AFM Adjustment

[cygnusx1]

I think thermistors are reverse. The resistance decreases as the temperature increases.

[cygnusx1]

EF Engine Fuel.pdf

Procedures for verifying temperature components in the 280Z

Edited October 5, 2011 by cygnusx1

[UR2H]

I think thermistors are reverse. The resistance decreases as the temperature increases.

I got .285 when warmed up and .8 when cold so the resistance did decrease as the temperature increased.

It was just weird that the longer I kept the prongs touching the connectors the resistance kept dropping.

I'm at a freakin' standstill.

According to the FSM, my resistance seems within range.

My spark plugs are consistent with each other and don't look like the fuel is rich. I still don't understand what all that soot is?

My fuel pressure is solid at idle and under throttle and increases accordingly to the loss of vacuum at the FPR.

I had new injector connectors installed a couple years back.

I replaced all the fuel hoses under the hood.

Yet I'm barely managing 12mpg without ANY aggressive driving...and the mechanic I consulted with used a machine to read my exhaust (kinda looked like the machine used when doing a smog check, but it wasn't) confirmed I am running WAY too rich.

Seriously I don't get it.

[Zed Head]

See the second paragraph in Post #4 again in this thread and think about it. I went through the same scenario, but I was sitting at 18 mpg for a long time, with signs of richness (gassy exhaust and dark plugs). Then, within a few days and one tank of gas (I do the math on each tank), mileage dropped to 15 mpg and the exhaust was full of unburned fumes. So I replaced the FPR with an aftermarket adjustable, set it to 36 psi and mileage jumped to 20 mpg and has been there ever since, with an occasional 21.

For whatever reason, the pressure looked fine when I measured it cold, but during driving it must have climbed to high levels. I never figured out exactly what was wrong with the FPR.

I had a theory that the aftermarket fuel pump (Airtex E8312) was pushing too much volume for the stock FPR but never confirmed anything. The new FPR (Aeromotive) made the difference though, in my case.

[grantf]

I think thermistors are reverse. The resistance decreases as the temperature increases.

We both said the same thing! The god of balance, you shall be.

[FastWoman]

Your warm resistance sounds like it's in the right ballpark. It would be great to get a cold resistance. It should be around 2.5 kOhms at room temperature. If you're not getting any reading at all, the CTS might be defective. That would make your engine run really rich when it's cold.

The slight shifting around in your readings is normal. If the numbers only change a little, you've got good contact. If they change a LOT, then you don't have good contact, and you need to have cleaner contact points. The lowest reading is the correct one.

[UR2H]

See the second paragraph in Post #4 again in this thread and think about it. I went through the same scenario, but I was sitting at 18 mpg for a long time, with signs of richness (gassy exhaust and dark plugs). Then, within a few days and one tank of gas (I do the math on each tank), mileage dropped to 15 mpg and the exhaust was full of unburned fumes. So I replaced the FPR with an aftermarket adjustable, set it to 36 psi and mileage jumped to 20 mpg and has been there ever since, with an occasional 21.

For whatever reason, the pressure looked fine when I measured it cold, but during driving it must have climbed to high levels. I never figured out exactly what was wrong with the FPR.

I had a theory that the aftermarket fuel pump (Airtex E8312) was pushing too much volume for the stock FPR but never confirmed anything. The new FPR (Aeromotive) made the difference though, in my case.

I don't have an aftermarket fuel pump but when my car is warmed up I do notice more gassy fumes. Whenever I can I will pull over to check if I'm leaking fuel somewhere in the hoses but it never is. Maybe my FPR is doing the same thing? Hmmm....maybe I'll look into replacing it with an adjustable one too.

[UR2H]

Your warm resistance sounds like it's in the right ballpark. It would be great to get a cold resistance. It should be around 2.5 kOhms at room temperature. If you're not getting any reading at all, the CTS might be defective. That would make your engine run really rich when it's cold.

The slight shifting around in your readings is normal. If the numbers only change a little, you've got good contact. If they change a LOT, then you don't have good contact, and you need to have cleaner contact points. The lowest reading is the correct one.

Hey what's a CTS?

[FastWoman]

coolant temp sensor

[UR2H]

coolant temp sensor

Oh you mean the same thing we've been discussing for the last dozen post? WOW! I feel :stupid:

[mayitin]

UR2H my advise to you is to see if you can find some other Z guys they can really be of help. Everybody here is giving you sound advise and I know from your side you can get itimidated on how to check for things, some times you will not be sure what are you loooking at, if its right or not etc. A lot of us have extra parts so we can swap the part and see if that was it. the cars has so many sensors relays etc and if you do not have experince checkings things out it becomes very difficult and frustrating.

Usually I start the path of simplicity and I move along to the hard things if I have not found the problem. log everything you have checked. Find a club near you or z guy they are there. I live on the gulf coast and many times I get a call or a knock on my door asking for help, some one told them about me or someone knows me. I found out that the Z community is very friendly and willing to help. Tell us where are you at and I am sure someone can tell you where a Z guy is near you.