need help diagnosing

[gonzalezj1943]

okay my car just started doing something weird that it never used to do if i rev it up when it comes back down and hits 2000 rpm it starts makeing a weird noise like if the cold start injector is shoting alot of fuel into the manifold iv had this car for a year and it has never done that it does it starting from 2000 rpm and stops when it gets back to idle the rpms just go down real slow has anyone had this problem before??? its a 1980 280zx

[roger.svoboda]

disconnect the cold start injector and see if that cures the noise. if not then something else is wrong

[gonzalezj1943]

iv tried that it still makes the noise it runs good and everything just the rpms drop down slow from 2000-idle ive been trying to figure it out for the last couple days dont know what it is

[gonzalezj1943]

how much resistence should the cold start injector have mine shows 5 ohms and the rest of my injectors are between 2.7 - 3 ohms i took everything apart today and still doing the same thing i checked all my connections too...

[19762802+2]

Take a video, if possible so we can hear what noise your talking about because it could be anything. If you can't make a video try to describe it better and I'm sure you will get some more help.

[BRAAP]

Being as the cold start injector doesn't make any sort of noise other than one click when it is activated and another click when it is shut off, other than that it makes no real noise, so what sort of noise are you trying describe? A hissing noise? If so, that is most likely a vacuum leak, which will make a noise, especially at lower throttle settings/idle, and will affect how the car runs while making that noise, i.e. engine breathing air that was measured by the AFM so the proper amount of fuel to combined with it.

 

If the noise is chattering clicking noise, especially in the neighborhood of 2000 RPM, check the B.C.C.D., put your hand it to see if you can feel it chattering. The BCCD that is the doohickey apparatus on the bottom of the your throttle body. If it is not operating correctly it could chatter and will cause the RPMS to hang at 2000 RPM for extended periods, etc.

 

As for your cold start injector, move on, quit messing/diagnosing it, that is not your problem. Unplug your cold start injector and forget about it for the rest of your cars life. Better yet, remove it, cap the hole it use to fill and plug the fuel line feeding it. It is a useless injector that sometimes leaks. I have NEVER in ALL the umpteen cold start injectors I have removed from mine, friends and customer Z cars cars since the late '80's (probably as much as 100 or more), from stock to modified Z cars, had an issue that would be resolved if the cold start injector was still there! At the south pole, it might be of use, in most of the continental US within the outside temp ranges a sports car would be driven, it is useless.

[gonzalezj1943]

Being as the cold start injector doesn't make any sort of noise other than one click when it is activated and another click when it is shut off, other than that it makes no real noise, so what sort of noise are you trying describe? A hissing noise? If so, that is most likely a vacuum leak, which will make a noise, especially at lower throttle settings/idle, and will affect how the car runs while making that noise, i.e. engine breathing air that was measured by the AFM so the proper amount of fuel to combined with it.

 

If the noise is chattering clicking noise, especially in the neighborhood of 2000 RPM, check the B.C.C.D., put your hand it to see if you can feel it chattering. The BCCD that is the doohickey apparatus on the bottom of the your throttle body. If it is not operating correctly it could chatter and will cause the RPMS to hang at 2000 RPM for extended periods, etc.

 

As for your cold start injector, move on, quit messing/diagnosing it, that is not your problem. Unplug your cold start injector and forget about it for the rest of your cars life. Better yet, remove it, cap the hole it use to fill and plug the fuel line feeding it. It is a useless injector that sometimes leaks. I have NEVER in ALL the umpteen cold start injectors I have removed from mine, friends and customer Z cars cars since the late '80's (probably as much as 100 or more), from stock to modified Z cars, had an issue that would be resolved if the cold start injector was still there! At the south pole, it might be of use, in most of the continental US within the outside temp ranges a sports car would be driven, it is useless.

 

 

thanks man ill check out the BCCD in the morning and as for the cold start its all in the trash now i just need to cut out plates to seal the holes but what you are describing about the BDDC sounds like what going on with my car

 

the noise im hearing is not a vacuum leak it sounds more like something is spraying somewhere around the intake manifold but can really tell where and i just replaced all my injectors today so its not that but like i said ill get back to you after i check out the BCCD sounds like thats the problem thanks again

 

the nois sounds like a vvvrrrrrrrrrrrrrrrrrr when its hanging at 2000 back down to idle but other then that car runs great

Edited August 22, 2010 by gonzalezj1943

[BRAAP]

thanks man ill check out the BCCD in the morning and as for the cold start its all in the trash now i just need to cut out plates to seal the holes but what you are describing about the BDDC sounds like what going on with my car

 

the noise im hearing is not a vacuum leak it sounds more like something is spraying somewhere around the intake manifold but can really tell where and i just replaced all my injectors today so its not that but like i said ill get back to you after i check out the BCCD sounds like thats the problem thanks again

 

the nois sounds like a vvvrrrrrrrrrrrrrrrrrr when its hanging at 2000 back down to idle but other then that car runs great

 

 

Good work on the cold start injector.

 

Sounds more and more like the BCDD.

 

Something I have found that that helps in diagnosing or pinpointing where a noise is coming from is a mechanics stethoscope, even the cheapo's from Harbor Freight Tools work great. Using the probe on the suspect item or removing the probe and letting the open tube act like a directional microphone of sorts, helps to pinpoint where a noise is coming from.

 

Keep us posted on waht you find or if have any more questions. progress

 

[gonzalezj1943]

okay so i finally figured out what it was ...

 

my air regulator was the thing that was causing me all those problems ...

 

were can i find a after market fuel rail for my l28?

[BRAAP]

Thanks for the update, glad you found the problem.

 

I recall seeing a couple fuel rails for sale in the past several months in the classifieds section. You might also try checking the vendor section and posting an ad in the Want To Buy section.

[gonzalezj1943]

thanks BRAAP....

 

is there any way i can bypass the air regulator so i dont have to buy a new one

[BRAAP]

You can delete the Air Flow Regulator, but it come with compromise. I deleted it on my the original BRAAP Z, at the time I was in my 20's and was wiling to tolerate some compromise in how the car ran fo rhte lceanup appearacne of the intake manifold, (see pic below of that car). The compromise for deleting the Air Flow Regualtor is;

1) If the idle speed for a warm engine is anythign below 1000 RPM, then cold starts in the morning or after the car had sat for more than a few hours at temps below 70-80 degrees outside required me to feather the throttlle for a few minutes till the engine developed some heat and would idle on it own.

 

2) If the idle speed was set to the bare minimum the car would idle without me having to hold the throttle on cold start withe temps in the 40-50 degree range in the morning, that meant a warm engine idle speed of 1100-1200 RPM.

 

I chose #2 and lived wit it that way for a few years. knowing what I have since learned about the stock Z EFI, and wanting to retain that clean appearance withe stock EFI, intake, its easier to just relocate the Air Flow Regulator to the under ht the intake or the fender and route vacuum lines, one before the TB, the other after the TB plumbed in under the intake for cleanliness sake.

 

Hope that helps,

Paul

 

Bone stock EFI, cleaned up, minus a few goodies, only real compromise was the Air Flow Regulator delete, everything else functions as OE.

[gonzalezj1943]

You can delete the Air Flow Regulator, but it come with compromise. I deleted it on my the original BRAAP Z, at the time I was in my 20's and was wiling to tolerate some compromise in how the car ran fo rhte lceanup appearacne of the intake manifold, (see pic below of that car). The compromise for deleting the Air Flow Regualtor is;

1) If the idle speed for a warm engine is anythign below 1000 RPM, then cold starts in the morning or after the car had sat for more than a few hours at temps below 70-80 degrees outside required me to feather the throttlle for a few minutes till the engine developed some heat and would idle on it own.

 

2) If the idle speed was set to the bare minimum the car would idle without me having to hold the throttle on cold start withe temps in the 40-50 degree range in the morning, that meant a warm engine idle speed of 1100-1200 RPM.

 

I chose #2 and lived wit it that way for a few years. knowing what I have since learned about the stock Z EFI, and wanting to retain that clean appearance withe stock EFI, intake, its easier to just relocate the Air Flow Regulator to the under ht the intake or the fender and route vacuum lines, one before the TB, the other after the TB plumbed in under the intake for cleanliness sake.

 

Hope that helps,

Paul

 

Bone stock EFI, cleaned up, minus a few goodies, only real compromise was the Air Flow Regulator delete, everything else functions as OE.

 

 

 

yeah mine just keeps acting up i guess ill just have to go buy a new one. The noise i was telling you about was coming from the air regulator it just got loud one day iand thats how i knew that was what was causing that ...

[gonzalezj1943]

i was reading another post on here that said you cou;d just take off the bcdd and plug the holes under the throttle body ... will it affect anything else ? what are the 2 hoses that are hooked up to it for?