Hello all, I recently joined this site and have already found a few problems on here that I can fix. So now my question. I recently had my 93 Z28 pumped upto a 383 and it was running really nice for a while. The lifters have needed to be adjusted so that's all that was wrong. But here's my problem now, eve since I brought my car over to Germany, it has been running bad. On the way back from the port my speedo stopped working and she started to run funny. I readjusted my lifters again and got the ticking sound removed but she started smoking and I smelled gas all the time. I checked my codes and she came up with the speedo code, a lean condition code and some other stupid codes that were old. So my main question is this. My car idles a lil higher then it should be, like around 900 and she shakes a bit more then she should. I checked all my plugs and # 6 and 8 were fowled a bit so cleaned em off and she was running better but still had the idle shake and very light missfire. So my main question is could my O2 sensors have gotten fowled by my lifter being out of whack and the speedo not working cause the computer couldn't adjust for the speed? I never get a SES light since I fixed my speedo so im guessing it's my O2 sensors but im not exactly sure... ANy help would be appreciated.

 

If the plugs are fouled, its running rich. They are both on the same bank of the engine, so it appears to be a problem with Bank 2. Could be an exhaust leak before the O2 sensors, or misfires causing a "false lean" on one side of the engine. Which Bank showed the "lean code" that you retrieved? Sort of hard to determine if the misfires are making it run rich and making it miss more, or if something else is amking it run rich and the misfires are the result of the problem, not the cause.

The speedo code will affect a few things, like A4 shifting, fuel cut on coast down, idle RPM follower on coast down, but it shouldn't have caused any problems with th A/F mixture.

If you could get a scanner or scan software on it, you could look at the long term fuel corrections (BLM's) and that may give you insight to whether its a problem affecting one bank of the engine or both. That helps you narrow down where to look.

I'd focus on the misfires. Look for exhaust leaks. Look for arcing wires. Listen for erratic injector sounds. Pull the rails up and look for drips from the injectors. And if the O2 sensors are old, and you feel they may be damaged, replace them.

 

One thing I think you overlooked about the speedo thing Injuneer was that the car is a 93. The 93 uses a 4L60 (no E) so the speedo is strictly a gauge on the 93s The throttle cable determines line pressure and so on.

But everything else Injuneer said is right (not that he needs my confirmation on that).

The 93 is batch fire and like Injuneer said the injectors are fired by bank and not sequentially, which would explain why one foul on that bank can effect the others.

I would check the speedo circuit, it uses and electrical pick-up that is gear driven from the tailshaft, I'll bet it's a wire or the pick-up. As far as the rough running as said before it could be simply a bad O2, an exhaust leak, or a vacuume leak. A scanner would help greatly for sensor diagnostics.
But again a 93 has only a few scanner chices (none cheap) so a multi meter can help determine if the ECM is seeing the correct voltages from the sensors ,you can use a pinout diagram and plug the multi meter into the appropriate wire to see what the ECM is reading.

 

I was gonna going to check my wires tonight when it's dark and try and see if I can see any blue light or arching going on. I know that the 93 has limited functions when it comes to scanning the computer and looking for codes. I'll have to check all the things you guys listed this weekend and I very much appreciate the help. I haven't gotten this engine to run perfect since I had it rebuilt and since im in Germany now, I can't have him fix it. *Sigh* Well this will get me to know every little part of my engine now. Oh one question... I have 26lb injectors on it and I have seen a bunch of 383's running 42lb's. Why the major difference? Am I not seeing all the power I should be with only 26lbs? My mechanic said they should be fine for it but I dunno.

 

If you havent already I would take a look at Shoebox's site to help with what the sensors should read.

http://shbox.com/1/4th_gen_tech1.html

 

At stock fuel pressure, a 26# injector is going to be maxed out (100% duty cycle) at about 430 flywheel HP. You don't want top run the injectors at 100% DC. So realisticaly, you are limiting yourself to less than 400HP. If that's all the engine is making, a 26# injector is fine. If its supposed to make more, you need larger injectors.

 

Code 27: Exhaust Gas Recirculation (EGR) vacuum control signal solenoid valve circuit

Quad-Driver Module (QDM) #2 circuit
applies to:
- 4L60 TCC control and temp switches
or
-T56 reverse lockout

Im not the smartest with all the code stuff so what exactly is it saying is wrong? That the solenoid is bad? God I wish I had my code book with me out here and not back in the states....

 

Injuneer thanx for clearing that up with me.... Im pretty sure she should have more then 400hp easy to the flywheel so I might wanna go with a bigger injector. What would be a good choice? Im pretty sure 42lbs would be way to much for what I have but if you get a bigger injector, does it always run more gas through it or just when it needs to?

 

Okay I know I might be posting a lot but just updating my results. When I got to my car I checked my EGR lines, started my car and she almost died. I left her running and reached back and played with the lines and the idle picked up and she ran smoother. How can I tell if my EGR is bad though? Hmmmmmmm I just read the article on testing the functionality of it. Some more things to try this weekend so im gonna be busyyyyyyyyyy. I'll let you guys know what happens and hopefully this helps a lot. Thank again guys for the suggestions. They have been a real help and I understand my car a lil bit more now.