98MistSE

Hey guys. I was really trying not to have to create a new post for this but, I am out of ideas. About 2 months ago I finished my swap and have been getting a random cylinder misfire ever since. The misfire is only noticeable from idle to about 1500 rpm. I have put about 300 miles on it since the swap, and on the highway, there is not a hint of misfire under load and the car has plenty of power. The only other problem I am having is a hard cold start, where I have to lightly hold the gas down for the first few seconds, then it idles but, misfires.

So, here is a little history. 4 months ago, before I started the swap, everything was running fine on the old VQ30 engine. I did a hybrid swap using a 2004 VQ35 with about 70000 miles on it. I used the old timing components and upper and lower oil pans and all old sensors(at first). I believe I must have read every post related to misfires on the org looking for answers and from that, have tested/replaced the following:

• Brand new NGK platinum plugs
• Fuel pressure at a static (vacuum line not connected) 51 PSI
• CPS - tested within spec
• CKPS(REF) - tested within spec
• CKPS(POS) - tested per FSM and failed. I replaced with new unit but still did not fix the problem.
• Both front oxygen sensors (FED Spec) - Bank 1 (firewall side) failed just out of spec (also tripped SES p0134) and was replaced. Bank 2 tested within spec.
• MAF - tested within spec per FSM at idle.
• ECT - tested within spec @ cold.
• Knock sensor was mounted in the original location (despite some posts recommending not to) and tested within spec.
• All coil packs were tested using the ohm method outlined in an old post I found. Everything seemed to test out fine. Also, I have a 2003 maxima, that I swapped 3 coils at a time from this engine into it, and got no misfire. The only thing I didn't try was swapping all 6 because the 2003 is my DD and I can't have it down for too long.
• checked for vacuum leaks using the old school propane method. Also used a vacuum gauge where it registered 19 PSI at idle, which again, is within spec.
• Tested and adjusted TPS per FSM and all values fall within spec. I even did both old method of TPS adjustment using the ohm reading and the new method of using the feeler gauge and open/close switch position.

The only other odd thing I came across when troubleshooting with the FSM is when reading the engine timing with my Auterra scantool, it registers anywhere between 5 - 15* (spec is 15 +/-2*) and jumps around while idling. I also confirmed this with a timing light as well.

I am turning to you for any suggestions before I just start throwing new parts at it until it works.

ampire

iTrader: (12)

Probably the obvious thought but could it be your tensioners and timing chain if the engine timing is jumping around?

t6378tp

iTrader: (69)

I don't care what that book says 19 is alittle low for a stock motor it should be higher. Is the vac jumpy or rock steady. I would confirm none of the teeth on the timing ring are bent or broken. Also I would either get a scan tool or pull out a timing light to confirm timing.

As for the cold start issue what tb and iacv are you using, depending on your setup it could cause cold start problems

98MistSE

Thanks for your suggestions, I will definitely take a look at my timing ring when I get home tonight. When I put the fly wheel back on to the new engine, I was pretty careful about timing ring after reading what Crusher went through with his swap and breaking some teeth on his ring.

As for vacuum, I was reading a steady 19 PSI, with no jumping around. You say it should be higher though...what do you think it should be around?

For timing advance, I verified the advance to jump around from 5-15* using my auterra scantool and then verified the rough readings I got from using a timing light and the FSM procedure. With the timing light, the engine keeps jumping around between the 0* mark and 15* mark on the crank pully.

For my cold start issue, I am running a pathfinder throttle body and stock IACV using stephenmax's adapter plates. At first, I thought it was the TPS, so I did both the old and new TPS adjustment procedure and idle air relearn procedure with no change in idle. I then swapped the TPS that came with the PFTB for my old one and still got the same results. I am thinking that the hose I used to go from the intake tube to my IACV is too long (about 3 feet). I mounted it to the left of the intake manifold elbow, and it shares the same vacuum port at my brake booster.

Nealoc187

iTrader: (23)

ckps (pos) not quite correctly aligned with flywheel timing ring maybe?

98MistSE

Well, the story about my ckps (pos) goes like this...When i first hooked up the timing light to the loop on the wiring harness, I got an intermittent flash from the light. I immediately thought the ckps(pos) sensor and proceeded to run the FSM screwdriver test for that sensor. If anyone is unfamiliar with that test, it requires you to unscrew the sensor from the transmission housing. Then while monitoring pin 2 (the center pin on the connector), with the car on but engine not running, pass a screwdriver over the pickup of the sensor. When I hooked up the dmm to the pin, I immediately read 5 volts without the screwdriver even being near the sensor. I began to pass the screwdriver over the sensor and noticed it intermittently got stuck at 5 volts and sometimes it would not. I really thought that was the problem, so I bought a new sensor. When I put it in, I made sure it was aligned with the timing ring by marking the transmission housing and centering the ckps sensor with that. After replacing the sensor, the intermittent flashing of the timing light went away and it was consistent now but, I still had the random misfire and my timing advance at idle was still jumping between 5-15*.

Also, on a side note, I am an electrical engineer in a test equipment group for an aerospace company, so I do this kind of electrical troubleshooting all day for a living. So, please don't spare the technical troubleshooting details, they don't scare me.

t6378tp

iTrader: (69)

Change this and give the iacv it's own source and your cold start problem should go away

98MistSE

Well, I will definitely give that a try this weekend. Do you think that not enough air at idle would also be causing the random misfire as well? The reason I ask this is that when the misfire trips the SES light, the freeze frame data for the Long term and Short term fuel trims indicates that the computer is trying to compensate for a perceived lean condition by adding fuel and not a rich condition that not enough air at idle would be causing. They are probably 2 separate unrelated issues but, I am tyring to not leave anything out. The last time the misfire tripped the code, my fuel trims looked like this:
Short Term:
B1: 10.9
B2: 10.9
B3: 19.5
B4: 21.1

Long Term:
B1: 9.4
B2: -3.1
B3: 18.7
B4: 7.8

I have been reading this article on fuel trims (FUEL TRIM(MING) DIAGNOSTIC TIME). It seem to be pointing me toward a fuel delivery problem. Possibly a clogged fuel injector/rail or a problem with my APFR setup. I am going to make some changes to how I have my fuel regulator setup and see if that helps. Unfortunately I do not have a WB02 reader to verify if either bank is running lean to confirm my suspicion. I was going to buy one eventually so I can tune the car when I finally got it running properly but I may need it now.

Thanks again for all your suggestions guys.

urmab

iTrader: (7)

Random misfire can also be cause by a faulty ignition coil, I had a issue with the same code and it turned out to be a bad coil on cylinder 6. The best way I would check this is since you have access to the front coils unplug one at a time if no change plug it back in and go to the next, as far as the rear once you have access to coil number 6 u can unplug it without taking off the IM, I'm not expert but at least this is how I was able to solve issue with my car when it was trowing code P0300

98MistSE

Well a little update for those following this thread. Since I thought I had a lean condition caused by dirty fuel injectors, I had them all sent out and cleaned. Unfortunately, that didn't solve the problem. I also purchased an ignition test light that goes between the coil and spark plug to show the coil firing. I tested each coil pack and all seem to be working properly. I swapped out my MAF, CKPS(REF), & CPS with working ones from my brothers' 99 maxima, with no change. I have a brand new CKPS(POS) sensor installed because I initially thought that was the problem. I am now left with my coil packs being the cause, even though they test out fine and seem to be firing properly. Maybe they are weak?
I am completely out of ideas. I am either going to take it to the dealer and get a scan with the consult and hopefully not get jerked around, or scrap the project and part it out.
Thanks again for those who offered suggestions.

Chris

Nealoc187

iTrader: (23)

This is a really, really long shot, but do your fuel injectors have the part number FBJC101 etched on them?

The reason I ask is because using an injector that seems exactly the same (externally identical, and has the same flow rate as stock) but has a different than stock lag time could cause issues at very low injector pulse widths (i.e. low RPM and idle).

I'm not sure if there is some issue that could affect the lag time of a stock injector (if your injectors are indeed the correct FBJC101 injectors), but incorrect lag time can cause issues like you are having.

98MistSE

Well, I was told that the engine was out of a 2004 Maxima and like you said, it should have the FBJC101 injectors. When I removed them, I did not find any markings on them indicating that part number, or any part number for that matter. Also, when I compared them to the injectors that are in my 2003 Maxima, they look different. The ones out of this engine have a thinner black body with a white band around the top. I am starting to wonder what I have now. I found some used, but cleaned and professionally serviced FBJC100 injectors on eBay for $100. I am going to buy those and give them a shot. From what I read, they are the 350Z/DEK injectors that have a higher flow rate than the 101's.

98MistSE

Could only one skipped tooth on one bank of cylinders (say, the front bank) cause this kind of problem or would I have something more consistent or worse problem? What does an engine sound like when the timing is off by only one tooth?