to this, a good ground for car audio applications will have a return resistance reading of 1/2 ohm or less. I have yet to have a return reading of 0 ohms. If a ground return reading cannot be made to get below 1/2 ohm by means of the "BIG 3", then it is adviseable to ground direct to the battery. Electricity is an algebra equation, what you do to one side you must do to the other. Pay as much attention to the ground wire as you do the power wire.

The BIG 3 is a great place to start for a good ground, however it is the assumed proper method of grounding. What we are talking about here is the older and wiser 4th brother to the BIG 3 (the BIG 4).

So a proper ground wire will be as follows.

- clean of residue and paint.

- secure.

- have a resistance return of 1/2 ohm or less.

- be of adequate guage to carry the return as compared to the power wire.

To simplify the measuring of the return, use your meter as described. Disconnect the - battery terminal and disconnect the ground wire from you amp. If your dmm probes are not long enough, you will need to create a jumper extension out of some primary wire or whatever wire you have handy. Measure this wire for any resistance reading and subtract it from the total.

Many installers are not aware of this nor practice this method. It takes time and time = $ so don't get all pissy if you had a professional install done and this was not checked. A poor ground connection or high resistance reading may seem trivial under no load, but once you are pounding your nice new amp and it is drawing large amounts of current, this little reading has become a monster reading that has caused many an amp to fail for no apparent reason. It may be noticeable as a extremely hot running amplifier in a short time period, poor output levels or diminishing levels and of course a blown power supply or output section in the amplifier.

While the original article was written for the years gone by, it still is applicable to the newer generation of vehicles. A good ground is not about the amount or size of the metal in the return to the battery but about the resistance through it. Todays vehicles are a combination of metals, spot welds, glued together unibody panels and isolated chassis components. The return through these components is where the resistance reading comes into question and this is what we need people to understand, why the BIG 4 needs to be done if the BIG 3 does not solve the problem.

Looks like the ECU is closed loop at this time. Can you post a log with the O2 sensor included? Also, if you unplug the O2 sensor (will prevent the ECU from going closed loop) do you still have the hesitation?

-Henrik

it gets a lot worse with o2 sensor unplugged for me

That is one thought of mine. I will post a log this shortly. Still in the early am here.

well then what would be a soloution if unplugging the o2 works?

I swaped out my O2 sensor and put a new one I had laying aournd in. Problem still there. here is a log.

well mine runs way better with the o2 unplugged... but it still stumbles alittle when engine temp gets to 216-232

For what it's worth, that car isn't in closed loop for some reason. Try to see what happens if the stock 02 sensor is connected to the ECU and compare it to what you have now. From what I've seen, in closed loop the afr will NEVER get to the high numbers your showing for afr.