Replaced Injector now car runs worse-help

[punkrock1992]

Alrighty well for the past few weeks my Z has been running rough, I narrowed the problem down to being a bad injector(#6). I did the dmm test and the screwdriver test. So I changed the bad injector and started the car up now its running even worse than before instead of one bad injector its all 3 on the drivers side including the one I just replaced. Any advice or help would be greatly appreciated and thank you in advance!

[300zxstanced]

Here are the 3 things I would look at.
1.The injector harness, typically old,broken, brittle, and have tons of corrsoion causing a poor connections to injector(s).
2.The stupid cam angle sensor on the front of the motor, usually loose connection, and corrosion. The pins from the sensor are loose inside the CAS harness.
3.The wrong injectors? Did you replace with the exact same injectors? If not you probably have to get your ecu re-mapped or re-flashed if possible.

There is also an injector test you can do where you turn the cam angle sensor by hand, while the car is in accessory mode, and not while running. You will hear each injector open/click one after another until all 6 have clicked. No clicky could mean no signal from sensor and or loose connections at injector.

[emiliog2276]

What are your ohm readings on all your injectors? What codes have you pulled from your ECU?

[punkrock1992]

Hey y'all! thanks for the responses! I finally had the time to check codes and I got 34. knock sensor if I'm correct?

[t.mcginley.jr]

Yes, code 34 is knock sensor. It's like a 50/50 shot of it being the sensor or the little subharness. Most people replace both just to be safe. Z1 even sells and upgraded subharness that is better designed and cheaper than a stock one.

OEM knock sensor ~$40

Z1 upgraded KS harness ~$20

Unless you plan on taking the upper/lower plenum off to get to the knock sensor, most people just relocate it to the back of the engine. You basically just unplug the old knock sensor from the main harness and leave it where it is. Then install the new sensor on the back bolt on the plenum (so it's easier to get to in the future while still being able to feel knocking) and use the new harness to plug it in. All you need to relocate it is a longer bolt. Here's an article about different places to put it:

Knock sensor relocation

[ThisIsSparTTa]

To be clear, knock sensor is not going to fix your injectors not working.

You need to ohm your other injectors, and make sure they are getting power from the harness, etc. Also, I kind of doubt you dropped all 3 on one side, because I'm pretty sure the engine wouldn't run at all.

[t.mcginley.jr]

Agreed, I was just letting him know how to fix his code 34.

If multiple injectors aren't firing and they ohm out correctly, then you have a bad CAS or the connector is loose or corroded.

[SleeperPower]

Make sure your ptu connection is not corroded or botched up. Sounds electrical to me. Check all connections.

[punkrock1992]

Really appreciate all the feedback and suggestions! Also to add : the other day I went to start her up again and she wouldn't, everything ohmed out fine so I figured i'd come back to it later after work (about 5 hours) I went to crank and she started. now it seems like it's back into the original state before I replaced the injector (which all injectors work) feels like only 5 cylinders. but has a new symptom of dropping in power like it wants to cut off under acceleration (I've noticed it around 2500-3k not sure if theres a pattern when it happens) but that's what I found out today...

10-26. No change in power when I disconnect #6 coil connector, I tested and swapped coils no change. ptu is fine and I cleaned it.

[J30tChumpCar]

You need to test #6 injector plug for a "pulse"

Fun fact, a VG30DE will idle smooth with one entire bank disconnected, heck it will still run on only 2 cyls

[t.mcginley.jr]

If its just #6 then the injector is probably bad. You might have already mentioned this, but do you have old style (square plug) or new style (oval plug) injectors? If you have the old style, its not surprising that another injector failed already. These are prone to failure compared to the newer style ones.

Also, you might want to try changing out your coolant temp sensor (CTS) on the front water pipe. When they go bad, it causes all kinds of hard/no start issues. They are only $20-25 from Z1 I believe.

[punkrock1992]

#6 injector has been replaced not even a week and a half ago. All are new style. It's a 94 engine in a 91 body . They all ohm out correctly, I replaced coil(had a tear in the boot), spark plug, and injector... I'm puzzled. I'm doing research within the forums but I haven't had any luck with my problem :l

[t.mcginley.jr]

Hmm ok so assuming the injector is good, are you sure the #6 coil pack is good? If it isn't the injector OR the coil pack, the only thing I can think of is a bad connection at the CAS. Usually when the CAS goes bad or the connector has corrosion or is loose, you get multiple injectors not firing. I suppose its possible for one wire/pin to be loose and cause only 1 to not fire.

[punkrock1992]

The coil pack is brand new from the parts store. Also I cleaned the CAS connector and pins last night didn't help. but I found out by accident that when I touched the CAS connector cable it shut the car off. That normally happen when your finger comes into contact with the cable? :l :o

[t.mcginley.jr]

No, that shouldn't happen. The connector should be able to wiggle a little bit without causing any problems with the engine running. I would make sure all the pins are fully intact (sometimes they get bent or even broken by accident). If they all look good, put some dielectric grease in there and see if it helps. Any auto parts store will sell it, usually in the same section as the silicone RTV.

If that doesn't work, you might be looking at either a new CAS, or a new connector.

[300zxstanced]

I hate to keep beating a dead horse, but I spent so much time tracking down a similar issue, I would hate for you to keep going around in circles. I did all of the same things you mentioned. I know you cleaned the the CAS connecter, but did you look at the female side on the CAS harness.



The female side usually has loose terminals, you have to close them down with a small flat tip screwdriver so they fit tight against the male side on the CAS. If you dont you will get erratic timing, back fire in the exhaust, unburnt fuel smell, harnes will just slide off with no effort, and you will have rough idle. There was a noticible difference once I fixed the harness, and re-gapped my plugs. IOn a side note I'm going to replace the harness end with a new one when I get some time.

[t.mcginley.jr]

I hate to keep beating a dead horse, but I spent so much time tracking down a similar issue, I would hate for you to keep going around in circles. I did all of the same things you mentioned. I know you cleaned the the CAS connecter, but did you look at the female side on the CAS harness.



The female side usually has loose terminals, you have to close them down with a small flat tip screwdriver so they fit tight against the male side on the CAS. If you dont you will get erratic timing, back fire in the exhaust, unburnt fuel smell, harnes will just slide off with no effort, and you will have rough idle. There was a noticible difference once I fixed the harness, and re-gapped my plugs. IOn a side note I'm going to replace the harness end with a new one when I get some time.

Good tip!!

[punkrock1992]

I cleaned both female and male, but I hadn't checked for loose terminals! Thanks I'll check that after work tonight!

[t.mcginley.jr]

I know Z1 sells new new-style connectors for the CAS and PTU, not sure if they sell replacements for the old-style ones. In that case you would need a new style CAS too, but it would be worth it.

[punkrock1992]

What year did they switch styles?

[t.mcginley.jr]

I think model years 1994-96 used the newer style CAS and PTU. You can install them on any Z though you just need to solder in a new style connector.

[punkrock1992]

Oh well Its a 94 engine in a 91 body :3 and I just got my sensor and harness today Woop!

[punkrock1992]

Okay sorry for the delayed response y'all, school and work have been unkind. What I have done so far: new plug, new coil pack, new ptu, verified spark, getting fuel, compression(160), new knock sensor and harness, cleaned connections, replaced injector, cas connection is tight. But still the cylinder is not firing. And I'm lost.. Got fuel, spark, compression... So any advice would be greatly appreciated.

[nissanfreak12]

Okay sorry for the delayed response y'all, school and work have been unkind. What I have done so far: new plug, new coil pack, new ptu, verified spark, getting fuel, compression(160), new knock sensor and harness, cleaned connections, replaced injector, cas connection is tight. But still the cylinder is not firing. And I'm lost.. Got fuel, spark, compression... So any advice would be greatly appreciated.

How do you know your getting fuel to that cylinder? Is the plug wet?

I had an issue once, where an injector went bad. Now these are the newer style, so I checked everything, spark, compression, orings, etc... The injector ohm'd in spec, it clicked, did everything it was supposed to, well except one thing. So as a last ditch effort, I decided to swap the injector to a different cylinder. Sure enough the problem followed. I had to explain to coz about it since it was still under warranty, he tested it, even flow tested, came back good.

He ended up sending me a new one, just cause he just a cool guy, sure enough, fired right up without a dead cylinder. Don't rule out an injector if you checked everything else.

[punkrock1992]

The plug is wet, and I have a spare injector laying around so I guess I can swap it and see if any difference. That injector is new but at this point i'll try just about anything.