RTrud

Need some help troubleshooting:

Have a 2004 I35 w/116k miles. Haven't driven it much the past year... During winter I had it up on jack stands for several weeks while I replaced the front suspension - everything but the inner tie rods. Drove fine until July when the alternator went out... Ended up replacing that and idler pulley about a 3 weeks ago due to having to do some travel. Drove great for a day and then had a cylinder 4 misfire. Decided I would just go ahead and swap out all the COPs and Spark plugs and discovered the spark plug in cylinder 4 was covered in oil. A few others also had some oil.

So that meant new valve covers. Got that all done and then I noticed that the car was running hotter than I would expect. Noticed one of the radiator fans no longer worked so replaced that. Also replaced the thermostat while I was at it.

Yesterday I had to drive 4 hours for a meeting and back (8 hours total)... Mostly highway about 70MPH average. Car drove fine for the most part. I have noticed lately that it doesn't accelerate as well as it used to and that the gas mileage has dropped... used to get about 28/29 highway... now more like 25/26.

What I noticed today is that the coolant temp is operating at about 220 degrees (high about 223). I have read that the normal range is 180-200. This has me a little concerned.

Last week the car was running a little rich... tonight it's running a little lean. Intake Air Temp is about half what the coolant temp is... is that good? bad? Reading some forums I've read it should be a few degrees lower than coolant temp and also that it should be half.

I have a P0328 Knock sensor circuit high code - impending (no CEL). I have a new knock sensor and I plan on going to the the dealership to get a new harness... may as well eliminate both.

Also on my to-do would be to replace the fuel filter and pump just in case there is an issue there contributing to the knock sensor fault.


All in all - if I wasn't monitoring the engine coolant temp - I honestly probably wouldn't care. I had noticed that lack of acceleration and my thinking was a new fuel filter may resolve it... it did with my Excursion.

What I'm concerned with is that if it continues to run hot - will it cause more damage down the road... or is the fact that the car is old (albeit relatively low miles) and it's just normal. I'd like to get at least 200K out of the car.

Thoughts? Suggestions?

I'm going to deal with the knock sensor first and then replace the coolant temp sensor to eliminate that. Other than the fuel filter and fuel pump, I thought about looking at maybe new O2 sensors.

I've heard that the water pumps don't typically go bad so I'm hoping that's not it... that would suck because it's not a simple procedure and I don't have the setup to do it mysefl. I would expect that labor for that would be pretty high.. It doesn't seem like there's anything with the water pump.

For now - it runs hot so the new radiator fan is almost always on high speed about 5 mins after startup. Also - I'm not hearing any knock or pinging.... engine operates pretty smoothly. Idle is pretty steady at about 675... although when the temp is at 220 degrees I notice the idle hovers up around 700 and stays there.

Thanks for any feedback/suggestions.

DennisMik

iTrader: (2)

You sure like replacing parts. And I'm pretty sure some of them were unnecessary.

Looking at your current problems, I would rule out the knock sensor and fuel pump.

The knock sensor code is telling you that it is detecting a problem. When the engine is not running correctly, it pings and stuff like that. That causes the knock sensor code. It is not that the knock sensor is bad. Fix the other things and the knock sensor code will disappear. Yes, they do go bad, but it is kind of rare.

If the engine isn't stumbling at higher rpms, it isn't the fuel pump.

Overheating is the clue. Like you said, the coolant temperature should fluctuate between 180º and maybe 205º when the a/c is off. And when the temperature is below 203º, the radiator fans should be off. When the a/c is on, the fans will never shut off and the coolant temperature will run higher, but 220º seems high with the a/c on.

You said that you replaced the thermostat. That makes warning bells ring if you did not use a Nissan thermostat. Aftermarket thermostats have a disappointingly high incompatibility rate. Many of them don't open up enough to allow sufficient water flow. You have to take the thermostat out and put it in boiling water and then measure how far the little valve has opened.
Page 18 - http://boredmder.com/FSMs/Infiniti/I35/2004/LC.pdf

But if the car was run for a long time without antifreeze, it could be the water pump. The impeller fins may be corroding off to nothing. There is no way to test for this, you just have to go on guts and remove the water pump and look at it.





Overheating can also be caused by lean fuel mixture. This can be caused by bad oxygen sensors, the sensor1 sensors as Nissan calls them, upstream sensors as the part stores call them. And this affects fuel mileage. But I would expect you would have check engine codes.

Another thing that could make the engine run lean is the MAF. It can also make the engine run rich, run rough, surge or not start. And while it is supposed to cause a check engine code, most of the times it doesn't. There is no real way to test those damn things. You just get desperate and replace it and hope that was it.

As for the intake air temperature, I don't know. Since it is outside air, my thinking is that it should be close to the outside air temperature.

You mentioned that the new radiator fan runs at high speed after about 5 minutes. How are you determining that it is running at high speed and not low speed? More importantly, what is the other fan doing? The ECU sends one signal to the radiator fans. The wiring splits the signal so that it goes to both fans, so whatever one radiator fan is doing, the other one should be doing the same exact thing.

I'm skeptical about the engine coolant temperature sensor (ECTS) being bad. I'm assuming that you are getting all these temperature readings by using either an OBD reader or an app on you phone or laptop. Take a temperature reading when the engine is cold and before you start it. The reading should be whatever the outside air temperature is. The official way is to remove the ECTS, put it in water and read the resistance at various water temperatures. See page 206 -
http://boredmder.com/FSMs/Infiniti/I35/2004/EC.pdf

dwapenyi

iTrader: (3)

OEM Thermostat I hope. Aftermarket ones usually don't work right.

Could be your knock sensor as you surmised. When the KS goes bad, the ECU automatically kicks in a safer fuel map, less advancing of ignition timing, less power. In other words the ECU automatically kicks in a fuel map more suited to 87 octane than 91 or better, regardless of whether you have 91 octane in your tank or not.

You are using a portable OBDII scanner to read the temps?

From this observation about lean and richness, I would look into replacing the primary O2 sensors. After 100K miles, they get "tired." They don't fail, but they just don't work as fast and responsively as they used to, and they won't throw a code either.

Yes replace the KS if you use 91 or better octane all the time. If you use 87 octane, don't bother.

Fuel issues are un-related to KS issues a majority of the time.


Hope this helps

RTrud

Thanks for the reply... I wish I could spend more time investigating but I honestly don't have the setup... I live in a townhouse and have no garage so everything I do I have to take into account outside light, temp and also the HOA *****....

To your points - The coolant has never been low in the car. Always been topped off... Always bright green and has been drained and replaced a few times. 3 years ago my radiator was leaking from a top seam and I replaced it. Radiator is still solid.

As another posted mentioned - I did use a Beck Arnley thermostat and that may be the culprit. I am picking up an OEM thermostat from the Nissan dealership today and will replace this weekend.

As for the fan - the temps I'm reading from the ECU via an OBDII sensor using the Torque Pro app... The temps get up to about 200 degrees by the time the car is fully warmed up and idle settles at about 700... The fans come in low shortly after (203)... after a few minutes of driving, the temps stay above 212 degrees and top out at about 223... Don't really drop (or rise) from that while I'm driving. So - my fan is at high speed constantly form that point on... this new fan is a little bit noisier... it sounds like I'm taxiing in a P-51 mustang if I'm at a red light.

Once I replace the thermostat - I should know if that's the culprit. I'll also replace the knock sensor just to clear (hopefully) the P0328 code.

On the lean issue - I tried cleaning the MAF and notice that there looked to be a little bit of corrosion on the wire. I put in a new MAF. Spectra model, I think... Is that another sensor I should shy away from other than OEM?

RTrud

Thanks for the reply... I"m getting a new thermostat from the nissan dealership today and sending AM one back. Now that I've done it once, I'll know how to do it quicker.

I use a Torque Pro app with a bluetooth OBDII plug... I have a handheld OBDII scanner and I will dig that out and see if it reads a different temp.

I'm hoping that replacing the thermostat with an OEM one will make a difference.

I'll also look at the O2 sensors. I have noticed that the voltages fluctuate on the O2 sensors from the OBDII scanner readings... From .01 volts to .68V and vice versa.... I think you may be right about that.

I have considered just buying a new car but we just adopted 2 kids and I got my wife a minivan... I hate car payments and want to keep this running as long as I can.

RTrud

DennisMik... per your comments - I installed the an OEM Thermostat from the dealership and the OP Temp is back down in normal range... Confirmed also that the fan kicked in at 203 then stopped completely at 190... As you stated - the "new" Beck Arnley Thermostat was the culprit.

Now just need to make some time to replace the knock sensor.... I'm going to go ahead and replace the O2 sensors at some point, too... In for a penny... I've already replaced a lot of components so may as well do the full recommended 100k/120K service and put almost all new components... as another poster stated- if I can get back to 2-4MPG I'm losing - it will pay for itself in less than a year... especially with gas going up again.

dwapenyi

iTrader: (3)

That's exactly what O2 sensors do. They rapidly change voltage indicating the ever changing O2 levels in the exhaust stream. Tired O2 sensors change voltage kindof of s-l-o-w-l-y, as if they're drunk. That behavior won't throw an engine code, but the your car's computer will keep adjusting the air-fuel ratio according to the tired "old" data that its constantly receiving from those worn out O2 sensors.
If you want your car to last, 2 other things I would recommend;

1. Refresh your tranny fluid.

DO NOT GO to Pep boys etc to have your tranny flushed.

Instead, drain some tranny fluid out from the tranny oil pan. Measure exactly how much came out, like maybe 3.5 quarts. Then replace with the same amount of fresh new tranny fluid through the dipstick. Then drive the car for a while, like 2 days or something, to let the old fluid mix in with the new fluid. repeat this process 3 times so as to get the fluid that's stuck in the torque converter circulated out.

This method is inefficient because you are never getting rid of all the old fluid in just one shot. But this method is also the safest way to bring fresh new tranny fluid into your tranny. You will notice your car shifting more enthusiastically.

2. Lookout for the dredded pre-cats debris failure.
In the 2002 and the 2003 Maximas, there are many stories of early engine failure due to massive oil consumption which was the result of the scouring and ruining of the cylinder walls. The culprit? pre-cats disintegrating and getting sucked back into the engine. Your engine is the same first gen VQ35DE. Since you have a 2004 I35, it's the last year that Nissan made that engine, and maybe by then they worked things out, but you never know.

Check this thread out;

https://maxima.org/forums/5th-genera...at-gutted.html

The simplest thing to do would be to upgrade your exhaust to a Y-pipe. This enhancement will get rid of your pre-cats so you will never have to worry about that.