Before I just go and buy new ones...(UPDATE)

[LSDrift]

Formerly known as: Before I just go and buy new ones...(Hard Starting/Misfire)

Just thought I'd add another TPS/Misfire thread to the heap there are out there already.

I've been trying to diagnose a slight misfire I'm having and come up with a few things and questions.

I started noticing the misfire at idle a couple weeks ago once the car warmed up. About the same time it also started stuttering at about 2800 rpms regardless of driving load and would miss pretty hard at about 5500 and then 6500 rpms. I checked the plugs (NGK BKR5EIX-11's with ~4500 miles on them) and every cylinder was almost paper white except cylinder 5 which looked like it was glazed brown.

So immediately I suspected a coilpack or injector. Haven't had a chance to test either but I immediately switched to NGK BCPR6ES gapped at 8mm. My upper rpm miss has since disappeared but the miss at idle is still there and only when it warms up.

As per various posts and the FSM I tested the voltage on the TPS and got the following:

0.38V closed (engine off, IGN on)
4.14V WOT (engine off, IGN on)

0.33V closed (engine running)
didn't measure WOT while running.

Steady 5.13V from the power wire to the TPS.

Now, the FSM states to measure resistance on the TPS and gives values of "approx 0.4" closed and "approx 5" at WOT. From what I can tell in the various posts on here where the FSM says resistance, it means Voltage. Is this correct? If so is 4.14V WOT and 0.33V closed too little?

I also suspect the coolant temperature sensor as I had a pretty good overheat in August that caused the ECU to shut the motor down.

Thanks!

-Eric

[platez808]

I'm pretty sure that when it says voltage it means voltage and when it says resistance it means resistance. In terms of voltage, it says that it should be around 0.6v at fully closed and 4v at WOT. So you would need to loosen the screws on the TPS and turn it until the voltage is .6v with throttle fully closed. Did you try to check the resistance like it said to?

[Gabes13]

There's a typo in the fsm in that section. Ive noticed it a couple of times when browsing through it. It says "resistance" but it should say voltage (~0.4v - 4v) instead. It gives the "actual" resistance values in ohms a step after.

LSDrift, try adjusting the tps while monitoring the voltage of the throttle valve switch. Try to get the voltage of the tps as high as you can without disengaging the idle contact. You can do this by monitoring the voltage of (i think) the top wire of the throttle valve switch (2 wire plug on tps). It should emit 8v-10v when throttle is closed and 0v when opened. Now rotate your tps so the throttle starts to open, when the voltage on your throttle valve switch drops to 0v, back off a little. The motor can be off when you do this, but make sure it's warmed up a little.

[Darius]

The TPS is providing a 0-5V signal to the ECU to indicate throttle position, not resistance. The readings you are getting are normal but might be a touch low. You can adjust it though. It does not necessarily go all the way to 5.0V. Mine only reads up to 4.7V or something similar. It won't matter because tuning will adjust the fueling as load is calculated anyways.

I'm betting it is something other than the TPS causing the miss. It is likely a coil issue.

[LSDrift]

Thanks for your input guys! I figured it was a typo but I just wanted to double check. I haven't had a chance to adjust the TPS yet but I should be able to this weekend. One of the reasons I think it is other than the voltage is, occasionally if I run up to say 5k rpms with ~30% throttle and then hammer on it, it will buck or hesitate, and other times it pulls like crazy. A lot of times 1st gear feels weak or hesitant and then shifting into 2nd the car feels like a different animal. --I'll update on this once I adjust the TPS.

I also forgot to mention that I pulled the coils, which looked decent and didn't show any visible signs of cracking or age really. I then coated them once with liquid electrical tape as per another misfire thread. I also daisy-chained ground wires to all 6 coils and then grounded them at the firewall at the same factory point that the manifold ground is at. Now, other than the manifold ground and a ground at the battery's ground, these are my only two grounds. I know that's not ideal but the car seems to run perfect till it warms up. Not sure if the liquid tape and grounding helped tons but I definitely have noticed an improvement since the combination of plugs and those two things.

I should also mention that if I hold the engine at any given rpm above about 1000rpm it will not misfire. Or at least if it is I cannot tell.

Darius - In terms of the signal the TPS is giving the ECU, if the max output of my TPS is 4.14V and the min is .33V like I said, does the ECU scale the signal? In other words, I have a total difference of 3.81V, and if your TPS is going from .4V to 4.7V you would have a 4.3V range. Would I be seeing a lower resolution? Or am I thinking of that the wrong way?

[LSDrift]

Just wanted to update this issue in case anyone's searching.

Since I last posted I haven't had a chance to touch the TPS because of school and laziness. Any upper rpm hesitation has been eliminated but there's still an erratic misfire at idle once warm. Sometimes it's really bad, other times it isn't - sometimes seems to get better with less electrical load, i.e. put e-brake on at stoplight instead of using brake pedal - dieing alternator?

Another problem has since developed. Cold starts. A couple days ago I went to start the car like normal and it kicked over right away with a slight stutter and then just died. Sounded like it maybe hit each cylinder once. Then, had to crank and crank and crank and crank while attached to a battery charger to get it to start after 20-30 minutes of intermittent cranking. Then it was fine for a day or two and did it again. So I replaced the coolant temperature sensor. This morning it started like a charm after sitting all night in 10 degree weather, but then gave me hell like before after sitting at school all day.

Today I checked all injectors resistances and all came out at a decent 11 ohms with in +- 0.1 of each other. When I swapped out spark plugs I suspected a bad fuel injector on Cyl #5. I checked the new plug after 2 months of driving and it looks ok.

SO, I just resistance tested my coilpack on #5 and bang, 1600 Ohms on what should be 0.6-0.9 Ohms. Is this so ridiculous it seems unreasonable? I'm using a Radio Shack $20 DMM and I know I'm doing the measuring process correctly, between terminals 1 and 2, but could they really be that bad? I checked the #1 cylinder as well and it showed about 1400 Ohms resistance so I'm assuming they're all that way. Does it matter that they're not warm?

[LSDrift]

One more update -- Measured all coilpack resistances and come up with 1.5k Ohms, 1.7k Ohms, 1.6k Ohms, 1.6k Ohms, 1.6k Ohms, and 1.5k Ohms for cylinders 1-6.

Now I know what you're thinking but no I don't believe I'm misreading the DMM unless it's mislabeled. It has increments for 200 Ohms, 2k Ohms, 20k Ohms, 200k Oms and 2M Ohms. So provided the labeling is correct then I'd be measuring in the thousands of Ohms on each coilpack. An testament to the accuracy/functionality of the DMM is that the injectors all came out to ~11 Ohms which seems high compared to the FSM 1.3 Ohms but in searching through the forum 11 seems to be fine.

I'd be inclined to think that would be high enough resistance that the car wouldn't even run considering the FSM specs 0.6-0.9 Ohms but I don't know I guess!

EDIT: After a few hours of searching now I realize the FSM specs are for an S1 coil pack with no igniter built into the pack. But I CANNOT for the life of me find what the resistance should be for the S2 coil packs...

[240z4u]

Many have found the coils to be shot despite what the FSM says to test for. They test good and just don't work. I have a full set of S2 coils I would let go for a good price if you want to PM me. They worked perfectly when taken off the car and are just hanging around in a box. I kept them as a spare set for troubleshooting.

Evan

[LSDrift]

Well I don't want to low ball you with my college budget offer at the moment and I think I may try and save for some supersparks a ways down the road here so I only buy new coils once for a good while.

The same issue happened again this afternoon when trying to come home from school. I didn't have my DMM with me to check the battery's voltage or what the coil packs were seeing but it finally started. It seems that it likes to finally kick over after a good 5 trys of 10-15 second start cycles with a few minutes break in between. I realize these are rather long but that's what it's been taking to get it started. A really long start cycle with the pedal at 75% is what finally does it.

EDIT: Just wanted to mention I'm running a Braille 17lb battery with 380 CCA rating and 1190 PCA rating. The battery showed 12.8V when I got home from the short drive back from school and the coil packs were showing 12.55V.

[LSDrift]

AAAAND it appears to be the #5 coilpack! I feel like an idiot for not doing this yet but I unplugged each coil pack one by one and found that cylinder #5 caused no change to the idle. I verified that all 6 injectors are firing - I need to get them flow tested still to be sure but I physically verified that all 6 are firing :P.

[LSDrift]

Just wanted to update the current prognosis on the issue. Since "determining" it was the #5 coil pack I ordered a set of SplitFire's and put them in. Thought the problem was gone and then had another hard start the next morning. Miraculously found out that the signal and ground wires to the #5 coil pack were switched and I have been running on 5 cylinders for longer than I'd care to mention. I never would have assumed this was the issue because I bought the whole harness premade from Wiringspecialties whom apparently made a manufacturing error.

Anyhow, in the process of diagnosing things I had the intention of switching injectors around between the #5 cylinder and another prior to the wiring discovery. And so as I attempted to pull the 16 year old injectors out of the fuel rail I managed to damage them enough to warrant new ones. So I go some 370cc Deatschwerks ones and popped them in. Problems solved right? Wrong.

After putting everything back together I took the car out for a spin, which was amazing. 6 cylinders is waaaayyyyyyyyyyy faster than 5. While the car was warming up after the injector install I noticed a bit of a bubble in the idle and didn't think much of it. Went for a spin and was just loving it but began to have a break up in the top end. Next morning the car was throwing fireballs on deceleration like I have never seen before. BIG popping fireballs, not cool ones, like 5 in a 500rpm decel accompanied by a worsened break up, as low as 4k rpm.

Problem possibilities(IMO): MAF does not affect bubble in idle, TPS does not affect bubble in idle, CTS is new, injector insulators need to be replaced, bypass recirc tube has potential leaks and will be replaced soon.

Other than those ^, I have no idea what it could be. Any thoughts?

God bless you if you've read this far.

[Darius]

How did the injector install go? Were they easy to pop in? Did you lube the o-rings up with lots of vaseline? The reason I ask is because I'm wondering if one of the lower o-rings got pinched and is dumping fuel into a single cylinder even under decel when there should be zero fuel. Try pulling the plugs after letting it idle to see if any of them are wetter than the others.

[LSDrift]

Ok will do. Yeah the install was easy and I used plenty of the supplied synthetic grease and they all went in as easy as the other. I just set them in and slowly screwed in each retainer screw side by side so they were evenly pushed in. One of the weird things is that it happens somewhat intermittently. Yesterday I even thought I had it 99% fixed, it stopped breaking up altogether on acceleration, no backfires on decel, and only a slight bobble in the idle. Then, I shut it off swapped out the old screws on the injector caps for some allen head cap screws, and went to give my buddy a ride in it and it started right back up with the popping and backfiring. The acceleration break up was not as bad as usual but it popped pretty good. An odd note is that if I decel in gear and then just barely tap the throttle, or get back on the throttle at all it pops the loudest.

Also, as I was diagnosing things there was a point where I ended up back on 5 cylinders, found out it was the #3, swapped coil packs with #2, no change, swapped injectors with #2 and it came back to 6...?

Thanks for your input Darius!

[Carl H]

dunno if you have done it but check the base timing, timing retard will cause fireballs.

also check the injector...its very easy to pinch and destroy an oring if you dont install them correctly.
trick is to have the rail and injector bore BONE DRY.
use some good engine oil and lube the orings as well as the injector bore till its shiny.
place the injector into the bore and find a socket that fits the 'circle' indent on top of the injector.
use a ratchet on that said socket to apply force with your palm directly over the injector, if all is well it will simply slide right into place.

bores must be dry as the gasoline acts as a solvent and will flow any lubrication away from the bore.

[LSDrift]

I know the rail was bone dry initially because it sat for like a week and a half as I waited for my injectors.

The funny thing about my timing is that I checked it thinking the same thing as you Carl, and it was retarted (like at 25 degrees) so I reset it with TPS disconnected and had to turn the CAS all the way ccw. I took it for a spin after that and that's when I ended up on 5 cylinders. Note that I simultaneously was attempting to compensate for my somewhat torn injector insulators by doubling them with a circular o-ring against the manifold. Quickly threw that idea out and that's where I was switching things between #2 and #3. I checked the timing again and at that point reset it and the CAS was back in the middle where it started...

[LSDrift]

Could a crappy PCV cause these issues?

[LSDrift]

Just wanted to update this again for future troubleshooters. Turns out the braided PVC Home Depot special BPV recirc line I was using had been charred to a burnt black crisp with a few holes in it by the exhaust manifold it was sitting above. It was difficult to find this initially because it was just on the underside of the pipe. Replaced that with a 4 ply silicone piece so that should be safe now. Problem instantly went away and it pulls hard all the way to redline.

Amidst all this trouble shooting/messing around I replaced the injector insulators/donut o-rings on all 6 because one had a decent rip in it, and a couple others were questionable. At the same time I pulled the injectors out and reinstalled them as CarlH recommended and replaced the PCV valve and seal.

The problem now is that every time I boost relatively hard, I smell pure gasoline. I've stopped quickly after boosting to look for leaks but all I can see is that the injector bodies are damp. I ordered a new set of o-rings from deatschwerks and re-installed them again carefully drying the bores, lubing them with a small amount of fresh oil, lightly oiling the o-rings, and pressing them in by hand with a correctly sized socket on a ratchet. But I'm still getting the same problem...smell goes away and doesn't happen under regular driving/low boost. --I'm headed to Dynojet within the week to put the car on the dyno and get a baseline run as well as monitor the injector area under load.

One last thing - My semi-erratic idle seems to be from a mildly leaky intake manifold gasket. Discovered via spraying starter fluid near intake manifold gasket/head boundary at idle. Strange since I re-gasketed the whole engine with new Nissan gaskets before I ever ran it...

[gawdzilla]

i wouldn't waste time or money going to the dyno until that injector problem is fixed. the injector bodies should definitely not get damp. could lead to a serious problem doing a pull. maybe try pressurizing the FPR vacuum line or pinching your fuel return hose temporarily to see if you can create the leak off idle. at idle the fuel pressure can be significantly less psi than under boost. ~38 fuel psi at idle vs 43 fuel psi +max boost pressure at full boost. say you're running 17 lbs of boost.. that's 60 psi fuel pressure compared to 38 on idle.

[RRRRB]

pinch the fuel return line, that will jack the pressure way up, it will simulate you being in boost or at least apply more pressure so you can see if you have a leak..

[TimTurboZ]

While reading you said you had a starting issue on coldstart overnight...made me want to ask if you have radiator fluid in your lines or just water...would be a funny issue if it froze on you.

I have a a cut at 5k I haven't checked my TPS yet, thx for the info on here about it!

[LSDrift]

Thanks for the tips on pinching the return lines guys. As far as the dyno run goes I don't think I have any problems bad enough to worry about there, and basically I just want to put enough load on it to boost a bit and watch the area around the injectors for any leaks. Looks like the line pinching technique will be the first thing I try.

Tim - At one point I was running about 50/50 or slightly less mixture of 50/50 coolant and distilled water a little too long into the cold months and had a small freeze in the radiator but was quickly remedied by dropping some of the coolant and adding more 50/50 till I was at approx a 60/40 or slightly higher mix (clearly I haven't been technically measuring my amounts but with the cold winter months here in MT it doesn't really matter as long as it doesn't freeze haha). I still occasionally have a hard start here and there but I've found as long as I barely blip the throttle on startup it starts like a champ every time. Vacuum leaks seem to have been the bane of my existence though between my BPV recirc line and my leaky intake manifold gasket that is still questionable. --What kind of plugs are you running and at what gap? Are they in good condition, no cracks etc?

[LSDrift]

Here's a video and some pictures of what I'm seeing. I guess it was somewhat misleading to say the injector bodies were wet, the pictures should explain what I was seeing...





[youtube]http://www.youtube.com/watch?v=DhKJ5tfH ... FxjdHR0%3D[/youtube]