Major problem

[deadlyvirus]

Hello to all and thanks for reading. Let me see where can I start... I have a 78' 280z 2+2/automatic california model.. I recently replaced the plugs, plug wires, cap, rotor, replaced vacuum lines and new fuel injectors. The injectors are the newest addition, well the car ran wonderful after the injectors, had increased HP and MPG, then exactly a week after they were installed the car has a very rough idle.

Now to explain this idle is tough, what it does is as soon as I start the car it revs to about 2k RPMs and drops to 0. It sounds like the car died then all of a sudden it revs right back to 2k RPMs. If I step on the throttle the motor shakes violently and it sounds like it's missing cylinders.

During this time there is white smoke coming out of the exhaust and I have even seen some coming out from what looks like just under the motor on the driver side. There is a heavy smell of gas to the smoke.

One thing that happened when this first started is when I fired her up I heard a loud pop, could have been a backfire but didn't really sound like it. Anyway, I noticed the boot coming off of the AFM to the throttle body popped off, could have been the source of the bang. Once connected it still has the same problem.

From what I can tell the oil doesn't smell like gas and the coolant is the normal color with no foam. I am at a complete loss here. Is it possible for the AFM to just go out without any signs of it going bad? Or what about a blown fuel injector? Or what about the timing being off? Those are the only things that I can think of. I sure could use some help on this one.

[grantf]

I could be wayyyyyyyy off but could it be a blown head gasket?

[esmit208]

DV

If it is not the AFM it is a sensor of some type that is associated with the AFM. Sometimes when the ECU is going bad the same symptoms will occur. The only way to narrow it down is to replace the current ECU with a known good ECU. If the issue still exists do the same with your AFM if possible. The 76--77--78 and a few 79's had some somewhat problematic electronics and it is not possible to plug them in to a computer that will read the codes. The problem can be sorted out but you may need to go to a knowledgeable DATSUN mechanic to get it sorted.

[Zed Head]

If you had enough backfire pressure in to the intake to blow the hose off of the AFM you might have bent the AFM vane. Datsun put a backfire relief valve in the vane to prevent damage but I would imagine that a big enough backfire might still bend something. See if the vane moves freely, closes all the way, and/or is warped/bent.

If you find that the AFM is the problem, doublecheck your firing order and timing before you start it to try to avoid another backfire.

[deadlyvirus]

Thank you guys for the quick reply. A quick question.. can I use a ECU off of an 82' in my 78'? A friend of mine has a junked 82 that I can get parts off of. I know the mechanics are pretty much the same but not sure if their ECU and fuel injection system is different.

I tried the AFM off that car awhile back and it was no good. It barely ran with that one on there.

[deadlyvirus]

I also want to note that this car has been my daily driver. I drove her home from work the night before and the next morning this happened.

[deadlyvirus]

OK so quick update. I went out to my car and gave a couple "raps" on the AFM and what do you know it started up and idled just fine. I took it for a test drive and she stutter and hesitates on take off with low throttle but if I give her a little more gas she revs through the stuttering just fine. At higher speeds the HP is there and runs fine.

My guess is the AFM is bad, or at least going there, plus the boot running from the AFM to the throttle body is duct taped covering a hole. That explains some of the stutter at take off but the AFM probably has more to do with that. I have replaced the TPS, forgot to mention that, so I don't think that is the problem.

Please correct me if I'm wrong. I'm what I like to call a weekend mechanic . I work on my car on the weekends when I can. I learn by you guys and by the FSM and fuel injection bible. I hope to get this car running good one day, but it seems if I fix one thing another goes wrong.

[argniest]

WOW what a bummer. I really hope you can figure out the problem without too much trouble. I will be replacing my injectors pretty soon. After I get my gas tank renewed. It was filled with a 1/2 thick of rust on the bottom of it. I removed fuel sending unit, and then saw all the rust. I was horrified. I should have tank back in a week or so. Then I want to put in my new injectors. And I am also getting a replacement bosch style original fuel pump. Beacuse I have a cheapo one on there now. And its been sucking on that rusty fuel for gosh knows how long....I have only had car for two years.

I have been methodically learning stuff about my 1978 z car all winter. Because it was getting bad gas mileage, stinky exhaust smell, not enough power either. I ran compression tests on the engine which turned out good, and then I did leak down tests which showed my piston rings and valve train was ok too. But I did find out I had a bad air temp sensor in the old AFM. So I have new AFM to put on there.

And I had a bad water temp sensor too. I feel like the car performance improved somewhat after those things, and then I changed oil and spark plugs and got back more performance. But with the completely crudded up gas tank, and the fuel filter was totally plugged up too with rusty metal debris because I cut it open to investiage that too. That is what lead me to investigate my gas tank. I also ran fuel pressure tests and vacuum tests. So I have been through a lot. And have a feeling once I get the tank back on there, and new injectors too, that she is gonna run a lot better.

But hearing your experience gives me the willies

Have you hooked up a vacuum guage to the intake side to see what kind of vacuum you are pulling? My vacuum is still low like 5 to 8 IN of vaccum. Which I have been told that if I have several bad fuel injectors, that can wreak havoc on everything. Which is why I am so interested in replacing them as soon as I can.

Oh yeah, I also cleaned up all the grounds in the engine compartment, added an extra 8GA ground wire to the engine, and cleaned all the sensors and fuel injector connectors. And I cleaned the fuse box, and added all new fuses.

I have more to do also....I just hope you can figure out what is going on. If anything I have said has triggered a thought, or you want to chat...give me a shout. I am glad to talk about things. Im just a noob...but I love talking about the z cars. And we both have a 1978

Edited March 10, 2011 by argniest

[deadlyvirus]

Sounds like you have been through some problems as well. But I think it's the fun part about owning an older car, especially one that you actually like. This is my first Z and there is just something about it. Can't really explain it except that it's like an addiction . I don't think I'll ever own another car again. Just keep fixing up Z's.

Man that's crazy about your gas tank, makes me scared to look in mine . I wouldn't doubt I would have the same problem with rust. I'll have to dive into that some day though, no doubt about it.

My biggest problem right now is I don't have anywhere to work on it. I live in an apartment so I'm doing all my work in the parking lot of the apartment complex. Makes it tough when there are a couple of other cars all crammed up next to my car. But hey, I make do and try to do what I can. Fixing things little by little, fix one thing and move onto the next. Would just be nice if I could fix the things on my own time instead of my car breaking down and deciding when I should fix it. I swear at times she's alive and has an attitude with me . I don't think she likes me very much.

So do you have a coupe? auto or manual? I would like to drop a 5 speed in my car but that comes way way down the road. After I get it up and running good I have to take care of the rust spots.... Anyway, I'm rambling on now, sorry bout' that, I'd love to talk with ya some more so you should hit me up sometime.

[argniest]

I have a 5 speed manual coupe. My car was running around last summer...but I know it can give a lot more. Ill bet my eyes light up once I get the main issues resolved. I have met many new friends, mechanics, etc both locally and online. And remember a cousin of mine who works on cars. So a lot of my free time has been spent troubleshooting this car. I cant believe how much I have learned in a few months of reading, testing, experimenting. But I am barely scratching the surface. However, I have done a whole lot of positive things to make it run better. And several new Z friends swear its going to be the fuel injectors. I know the car sat for a while, because of evidence of all the rust in tank. And all old tires had flat spots. But overall the car was kept clean, undercoated, etc....I just cannot wait to get it purring along.

Since I removed the gas tank 3 weeks ago, I am also replacing all the fuel lines in the car. And fixing some minor surface rust back there by the filler neck. Places you cant get to unless the tank is off.

If I had a month of free time I would work on it non stop :-) and then I think it would be ready to rock!

And oh yeah, I also read about how to do the fog machine tests. So I was blowing fog from inside the car to the outside, to track down where any major leaks are at. I have collected evidence from that experiement and its on my secondary list of things to fix next winter. Good luck I hope you get her fixed up soon. So how long have you had your Z car? Is it from the south??

Edited March 10, 2011 by argniest

[deadlyvirus]

I've owned my Z car for about 8 months now. It's from the NW so the body has quite a bit of rust. I need a new hatch and repair some panels but I believe those are the only major spots. Or at least I hope so. I picked it up with 135k miles on it and the inside is black leather all in near perfect shape. I say near perfect because the dash needs some work, it's not cracked but that plastic near the bottom and the steering column are messed up and there is a small chunk taken out of the driver seat. Other than that there is no fade in the carpets or anything.

I hear ya about having a month of free time, but I would also need the cash to cover that month. I would strip the car and start from the ground up. I think I might sleep in my car after that.

I never even thought about using a fog machine to catch the leaks. That is a great idea, I have a condensation problem so I need to fix that eventually. I know I need new seals for doors and windows though but once I get those replaced I am definitely doing the fog machine test.

[argniest]

Look up fog machine on the search on this forum, there is a great article with pictures. I did exactly that. It worked great. Helped me find out where things were leaking the worst. The Z emblems behind the back windows are supposed to let air out. So dont be alarmed if you see fog coming out like a steam train from those areas. I am not done with the testing, but for the most part I know where all the problems are at now. Even if you dont have a fog machine you can rent one from a party store I suppose. Or buy one for 25$ at a pwan shop I suppose too.

Thats funny about sleeping in the car :-)))) hehe And yes, I know what you mean about the feeling you get with the Z car. Its just special kinda warm fuzzy feeling that wont leave you ever. As long as you have your Z car. Its the happy place. Its making me crazy having to wait for parts to get here. And the time it takes....I have done alot to the car over the past 4 or 5 months, and had a relative help rebuild most of the important mechanical stuff. So I am basically going to be down to the fuel injection system for the source of trouble.

This forum was like finding the Z gods ;-)))))

Edited March 10, 2011 by argniest