80LS1T Posted July 26, 2003 Share Posted July 26, 2003 Well as you may know I have my 1980 LT1/T56 280ZX on the road! Now heres the sucky part...it kinda runs on the rough side. I cant seem to get the idle down from 1500 RPMS. I would like it to be around 800-900 if possible? I have the set screw all the way back but it just wont idle down? Could this be caused by the Idle Air Control unit? If so how can I fix it? My car also isnt accelerating as smooth as it should. It is ok after about 2500 RPMS but before that it seems not want to take off. When ever I am not moving and not in gear it runs fine all the way through the RPM band. Could this be tranny related? I am not really sure what to look for with this? Thanks for all the help! Guy Quote Link to comment Share on other sites More sharing options...
mas28O Posted July 26, 2003 Share Posted July 26, 2003 Check your engine codes, I found out that I have 2 engine codes on mine that I am working on. But it sounds like you have a vacuum leak. Mike Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 26, 2003 Share Posted July 26, 2003 Yeah it could be the IAC valve. Another consideration would be an electrical problem. The will run the idle up if the alternator isn't charging enough. 1500 seems a little high though. It's weird about the power before 2500 because the LT1 makes it's torque peak at 2800. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 26, 2003 Author Share Posted July 26, 2003 I will check for a vaccum leak. I have 3 codes present. 22(TPS Signal),44 (left bank running lean) and 65(right bank running rich) I am going to see if any of those lead to anything this weekend. I already replace the TPS but the code is still there. I even went through the diagnostic procedure for code 22. Guy Quote Link to comment Share on other sites More sharing options...
Guest benjlv Posted July 26, 2003 Share Posted July 26, 2003 pull a plug from both sides and see if its actually running lean and rich on the opposing sides. I dont know what would be causing that...but if the plugs arent showing it...then its probably a problem with the oxygen sensors or their wiring. But if its actually running lean and rich that would explain the lack of power and rough running. i would start by fixing the TPS signal..and see what the other codes do from there Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 26, 2003 Author Share Posted July 26, 2003 Oh yeah and I am getting a backfire out the exhause once and a while too. Well when I checked the code out with the diagnostic procedure it says that it is an "intermintant probolem" The TPS signal is normal when I test it with my DVOM(volt meter). Everything seems normal there but the code keeps coming back? What is the firing order on a SBC? I am wondering if I am having a cross firing problem? I have the back 2 (6 and 8 cylinder) passenger side plug wires running right along one another so they could be crossfiring....couldnt they? Guy Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 27, 2003 Share Posted July 27, 2003 Get a spray bottle filled with water and turn your garage lights off. Start the car and spray the wires. You'll know if you've got a crossfire problem. Did this on a 944 with a starting problem once and found it very easily. Jon Mortensen Quote Link to comment Share on other sites More sharing options...
Guest Your Car is Slow Posted July 27, 2003 Share Posted July 27, 2003 Two areas id check first. EGR...and the optispark EGR would throw a code however...the opti wouldnt. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 27, 2003 Author Share Posted July 27, 2003 I dont have an EGR (eliminated in computer also) and my optispark is new. I am going to try the spray bottle method and check my plugs tommorow to see if any are fouled out. Guy Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 27, 2003 Author Share Posted July 27, 2003 Ok I tried the water bottle trick but they arent crossfiring. Also I erased the codes and took it for drive tonight...code 22 is back and code 44 is back . I dont understand why my TPS code is there because as far as I can tell it is functioning properly! Guy Quote Link to comment Share on other sites More sharing options...
Mudge Posted July 27, 2003 Share Posted July 27, 2003 Not only is it possible, but there is no idle in the PCM higher than I believe 1200 or 1250, you have a vacuum leak perhaps and possibly its not even entering closed loop? Quote Link to comment Share on other sites More sharing options...
Mudge Posted July 27, 2003 Share Posted July 27, 2003 EGR would throw a code however...the opti wouldnt. It sure can, low/high res pulse error, I've had it myself when I found oil and coolant inside my 94 Optipuke. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 27, 2003 Author Share Posted July 27, 2003 Ok well about the code 22 TPS low voltage....I went back out and tested it again and it is supposed to read atleast .230 volts/230mV...I am however getting .092 volts/92mV. Is the TPS adjustable? Guy Quote Link to comment Share on other sites More sharing options...
JasonE Posted July 27, 2003 Share Posted July 27, 2003 Guy, Are you using the stock exhaust manifolds on each side? From your other posts I got the impression that you have a stock exhaust manifold on the drivers side and a header on the other. If that is true, is it possible that could be one of your problems. To me it seems having the better flowing exhaust on the one side and the more restrictive stock manifold on the other would cause some sort of problem. Not sure but hope it helps. Jason Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 27, 2003 Author Share Posted July 27, 2003 Yes I have the stock manifold on the drivers side and a header(if thats what you can call it, cause its not much of one thats for sure!) on the passenger side. The header is more like a shinny manifold because its so short and small. I dont think it flows more than the manifold on the other side. Im going to go check the plugs right now, so I'll let you guys know if there are any problems with those. Guy Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 27, 2003 Author Share Posted July 27, 2003 Well I think I might have figured out why its running so rough....I just went out to the garage to check out the spark plugs and when I pulled the #6 and #8 plug wires off and checked them, I noticed that half the insulation on them was gone because they had been touching the manifold! I have those 1200deg protective boots(those metal mesh wire covers) on them but I guess it just got too hot for too long for them to work. I doubt they are supposed to touch the manifold. I guess its off the parts store to get some wires. Then I will see if my codes go away. I dont think it will help code 22(TPS) but maybe 44 (lean exhaust) will! Guy Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 28, 2003 Author Share Posted July 28, 2003 Well I installed the new wires on #6 & #8 cylinders and boy does it run smooth now! However, I still dont know why my idle is up at 1500 rpms. I am going to investigate tommorow with the help of a scanner. Guy Quote Link to comment Share on other sites More sharing options...
Guest tom sixbey Posted July 29, 2003 Share Posted July 29, 2003 i'm not familiar with the SBC's, but could having different headers on each side put the egt sensors in locations different enough to produce a big enough differential in their readings to cause a problem? Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 29, 2003 Author Share Posted July 29, 2003 I dont have EGT sensors(exhaust gas temp sensors). My running rough problem was the #6 & #8 cylinder wires but my high idle almost has to be a vaccum leak. I think it might be coming from the spot where the EGR valve was mounted. I only have a block off palte on it and not a gasket. I am going to seal it up tonight to see if it does the trick. Guy Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 29, 2003 Author Share Posted July 29, 2003 Well I sealed up that block off plate but it is still idleing too high?! I am not sure which direction to head here? Any ideas? Oh and I am still getting the code 22(TPS) code 44(lean on left bank) and code 65(rich on right bank) Guy Quote Link to comment Share on other sites More sharing options...
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