My car has developed idle surge after a recent injector upgrade when i installed 24lb Cobra Injectors. I posted a thread in the TPI forum and asked what to do and i was told i need to do some tuning and adjust the injector constant. So ive bought a Autoprom and all the necessary things needed to read and burn a chip. Ive even burned a chip with the adjusted Inj. constant and the car is doing better. Its still surging but it doesnt die when its warm and put in gear anymore. Ive read the topic under the beginners guide to prom burning on Common idle issues and i just dont fully understand what parameters to adjust for the fuel at idle. Can anyone give me some hints. And before anyone says datalog, i plan on doing it this weekend. Just looking for a few hints.

 

Need to change the injector compensation values first. There are two tables for them.

Then if it continues to surge only during closed loop, tweak the proportional gains.

RBob.

 

^ That.

And before that make 100% sure that you don't have a mechanical issue like some spark plugs that are still fuel fouled, or an exhaust leak upstream of your O2. Also check for fuel pressure regulator leaking into the vacuum line, leaky cold-start, etc...

A wideband, even just stuck in the tailpipe would be helpful, and even if you have to borrow one.
A lean condition can also cause surging and fuel smell in the exhaust.

 

Ok so today while fixing a few exhaust leaks i realize that my car has no O2 sensor at all. It must have got deleted when the previous owner had the exhaust done. Does this mean my car is staying or tuned for open loop. Also should my car have one sensor at the Y before the cat, or should it have 2, one at each collector because i was only able to find one sensor plug for the wiring. Could me not having an O2 be causing the surge because it idled fine before?

Also the wiring connector i found is a 3 prongged one with a weather tight connector. But all the O2s i look up online from my parts store look like a 1 wire. The connector i found is on the driver side tucked up by the bottom of the windsheild wiper motor. I figured if that the factory sensor connector should be by the passenger side before where the factory cat was. Also my parts store is asking me if its upstream or front. Is there a difference?

 

Stock O2 location is the drivers side exhaust manifold. Uses a one wire sensor.

Get enough noise on the open O2 signal wire and they can go closed loop. Not a good thing when the signal is invalid.

RBob.

 

If your car has a closed-loop tune, then if you change anything on the engine, like injectors, then it will have to have a tuning adjustment since there is no adaptive fueling going on anymore.

Datalogging still works, though you will not have an BLMs/fuel trims to look at. You would need to use a wideband O2 for monitoring AFR so you can adjust fueling.

There are several advantages to running an open-loop tune, but you must have control over the tune to keep up with any changes you may make to the combination.

This is assuming you do have an open-loop tune, which I don't know if you have.

 

Well im adding in an O2 today. Can anyone look at my bin and give me some info on whether its an open or closed loop tune. Im not begging for a new prom or bin, just want some insite on what i already have. If so email me at simsc88@gmail.com and ill send you a copy, it would be much appreciated.

 

email sent.

 

Ok so after I did some logging I determined that my car is staying in open loop. Also the surging gets worse one it reaches around 120F. Also the warmer it gets the worse the surge gets. All my parameters look close to a stock tune. Any clue why my car is hung in open loop. I also ran it on a stock tune and the surging was the same and it stayed in open loop then too.

 

did you get the o2 sensor installed?

O2 sensor is vital for closed loop operation. Could be its not entering closed loop because theres no O2 signal? idk on that. I can tell you i usually enter CL at about 130F or so.

 

I just now looked at your BIN.
You do NOT have an open-loop tune.
The requirements for going into closed-loop are factory calibrations.
Your open-loop calibrations are NOT suitable for good full-time open-loop operation, and would cause you to run quite rich most of the time.
That is very bad considering your injectors are also too big.

Normally you should have an O2 sensor installed into your driver-side exhaust manifold, and a Purple wire running to it.
The 165 ECM pinout shows this: http://www.eecis.udel.edu/~davis/z28...165v8tpi-6.jpg

I don't remember you describing your exhaust, so do you still have the manifolds? and is there an O2 port on your driver-side manifold?

I can't guess why the O2 was deleted if that was the case, or how your ECM will react once it's plugged back in.
In either case I think I would continue increasing the value of your injector constant until your AFR comes back in line and you have more stable running, at least until you can resolve what is going on with your closed-loop.

I will now try to take a look at your logged data, though my files may not read them the same as yours.

edit: ^didn't work. I will need your datastream reading file to look at your datalogs. I use an older and modified version and it's not compatible.

 

Yes I installed the o2 Sunday and it made no difference. My exhaust consist of long tubes and the y is just a little past the trans xmember. I put the o2 in the y right where the 2 pipes murge. In my logs u can see the milivolt readout from the o2 And it varies but further down it shows o2 status and it says not ready. Anyone got a clue why that is?

 

That's WAY too far away from the exhaust ports for the factory O2 to work correctly. It would never be able to maintain closed-loop that way.
One solution is to install a heated O2 sensor, - which has 3 or 4 wires to power the internal heating circuit. It may also help to thermal-wrap the exhaust down to where you have your O2 mounted, but this will eventually damage your headers and Y-pipe if they are not stainless.

The previous owner may have already tried a heated O2 and still failed, which would explain it not having an O2 sensor.
It seems your choices are to make some changes, get better at PROM tuning and attempt to make the closed-loop work, OR make it an open-loop tune - not using a narrow-band O2 sensor.

OL tunes are not the easiest for even some experienced tuners to get everything right, and there's no way to do it remotely (by mail or online).

Given feedback (datalogs) that included the readings from a WBO2 I could only get you in the ballpark. The only way to get everything right in an OL tune is for the tuner to spend a good bit of time with the car over several days.

CL tunes have adaptive fueling and can learn many adjustments. OL tunes have no adaptive fueling. That means the calibrations you put in have to be right on. That explains why it's a bit harder for some tuners to accomplish and get everything within an acceptable window.
You will need a WBO2 to do it, or you would need to take your car to a tuner with experience doing this.

If you think some of your running problems are from the ECM attempting to go closed-loop, then you can change the coolant temp threshold for closed-loop to something very high >250*F to prevent this and see if it smooths out any.

 

Also, in your BIN the O2 diagnostic code 13 is set, so you should be getting the error code for the O2 not working correctly.

 

Do you think moving the o2 to the header collector would work. Might try a heated o2 but how should I wire it up?

 

Closer to the exhaust port helps. The heating wires are just 12v and ground.
Do a search here for heated O2.

If you manage to get it running closed loop and get lots of negative BLMs (below 128), then you probably still need to increase your injector constant size until you get 128 or just slightly under, like 125-ish.

With an active O2 sensor you have to make certain there are no exhaust leaks between the exhaust valve and the sensor. Otherwise closed-loop will never be right.

 

Well im gonna get a heated o2 tomorrow and try it out soon. Let yall know how it goes. Thanks alot 305sbc for all the help!

 

Well it looks like the heated o2 did the trick. As soon as it was installed most of the surging was gone and it was idling the best it has since the new injectors. It still dies sometimes when going into gear but it's going into closed loop now and seemes to be running great. Thx again for all the help 305sbc!