Well, I had to put the car back together today, because I planned to take it to get new exhaust flanges welded onto the front pre-cat manifold. No issues there. But when I started it up, it made a few very loud knocks and started smoking like a chimney. It did not continue knocking, but the smoking did continue. I think my little annoyance may have just turned into a pretty good sized repair. I have not had any time yet to run a compression test. That will probably have to wait until tomorrow, but I have a feeling that I popped a headgasket. It's also smoking from just below the front exhaust manifold and pluming out of the engine bay, but there is no smoke when I remove the oil filler cap. I find that kind of odd, personally, but I don't know.

In any case, thought I'd share that. I'll be keeping this updated as often as I have progress.

-Nathan

 

^ might be an exhaust leak


not usually a symptom of a blown head gasket is smoke ..unless it is white smoke

also if youy have bubbles in your overflow and it runs hot, thats a blown head gasket...

coolant in oil or oil in coolant is a blown head gasket.

 

The smoke is white, and I didn't let it run for much longer than about 30 seconds after it started all that up. I will look into it further tomorrow.

How would an exhaust leak cause smoke though? It hasn't smoked one bit until this instance, and it does not sound as though the exhaust is leaking from anywhere.

I'll check the oil for water and vice-verse, and try to get a compression test done and update this.

-Nathan

 

if the smoke is white, is it coming from the tail pipe?


smell it, does it smell " sweet " ?


usually coolant burning smells like maple syrup, if it smells sweet then yep, blown head gasket...but not sure how you blew the gasket?

these motors are supposed to be solid

 

The smoke is white and coming from the tailpipe and from a location underneath where the exhaust manifold meets the head on the front bank. I do not know exactly where that smoke is emanating from, but it's around the manifold.

I know what to smell for and what to look for, I just couldn't be bothered to give it the time of day earlier. I'll take a good look at it tomorrow under the carport in the dry, I was just making a guess based on the fact that it compression tested perfectly not too long ago, and, in my experience, if an engine compression tests normal and then something blows, it's more likely to be a head gasket than rings, valve seals, etc.

I have no clue how it would have blown either. The oil level was slightly low, but it couldn't have been more than half a quart when I topped it off. That's 1/2 quart in approximately ~3,500 miles.

I would go check it out right now, but I just put my daughter to bed, so now my wife and I are going to watch a movie and relax.

-Nathan

 

I read through your entire post. I had the exact same bogging issue. Car had a hard time ideling and would bog down under accelleration. I replaced the fuel filter, fuel pump, coils and plugs. This did not help at all. The dealor said replace the MAF and reprogram the ECM ($350). I replaced the MAF sensor myself and it did not help. I took it back to the dealor to have the ECM reprogrammed. The ECM would not reprogram because the fuel pressure was low. They replaced the fuel pump (second fuel pump in 10 days). Then they reprogrammed the ECM and eureka! Ran like new again. I'm not sure that the second fuel pump replacement was needed.

 

Interesting. I've changed the fuel pump, but I have not yet taken the car to be reprogrammed. Did you still experience the bogging after the fuel pump replacement and before the reprogram? Thanks for the reply mate, very much appreciated.

In other news, I gingerly strolled out to the car today expecting the worst and decided to take a look and see if I could figure out what might have gone wrong without having to do a compression test. Checked the oil cap; no coolant. Checked the radiator cap and overflow; no oil. Checked under the car; no fluids or stains. So I thought, well, I might have really roughed something up in there.

So I decided to start the car and monitor the smoke and see if I could determine where it was coming from and what it was. Started it up, and there hasn't been even the slightest single tiny puff of smoke from anywhere. I am officially confused by this car. Maybe it was just whatever SeaFoam might have been left in the crankcase? I don't see how of course, because I SeaFoamed it more than a month ago, and at least 1,000 miles ago, and have changed the oil since then, and the tank of gas that held the rest of the SeaFoam has long since been used.

So, once again, I'm quite befuddled by this car. I put off going back to Tyler due to this, and now I'm not so sure I needed to, but, at the same time, I'm not certain I should trust it completely just cause it stopped smoking. Anyone ever had such a temperamental car before? I know I haven't, and this is the 23rd car I've ever owned. Lol.

-Nathan

 

The cars still bogged down after the new fuel pump was installed. They were also still getting a low fuel pressure indicator after the new fuel pump was installed but the Dealor said reprogramming the ECM would take care of that (not sure how). At first the ECM would not take the reprogramming. They reset the ECM by letting it sit overnight without power. That did it. They reprogrammed the ECM the next morning and it has been running smooth since.

 

Wow. That's wild! Didn't think reprogramming could solve that. Maybe it's time to reset the ECU completely and reprogram. Thanks for the reply mate.

-Nathan

 

There should be no need for a reprogram. A reset should do it, and you can do that by yourself. Search the threads for the procedure...

 

Interesting. Does the ECU reset procedure bring the ECU back to square one and then it relearns fuel mapping, etc. as it would from brand new? I was under the impression that a reprogram was needed along with the full reset.

I've got a link to the reset procedure, just curious because my understanding was different. Thanks mate.

-Nathan

 

In the 4th gen maximas, dis-connecting the battery for a short time makes the ECU forget any stored codes, CELs etc. Leave the battery dis-connected for over 24 hours,however, and the ECU forgets everything. Starting the car after more than 24 hours of dis-connected battery has the ECU learning the motor from scratch.

It is probably the same for the 5th gen as well.

DW

 

Alright, well, I need to find an exhaust shop around here or at least someone who can weld and get this friggin nightmare of a pre-cat off and changed out, and then I'll give it a full reset. Thanks for the info gents.

-Nathan

 

There are ways to check for clogged exhaust using vacuum gauge. This might confirm the diagnosis and will NOT involve visiting a muffler shop.

 

Unfortunately, I'm home in Louisiana, which is 220 miles away from my shop, so I don't have access to the tools that I normally do. I'm stuck with basic hand tools now unfortunately, and the local auto parts shops don't have a back pressure gauge to rent or buy.

Worst part is, the closest muffler shop is almost an hour's drive away. There are definitely things that suck about having a house in the country. Lol.

-Nathan

 

this


also a backpressure gauge costs an arm and a leg whereas a vacuum gauge doesn't

 

Good point. My neighbor might have one I can borrow as a matter of fact. I don't know why I overlooked that and just thought he was referring to a back pressure gauge. I'll plug a vacuum gauge up to the manifold and see what happens. Thanks for bringing that back up Amave.

-Nathan

 

I read on the blogs about disconnecting the power 24hrs to reset the ECM. I tried that twice before I took it to the dealor. That was not the issue. I don't know what they do when they reprogram the ECM, but it worked for me. The part I'm interested in is how they could not get the ECM to reprogram one night and the next morning the ECM instantly took the reprogramming and the car ran awsome.

 

no prob. just make sure you connect the vacuum gauge BELOW the throttle body to get an accurate reading....if connected close to the throttle body you might get an erroneous reading due to the throttle plate opening and closing when revving the engine.


when connected the needle should stay steady


see this for an example


http://www.youtube.com/watch?v=vh3Z-F6KGkI&feature=plcp

 

Wow, that is a fantastic video. Thanks!

 

+1. Killer video mate.

In complete honesty, I was completely unaware that you could test for a clogged exhaust using a vacuum gauge. It makes sense now that I'm thinking about it, but I wasn't aware before.

I tested the Maxima today after researching how to test it and what to look for, and the vacuum eventually increased 2 in/hg, which is basically to say that my exhaust is clogged up nice and tight.

For reference, if the vacuum does not increase after idling until warm then there is no clog.
If the vacuum increases by ~1 in/hg after idling until warm then there is a significant clog.
If the vacuum increases by ~2 in/hg; then your car is trying to s*** through a straw.

I really wish I had known to do this test before throwing all that money at it; I would get order some Cattman headers and call it a day. Argh..

Thanks again for the guidance everyone. There's always something new to learn, and I very much appreciate all the help. Truly. Cheers.

-Nathan

 

Please do pull the exhaust and get some photos of how bad it is.

 

Definitely will mate. I'll definitely keep you updated.

-Nathan

 

Awesome! Glad you got it figured out...and we all elarend something too.

DW

 

Nathan, how exactly did you test this? Just following that video?.. More specifically I guess, where did you hook the gauge up at?

I'd like to do the same check on mine, as I've thought it was the exhaust for quite some time.

Good luck man! Hopefully this is the end to your problems (and mine!) :-)

 

Actually, it's funny, Nissan practically had this test in mind when they crafted the intake manifold for the 5.5. I plugged it into the vacuum stem that runs to the VIAS solenoid. It's right there at the front and after the throttle body, which means it gives an accurate reading. Super easy, super quick.

Plug up the gauge, start it up, let it idle until it warms up to N.O.T., and refer to my previous post for a guide as to whether it's clogged, and how badly. Let me know what your results are too mate, I'm curious.

And good luck to you as well. I definitely hope this will end these problems. Yours and mine both.

-Nathan

 

Nathan -- wanted to provide you with an update..

I didn't test the pressure/vacuum but I did pull off the y-pipe, and pre-cats. Actually pulled all 4 o2 sensors as well. Top o2 sensors on both front and back were badly damaged (metal ripped/broken from tip) and seriously needing replaced. bottom actually wasn't that bad..

With open headers, no pre-cats, and no o2 sensors connected to the car, it still bogs just as bad as before.

I'm wondering if running the car with open headers and no o2 sensors would trigger limp mode. If so, then I won't know until I replace the ypipe and o2 sensors, and gut the pre-cats.. but if not.. then a different problem i'm afraid is lurking for my max...

I did notice for sure this time though when test driving that you can't apply hardly any accelerator.. if you push down.. it just bogs..and also noticed while accelerating the car WILL NOT rev over 3500 no matter how hard I try. Sitting idling though, I can rev over 3500 with any placement of the accelerator.

 

Sounds like a classic fuel starvation issue...fuel pump, fuel filter. Replace the fuel filter 1st if it hasnt been done in, like eons.

DW

 

DW has the right idea here. I will add though that if the o2 sensors aren't plugged in then the fuel mixture can be way off and can cause the computer to be unable to adjust accurately. If they are as badly damaged as you are observing then that can also cause a very poor mixture. There's no guarantee though.

I would start with DW's recommendation on the fuel pump and filter. Test the fuel pump before replacing it though, they're a bit pricey and there's no sense replacing a part that's still good. I would replace that filter regardless however, it seems to be a commonly overlooked problem when picking up these Maxima's second-hand, which is why you see it stressed all over this forum.

Beyond that, I would check every one of your injectors for a clog or leak. Either not enough flow or excess flow can also cause bogging.

Definitely let me know if replacing the pre-cats and y-pipe fixes it though mate. I've ordered a fresh Y-pipe from a member here, and after it gets here, I'm going to replace it all. My exhaust system was kind of a hack-job by the previous owner, so I'm probably going to end up piecing together an entire exhaust system from the pre-cats back. Should be fun. Lol. I've got a lead on an Option cat-back exhaust that was made for the Maxima, but I suppose never got popular and was discontinued. We'll see if I can get my paws on it. Lol.

-Nathan

 

Do you know which part of your exhaust is plugged dfj240 ? Upgrading your exhaust may fix your problem ^^

 

The pre-cats. I've been looking for a good deal on some obx headers or the like, but I haven't come across one so far. I've got a replacement front pre-cat already, and I've got a y-pipe headed my way. I'm going to be getting a 240SX Test pipe, and a catback as well.

I had the same thinking you did; if I'm going to replace, I might as well upgrade. Lol.

-Nathan

 

I have this bogging issue on my 4.5 max, after i pass the 3,000 rpm my A/F wideband goes on 10.0 and the bog began... I might be thinking it could be a injector problem, leaking maybe.. Im desperate too here!!

 

That actually really sounds like a pump issue in my opinion mate. It could be an injector, but I had a 240SX and an AE86 Corolla that did the same thing. It started as a bog in the high rpm, that I thought might be a dirty air filter or something simple like that, but it got progressively worse until it would bog in the mid-range. I changed the fuel pump on both, and it solved the problem.

Testing the fuel pump while stationary won't tell you anything unfortunately, if there's a way to get it load tested then that would tell you for sure, because as the revs increase the voltage output on the fuel pump increases. If the fuel pump is dying and only able to output voltage to a value lower than the needed value to pump fuel at the proper rate then you will have get a bogging condition. See if you can find a way to monitor the fuel pumps output voltage while driving, or get it load tested and see if that tells you anything.

-Nathan

 

Any update to this? I'm curious.

 

Yes. And my apologies to anyone who was trying to look through this thread for help wondering if this was ever solved. IT WAS! I finally got it sorted out.

I performed a manifold vacuum test and monitored the increase, if any, in the vacuum from starting the car cold to letting it idle to normal operating temperature. My vacuum increased by over 2 in/hg! Which is massive! This means that there is an obvious and substantial clog in the exhaust. I was able to determine that the cause of this clog was the front (bank 2) precat.

Changing out the precat (or in my case, gutting it) was a successful solution to the P0300 and the bogging. Problem solved.

I really wish I had done a lot more testing than replacing. Hopefully my mistake will be a lesson to anyone reading this. SAVE YOUR MONEY, TEST BEFORE REPLACING!

Anyways, I hope that this can help someone avoid a serious headache.

-Nathan

 

Then it seems I know what plans I'll have this weekend.

 

i have the same bogging issue at 3500 then would accelerate fine through redline....thanks for this informative thread. I'll start with testing the exhaust system and go backwards hehe

 

Is on ***** Moe the cam sensor or crank sensor is dead so there for the ecu is doing the timing blind

 

To me, it sounds like a clogged CAT. Worth a look.

 

This has been resolved for a while now. It was the precats. My post tells how I tested and determined the source of the problem.