Replace 1 injector, or all six?

[daneo]

Hi everyone. I've been reading these posts for a long time, so thanks for all the help! But, now I come seeking advice.

I have inherited a low mileage (30k) 1990 300zx 2+2. Clearly, it has spent a lot of time in the garage, and thus has had its share of old gas sitting in it. When I first fired it up, I let it idle a while. Some light white smoke came out the exhaust. I think this was due to the ancient gas it had in the tank and lines. The idle was rough and had a miss. After getting new gas the car ran well and the miss worked itself out. Then, I had to leave the country for 9 months and the car sat again. A tiny bit of white smoke came out the first time it was started again, and the miss was back. I've been putting seafoam in every other tank of gas to try to dissolve gunk and absorb water from old fuel. The miss seemed to fade in and out. For certain, there was a week where everything was running smooth. This week, however, the miss was really bad and the power loss was extreme.

Today I started doing some investigation. By pulling plugs from ignition coils, I found that cylinder 2 was the culprit. I did the ol' big-screwdriver-on-the-injector-body trick to listen for clicking. The injector was clicking, but not as loud as the others. I popped off the injector harness and checked the injector resistance. it was 782 ohms rather than the 10-14 spec... So, it seems that my injector has probably been slowly dying.

Now, like the title of the thread indicates, I'm trying to decide with replacing the P1 pintle-style injector via the dremel method (90 bucks and a few hours) OR pull the plenum and replace all six with P2 injectors using the Deatschwerks kit (700 bucks and all weekend).

What are your experiences with injection failures? Everything I've read shows people swapping out the 6 once the first is dead. This is under the pretense that "the others aren't far behind."

Thanks for the input.

[Z31toZ32]

imo it depends how long you plan on keeping the car. if it is a long time, i would consider replacing all the injectors, because like you said, they start to drop off one after the other. if you plan on selling it soon, I would just replace one at a time. those things are expensive.

if you dremel, you can have an injector replaced in 20 minutes (probably 40 if it is your first time).

[Chattzx]

When one of mine went out I just replaced that one with a used injector from Z1. Maybe 8 months later and almost all of them are going bad. Needless to say, just replace all of them at once, I wish I did that the first time. I just got all 6 new injectors in the mail yesterday, so I'm excited to have full power back

[txQ45]

When replacing injectors be sure to
1. Replace with new style
2. If your car isn't a 94 or newer do the switched injector rewire

[daneo]

Looks like its all 6 then. Any reason not to go with the cheaper Deatschwerks injectors versus the nissan OEM? DW says they do flow matching also, which wouldn't be included with the nissans or JECs.

It seems like someone would have done it before if it were possible, but instead of doing a plenum pull, could one do a plenum "scoot" where most of the lines are kept attached and the plenum is just moved a bit? To access the injectors, one only needs a few millimeters of clearance from the plenum. Seems like this should be possible and would save a ton of time.

One more question. Searched the forum and didn't find anything talking about the "switched injector rewire." I assume we're talking about adding a relay so the injectors don't get the +12v all the time. Anyone written an article about this? I'm pretty confident with electronics, so I might do it after everything else is up and running.

[GerryO]

Timing belt has never been replaced?

[daneo]

Interesting change of subject...

No. Only 30k miles.

[GerryO]

Don't know what sort of roles age and storage conditions play when it comes to causing things like hardening/cracking of hoses and various belts, moisture/rust in the fuel, braking, clutch and PS systems, coolant breakdown induced corrosion that could affect gasketed engine surfaces and water pump seals, and hardening/flat-spotting of tires, oil seals and the like.

My first injector failed at 178K/15 years and water pumps should be replaced every 60K along with the timing belt, but there's also probably an age related factor when it comes to many elastomer components.

Scooting the plenum wouldn't be a good idea, as there's so much to be learned/gained by pulling the plenum, the amount of work would be almost the same and the thin paper gasket would be ruined for sure.

[es.biggs]

I agree....just dive into the deep end and pull the plenum off

Here is the write-up for the re-wire: http://www.twinturbo.net/nissan/300zx/f ... 1-2-3.html

[Z31toZ32]

ya id look into that timing belt replacement. from the sounds of feedback on here, the timing belt itself won't snap, but the idlier pulleys will break and cause everything else to go to hell.

[daneo]

I agree....just dive into the deep end and pull the plenum off

Here is the write-up for the re-wire: http://www.twinturbo.net/nissan/300zx/f ... 1-2-3.html

Nice! Super-easy. Doesn't even require a relay!

I think I'll go with the Deatschwerks injectors/kit and get the gaskets suggested by the tt.net writeup as well.

I have a hard time justifying a timing belt replacement at the moment. Everything under the hood looks brand new. The lettering on the belts is still white like it came off the showroom floor. All the wires and tubing are still flexible. I don't think the car has ever been in a temp below 40 degrees. It's only been wet a handful of times. I agree that it would be the cautious thing to do with a 21 year old car, though.

[es.biggs]

All I'm gonna say is my timing belt failure costed me $1800 and countless nights with all the repairs done by myself - it's not worth it to chance it.

[Ace2cool]

"I've seen timing belts look brand new, except for the point where they broke...."