Alright as we all know i've been getting poor gas milage. I raced a Mazda idk wtf it was but i kicked its *** but my car didnt want to go over 115 and i KNOW that its capable of much better than that...would plugs be a cause for something like that?

 

my 93 has a speed limiter at 120

 

Probably in need of a tuneup:

- check the intake manifolds check for carbon buildup
- new plugs/wires (check em)
- check your timing.
- get on a dyno (the only really good way to check)

 

when i got codes ran on the car my timing came up fine. Intake is clean, did that about a month ago, i need to check the manifolds. New plugs are the only thing i can think of they come in coil packs so no wires are needed, my car is a 91 and i dont think they are supposed to have speed limiters, most z32's NA top out around 140. I also do need an oil change.

 

speed limiter is around 155

i had some trouble getting over 120 a while back. i did the seafoam thing, and that worked pretty well.

i havent really gone much faster than 110 in my Z anywayz...

 

i never really speed (anything above 70), but it just makes me curious why im loosing all that speed and i want to get it fixed just for the sake of it. I think i just need plugs and oil change, oil is looking pretty damn nasty

 

Here are some of the general tune-up items for the Z. Some you have done. Some you might not have. If you don't have any ecu codes, all of your sensors are in proper working order. If you read the ignition timing from the ecu, with a ConZult or equiv., that is only the programmed timing. You still need to check your base ignition timing with a timing light at the crank pulley and adjust it, if required, by rotating the CAS.

This is basic Z maintenance. If you don't know when any of the following items were last done, they should be done now.

Replace Spark Plugs
Check base ignition timing
Clean air filter
Replace fuel filter
Replace PCV valves
Vacuum test the EGR valve, fuel pressure regulator & damper
Clean the throttle bodies and IACV (IAV) valve

Closely check all fuel lines and clamps for leaks, tightness and cracks. If they're 10+ years old just replace them now. Leaks can cause fires, and insufficient pressure at the injectors in high rpm conditions

Closely check all vacuum lines for cracks, hardness, or being disconnected. If they're 10+ years old just replace them now. Bad vacuum lines are the cause of vacuum leaks which cause all kinds of running problems

Inspect all of the electrical connections for frayed, cracking, loose wires and make sure all connectors are tight. If there are any signs of corrosion, remove the corrosion and apply dielectric grease on the pins. Z'zzzz are famous for having problems due to corroded electrical connections.

Check the throttle cable where it connects to the linkage. 90% of the cars I've looked at, the cable is not properly adjusted. If the cable is too loose the t/b butterflys will not open all of the way. Also check for fraying of the cable.

When you change your oil, look closely at the oil as you're draining it from the drain pain. Look for water or small metal flakes in the oil. What you see, or don't see, will give you a good idea on the internal condition of your motor.

I'm sure there are some things I forgot......

Also, keep in mind, most of the above items will not cause an ecu code if they become defective. They will cause your motor to run badly nonetheless.

 

hmm...once my n/a hit 120 it slowed down a bit but i got to 130 and had a little more left in it. i want to go again but thats scary as *****. cops and traffic and crap.

 

i have tooking my 1993 300zx well over 120mph right around 145 or so my 1993 is a 3rd month of 93 and i have the very best spark plugs money can buy.. IRIDUIM NGK spark plugs

 

whats your point?

 

91zman,

I totally forgot about the throttle cable, have your wife/bf/gf get in the car and push the accellerator all the way to the floor. Look at the throttle botties and make sure they are opening the butterflies all the way. If not the cable could be worn/stretched and need adjusting.