ZCar Forum banner

Injector problem I think

3099 Views 44 Replies 8 Participants Last post by  vigman
Ok so here's my story I'm gonna keep it as short as possible, first of all it's a 90 300zx na 2+2 and it's missing on 3 cylinders 1-3-4 (if no. 1 cylinder is front passenger side) it's blowing raw fuel out of the exhaust but it will run and idle ,did a power balance test to find misses. here is what I have tried ,cleaned all connections ptu ,tps ,cas, coolant sensor, maf , and some others that I don't even know what they are. New injectors ,new injector connectors , new plugs( NGK pfr6g-11) ,new/used cas, new/used ecu checked for vacuum leaks ,all injectors ohm correctly. The only thing is that three of the injector connectors were put on by one shop and three by nissan ,I checked the voltage going to the injector connector (with the car off) and on one of the good cylinders I got 12v on both wires and on the bad cylinders I got 12v on one wire and the other wire was erratic and low like jumping from 3ish to 9ish volts. I did check the ohms on the injectors from the ecu also and it would jump between 14 and 15 ohms on all cylinders. The three bad cylinders are the three connectors that the first shop put on, I don't think that is a coincidence. Oh and I did check codes and got a 55, any suggestions would be much appreciated I'm out of ideas. Thanks Jason
Not open for further replies.
1 - 20 of 45 Posts
Did it run after you got it out of the non-nissan shop.
Who's injectors are you using?
it ran enough for me to drive it the 1/8 mile to get it home after I got it out of the non nissan shop they had it for a really long time and couldn't figure it out so I just went and got it , and I am using genuine nissan injectors brand new but it did sit awhile after they were put in. I also did the screwdriver to the injector trick to see if they are ticking and all of them are and also moved the coil packs around and the miss stays with the cylinders. Thanks for the speedy replies. Jason
Two thoughts here 1 how were the injectors replaced. Manifold pull? If the injectors are clicking maybe the o rings are leaking due to a bad install, confirm that you have good fuel pressure in the rail and spark in all holes... Plus inspect the actual coil for cracked insulation.

If fuel is coming out the back doesnt that mean the bad cylinders are getting fuel but no spark? I don't want to insult your intelligence but have you made sure the coils are plugged in fully? Here's some recommendations;

Check the coil ohms
Swap for a known good PTU (Since this controls the coils I think)
Pull the plugs and check them

Once you find out what is wrong, take it back to the shop and raise ****. Sometimes people can forget some simple things like plugging stuff in etc etc but it's likely money back if they do. Also, if all the coils are suddenly bad on one side, which is an astronomical possibility, it's something they did and they need to replace them out of pocket.
Hey mike yes they were replaced with the manifold off , I did inspect the coils they all look good and I ohmed them and they all ohmed the same will verify spark putting old plug in the coil pack and grounding plug ,I thought about the o rings but what I can't figure out is the voltage on the injector connectors the good cylinder measures 12v on both wires and the bad ones don't could that be a ground problem do they not ground through the ecu. I'm also trying to find a fuel pressure gauge the only one I can find locally is 50 bucks. I really appreciate the input this thing is driving me insane.
Thanks Jason
Hey oninous , yes it does seem like it would be spark but I did ohm the coils and they ohmed the same and I would like to find a good ptu to use but there are no z owners in my area to bum one from (would hate to buy a new one unless I new it was the problem) and mine is the new ptu type too. Oh and plugs are brand new from coz. Thanks for your input. Thanks Jason
See less See more
Oh and as far as the non nissan shop they didn't get paid sh$# because they didn't fix it all I paid for were the parts.
Thanks Jason
FYI you might want to dissconect the battery , pull the ECU and buzz the harness out... BRB...

Sometimes the ECU connector needs a clean & reseat.....

Yeah mike I did that when I swapped out for the other ecu I inspected it (it looked perfect) and was really careful when I went to reseat it. Went down and tried to test ptu last night but couldn't figure out how to do it using the online manual the only reading I could get on the meter was about 12v on the plug on the top of the ptu. Tried to get reading across pins on the ptu but nothing. I've read about other people having problems doing this any suggestions ,don't have another one to swap with. Thanks Jason
And where are you located??

Is your PTU series 1 or 2 ( series 1 has a aluminum heatsink )

Ok so I have alittle bit of an update, I pulled the coils out and put a spark plug in and grounded it, I got spark to all 3 coils, no. 4 cylinder had spark but it was weaker than the rest so does that mean my ptu is ok? now this is where it gets weird I was rechecking the injector connectors and I pulled off no. 3 and the engine idled better then plugged it back in and the car almost died , then I ran out of gas so I went to get gas got back started it up and pulled the same injector plug and it did the opposite when I unplugged it almost died ,like the cylinder was running like it was supposed to. also I found out that I can unplug a vacuum hose from the balance tube and it idles better, which I guess it would do because it is getting to much fuel.
Mike I have the series 2 ptu and I am located in Jefferson City that's about 30 Min. east of Knoxville, you wouldn't happen to know of a good z tech in my area would you or a good z exorcist . Thanks Jason
I wouldn't bet on the PTU ( yet )....

Do not EVER let the tank run out... your just askin for trouble...
Swap the #3 coil into the #4 posiition see if the spark is still lame...
I assume your using the SAME NEW PLUG while checkin spark?
If you were in California I could help.. Sorry

The raw fuel can't be doing the cylinders any good and may have washed one or more and be causing compression problems. Raw fuel can also have major problems for catalytic converter. Pull plugs to see if fuel is sitting in cylinders and run compression check.
Sorry mike I forgot to say that when I did the test I did change out those two coils and got the same spark.
And alwzpkn someone took the cats off , there was a compression test done a while back and all was good but will do another if I can find a compression gauge to steal/borrow.
Thanks Jason
Have you checked the adaptor between the old harness and the newer style PTU??

Yeah mike I did check that harness and it was somewhat corroded, I cleaned it but didn't help. I'm going to go back and recheck the connections I don't know what else to do.
I just did my injectors last summer and had 3 dead cylinders. I had replaced with injectors that ohmed out in spec that I had laying around but were used. I read that they stick if unused for a while. Someone had written on the forum that if you take a direct 12v from the battery to the injector pins you could free them up sometimes. After I did that all cylinders fired up. You said you have new injectors and hear them ticking though and it may not be your problem, but you can do it without removing them. I might suggest using multimeter leads hooked up to wires although I just used wires. Also I had raw fuel coming out of the exhaust which was a result of a pinched O-ring that was leaking fuel. I got to do the injectors twice. Second time through took about half the time.
That's why I like the dremel method for injector replacement...

No plenum pull !


1 - 20 of 45 Posts
Not open for further replies.