misfire after plenum pull

[solaire]

So I've been working on a 91 lately pulling my hair out. I did a plenum pull to fix valve cover gaskets. I know the car was running good before. It ran great after I got it back together and let it warm up. It pulled good, idled great and had no issues. Next morning I went out and it started up great but after a few seconds it started missing and sputtering bad. it would barely stay running and won't idle above 1000rpm no matter what. I pulled easy plugs I could get to for now and i've got fuel soak on #3. #1/2 were decent. They are the correct NGK numbers. The misfire will go away after 3000rpm but is still noticable in driving range.

Did I mess something up in the harness pulling the plenum or is it maybe just some bad coils? It ran great the day I got it together... I had to replace the fuel injector connectors because they were beyond corroded and had no plastic left to hold the metal retainer clips. For the repair, I stripped, twisted together, used brass crimps with special crimp tool then soldered that and heat shrinked them all. I did the same to the IAC connectors (x3) also.

I noticed the connector for the timing control (i think that's what it is? on the driver side exhaust cam) has no retainer clip. Touching this wrong will make the engine die. Not sure if that's got anything to do with it.

I'm thinking of pulling coils from my car to put on it and see if it gets any better. Right now there's freezing rain and it's about 20 degrees outside so I'm brainstorming for now lol

[t.mcginley.jr]

First, did you try checking for codes yet?

http://www.nicoclub.com/archives/nissan ... ostic.html

Second, try unplugging your MAF sensor and then starting it. What you describe sounds like bad/dirty MAF problems

[solaire]

When the weather gets better that's what I plan to do first. It was freezing rain here when I got the car home after changing the oil.. sad because the day before when I finished the job it was 70 degrees I saw a video of what the car does with a bad CAS and the fact that I've got a loss of spark on some cylinders it would make sense. I had issues with the CAS connector having to play with it to get the car to start when I was done with the work. The pins looked fine but they may be spread just enough to make a poor connection. Doesnt help the connector is broken to the point there's no clip to hold it down.

[solaire]

I think I may have found my culprit.. I saw a boot on the back of the PTU connector was split so I had to inspect to see if it had any moisture in it. I remember moving this harness but never unplugging it but here's what I've got





Here's my other PTU connector, it's in great shape



I sure hope cleaning this out takes care of it because I'm out of options otherwise

[solaire]

So I got contact cleaner in there and cleaned it with a brass wire brush. It will actually stay running now! But its missing on 1 and 3. Pulled coils and they spark to the intake but idk if they're sparking enough? They seem to spark more when case isn't touching intake. If I touch the coilbracket that bolts to the intake and touch the intake I get zapped. Tried coils in my car. No grounding issue but still misfiring. Here's a video of how it runs. I'm thinking fouled plugs since I smell gas and it idles like a muscle car ( watch near end and of video and listen to the exhaust)

http://m.youtube.com/watch?v=9gyQyHk5xzg

[solaire]

Pulled codes today. The guide showed me a good way to get to ECM. Putting it in mode 2 on this car the LED didn't flash but it did flash the CEL. Codes flashed were: 11, 13, 33, 34, 53. The 11 is because I was playing with the connector for the CAS and it died. I'm not sure how the coolant sensor could cause issues. The 53 is a knock sensor circuit code and that's common for a VG engine. nothing to do with my problem. The 33 and 53 conscern me.. There's a video on youtube about the same problem, these 2 codes and a random misfire and he's checked CAS, PTU, coils, injectors etc.

I've swapped my coils from my 90 and no good. I have the original style PTU on my car and put it on and no good but would I really want to rule out the PTU? Thinking of swapping my ECU next but that's alot of work to take out lol

[solaire]

Think I"m on the right path. Noticed today when it was running that occasionally it'll blow a puff of smoke out from behind the engine near the battery.. I had to bend the EGR tube a bit to get the exhaust valve cover off. I ended up not replacing the driver side exhaust cover because of this. I'm wondering if there's a crack in that tube. Going to try and get the tube out this afternoon and see if I can find it.. Looks like I've got an intake leak.

Tube seems fine. Holds air if I blow in one end and close the other. What a pain to remove but now I need more clamps and such to get it back together along with some silicone for that coolant line. I found the EGR vacuum hose was hard as a rock and split wide open but that small of a leak shouldnt be a problem because the feed hose was off completely before I pulled the plenum so I'm back to square one..

[solaire]

So I've pulled the plugs and it's running some copper NGKs. I told the owner this must be replaced with platinums before I can keep going. I found a video of exactly what my car is doing and it says bad injector in the title. Not sure how they just went bad overnight...

https://www.youtube.com/watch?v=AgE2jwX4kmE

[shuswapz32]

Mine ran exactly like yours before I did the injectors. I replaed mine with the Z1 new style injectors with the adapters to fit into the old style fuel rail, plus the pigtails and o-rings. It runs great now. Hook up a scan tool and check the injector pulse timing, or use a stethoscope to listen to them.

[solaire]

Yeah 3 of them were over 14 ohms resistance. They all click but that doesn't mean they aren't sticking open since they're the originals. I finally talked the guy into buying a set of remanufactured new styles from TLF on ebay for $300 with connectors. Told him I make no guarantees it'll fix it but they need to be replaced regardless.

[shuswapz32]

Keep us posted!

[Ziggy1621]

Make sure you unplug the battery and clear the codes before you run them again.

[ZL8NING]

Would like to know how it goes. Subscribing.

[solaire]

Yea as for codes the only one that kept coming back was the knock sensor code after battery reset. As of now I've got some injectors on order from TFL. Guy is driving me nuts since they still havent shown up after a week but I'll keep you guys posted.

[shuswapz32]

You can do the knock sensor relocate to eliminate the code.

[300zxstanced]

This is what I would do. Check for spark first. While the car is running unplug the each ignition pack harness one at a time (see if the engine idles rougher) and plug back in. If the idle does not change check the harness connection associated with that coil pack for corrosion and that the pins have a snug fit into the harness. If the problem still exists then clean and repair the PTU harness, if you have corrosion in there then it is very likely there is more in the injector harness, coil pack harness, coolant harness, tpu harness, you get the picture. One thing that contributes to all of the corrosion is while the plenum was off of the vehicle the harness was exposed to air and moisture (especially if the car say outside in the rain . Also if you painted the plenum make sure that your grounds are hooked up to bare metal. I believe there is only one grounding point on the plenum, located at the rear of the plenum near the center, this can cause your coil packs and injectors to run poorly). I went through each connection and ended up replacing my injector harness connections, hardwiring my ptu, made a world of difference and the car runs perfectly. I am going to change my coil pack harness connections also because they are loose., and add a few more grounding points ( I removed the one grounding point on the firewall and found out that was a no no) so I put it back on .

[Ziggy1621]

You can do the knock sensor relocate to eliminate the code.

Do not relocate the knock sensor.

[300zxstanced]

@ziggy1621, im just curious, why not, I was think of relocating mine if it was faulty? What are the draw backs?

[Ziggy1621]

It is in that location for a reason. If you move it to the side like a lot of guys do, you are running the risk of not catching the other side. It's not something that needs to be replaced often, so just replace it with OEM, and you won't see it for a while

[shuswapz32]

Yes, however if it fails, and you have a code, then relocating it to the top of the plenum is great to get rid of the code and make the car run properly until you pull the motor/trans to change it in the OEM position. I bought my car with the "resistor" in place of the knock sensor and had the code. I relocated it to the top of the plenum and the code is gone. If you don't mess with your timing, and run the proper fuel, you won't have knock and therefore don't have to worry about grenading the engine. If your OEM knock sensor is functioning properly, then you don't need to worry about touching it.

[Ziggy1621]

You don't pull the motor/trans to change a knock sensor. You pull the upper and lower plenum. Do not relocate the knock sensor, just replace the malfunctioning one and it's harness with a new OEM one

[300zxstanced]

@ZIGGY1621, makes sense, but I can see where shuswapz32 is coming from. If is isnt working anyways the next best thing would be to relocate until you get a chance to change it.

[solaire]

I'm within a few days of having the car back together but I thought I'd update. I pulled the fuel rail a few days ago and found these results:

Fuel Psi: less than 5, no pressure when I took rail off after sitting for a week.
All 6 lower insulators between rail and intake were split exactly 180 degrees apart from each other.

Injector #1 OEM, Covered in fuel, Found dried up crusty fuel on inside of fuel rail around screen and O-rings, pintle at base where fuel comes out was corroded.
Injector #2 Aftermarket, Covered in fuel, pintle at top was missing and brass portion broken, cap insulator was missing.
Injector #3 Aftermarket, Covered in fuel
Injector #4 OEM, covered in fuel, crusty fuel around o-rings and filter screens.
Injector #5 Aftermarket, Firing correctly, no fuel on tip
Injector #6 OEM, black from years of dirt and oil, tip very dry as if it wasn't firing at all.

The 3 OEM injectors literally crumbled when I grabbed the top to twist them out.

[t.mcginley.jr]

Lol wow, I would say you've found your problem(s). I would definitely get an adapter kit and drop in some new style injectors

[solaire]

Got it back together today. Runs like total dog crap. It will stay running and idle a bit rough but has no power and won't get out of it's own way. It seems 1/3 are still dead and 4 is weak. I have no idea where I'm going to start next. I think the owner is going to kill me.. literally

[ZL8NING]

It is possible you pinched and/crushed the o-rings around the injectors when u installed them. Vaseline on the o-rings and twisting back and forth as you put the injectors in will ensure there's no pinching. Check that. If that wasn't the case, then maybe the connectors?!

Good luck! I hope you survive the owner!

[solaire]

I was very careful with the o-rings. I put a ton of grease on them and twisted and tapped them in very gently. (couldn't push them in by hand). Also I took the connector wires, twisted them together, used brass crimps, crimped them then soldered the crimps and heat shrinked the whole thing. The connectors and the repair are flawless. This repair is used on modern diesel oxygen sensor repairs and I've had no problems with this electrical repair. Also a warning for anyone who gets the modern connectors from TFL you'll need to cut the #5 and 6 connectors to make them fit. They will contact the fuel rail and won't make contact and lock. Just cut the cover off the lock tab on the connector.

I put a pressurized machine we use to clean fuel rails with a bottle of fuel on the fuel rail before I put it back and at 60psi i had no leaks. I'm still getting the code 34. The harness for the detonation sensor is really messed up. It looks like someone has tried to repair it in the past. There's 1 wire with a silver insulated wire around it that someone has connected to the #2 terminal in the connector kind of half assed it too. It's a silver wire going to a copper wire and just a big mess. I'm wondering if that's causing the timing to retard because if I rev the engine past 3000 rpm it smooths out. Thinking I'll try a detonation sensor relocate before I give i back to him and tell him the car is destined for the junk yard.

[ZL8NING]

Well, it looks like you have done a thorough job with the car. I don't think it's bad enough to be destined for the junk yard. I've seen a thread referenced/linked to from here that includes the 02 sensor as part of the trouble shooting process. I've been reading so much lately I may be mixing up the forums. But the 02 sensor plus the wiring mess you refer to may hold the answer. Keep eliminating all the possibilities, and you will get it finally, as well as fix things that would have needed attention later on anyway.

[solaire]

yeah I'm trying to hold off on o2 sensors as a last resort since I didn't touch them when I pulled the plenum, even left the wiring alone and pushed it all out of my way. The fact that the car clears up over 3000 rpm (when computer stops monitoring detonation) and runs like it's out of time when driving kinda makes me suspect knock sensor and since it's got a code 34 it seems a likely cantidate.

[ZL8NING]

Alright. Keep us posted.