Hey guys I’m new to this website but I have read a ton of stuff on here and it’s been a great help so that’s why I’ve joined. Anyways my 78 280z has been running fine for a while, I have all new fuel injectors, fuel pump, and afm. My fuel pump relay was bad so I wired up a switch to the wires where the fuel pump relay normally connects to and it’s worked fine. Recently however it has been idling horribly at around 500 rpm, but when I flip the fuel pump switch to off it jumps right back up to 1000rpm and idles fine until it dies from fuel starvation. It will also occasionally die out in addition to not accelerating sometimes. I’ll be driving and suddenly the power will not exactly cut out but not change if that makes sense. It’ll hold steady but stop reving and accelerating. It also blows darkish white smoke out of the exhaust when I rev it.

I know it’s a lot of info but I can’t figure this out if anyone has had a similar problem or a solution please let me know!

10 minutes ago, EuroDat said:

You could have a couple of issues that cauld cause an overfueling problem.

Most common are leaking injectors, leaking CSV or a bad temperature sensor or wiring going to the temperature sensor. The more resistance the colder the ECU thinks the engine is and compensates with more fuel. 

You seem to be getting a lot more fuel than a faulty temperature sensor would allow, but doing the checks will confirm or dismiss it. When you check it, do the check at the sensor (sensor to ground resitance) and than again at the ECU connector (Connector pin 13 to ground resistance) They should be the same. Refer to the bible for the correct resistance for temperature range.

Note: Use the 1980 Bible. It is for all models 280Z, 280ZX en 810 Maximas up to 1980.

The other book is for the 1974 to mid 1976 models.

Sweet! Mines a 78 so I’ll use the former, all my injectors are new and while the CSV isn’t working, it also isn’t leaking, it’s completely gummed up with black soot, I’ll still be doing all the tests to be certain but I’m hoping I won’t have to buy injectors twice. Also for the tests what in line fuel pressure gauge do you use, my local auto parts stores don’t carry them for some reason and a lot of what I’ve been seeing online doesn’t look like it would work.

have you pulled that black cover off and tried fingering the sweeper vane in the AFM?  I bought one and that thing was stuck by spider webs.  10 minutes and i had a good running '76 for dirt cheap.

 

is there a harbor freight near you?

they have them, 30$ish IIRC

 

90% chance its the CTS, either it or the wiring to it. It lives in a harsh environment (coolant) that can corrode not only the sensor but the connector to it as well if there is any kind of leak.

Edited June 28, 20195 yr by Dave WM

2 minutes ago, Jack Pearcy said:

Sweet! Mines a 78 so I’ll use the former, all my injectors are new and while the CSV isn’t working, it also isn’t leaking, it’s completely gummed up with black soot, I’ll still be doing all the tests to be certain but I’m hoping I won’t have to buy injectors twice. Also for the tests what in line fuel pressure gauge do you use, my local auto parts stores don’t carry them for some reason and a lot of what I’ve been seeing online doesn’t look like it would work.

you can get a pressure gauge from Lowes in the pool section.  It's for the pool filters pressure.

https://www.lowes.com/pd/aqua-ez-pressure-gauge/3151541?cm_mmc=shp-_-c-_-prd-_-lwn-_-google-_-lia-_-241-_-poolproducts-_-3151541-_-0&kpid&store_code=1640&k_clickID=go_1792976560_68785408469_346853782070_aud-299487635210:pla-416743622626_c_9012730&gclid=EAIaIQobChMIrNyVgeyM4wIVChgMCh0LowYKEAQYASABEgLOcfD_BwE

27 minutes ago, siteunseen said:

When you have some reading time here's where I started.  Thanks @240260280

http://atlanticz.ca/zclub/techtips/EFI&fuel.htm

main page...

http://atlanticz.ca/zclub/techtips/

Thanks it was a good read, I’ll be sure to reference it if I end up doing any AFM tuning, but I’ll wait until I run the tests like the instructions said

24 minutes ago, siteunseen said:

you can get a pressure gauge from Lowes in the pool section.  It's for the pool filters pressure.

https://www.lowes.com/pd/aqua-ez-pressure-gauge/3151541?cm_mmc=shp-_-c-_-prd-_-lwn-_-google-_-lia-_-241-_-poolproducts-_-3151541-_-0&kpid&store_code=1640&k_clickID=go_1792976560_68785408469_346853782070_aud-299487635210:pla-416743622626_c_9012730&gclid=EAIaIQobChMIrNyVgeyM4wIVChgMCh0LowYKEAQYASABEgLOcfD_BwE

That’ll do, thanks!

The wiring of the CTS and the CSV can get mixed up, bullet connectors and sensor plugs that can interchange. That's why its important to check at the 36 pin connector, it will account for any mixups. My guess is that pin 13 to ground will be wide open.

27 minutes ago, siteunseen said:

have you pulled that black cover off and tried fingering the sweeper vane in the AFM?  I bought one and that thing was stuck by spider webs.  10 minutes and i had a good running '76 for dirt cheap.

 

My AFM is brand new so I don’t think it’d be stuck but it might be worth a shot

2 minutes ago, Jack Pearcy said:

My AFM is brand new so I don’t think it’d be stuck but it might be worth a shot

If it's brand new I wouldn't do it. You'll have a brand new afm with a zip tyed plasic cover, not a good thing. ?

Have you looked at the throttle position switch? They cut in around 2,500rpm. Up until then they're on the low side, rpm, contact. Then at 2500 they are on neither for a second. Then they'll click onto wide open.

Lots of info on those. Just a bunch of reading.

https://www.google.com/search?client=ms-android-americamovil-us-revc&ei=2moWXf_gLqHm_Qb-3LY4&q=tps+classiczcars.com&oq=tps+classiczcars&gs_l=mobile-gws-wiz-serp.1.0.33i160l2.15674.26999..29083...0.0..0.160.1231.4j7......0....1.........41j33i299j30i10.a2JfS2XZEAA

22 minutes ago, siteunseen said:

Have you looked at the throttle position switch? They cut in around 2,500rpm. Up until then they're on the low side, rpm, contact. Then at 2500 they are on neither for a second. Then they'll click onto wide open.

Lots of info on those. Just a bunch of reading.

https://www.google.com/search?client=ms-android-americamovil-us-revc&ei=2moWXf_gLqHm_Qb-3LY4&q=tps+classiczcars.com&oq=tps+classiczcars&gs_l=mobile-gws-wiz-serp.1.0.33i160l2.15674.26999..29083...0.0..0.160.1231.4j7......0....1.........41j33i299j30i10.a2JfS2XZEAA

I messed around with mine, it would change slightly in rpm when I adjusted it but then go right back to 2500, I took a video but it won’t let me upload it

Well I got the pressure gauge but I can’t find a t connector anywhere, this really sucks I’ll have to look online I guess.