80LS1T Posted June 30, 2004 Share Posted June 30, 2004 Incase you didnt know, I have been working out the bugs for my LT1 for about a year now. The biggest issue has been the fact that it ran really rough under a light load and at idle. A little background.... I bought my wiring harness and computer from "Darius"(yes the guy with SC LT1, 600HP+ Monster 240Z) and he bought it from Street and Performance. Once it was installed it seemed to run rough at idle and under a light load. It ran good under WOT though. My first issue was a burnt plug wire on my #7 cylinder. This happened because it was laying on the header. I thought those 2000* wire protector covers would prevent this from happening but I learned the hard way that it will not. They are not ment for that kind of heat consistenly. Next I found out that my IAC motor was not wired correctly for the 93' IAC motor. It was wired up for a 96' IAC(Darius had a 96' LT1 but was using speed density not MAF). So after I chase my tail on that one for like a month last year, checking for vaccum leaks, compression, adjusting the idle screw......l I finally decided to check the wiring. Once that was wired up correctly the idle smoothed out a lot and I could now idle at 800rpms like I wanted to! Then this year I installed a A/F ratio gauge and wired it up with a toggle switch so that I could switch from the left bank O2 to the right bank O2 when I wanted to. I only installed the gauge because I needed to take up a spot in the dash cluster to make it look uniform with the new fuel level gauge. However, I kept getting a stumble and sometimes the check engine light would come on every so often and then go back out? But what I noticed with the A/F ratio gauge was that my "right bank" would run lean a lot and my "left bank" would run rich a lot. My exhaust was also very dark(like it was running very rich. I also notice that my fuel milage was about 8mpg! So I pulled the codes out and I had a "right bank lean" and a left bank rich" code. I started think about that A/F ratio guage and I thought "hmmm is it possible that the O2 sensors are crossed?" There was no way that I could have swapped them from left to right with the lengths of wire but if they were wired wrong that might cause this. So I check the wiring to see if they were wired wrong and sure enough, they were wired backwards! As soon as I swapped them around, my mpg went up to close to 20mpg, the black smoke from the exhaust stopped, it runs great under all types of loads/rpm ranges, and my A/F ratio gauge showed stoicho all the time at cruising speeds and goes slightly rich at WOT. It would have taken for ever to find this problem if I hadnt of installed that A/F ratio gauge. I only installed it to take up space but it solved one big issue for me! Now that I think about how those O2's were wired up and how the black smoke under heavy loads would come out of the exhaust......look at Darius's videos....guess what he had them backwards when the harness was on his car. Every shot that shows him flooring it there is a lot of black smoke pouring out of the exhaust. I know he didnt mess it up but Street and Performance sure did! Im just glad I finally figured it out! I think my engine bugs are finally worked out. Guy Quote Link to comment Share on other sites More sharing options...
Tim240z Posted June 30, 2004 Share Posted June 30, 2004 Glad to hear that you are coming right!!! I too chased a low RPM stumble for months, but have it sorted now, so I know the feeling!!! Well done! Quote Link to comment Share on other sites More sharing options...
DaleMX Posted June 30, 2004 Share Posted June 30, 2004 Boy I know that it feels good to finaly find the problems. Thanks for sharing that data. Thats a couple I can put under my hat. I have a S&P harness here at the house that's for sale, but will use one from Speartech on my car. I was checking the wiring on the S&P harness and it just didn't make sense to me so I dont trust it. I also have one done by another guy that I dont want to use that is for sale also. It is wired correctly, but looks like crap. Dale Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 9, 2007 Share Posted July 9, 2007 I'm going to verify my O2 wiring as I've been chasing down a similar problem as well. I guess the stumble problem is actually pretty prevelant, but there seem to be many possible causes and threads that aren't updated with the problem resolution. I've also found that Tim240z had this problem (that's where I got my engine from), but I haven't been able to find how he fixed his problem. Quote Link to comment Share on other sites More sharing options...
piston Posted July 9, 2007 Share Posted July 9, 2007 are you sure the o2 sensors from left to right would make a difference? they are the same sensors left and right! exhaust gas comes through same on both sides, i would assume it wouldnt make any different...or is one side of the exhaust gas is acutally richer than the other? because then, how would the pcm tell the difference between left and right? just a thought! Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 9, 2007 Share Posted July 9, 2007 are you sure the o2 sensors from left to right would make a difference? they are the same sensors left and right! exhaust gas comes through same on both sides, i would assume it wouldnt make any different...or is one side of the exhaust gas is acutally richer than the other? because then, how would the pcm tell the difference between left and right? just a thought!I've made a recording while I was experiencing the problem, and one side is showing rich while the other side is showing lean. Here's the thread I started a while back rgarding my problem:http://forums.hybridz.org/showthread.php?t=122403 Quote Link to comment Share on other sites More sharing options...
piston Posted July 9, 2007 Share Posted July 9, 2007 i hope the passenger side is suppose to be hotter or richer then, because my exhaust manifold ir more gold and hotter on the passenger side compare to driver. i always thought my pcm or injectors were off.. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 10, 2007 Author Share Posted July 10, 2007 Wow talk about bring a post back from the dead! LOL My problem was that only old 1993 harness that I bought from Darius the O2 sensors were wired wrong from the left to the right bank, so when the PCM saw a rich condition on the right back it would lean out the left bank. Once I had the wiring ok my problem was gone. Now I have the 1995 wiring and pcm in my car but haven't had it running yet so I don't know if everything is still good. I hope it is cause I really don't feel like tracking down new problems! Piston, the manifolds/headers should be close to the same in temp from side to side, if not then you have a problem. Guy Quote Link to comment Share on other sites More sharing options...
Bartman Posted July 10, 2007 Share Posted July 10, 2007 Yes this is an old thread, but it sounded just like the problem I'm experiencing; one side being rich the other being lean. Anyway I verified my O2 sensors are wired correctly, so unfortunately I'm still looking for a solution for my problem. Quote Link to comment Share on other sites More sharing options...
piston Posted July 10, 2007 Share Posted July 10, 2007 the last thing i can think of why my car is running crappy was because my rockers were too tight and my valve were not closed all the way... Quote Link to comment Share on other sites More sharing options...
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