Bartman Posted July 24, 2006 Author Share Posted July 24, 2006 ... Is your harness a stock harness or a painless? Guy My harness is stock and was modified by the previous owner. I'll be sure to verify the oxygen sensor wires aren't crossed when I change the sensors and check everything else. Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 27, 2006 Author Share Posted July 27, 2006 I got the new O2 sensors delivered last night and I had them installed within about a half hour of their arrival. I didn't hook up my laptop to get a DataMaster log, but I took it out for a test drive anyway. The good news is that the O2 sensors seemed to do the trick. I drove it around for quite a while and the stumble never happened. I'm pretty sure the system is still going into closed loop, but I will make another test run while logging the data with DataMaster to make sure. Thanks to everyone for their help. Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted July 28, 2006 Share Posted July 28, 2006 Thank you for sharing... Quote Link to comment Share on other sites More sharing options...
Tim240z Posted July 28, 2006 Share Posted July 28, 2006 Bart, I still have the TunerCat system for that engine...... Tim Quote Link to comment Share on other sites More sharing options...
Bartman Posted September 27, 2007 Author Share Posted September 27, 2007 Believe it or not, I'm still working on this problem. There's been a few times where I thought it was resolved, but it wasn't. For some reason the stumble is really bad some times and not so bad at others. The problem is actually a few years old as Tim240z was experiencing the same thing when he had this engine in his car. So I've been thinking that there's a vacuum problem somewhere although I couldn't find one anywhere. I finally got a good deal on an intake with ported runners that match my heads, and installed it. It looks like there was some internal leaking between cylinders where the intake manifold connects to the heads, so I had high hopes of finally getting rid of the stumble. So I buttoned everything up and it sounded better, but I still have a stumble. It appears that I have much better vacuum, in fact it looks like there's so much vacuum that it's sucking oil into the intake and blowing smoke out the exhaust. I've found some posts on another forum that talks about oil getting into the intake through the vent line between the throttle body and valve cover as well as through the PVC circuit. I'm going to repace the elbow on the valve cover with a Purolator breather B23165 that's supposed to resolve the problem in the vent line and possibly an inline compressor catch can for the PVC circuit. I'm taking my car into my firends shop on Monday to see if he can figure out what going on, as it doesn't appear I'm making much progress. Any other ideas before I bring it in? Quote Link to comment Share on other sites More sharing options...
mark Posted September 27, 2007 Share Posted September 27, 2007 How old is the optispark? Do you still have the vent line from the passengers side valve cover to the intake? This was my source of oil into the intake that quickly fouled the O2's. Are the throttle blades clean or carboned up? This will cause a hard starting issue and a stumble. Hope you get this fixed. I loose sleep over crap like this. Quote Link to comment Share on other sites More sharing options...
Bartman Posted September 27, 2007 Author Share Posted September 27, 2007 How old is the optispark? Do you still have the vent line from the passengers side valve cover to the intake? This was my source of oil into the intake that quickly fouled the O2's. Are the throttle blades clean or carboned up? This will cause a hard starting issue and a stumble. Hope you get this fixed. I loose sleep over crap like this. The Opti is a new Accel unit. The vent line from the passengers side valve cover is routed to my throttle body and it's still there, but I'm planning on using a breather that should prevent oil from going through. The throttle body is fairly new as well, so it's not carboned up, but it had an oily film that appeared to be from the vent line. This problem has caused me to lose sleep for quite a while, and I've just about given up. I've run out of ideas, so I'm hoping someone can come up with something or else I'll have to see if my friend's shop has any luck with it. Quote Link to comment Share on other sites More sharing options...
mark Posted September 27, 2007 Share Posted September 27, 2007 Bart, I've got a 93 pcm in my Z. Will it fit the 94 harness? There is no mass air but if the plugs to the pcm are the same, I'll ship it out there for you to give it a try. Just send it back in a day or two. Quote Link to comment Share on other sites More sharing options...
Bartman Posted September 27, 2007 Author Share Posted September 27, 2007 Bart, I've got a 93 pcm in my Z. Will it fit the 94 harness? There is no mass air but if the plugs to the pcm are the same, I'll ship it out there for you to give it a try. Just send it back in a day or two. I appreciate the offer, and I'll let you know based on what my friends shop can find. With all my upgrades a stock tune probably wouldn't work to well with my engine. I had the problem with the tune from the previous owner as well as a new tune that I got from PCM for less after all my upgrades to the engine (cam, heads, etc.). Jody (jbc3) was kind enough to edit my PCM for less program a while back so that it would idle in open loop, which really helped it run better at idle. We did this thinking that the cam overlap was causing the O2 sensors to think it was running lean when it wasn't. Quote Link to comment Share on other sites More sharing options...
mark Posted September 27, 2007 Share Posted September 27, 2007 I appreciate the offer, and I'll let you know based on what my firends shop can find. With all my upgrades a stock tune probably wouldn't work to well with my engine. I had the problem with the tune from the previous owner as well as a new tune that I got from PCM for less after all my upgrades to the engine (cam, heads, etc.). Jody (jbc3) was kind enough to edit my PCM for less program a while back so that it would idle in open loop, which really helped it run better at idle. We did this thinking that the cam overlap was causing the O2 sensors to think it was running lean when it wasn't. Not stock, about 425 hp and torque. 383 lt1. Similar numbers, tune is great. Quote Link to comment Share on other sites More sharing options...
Bartman Posted September 27, 2007 Author Share Posted September 27, 2007 Not stock, about 425 hp and torque. 383 lt1. Similar numbers, tune is great.Great numbers Mark! do you think the actual PCM could have problems or just the tune? If it's just the tune, maybe you could just send me that and I could give it a try (if you have the file). Quote Link to comment Share on other sites More sharing options...
mark Posted September 28, 2007 Share Posted September 28, 2007 Bart, It sounds like everything is functioning properly. If you have no codes then I would think it is either the tune or it is mechanical. It should be fairly easy to try a different pcm, even with a stock tune, you could make a determination about you stumble. If you use the stock tune on you motor you obviously don't want to hammer on the car too bad. The knock sensor would pull timing and keep you from melting a piston but still use some restraint. I had a similar issue for a while at high rpms. At 5200 the car would fall on its face. Turned out to be valve float. Easy fix but I'm a slow learner and it took a while for me to figure it out. One other thought, I remember when I started my swap, some guys were already using the mass air equiped cars and were having problems with stumblling caused by turbulance at the mass air sensor. I'm not sure what you,ve got from you filter to the sensor but you may want to try a few different configurations of ducting to the mass air sensor. If I remember correctly, the problems was related to the air taking a sharp turn just before the sensor. Good luck. The offer stands. Quote Link to comment Share on other sites More sharing options...
jbc3 Posted September 28, 2007 Share Posted September 28, 2007 Bart, If you are still having issues, and the O2's seem to be stable, look at your MAF. Did someone port the MAF, de-screen it or take out the center section? If they did, it could be causing you some issues. You could also try cleaning the MAF with contact cleaner. I ported and de-screened my MAF, but I have heard that some people have had issues after doing it. Lastly on the MAF, if you know someone local to you with an LT1, try their MAF. Occasionally I have had issues where the car just doesn't seem to run well and I look in the throttle body and you can see it's all black. A good dose of TB cleaner and all is good. I am guessing, large cam, lots of reversion and it causes exhaust deposits in the intake track. Jody Quote Link to comment Share on other sites More sharing options...
Bartman Posted September 28, 2007 Author Share Posted September 28, 2007 My MAF is a Grantelli unit (like this one http://cgi.ebay.com/ebaymotors/Granatelli-MAF-sensor-for-LT1-camaro_W0QQcmdZViewItemQQcategoryZ33557QQihZ017QQitemZ270169499152QQrdZ1QQsspagenameZWDVW), but I still have the stock one as well. I removed it completely to see how it would run using speed density and it didn't seem to run any different (although it was throwing a code, as expected). I don't have any bends in my intake, but I'll run without the hood to see if the airflow is being restricted before my air filter. Thanks for all the suggestions, I'll keep playing with it this weekend and see if I make any progress. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 30, 2007 Share Posted September 30, 2007 Ok so you had the same problem with... *the old heads and cam *old oxygen sensors *old intake set up *stock tune *new tune *old OPTI *new OPTI *stock MAF *new MAF Sounds like the PCM itself might be a problem. What kind of spark plugs are you running? Can you post a datalog again? Guy Quote Link to comment Share on other sites More sharing options...
Bartman Posted October 1, 2007 Author Share Posted October 1, 2007 ...What kind of spark plugs are you running? Can you post a datalog again? Guy I'm running NGK TR55 plugs. I've also replaced almost all the sensors to no avail. I couldn't wait, so I took the intake manifold off again to try and see why the car is smoking since I replaced it. The intake and throttle body had a significant amount of oil in them; so that explains the smoke, but I don't really know why. I'm waiting for another fel pro 1284 intake gasket set before I can install everything again and see how it does. I was planning on taking it to the Japanese Classic Car Show on Saturday, so hopefully it'll be running good before then. I'll make another datalog after I get her running again. Quote Link to comment Share on other sites More sharing options...
mark Posted October 1, 2007 Share Posted October 1, 2007 Have you done a compression test? Quote Link to comment Share on other sites More sharing options...
Bartman Posted October 1, 2007 Author Share Posted October 1, 2007 Have you done a compression test?No, but that's next on the list. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted October 1, 2007 Share Posted October 1, 2007 Do you have extra ground wires going from the engine to the body? Do you have anyway to monitor the fuel pressure while the stumble is happening? I really doubt it a compression issue just because the issue comes and goes. I would still check it just to be sure though. I would try to borrow a PCM from someone local and load up your program into it and see if it goes away. Either that or just buy another one and see if it goes away, if not just resell it on ebay. Guy Quote Link to comment Share on other sites More sharing options...
sweetride2go Posted October 1, 2007 Share Posted October 1, 2007 wow, still struggling w/ this one eh??? well its interisting, cause i hav the same problem w/ a LT1 in a '67 camero.. and ive done much of the same, changing parts n sensors, w/ no or little gain, and the stumble comes back again and again, and sometimes its not there... gahhhh!! but im thinking it mabe a ground issue mabe??? and i dont hav the MAP on mine... stupid thing of it is that the car ran perfect for the first 4-6 months... and sometimes it throws codes, and sometimes not... so frusterating... i still need to come up w/ another ECU and see if that solves the issue, one test i havnt done yet... ryan~ Quote Link to comment Share on other sites More sharing options...
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