Bartman Posted July 20, 2006 Share Posted July 20, 2006 So I recently upgraded my engine and I’ve been working out a couple of bugs since I put it all back together. One of the last things I fixed was a problem with my Knock Sensor so that my system is no longer throwing any codes. Now that I’ve gotten rid of that code my engine can go into closed loop and as soon as it does it starts stumbling. I hooked up TTS Datamaster to take a recording of a test run. When the engine is in open loop everything looks fine, then as soon as the system goes into closed loop the fuel trim numbers vary wildly. So is my problem the O2 sensors or maybe the wiring to them, or could it be something else? I could post the Datamaster file if someone can read it and help determine what the problem is. Quote Link to comment Share on other sites More sharing options...
mark Posted July 20, 2006 Share Posted July 20, 2006 02 sensors would be the first place I would look. When I have a snesor go bad the car runs like crap. Are you using new sensors? Are you sure you sure you have the right sensors? Do you have a good connection from the sensor to the ECU? Will the car run correctly if you disconnect the 02 sensors after it starts to stumble? How far down stream are the sensors? Quote Link to comment Share on other sites More sharing options...
strotter Posted July 20, 2006 Share Posted July 20, 2006 Bartaman, can you post your datalog in a text format so we can all see it? Quote Link to comment Share on other sites More sharing options...
mark Posted July 20, 2006 Share Posted July 20, 2006 One more question, Where is your knock sensor located? Quote Link to comment Share on other sites More sharing options...
wheelman Posted July 20, 2006 Share Posted July 20, 2006 Bart, Post your datalog, I've got Datamaster and can look at it, not that I'm any kind of expert but I can at least look for obvious things. Try and log it in open and closed loop. You might have to save a couple logs if you are using the eval version as it will collect only 30 seconds worth of data. How baddly does it stumble? What cam are you running? Do you see the O2 sensor outputs varying between 150 and 900 mV in the Datamaster display? Both left and right should jump around quite a bit at idle, at least mine do, they smooth out when the engine is revved. Have you changed the programming in the PCM and if so how? How does it run when revved? What does the output from Datamaster show when the engine is revved? Wheelman Quote Link to comment Share on other sites More sharing options...
jbc3 Posted July 20, 2006 Share Posted July 20, 2006 Post the log. I would look at the intake hose/connections and make sure the intake hose is on tight and there are no leaks after the MAF. The O2's and KS don't usually cause idle issues. Jody Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 20, 2006 Author Share Posted July 20, 2006 Thanks for all the questions, suggestions, and general information. I did not replace the sensors when I did my install, but they were replaced within the last 1,000 or so miles with original GM units (I've heard the Bosch replacements aren't that great). I plan on checking the continuity of my wiring from the PCM to the sensors to ensure that is not the problem as well. I've been wondering about the location of my sensors, they're connected down around the transmission area. Could this be to far down stream? I will try and post the datalog tonight or tomorrow (I can post it in text format as well?). I was able to get a complete recording including data while it was still in open loop and after it went into closed loop. I'm pretty sure I got more than 30 seconds of data, but I will verify that. My Knock Sensor is located just above the oil filter. Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 20, 2006 Author Share Posted July 20, 2006 ...How baddly does it stumble? What cam are you running? Do you see the O2 sensor outputs varying between 150 and 900 mV in the Datamaster display? Both left and right should jump around quite a bit at idle' date=' at least mine do, they smooth out when the engine is revved. Have you changed the programming in the PCM and if so how? How does it run when revved? What does the output from Datamaster show when the engine is revved? Wheelman[/quote']The car stumbles quite a bit coming off of idle and low RPMs, but seems to go away at higher RPMs. My PCM was just reprogrammed by pcmforless based on my recent upgrades. The cam with my 1.6 roller rockers has a total lift of .580 and .587 with 112 lobe separation. I'm not quite sure which figures you generally use for duration, but the cam card states: duration @.006 tappet lift 286 304 duration @ .050 236 242. I'll get the datalog posted up to show what it reads when the engine is revved. Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 20, 2006 Author Share Posted July 20, 2006 I just found a post over at LT1tech where someone talks about O2 sensors. "If they are fairly old, it would be a good idea to replace them... Also, since the car's been sitting a while, if the O2's have been sitting un-installed they may have already gone bad... My personal experience can attest to that. I removed mine while doing a head gasket repair and left them sitting on the bench. When I put everything back together they didnt work anymore... A good friend of mine (a GM tech) said that because they werent in the pipe, the part inside the sheild (sensor part) had excess moisture exposure and corroded, causing the failure. He also said that here in humid FL that this can happen with the O2's removed for more than a few hours or so. I guess they stay in good shape so long as their still mounted in the pipe because the pipe itself acts as a barrier from the condensation that would otherwise kill the sensor... Im sure the fact that they're used and have been exposed to many heat cycles helps this corrosion process to happen faster." Well, mine aren't that old but they were sitting out for quite a while when I did my swap and again when I did my upgrade. I found some NGK replacements at Summit Racing for around $35 a piece, maybe I should give them a try. Quote Link to comment Share on other sites More sharing options...
deja Posted July 20, 2006 Share Posted July 20, 2006 Too bad there is no easy way to test those things. You said something about where yours are mounted. I thought they were supposed to be reasonably close to the engine. Quote Link to comment Share on other sites More sharing options...
wheelman Posted July 21, 2006 Share Posted July 21, 2006 Bart, Thats a fairly agressive cam, it should have a pretty good lope at idle. Based on what you described above it sounds like you have a stumble coming off of idle not while it's idling, is that true? If that's the case I'd also check the TPS connections as well as the MAP and MAF connectors and look for vacuum leaks. Do you notice it runs rough whenever the throttle position is changed? I'm a little skeptical about the O2 sensors being that fragile. Mine rattled around in a box for more than 1 1/2 years while I got the car ready for the engine and they're fine. Not sure how old they are either, they're the original units pulled from the donor along with the engine. Wheelman Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 21, 2006 Author Share Posted July 21, 2006 I've got my datamaster file, not I just need to figure out where to upload it. It does stumble coming off of idle as well as changing throtle position at lower RPMs. The idle is also really low when it's in closed loop. I'll get the file posted somewhere and then post a link. Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 21, 2006 Author Share Posted July 21, 2006 Okay I upoaded the DataMaster file to my web site www.570z.com. There's a link on the main page called "DataMaster file" located just above the Latest Updates heading. Just right click and select "Save Target as...". The file is called 'test2.uni'. Let me know if you have any problems getting the file. Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted July 21, 2006 Share Posted July 21, 2006 Bartman, I tried to download your data file and it saves as a test2.htm file. If I just double click it, a screen of code shows up.. Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 21, 2006 Author Share Posted July 21, 2006 Bartman' date='I tried to download your data file and it saves as a test2.htm file. If I just double click it, a screen of code shows up..[/quote']When the "Save As" dialog is displayed it wants to save the file as an HTML document by default. You need to change the "Save as type:" field to "All Files" and ensure that you save the file without a .html extension. The file should have a .uni extension to work in DataMaster. Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted July 22, 2006 Share Posted July 22, 2006 I don't understand why it insists on downloading as a html but I just changed the file to a uni after I downloaded it and it works fine. Now I wish I had some advise for your problem... I don't... Quote Link to comment Share on other sites More sharing options...
jbc3 Posted July 23, 2006 Share Posted July 23, 2006 Bartman, OK, even in open loop your right BLMs are telling you that there is a problem, they should be reading 128 and yours is 135-141. I am not sure why. As soon as you go into closed loop the left O2 is lazy and is not alternating like the right is. Your BLMs are all over the place and are seriously split. 128 is where your should be shooting for and you have 108 (rich) on the left and 153 (lean) on the right at times. First of all, I'd reset the computer and see if the open loop situation goes away, your numbers should be locked at 128. Then I'd swap the O2's to see if the problem of the lazy response follows that left O2. If it does, replace it. If not, you could have a bad wire, or connector. Then re-record and see where you are. If the problem stays on the left side also make sure you don't have a vacuum leak (TB gasket, cracked injector O-ring etc..) that could be part of the problem. Also is your exhaust tight before or near your O2 sensor, a leak could cause funny numbers also. I had split block learns at idle in closed loop, so I reprogrammed my computer to run in open loop idle all the time. It helped me out a ton! The big cam can throw the numbers off at idle easily. I have never personally had a big problem with split block learns other than idle with larger cams, but many have. You are getting knock counts and retard at 5 mph and no acceleration, so I would suspect that you have something banging around, like the exhaust. The knock that was on the file should have nothing to do with the problems you are describing. Do you have Tunercat or LT1-edit? Jody Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 23, 2006 Author Share Posted July 23, 2006 ... Do you have Tunercat or LT1-edit? Jody No I don't, but I may get it soon; especially if I can use it to help solve this problem. I've got a couple of new ACDelco Oxygen Sensors on order, so I'll see what difference that makes. I don't think I have any vacuum or exhaust leaks, but I will check that out as well. P.S. - Thanks for looking at my file, it seems like a great diagnostic tool and I've learned alot about how my car operates from this recording and studying the data. I'm hooked now and I just need to decide which editing program to purchase. Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted July 23, 2006 Share Posted July 23, 2006 Bart, I hope you post the results. jbc3 comments seem very useful. When I view the voltage of my 02 sensors on my scan tool they are all over the place. I was told that this was normal. It seems by jbc3's comments using the data master software things should be more stable. I should get my pcm back from AKM electronics Monday or Tuesday and I expect to have some of my own issues...Also check your yahoo email... Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 23, 2006 Share Posted July 23, 2006 I had a similar issue when I was running the 93' PCM and harness. Turns out my o2 sensor wires were crossed from the PCM so my left bank o2 sensor was controlling the right bank and vise versa. My harness was a modified stock harness(it was Darius's old harness before he switched to a stand alone). Also make sure your injectors are plugged into the right ones. I could see those getting crossed from side to side pretty easy. Is your harness a stock harness or a painless? Guy Quote Link to comment Share on other sites More sharing options...
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