Runs rich, wont rev past 2-3k

[Dave WM]

I redid my test using a  9v  battery

 

battery not in circuit 9.5v

6 neg term

8 pos term

DMM/analog meter

6 neg lead

7 pos lead

flap closed 1.8v

sweep shows an increase non linear. I had a momentary 0.00 reading in one spot (right around 6v around 1/3 open) but could never get it to stay. the analog meter duplicated the voltage readings and sweep but was unable to catch the momentary 0.00 (it would only last a fraction of a second). It was consistent as far as happening and happening in approx. the same location of sweep, just could not maintain long enough to diagnose reason.

flap fully open 8.5v

This is an UNTESTED IN USE AFM so use as comparison only, if your readings are nearly the same I would assume both are good.

 

 

Edited February 16, 2018 by Dave WM

[Zed Head]

On 2/15/2018 at 11:10 AM, 240260280 said:

For rev limiting, I have witnessed three causes:

1. The EFI system has a false Idle signal from the TVS due to a short.  The ECU thinks that the foot is off the pedal and will not flow gas above ~2800rpm

2. The ignition system has a fault. I'm my case, a points distributor was the cause.  The power died under load at high rpms as if there was a fuel cut-off.

These two seem to be still on the list.  When people wash their engines they often describe a wet TVS/TPS as acting like a violent rev-limiter.  The engine just stops at higher RPM.  The water shorts it.

On the ignition system, with reference to EFI and electronic ignition, the ECU uses just simple voltage pulses on Pin 1 to count engine revolutions and determine when to squirt fuel.  If it sees too many it will squirt too many times.  When the electronic ignition systems go bad they often spark too many times.  When mine went bad the tachometer would read about 1.5 times actual engine speed.  That's why I asked about the tachometer reading earlier.

Just seeing spark doesn't mean it's working correctly.  You might dig in to ignition.  The GM HEI module is cheap, easy to connect, and good to have around as a spare anyway.  The old factory modules are getting old and fail on a regular basis.  And the pickup coils in the distributor are known to fail, with wires cracking and shorting as the breaker plate moves.  Plus, pickup coil voltage increases with RPM and gets very high.  High voltage shorts easier than low voltage.

Still wondering about your part numbers.  And if your AFM has been adjusted.  The glue blob.

Edited February 16, 2018 by Zed Head
traded coil for module

[240DL?]

I seem to be doing a slightly different test, I applied 9 volts to 9-6 and measuring it at 8-7 as I opened the flap. Ill give yours a try and see if the voltage goes up instead of down.

This screenshot is from the 1976 FSM PDF I downloaded 

Edited February 16, 2018 by 240DL?

[240DL?]

The TPS shows no continuity when depressed between pins 2-18. I have tried unplugging it with no effect. Would there be anything else to do to eliminate that as an issue? Last night I tried removing the AFM from the intake and holding it open just enough to run the fuel pump, when doing this it would rev past the 2800-3200 rpm fuel cut spot that makes me think It wouldn't be that.

 

The revolutionary trigger signal has a slight voltage drop from battery voltage(pin 1-ground ignition on), Ill check connections...would this maybe cause an issue?

 

The only part numbers I can tell you off the top of my head is the ECU is a A11 600-000 unit. I bought a A11 601-000 but it doesn't make any difference. 

Edited February 16, 2018 by 240DL?

[Dave WM]

the only diff I can see is a voltage drop across the resistor that is between 8 and 9, prob why you were seeing 4v in there some where at one extreme end. Your 8 and 9 is a fixed resistance value. 6 and 8 are the outside legs of the pot, with 7 as the center wiper. Standard test of a pot would be as I described. I guess they wanted to test the fixed resistor as well, but that is a simple resistance test between 8 and 9 (resistance should not change with movement of flap between those pins if I read the schematic right).

Lets see what you get when you test like I did.

[Zed Head]

On 2/14/2018 at 11:30 PM, 240DL? said:

My 1976 280z won't rev past 3500 when not in gear, and about 2000 when in gear. When in neutral it will blow clouds of black smoke at higher rpm. It has run way to rich like this since I bought it. I have checked the wiring and sensors and rectified the issues I found to no avail. The water temp sensor was the first place I looked, I replaced it when I first got the car. It is giving the correct reading all the way to the ECU and has a noticeable effect when I unplug it.

It's looking like everyone is so hopeful that there's some simple cause for your problem, that we haven't really considered the other parts of the engine.  Won't rev, blows black smoke...  why'd you buy it?

Just kidding, but there are so many unknowns here that you should really go back to the very basics of engines.  At least verify that each cylinder creates pressure (measure it if you can), check that the cam timing is correct (there's a notch and a groove), check/set your ignition timing (don't see that mentioned anywhere.  Retarded timing will stop engine revving), at least eyeball the valves (set lash if you can), stuff like that.  Go back to fundamentals before you get in to the details of the EFI system.

The most common AFM problem is running lean in the mid-range.  The engine will stumble and buck, you get mad and punch the gas, and it takes off because full throttle adds 27% extra fuel.  Or the vane gets stuck and chokes air flow.  But if the vane moves freely and you get 180 and 100 ohms on those two measurement, they usually work fine if nobody has messed with the vane spring setting.

Just saying, you're starting in the middle of left field.

[240DL?]

On 2/16/2018 at 6:34 PM, Zed Head said:

It's looking like everyone is so hopeful that there's some simple cause for your problem, that we haven't really considered the other parts of the engine.  Won't rev, blows black smoke...  why'd you buy it?

Just kidding, but there are so many unknowns here that you should really go back to the very basics of engines.  At least verify that each cylinder creates pressure (measure it if you can), check that the cam timing is correct (there's a notch and a groove), check/set your ignition timing (don't see that mentioned anywhere.  Retarded timing will stop engine revving), at least eyeball the valves (set lash if you can), stuff like that.  Go back to fundamentals before you get in to the details of the EFI system.

The most common AFM problem is running lean in the mid-range.  The engine will stumble and buck, you get mad and punch the gas, and it takes off because full throttle adds 27% extra fuel.  Or the vane gets stuck and chokes air flow.  But if the vane moves freely and you get 180 and 100 ohms on those two measurement, they usually work fine if nobody has messed with the vane spring setting.

Just saying, you're starting in the middle of left field.

I didn't state a lot of stuff when I first started asking questions my bad. I got the car "needing a head gasket", it war torn apart when I brought it home. Needless to say it was more then that, so after a head gasket, valve stem seals, trying a whole different head, then rings the blue smoke went away. But there was still black smoke and plugs would still get fouled. I have done a compression test (even across all cylinders), torn the valve cover off to look at timing a bunch of times as I thought that was the issue, it is defiantly on. I have adjusted valves and checked the ignition timing to no effect.

I will check ignition timing again but I know everything else mechanically is sound, what makes me think its an EFI issue is how rich it runs. I still will look into the ignition system like you mentioned as there are a lot of old parts that I cant speak for there condition. 

[Zed Head]

If somebody adjusted the vane spring on your AFM it could be going full open at low air flow.  246 supplied a re-calibration procedure in the atlanticz.ca link.  Out of adjustment AFM fits what you're describing, at least the rich part.

Are you sure that nothing is blocking the air path?  Air is what allows the engine to rev.  Is your throttle body blade opening completely?  No rags in the intake ports or intake manifold?  If everything is right mechanically it should rev high easily with no load.  Try removing the oil filler cap and some vacuum lines and see what happens.  Let some air in to blend with all of that fuel.

[240DL?]

Ill give that a shot, if I hold the AFM closed a little and rev the car will go to about 4000 with no load. By a little I mean just open enough to run the fuel pump

On another note I took the car for a test drive to see if It would pull any higher then before. Within a mile down the road it couldnt pull at all and shut off. Once I pulled it back home I took out a plug and found it covered in gas. Gonna get a new set of plugs for it and try making some artificial vacuum leaks 

Edited February 18, 2018 by 240DL?

[240260280]

The coolant temp sensor usually causes that problem.  Double check the connections to it as well as ~ 1 foot deeper in the wire harness down stream. There are bullet connectors that can corrode in the harness.  Also make sure the connectors to the coolant temp sensor are not mixed up with another sensor.

[JSM]

3 hours ago, 240DL? said:

Ill give that a shot, if I hold the AFM closed a little and rev the car will go to about 4000 with no load. By a little I mean just open enough to run the fuel pump

On another note I took the car for a test drive to see if It would pull any higher then before. Within a mile down the road it couldnt pull at all and shut off. Once I pulled it back home I took out a plug and found it covered in gas. Gonna get a new set of plugs for it and try making some artificial vacuum leaks 

So it runs fine cold until it warms up and then goes pig rich once warm?I’d have to agree with the above comment but i thought you said you already checked resistance at the ECU plug for the CTS? The other easy thing to do is swap the thermotime bullet coonectors with the CTS ones. 

[240260280]

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