1977 280Z Stuttering

[Racer X]

36 minutes ago, BayAreaZ650 said:

 

- Is the EGR valve worth replacing? 

Is it bad?

Have you tested it?

The key to successful repairs is thorough diagnostic testing.
 

Avoid the tendency to guess and throw parts at it. Sure, eventually the problem will be fixed, and you’ll have lots of new parts on the car, but you won’t have money left over for beer, or to take your girlfriend out for dinner.

 

 

[Zed Head]

3 hours ago, BayAreaZ650 said:

Thank you for all the replies so far. Here's what I have planned this weekend.

- Add an inline fuel pressure gauge. Is it best to add it after the fuel filter?

Yes, the goal is to know what pressure the injectors see.

[BayAreaZ650]

I just pulled the FPR out. There isn’t gas in the vacuum line (vacuum line is dry). Does this mean that the FPR is working? 

[siteunseen]

From all I've read on here the FPRs rarely fail. I think it's a simple diaphragm but I'm not positive.

You can clamp the return line to increase fuel pressure. That's how I discovered my coolant temp problem. The shitty running up until 2,500rpms.

[Yarb]

Fuel pressure gauge??

[siteunseen]

I ran a gauge up to the driver's side windshield, under the wiper blade. Had good pressure constantly. The ECU was getting a lean reading and feeding less fuel because of the coolant temp sensor function. I forced more fuel by clamping the return, it ran way better. I realized I was on to something and asked on this FANTASTIC forum and then went to RadioShack and spent $5. Runs like it should plus I control the fuel flow. I can lean it out on the interstate and run cooler. I've thought of putting a camed up head on and fattening up the fuel? I've read EFI can't compensate for small lobe cams. One of these days, when I'm bored...

[Yarb]

To start it would be interesting to see what the pressure is doing when it’s fluttering and after t smooths out.

[S30Driver]

1 hour ago, BayAreaZ650 said:

I just pulled the FPR out. There isn’t gas in the vacuum line (vacuum line is dry). Does this mean that the FPR is working? 

 

Its a good sign.  When you have everything re-assembled you can test the regulator by disconnecting the vacuum line at idle to see if the fuel pressure increases by about 6 or 7 psi.   If at idle your gauge reads 30 psi, it should go up to 36 or so.

[siteunseen]

30 minutes ago, Yarb said:

To start it would be interesting to see what the pressure is doing when it’s fluttering and after t smooths out.

That was suggested to me so I ran the gauge to the windshield. It let me see what was what at idle then through the range of throttle.

@FastWoman helped me through all of this. I miss her help on our cars but she moved on, I guess?

Edited February 20, 2021 by siteunseen

[BayAreaZ650]

I replaced all the fuel lines on the rail and the Z runs as it should! I just got back from a 20 minute drive. One of the rubber hoses had a pinhole leak and was squirting a decent amount of fuel. I appreciate everyone’s help!

 

 

[siteunseen]

Congratulations!

If that's a before and after shot, wow! It looks great. Enjoy that car.

Edited February 20, 2021 by siteunseen

[BayAreaZ650]

Hi everyone,

The issues (bouncy idle while warming up the car and the Z intermittently bucks during acceleration) hasn’t gone away. I installed a fuel pressure gauge. During idle, I’m getting roughly 39 psi and with the key in the ignition on “on”, it’s at 0 psi. Yesterday, I cleaned the throttle body, afm connector and used rubber gasket to plug a small crack in the tube between the afm and throttle body.

Edited February 23, 2021 by BayAreaZ650