1993 LT1 Closed Loop Hell......Part 2

[Deviant93Z]

Alright guys, after a few months of driving my car around locked in open loop I am trying to tackle my closed loop problems once again. Yesterday I was finally able to get my datalogging setup working correctly so I now have good values to work off of. I am using Tunerpro RT and a Moates CABL1. I will start by saying that the car runs normal in open loop, after it shifts to closed loop things begin to fall apart. The idle will fall below 500rpm at a stop....the idle will also bounce on decel. The engine runs rough and at times will violently buck and miss. When the car starts to do this my BLM values will fall well below 108, into the 90's range. In the datalogger, errors show up on both o2 sensors and closed loop shows timed out. Also the o2 graph seems like they are cycling very lazily and at times they will plateau and not work at all. These o2's are fairly new, within a year old, and are bosch 1 wire units. (I am not sure if they are heating properly as I have long tube headers.) The car has EGR and AIR tuned out.
Things that are new:
ECM
Engine Harness
ECM Coolant Sensor
Optispark
Plugs/Plug Wires
TPS
Knock Sensor
MAP
Coil/ ICM

I also have errors on both injector banks but I am not sure what causes that (or why these errors are showing as the car will run fine in open loop). Finally, I have a periodic injector driver error.

Any help would be greatly appreciated

[Z28pr0jekt]

Did this start happening before or after the Longtubes?

[Deviant93Z]

Almost a year after the longtubes, however some similar symptoms would show up from time to time during that period. It was never this bad though.

[Z28pr0jekt]

Typically on 93s when you switch to LTs you should convert to 4 wire O2s. Otherwise, the O2s will not heat up and can cause the car to go in and out of closed loop. But thinking on it further this doesn't sound like your problem.

[Deviant93Z]

I have been looking at the graphs and there are points where it seems to switch between open loop and closed loop. After the car warms up it should stay in closed loop, correct? As far as the heated o2's, that is about the only thing left that I can think of. I have tried almost everything besides that. I have the log files if anyone is interested in viewing them

[Z28pr0jekt]

I have been looking at the graphs and there are points where it seems to switch between open loop and closed loop. After the car warms up it should stay in closed loop, correct? As far as the heated o2's, that is about the only thing left that I can think of. I have tried almost everything besides that. I have the log files if anyone is interested in viewing them

Yes as the car warms up it should stay in closed. I'm not sure if Fastbird still has some leftover conversion kits but he used to manufacture and sell them to convert to 4 wire. Plug and play you just have to buy the 4 wire O2s

[Fastbird]

*ahem* Still do make the kits. Can't update my website cause of my horrid internet connection. Pm me if you want to get a heated O2 kit op.

Sent from my ADR6425LVW using Tapatalk

[Deviant93Z]

I will let you know as soon as I decide what to do, fastbird. Do you guys think there is a good possibility that this is the issue?

[MoeHorsePower]

yea, you pretty much answered the problem yourself by saying that the O2's are lazy and falling back in and out of CL. Once in closed loop the PCM will read off the O2, what happens with lazy O2's, it senses a lean condition and add fuel, then a rich and try to pull some out then going into open loop it goes back to the commanded A/F, so all of this will cause the symptoms you are describing. I'll bet your plugs are a little fouled looking...

[Deviant93Z]

I just picked up some delphi heated o2 sensors and ordered one of fastbird's conversion harnesses. Let's see what this will do...

[Fastbird]

PayPal didn't notify me of the order, I happened to see it Monday. I work m-f from 8 am to midnight right now, so I will have your kit done this weekend and out on Monday.

Posted from my Rezound

[Deviant93Z]

No problem, I was going to PM you for confirmation sooner but LTXtech has been acting screwy with my phone... plus the site being down. (It hasnt been letting me send PM's)

[Deviant93Z]

Installed the heated o2 sensors and fastbird harnesses this morning. Still has idle surge but otherwise the other issues seem solved......I wonder if my tune is contributing to the problem

[Fastbird]

Check continuity on the factory O2 wiring. See if any of it is burned. Were the stock one wire feeds for the O2's extended at all?

Posted from my Rezound

[Deviant93Z]

I built a new harness for the car last year, so the o2 wiring is in mint condition. I can see the o2's cycling on my datalogger and the CEL I was previously getting seems to be gone. My decel quality vastly improved, whereas before it would backfire and pop. The last remining issue is that the car will RPM hunt between 850 and 500 when is is moving but in neutral. If the car is stopped it quickly finds its idle and smooths out.

Perhaps it needs an exorcism?

[Fastbird]

That could simply be your throttle follower settings in the tune. I misread your last post and thought that the other issues were still present too.

Posted from my Rezound

[Deviant93Z]

I still have a factory tuned chip so I will swap it in and see what happens....Hopefully the issue will go away.

[OutCast]

I have been looking at the graphs and there are points where it seems to switch between open loop and closed loop. After the car warms up it should stay in closed loop, correct? As far as the heated o2's, that is about the only thing left that I can think of. I have tried almost everything besides that. I have the log files if anyone is interested in viewing them

What are you using to log? If Datamaster, send me the .uni file and I'll be glad to look through it.

[Deviant93Z]

What are you using to log? If Datamaster, send me the .uni file and I'll be glad to look through it.

I am using tunerpro RT, would you be able to look at a log from that?

Its actually doing some interesting things....I have 2 injector bank errors, 2 o2 sensor errors, occasional injector driver errors, and a closed loop time out. I'm not sure if the program is reading 100% correct but I do know that other than the RPM hunting the car seems to run fine. The graphs start to do screwy things during the surge though. I am at a loss...I do not know enough about this system to figure this out on my own .

[Deviant93Z]

Tried the factory tune...no dice.

[Deviant93Z]

Alright, I have the o2 sensors now responding, and the DTC's went away. What I am dealing with now is idle surge ONLY while the car is moving and in neutral. I have scoured the internet looking for an answer as to why and cannot find a conclusive one....anyone have any idea?


As a side note I think the site is still broken....just about everytime I try to post it crashes

[05hd]

Alright, I have the o2 sensors now responding, and the DTC's went away. What I am dealing with now is idle surge ONLY while the car is moving and in neutral. I have scoured the internet looking for an answer as to why and cannot find a conclusive one....anyone have any idea?


As a side note I think the site is still broken....just about everytime I try to post it crashes


What else does the car have done to it besides headers and a tune? Does it have an aftermarket cam? Stick or auto?

Site has been working ok for me.

[Deviant93Z]

1993 Z28 M29 Manual
SLP CAI/Trickflow 1LE Elbow/ Airfoil
160 Thermostat
Longtubes
2.5" OTA True Duals
TB Bypass Mod
!AIR/!EGR
Accel 24lbs Injectors (The tune is supposed to be adjusted for them)
Walbro 255lph Fuel Pump

[Fastbird]

Just a thought, but have you tried pulling your IAC and giving it a good cleaning? Could be that its sticking when you go to neutral coming off of throttle cruise where the IAC closes down low.......

Posted from my Rezound

[Deviant93Z]

I would say so too, problem is the car only does it in closed loop. I did just find something though...gas shot out of the regulator when I removed the vacuum line. That would explain the split BLMs....

[Fastbird]

Def fix that, though it shouldn't cause split blm's. Make sure the airfoil you have isn't blocking your IAC port.

Posted from my Rezound

[Deviant93Z]

Wouldnt the excess fuel being sucked into cylinders 6 and 8 through the vacuum line cause the passenger side to consistently run rich?
I am going to remove the air foil and see if that helps any. Also, do you know of a good brand of regulator to buy? I see there are a few different ones available.

[05hd]

Unless you have a reason to adjust the fuel pressure, I would go with a stock replacement regulator from GM or Borg Warner. A burst diaphragm will certainly case some issues.

If you still have the RPM hunt after the regulator is fixed, I would start looking closely at the tune. I don't see anything in your mods that would cause the issue.

[Deviant93Z]

I am going to order a delphi FPR tomorrow and see what that does for me. As far as the tune....the car has the same issues with this tune and the factory tune.

[Fastbird]

Wouldnt the excess fuel being sucked into cylinders 6 and 8 through the vacuum line cause the passenger side to consistently run rich?
I am going to remove the air foil and see if that helps any. Also, do you know of a good brand of regulator to buy? I see there are a few different ones available.

No because when the regulator fails pressure across the system gets jacked up. That regulator works by limiting the flow of return fuel to maintain pressure on the front side. It is positioned where it is because that's the first point past all the injectors that is can function properly, so it won't have an impace on just the nearby injectors.

Posted from my Rezound

[Deviant93Z]

Oh ok that makes sense... I removed the TB Airfoil last night and the surge remains. I had a few guys from my local club look at the car as well and they have come to the consensus that the issue is not electronical, but mechanical. So I ordered a regulator to fix the fuel issue and we will see what happens from there. I am going to fix this car if it kills me ! :shiner:

[Deviant93Z]

Replaced the FPR and still surges.....I guess the next logical thing is to do a super thorough vacuum leak check.

[Fastbird]

Have you tried cleaning the IAC yet, just to rule it out? Whats your TPS voltage doing while the surging is happening. You said you're data logging right? What program are you using?

Posted from my Rezound

[Deviant93Z]

TPS voltage sits level at .74 during the surging...About the IAC, what should I clean it with? I am pretty sure the service manual says no liquid solvents. I did reset its position as well. I am using tunerpro RT and a moates CABL1.

[Fastbird]

Brake cleaner, and a brush. You're just cleaning the pintle and screw area, nothing internal.

Posted from my Rezound

[zooguy]

a pic would help ...

[Deviant93Z]

The saga continues.....I pulled off the throttle body to remove the IAC and the IAC itself ended up cracking. So, now I have a new Delphi IAC and the problem still persists. Again, what would cause the car to surge ONLY when it is moving, in closed loop, and in neutral? There must be some common denominator between those three conditions that I can't seem to find. I think it is time for an exorcism!
!:hang:

[OutCast]

.74 is pretty high for the TPS when the throttle is closed. What are the IAC counts showing at idle? Should be in the 30 - 40s. If the TPS voltage is high and the IAC counts are also high, then you need to open up the two mounting holes on the TPS (slot them) so you can slightly rotate it until the voltage is around .45 - .65 when the throttle is completely closed.

Also check to be sure that the throttle is closing all the way and someone hasn't adjusted the throttle stop screw on the throttle body to hold the blades open.

[Deviant93Z]

Alright, after I get out of class today I will try adjusting the tps. The throttle blades are closing all of the way, I checked while I had the throttle body off the car. I will get back to you on the IAC counts when I get to my laptop. Although I seem to remember that it was somewhere in the 60s range.

[Deviant93Z]

I adjusted the TPS to bring the voltage within the required range and the problem persists. I did notice something interesting though....at idle one bank's 02 will read in the 800's and the other bank will read way down in the 40's. Could one bank be severely lean causing the idle surge and if it is would the problem be with the injectors?

[OutCast]

What were the IAC counts before and after you adjusted the TPS?

If there's a big difference in the O2 readings then can you also confirm if you're getting split BLMs?

Some things I can think to check...

verify there are no exhaust leaks on the side where the O2 is reading low
you can swap the O2s to see if the problem follows the sensor or not
verify that both O2s are getting power and ground for the heater circuit
verify the wire carrying your O2 signal to the computer is not burnt or damaged, especially near the pass side header where they come up (no butt connectors should be used on these signal wires due to the low voltages involved)
check/verify there are no fluctuations in fuel pressure

in the end.....it's prolly the opti:doh:

[Deviant93Z]

I will have to make a new datalog because of the things I have replaced and fixed since the last log I made. Is there anyway I could just send you the file for viewing rather than trying to explain everything that is going on?

[OutCast]

You can try uploading the file as an attachment to a post but you HAVE to zip the file first. OR I have also sent you my email address in PMs.

[Deviant93Z]

I ended up spending much more time studying for my exam yesterday than I had originally planned so no datalog yet. I will post one up early next week when I get back home. BTW Outcast, I tried to respond to your PM but the site is still crashing when I try to send messages. (It has crashed 3 times just trying to type this post...)

[firebird_1995]

I ended up spending much more time studying for my exam yesterday than I had originally planned so no datalog yet.

I just thought of jack black in orange county.... "I didn't go to college and look at me, im kick ass." Lol sorry. Good luck with with the exam.

[Deviant93Z]

Here is the log file, It is basically a run around town. This was logged in Tunerpro RT, I hope someone can discern something from this. Thank you all for your help so far

8905

[OutCast]

attachment is not working, did you zip the file with WinZip or similar app?

[Deviant93Z]

Yes, I used the winzip trial version I think. I will have to look at it again today.

[Deviant93Z]

Here is a Datamaster log. Maybe this one will work ok.

8921

[OutCast]

Nothing really jumping out in that log but I do see the fueling/de-fueling going on. I would check all your grounds and look for a leaky or clogged injector. You should be able to unbolt the fuel rails and pull the whole assembly (rails/injectors) up just high enough to see if any are leaking when the rails are pressurized. Triple check around the header flanges and collectors for exhaust leaks.

How do the plugs look?

[Deviant93Z]

On the drivers side bank the plugs look okay, I will have to pull the passenger side to see. I am definitely going to check for a leaky injector and I will check the header gaskets too. The grounds are all good. Thanks for looking, I really appreciate the help.

[Deviant93Z]

The problem is still ongoing, been swamped with school. I hope to have an update sooner or later.