Help with AFM Issue?

[SilverSurfer]

Hello! I have a 1977 280Z stock 5-speed. The original AFM seemed like it was having some issues. The engine was running rich (you could smell it and I was getting horrible gas mileage), at idle the engine did not run steady/consistent (it revved up and down sort of like ooooOOOOooooOOOOoooo ... if that makes any sense ... and the tach would move with it below 1000 RPMs to slightly about 1000 RPMs), and, lastly, sometimes when going slow in third the car would hit a point where it would jerk until you either sped up or slowed down even further.

 

I had a spare (used) AFM and swapped it out today. The first thing I noticed is the car idled smoothly/evenly right about about 1000 RPMs. This is the best this car's sounded since I've had it. So, I took it for a ride. That's when I ran across another problem. The car seemed to do great when driving in the city (no jerking when running slowly in 3rd gear), but I ran into a problem when I went on the highway. The entrance ramp I was using is pretty steep (uphill) and the car chugged. I could barely get 'er over 35-40 and so I could not get up to highway speed. Once on the highway I was able to get her going, albeit slowly. Once up to speed, she had a lot more pep.

 

I am assuming that she is now running a tad lean? But I am no mechanic. Not by a long shot. Obviously the new AFM made a difference, solving a few issues and introducing a new one. So, where do I go from here? What should I check? And how do I tweak this?

 

Any help would be appreciated. Thanks.

[Zed Head]

Done.

Edited October 23, 2015 by Zed Head

[SilverSurfer]

 

"chugged" is not very informative.  RPM while "chugging"?  Maybe you just need to shift down a gear.  Throttle wide open?  What gear?  Manual transmission?  (Autos have numbered gears also).

 

Typically when one says they have a 5-speed, they mean they have a 5-speed, shifted transmission, not an automatic. And I stated this in the first sentence.

I was in third gear while going up the entrance ramp. With the previous AFM I could easily go up this same ramp in third, shift to fourth, and enter the highway at 55 with no issues. As stated above, I could not get the car past 35 MPH. I did not see the RPMs but will look the next time I take the Z out.

 

 

Give more details on the engine.

 

As stated, it's a stock engine (inline 6). I assumed (yes, dangerous) that people understood what that means. There have been no modifications, etc.

 

 

What have you checked on the engine  and EFI system?  Have you gone through the Engine Fuel chapter?  Given it a tune-up?

 

The car had a decent amount of work on it from a mechanic who is reliable. The fuel lines are all new, as is the fuel pump and filters. The plugs, wires, injectors, pig tails, are all new, too. The AFM was not and, as I stated, swapping out the AFM caused the engine to idle beautifully compared to the original one. From what the mechanic had said, fuel pressure was fine.

[Zed Head]

Done.

Edited October 23, 2015 by Zed Head

[SilverSurfer]

Sorry. I assumed I was looking for help, not an attitude. You came right off with one. Sorry that I am not a mechanic to describe things to your specifications (also, as stated in the first post). I suppose you missed that one, too.

 

"Chug" pretty easy to figure out. If you read books (those things with a plethora of words in them) that tell stories, often descriptive words are used to help someone see an image, etc. In this case, chug, when not being used to describe drinking a liquid, means to move along slowly. In fact, the word "chug" has a specific definition when it comes to cars and engines, as per this definition (straight from a dictionary):

"emit a series of regular muffled explosive sounds, as of an engine running slowly."

 

It's not my fault if you do not understand a common English term nor how it is commonly used (especially when Google is so near at hand).

In any case, thank you so much for attempting to ruin my experience here. I would appreciate it if you would back out of this thread and allow one of the more helpful people to assist me. If my words are not correct or I am not describing something properly (again, I am NOT a mechanic), then I hope that one of these other helpful people will be so kind as to help me by pointing me in the right direction.
 

[Zed Head]

Done. Dude.

Edited October 23, 2015 by Zed Head

[SilverSurfer]

Dude. I asked you to stay out of this thread and let others help. I care how the information is given. There are plenty of doctors one can see that can provide basic care, but I won't go to one that is an arse. Same goes for help here.

 

I did state the car had new plugs, new wires, etc. While I should have said it was tuned, normally swapping out the plugs and wires, etc., is a part of tuning the car (and, yes, there is more to it than that).

 

No, I have not gone through the Engine Fuel chapter. I will look that over.

[sweatybetty]

i am curious as to what "AFM" means. not everyone understands abbreiviations (sp?) dude

Edited October 23, 2015 by sweatybetty

[SilverSurfer]

AFM = Air Flow Meter.

[EuroDat]

These things lean out over time. If the AFM improved its idle, but now it seems to be running lean, your problem could be the ECU creating a lean condition. Spark plug should be able to tell you more, but you may need to drive it a while like this to get an accurate reading. See link below for some info on the spark plugs. If you pull the spark plugs, take some photos of them and post them here. It can tell you a lot about the fuel ratio.

There is a trick you can do to correct this lean condition by adding a variable resistance in the temperature circuit.You could try that. Its not expensice and its easy to do. It helped mine a lot.

Here is a good write-up on what it does and how to do it.

http://atlanticz.ca/zclub/techtips/runningrich/index.html

[siteunseen]

I would try what Chas has recommended, it's cheap and easily done and reversible.  Heck, mine runs so much better with the potentiometer I just coiled up the wire and threw it in the passenger's floorboard.  I guess I should explain that better.  I bought the volume knob at Radio Shack, $3.95, solder it to about 6 feet of speaker wire on one end and put the appropriate "butt"? connectors on the other end.  Ran the wire through the firewall, plugging it into the wires behind the thermostat.  The adjustable knob inside with me, drove it for a month adjusting little bits at a time until it was perfect (to me).

 

Before I did it, it would cough spit and sputter until 2,500 RPM then pull like normal.  Now it'll paint black marks out of my driveway, with a little clutch work. 

[SilverSurfer]

Thanks, guys. Great info! I appreciate this.