I have a '90 2+2 that I have installed an Injen cold air intake, and have installed a 3" exhaust system with Flow Master American Thunder mufflers. The exhaust system does have 2 Cat. converters, and 2 resonators as well. It seems to run rich below 3200 RPM. When it is cold, it runs fine. Once it warms up, it is definitely rich. I have installed a new temperature sensor and fuel pressure regulator. When you remove the temperature sensor connection, the idle does change, telling me that the computer is getting the signal. I have recently changed all of the spark plugs as well. I have also recently put a new water pump, thermostat, timing belt, and timing belt tensioner, though I don't believe that any of these items would, or did effect this issue what-so-ever (just some maintenance history ). The car has about 100K miles on it. I am thinking that there is not enough back pressure on the heads with the 3 in. exhaust system, but after reading the other thread on back pressure, I don't think this is the issue either. Does anyone have any experience with this situation?
Thanks for any help in this matter, it is driving me crazy!

 

Sounds like the timing might be a bit off.
Double check it and adjust as necessary.

 

Been there - done that! I had this problem before I changed the timing belt. Then when I did the timing belt change the first time (Yes - I had to do it twice! ). I went to change the water pump initially. Since I had to disassemble the front end of the engine to do the water pump, and I didn't know the history of the vehicle, I went ahead and changed out the timing belt. Unfortantely, the new water pump end shaft was not machine correctly, and the clutch fan bushing at the end of the water pump shifted, which took out the water pump bearings on test drive - So... I had to do the timing belt again. I didn't want to run a glycol soaked timing belt. I checked, and double checked the alignments of the cams and crank. Then I had my son check my alignment before I put it back together. Since I had this problem before, in between, and after the timing belt / water pump issues, I don't believe that it is a timing belt issue, unless its the cam wheels. I couldn't feel any 'slop' between each cam and its timing wheel, though I didn't put an indicator on them. Only checked based on feel.
Can you think of anything else?
Thanks!

 

Did you reset the ecu by disconnecting the battery for ten minutes or so? This should have been done when the new intake went on. Have you checked for any ecu codes? Another thing to do would be to clean the throttle bodies and IACV. It definitely smoothed out my idle.

 

I haven't reset the ECU. I will try that tonight and see if this changes anything. I haven't checked for any codes. I don't have the appropriate equipment to do so. Any suggestions? I would like to go with something that I can interface with a laptop computer. I have a '90 2+2 N/A, '93 Coupe N/A, and my son has a '85 Z31 N/A, and recently bought a '88 300ZX SS Turbo (stage III). I would like a system that would be able to interface with all 4 of these cars to acquire ECU codes.
Thanks for the help!

 

There are a host of company's selling a consult software programs, I don't believe that there is one to do all of your Z's.

I went with the BlaZt system, check out this post www.zdriver.com/forum/showthread.php?t=13189 good information.

You can reset your ECU by disconnecting your battery for at least 30 minutes.

My Z did something simular to what you have discribed, but my problem ended up being a bad O2 sensor on the left/side, but replaced both.

I read that the ECU goes to a default mode on the O2 sensors when the engine is cold and at Wide Open Throttle-(WOT)

Good luck in your hunt for a solution.

LATER

 

you can check your codes without any machine. you just need a scrw driver and a code chart. Here's a good write-up on how to do it. As far as the running rich problem, any of the above solutions may be able to fix it. You should reset your ECU after ANY and all upgrades. O2 sensors are to blame for a lot of rich issues, and the MAF obviously will affect it as well.

 

sorry forgot to post the write-up
http://www.ttzd.com/tech/diagnostictech.html

 

Also, you're talking about a stand alone. Stand alone systems are usually pretty expensive and are a little overkill unless you're trying to get every ounce of performance out of your heavily modified car. You would do great with an Apexi SAFC.

 

MGH?? lol...... I tried replying back to your pm at the time the forums went down. I still haven't got my BlaZt yet. It's been 3 weeks today since Jason said he mailed it. I emailed him and he said he'd send another one if it didn't show up. I'll give it another week.

Kevin, you might want that BlaZt package. I speculate that it might work on most OBDI nissans......... not sure tho.

 

When was the last time you change your O2 sensors? It is highly recomended that you change it with the mileage that you have on it. Check also your sensors such as: MAF, ECT, O2 sensors and others that has to do with your air and fuel. It should run rich during cold start up. The ECU goes to open loop during start up and full throttle. It goes to close loop during normal operation (cruising) engine is warm up. I am not going to all the details but your best bet is to get check by a good tech. Just a note if you use a scan tool some of the problem might not show up because you still have the OBDI. Good luck!!!

 

Yeah, thats me...some forums I'm MGH and Topless93...go figure...10 different forums total, Z and nissan.

Sorry to hear about the delay on your program...thats gota suck...yeah, I wondered what happened, I kinda felt like you didn't want to talk to me any more.

Anyway I'm still learning that whole system, when you do get yours and if you need any help let me know...I think I know just enough to be dangerous.

LATER

 

Try cleaning your throttle bodies. You should also check your TPS and make sure it's properly adjusted. ECU may think you're at WOT well before you really are.

 

I reset the ECU by removing the positive battery terminal for about an hour. I then reinstalled the batter terminal and took it out for a test drive last night and this morning. WHAT A DIFFERENCE! The car runs significantly better! I love these easy fixes! I have purchased replacement O2 sensors, though haven been able to install them. I bought an O2 socket to assist me in the change-out. The left bank one appears to be frozen. I can not get it to break loose. I have sprayed with WD-40 numerous times and it still won't break loose.
Any suggestions? Also, it would appear that I have to remove the battery box in order to gain access the the right bank O2 sensor. Is there another approach to get this one? I've worked on allot to cars in my life time, though I am new to Z's. I now have two Z32s, and my son has two Z31's. I guess we got the 'Z-BUG!'
Any help would be appreciated!

 

I've heard of individuals getting the engine warm and this expands the exhaust manifold and the bushing that O2 sensor is in, and sometimes it will break loose.

The only drawback is now everything is hot ! ! ! ! !

One thing that I did was, my O2 sensor socket/tool is 3/8" drive, and I had to use a 3/8" to 1/2" drive adpator so i could get my 1/2" drive breaker bar on that puppy....it then came loose.

Good Luck
LATER

 

Heat works wonders, especially on exhaust components....... even turbocharger bolts, that is if you were to take one apart.

 

Try spraying some liquid wrench or something like on it and let it soak for a good few hours or overnight. Then try. You might need to pull out the breaker bar! Glad to hear that it was an easy fix.

 

I think that I have tried every product like liquid wrench out there. I tried multiple applications of liquid wrench with hours of soak time in between. I can't seem to find enough clearance for a breaker bar. I put the O2 sensor socket on it, then tried a box wrench on the end of the socket. I get bruises on my fore arms because it is so tight trying to reach on both sides of the shock tower to get to the wrench. Don't have the clearance to go down from above. May have to take it to a shop and get then changed out

 

That sucks....hope you can get it eventually...somehow. I hate when cars do this! Doesn't it make you want to light it on fire!!! Things like this put me back on projects....simply b/c I end up cussing my car out and when that happens I just have to go inside and quit for a while.

 

I used more than one extension stacked on top of each other and had my breaker bar well above the fender.......worked like a champ.

 

First of all, I'll have to get an adaptor from 3/8" to 1/2" drive. Then I'll be able to try the multiple extensions. You must have had at least 1 universal in that stack up, because mine is not a clean shot. Maybe I'll try again this weekend.
Thanks!

 

PB Blaster spray works best for breaking these things loose. Numerous auto parts stores sell it. I bought mine from NAPA auto parts.

 

topless is right..you can let the engine get warm and it will help a little. We had to heat my o2s when i replaced the stock pre cats on my TT with the spilt flange down pipes. When u go to do the 02s on the NA, I suggest a swivle and about 12 or so inches of extension. I had 18 between my tool box and my dads. And another thing..go by a can of PB blaster and some antiseize compound. Spray the PB blaster on the O2s and let it set..then when u go to put the new ones in smear some anti seize comound on the threads to make the change a bit easier the next go around.

As for the cheap mods/fixes..there are alot of them around. you just need to know where to look and who to ask

 

I bought some PB Blaster and a 3/8" to 1/2" drive adaptor and attacked the O2 sensors today - again! I finally got them out with allot of persuasion with a 1/2" drive breaker bar. I broke a 3/8" drive universal in the process, and had to resort to the 1/2" drive universal, which was not easy getting a 1/2" drive extension between the firewall and the back of the block with all of the wiring harnesses etc. in the way, but I got it! And I am not cut up too bad! I removed the battery and battery tray to gain access to the right bank O2 sensor. Now it purrs like a kitten at an idle, and roars when it should! Thanks so much for all of your help and advice in resolving this issue. Can't wait to see what kind of fuel economy I get now!

 

Awesome! good job! I love that sense of accomplishment when you fix something!