celticwarlock

Greetings.

I have searched in a number of places here for viable information (stickies, other posts, etc.) , but I haven't found precisely what I'm looking for.

I have a P0303 code I can't shake ('97 Maxima, 3.0, no mods., automatic, 128K miles). When it popped up, I was only having problems under load (lag and/or hesitation), and it's only just barely interfering with the idle (nearly imperceptible "hiccups" now and then, entirely random). When things get particularly rough, the CEL blinks (which I am aware is highly undesirable).

I removed the coil and switched in with #1, but the code remains associated with cylinder #3. The spark plug tube has no oil or moisture in it, and the plugs are NGK Iridiums with about 10K on them. I also use premium fuel (93) at all times, no matter how expensive it gets, so I doubt I have an injector issue. The wiring looks great (this car has spent most of its life being driven, but parked in a garage more often than not). I REALLY want to chase this issue down WITHOUT throwing parts at it, and without taking off the UIM needlessly. I'll be properly pissed off if I do all that, change the injector, and still have the same issue.

I have heard that a bad O2 sensor can result in this code, but that seems a bit dubious, even with how ham-fisted and sloppy OBD 2 systems tend to be.

Any help is appreciated.

Turbobink

iTrader: (2)

If you’re going to be pissed off by the process of updating parts in a 27 year old vehicle, as it may turn out, simply for the purpose of updating 27 year old parts, then may I suggest updating the vehicle all together … one of the trials, tribulations and responsibilities of keeping an old car.

Based on what you say you’re already sure of, as pertains to your specific issue, it’s my opinion (based on my experience with my 25 year old vehicle) that you may want to also investigate the air intake parts for splits, cracks and the like. If that turns up no issues then I would not be surprised if you’re entering the stages of a fuel injector failure and the rebuild of your injectors may be in order.

celticwarlock

The prospect of engaging in fruitless work is a source of irritation for many people. I don't think it's that unusual.

I have 6 vehicles to maintain by myself (I run a transportation business with a few of them). Over half of them are over 20 years old, so I am very much aware of what's required to look after them.

I don't see why performing actual tests and gathering real information should be second to just buying new parts for the hell of it. I'm simply asking if the failure of any other component can cause a misfire in only one cylinder. It doesn't seem terribly plausible, but I figured I'd ask people 'in the know' before I start spending money.

If I have to take off the UIM, however, I will definitely be replacing the injectors whether they test bad or not. I just want to run conclusive tests before tearing into anything.

Turbobink

iTrader: (2)

The perspectives espoused, in reply to your initial inquiry, not only come from an individual who currently owns a 25 year old Nissan Maxima, they also come from an individual who’s owned that very same vehicle for those same 25 years.

Those perspectives also come from an individual who’s performed all of that same vehicle’s maintenance, repairs and upgrades since the expiration of said vehicle’s manufacturer warranty.

That all being said, feel free to consider those perspectives or ignore them.

98 i30t 5spd

Are you getting hard/long cranking starts? You have a bad fuel injector in cylinder 3. You can have your original injectors rebuilt or you can buy rebuilt OEM injectors. Here’s a link…

https://www.ebay.com/itm/302784935698

I wouldn’t suggest replacing with aftermarket injectors. I purchased the same set for my 99 maxima which has a leaking fuel injector in the same cylinder as yours. Luckily for you, it is given you a P0303. I kept getting a P0300 (random misfire).

celticwarlock

There are no hard starts at all. It fires up immediately.

If both of you can say confidently that the injector is indeed bad even without my having tested it, I'm willing to go the reman. route on all 3 back there when the time comes. I may have to pull the manifold off for other reasons anyway.

The ones in that link are the ones you're using? Wow, that's crazy cheap. I assume they're trustworthy, as you've had good results, yes?

KP11520

If you're getting a misfire in #3 and the code comes back after wiping it, I don't know of anything other than it's either a bad plug, a bad Coil Pack, or a bad Injector, if there's no oil in the plug tube. Maybe check the wiring harness and plug to the coil pack and injector (Mouse, dried and cracked open and shorted?)

If you exhaust all options and the only thing left is the injector, The eBay link to MotorMan Fuel Injectors is the way to go. He rebuilds JECS brand ONLY, and sells the flow matched kit with no need to return your old ones. JECS are what Nissan put in these. Many of us have used his kit and I don't think a one of us had a bad one. He offers a year replacement if any go bad. Too many problems with wanton after market Injectors so most of us recommend only a few sure thing choices, MMFI is the easiest and no hiccups so far....We've been getting a lot of "Mysteries" like yours the past 5+ years, as low miles doesn't save these injectors anymore. They just time out. Fuel and plastic????? They don't really owe us anything, anymore, if you think about it. I'm not aware of any way to test an injector in these 4th Gens other than there's nothing else it can be... Sometimes there's a gas odor out the exhaust when these DUMP too much fuel in the cylinder, But that isn't always the case. That happens when the nozzle fails and gets eaten in the cylinder. Maybe plastic is a good thing? LOL

If you remove the UIM, there's a host of midlife refreshing you might consider doing. There's a bunch of things that really wind up being consumables at almost 3 decades. Get them while in there cause it SUX. LOL Double check (replace) every gasket and air hose and vacuum line when reinstalling. So many times something gets away from us and what should be running great, doesn't, and now the problem has moved. These cars refuse to play nice with vacuum leaks. Remember to clean the EGR tube and replace both (different) gaskets. AND...Even if it isn't leaking, maybe the rear Valve Cover gasket and use Black Oil Resistant RTV in the compromised corner areas. Fel Pro and Victor Reinz make, IMO, the best VC kits.

Keep her purring and before you know it, you'll double what's on the clock! I bet you make up a few new curse words if you do the big job! LOL... I couldn't believe how creative I could be.

98 i30t 5spd

I haven’t replaced my injectors yet, but I purchased the injectors in that link because many members here have used MotorMan injectors with no issues.
Like KP had mentioned, I would check your connections at cylinder 3. You already swapped coils, so that leaves a bad plug or bad injector. I pulled all my plugs and found that the plug in cylinder 3 was soaked in fuel. Pull your plugs and check them if you haven’t already.

Reality sucks

iTrader: (3)

Did you by chance remove the boot from the Coil... Have a look at where the spring sits against the point, down in the hole of the coil. Often times corrosion here is overlooked.
How does the sping look.? any burn marks.? How does the boot look.? any rips or holes.?

Imo, do not replace anything until you have verified the failure. Test First.

KP11520

In his first post, he said he moved the coil packs and the problem stayed on #3.

celticwarlock

Indeed, the plug was removed, and looked perfect. The slightest haze of tan was on the electrode, and nothing was built up. The connectors and wiring are without corrosion, and look to be in fine shape.

Looks like I'll be diving in. Everything will get changed out....gaskets, vacuum hoses (if the least bit suspect), the injectors, and anything else along the way that would otherwise be buried beneath the upper intake.

I appreciate all the information and input.

celticwarlock

The upper intake manifold has been removed. Everything is pretty much going according to plan, and I definitely plan to reroute the coolant lines to make this task less difficult if I ever have to do this again.

I didn't run into any surprises regarding the wiring or anything else. The cause of this misfire remains unknown, though there is something I did see when taking everything apart that seemed unusual. The deposits around the EGR ports were not only black but also moist, along with the intake ports going into the motor. Also, the smell of gasoline was prevalent even before I took the injectors out. I've never seen this on a MPFI motor. Could this mean one or more injectors were leaking?



Do these look normal? I don't see any obvious signs of trouble.

Fortunately, none of this is a waste because the valve cover gaskets were leaking anyway and had to be replaced. I'd still like an opinion on the appearance of this injector (#3), though. The other injectors looked a lot like this one. None had obvious signs of damage.

KP11520

I only replaced my injectors once so I don't really have enough experience to say anything about the picture. But I can say that I replaced the Grommet type seals that the injectors fit into (description of leak) and also the insulators on top under the screwed on cap. And then SS screws. I also replaced the Fuel Pressure Regulator while under there and fuel and return lines.

The Grommet type insulators are:
Fel Pro ES71045
Victor Reinz 151104201
The top Insulators: Nissan 16635-53J0A

I used STANDARD MOTOR PRODUCTS PR59 w/ O-ring Fuel Pressure Regulator from RockAuto.$48. They have the Fel Pro and VR Grommets too.

I wanted the entire FI system to be as new to reduce problems and any chance of leaks, because so many have had problems after replacing Fuel Injectors. Don't forget to replace the knock sensor while in there as well.

pethelman

I can comment on your wet EGR tube...
I was periodically getting heavy gas smell from my 96 for a good while after shutting the car off. Initially I thought it may have been a weeping connection at the fuel filter, but as much as I wanted to see something there, it just stayed dry. Interestingly, I had a fuel injector just up and quit at some point after I started noticing the smell, prompting me to do a complete injector refresh.

Prior to this I also had the warm-engine hard start issue after the car would sit 30-45 minutes AFTER driving. Essentially, the injectors weren't shutting off the flow of fuel when the car was turned off. At least one of them was dripping slowly and loading the intake with fuel until the pressure in the rails dropped. Consequently, when I finally got to the point of removing the lower connection of the EGR tube (after carefully Dremeling off the extra bolt length to access the 12 mm nut), fuel literally dumped out of the lower part of the tube. Like a LOT of fuel. By the way, it's no joke cleaning that EGR tube. Don't forget to remove the exhaust temperature sensor and clean that area as well. Whatever you do, don't break those fine wires... that little sensor is $$$.

Now, in my case, not only was the EGR tube almost completely occluded by carbon, but the short (2") rubber tube that connects vacuum to the underside of the Back Pressure Transducer (BPT) valve was completely hardened and broken. The BPT is the small "UFO" looking disc just behind the actual EGR valve. So pretty much I was going to get ZERO air flow through that EGR tube no matter what, and I'm sure this didn't help the gas accumulation problem. Definitely check that short rubber tube while you're in there. Also, prior to the job, my long-term fuel trims were extremely negative (rich conditions), like in the -15 to -17 range. After completing the full injector replacement job, everything returned to normal, including the fuel trims.

Good luck!

celticwarlock

It's all back together. I replaced one of the rubber fuel lines between the rails, bypassed/looped the coolant lines to the *** end of the manifold, and cleaned out the EGR passeges in the tube and manifold. The deposits weren't extensive, and I saw no evidence of hardened rubber tubing in that area or anywhere else, except the connecting vent hose that connects the two valve covers.

The injectors fit in snug, the engine went back together without any major hang-ups, and I replaced the fuel filter while I was in there. I'm not convinced the knock sensor is bad, but I should be able to replace it later if I suspect it's causing issues (I know it's more difficult to reach, but it's not impossible).

The misfire code and odd driveability issues are no longer present.....so far. I still need to replace the downstream O2 sensor, but other than that, things appear alright....no leaks, and it runs pretty well. The only other difference I noticed is it doesn't start quite as quickly at it used to. It starts readily, but takes a second or so longer to fire up when cranked.

As a side note, I have literally no idea how someone can do all this in a few hours if they've never done it before. There is just SO MUCH CRAP everywhere, and if you don't know the order of operations, you'll wind up taking some things apart more than once. Also, if you're replacing everything you can't reach with the intake in place (including the valve cover gasket), all that preparation and cleaning takes time. Maybe for others a couple of hours makes sense, but for me, this job took about 8 - 9 hours spread out over a few days. It's fairly straightforward (sort of....the order you do things in is really important), but it's extremely time consuming.

celticwarlock

The engine now has a misfire code at the #1 cylinder. This isn't fun. I'm in no mood to do any of this again.

This is exactly why I want to veify, unequivocally, what a problem actually is before turning a wrench.

Turbobink

iTrader: (2)

Were the injectors rebuilt or replaced or simply removed and refitted?

celticwarlock

I bought a set from the vendor on Ebay that was recommended by someone who responded on this thread, and installed them all. There's no way I would go through all this without replacing all 6.

pethelman

So if this were me, Murphy would be tracking my every move, and he would wait until I had everything buttoned up to cause a coil to fail immediately after fixing an injector issue.

Is it back to that exact same hiccupping situation that you described in the OP or does it feel different now?

I think you can get a reasonable "listening device" into the space where injectors #1 and 5 live, so you should be able to at least verify that they're "clicking" normally.

celticwarlock

It's not as bad as before. The car sometimes just doesn't feel like responding the way it should. It gets a bit sluggish. Overall, I'd say it's more subtle, but still evident....though, it's random. It doesn't always happen.

pethelman

Well, if you have access to an OBD reader with LIVE data capability, it'd be very interesting to see what your fuel trims look like while holding at 2000 rpm. Might shed some light on the situation. If injector is good and you're missing spark on occasion on #1, then bank 1 will tend toward negative trims (rich conditions), but if you're not getting fuel then the trims will swing positive (lean condition). May have to drive it for a while though to really see it in the long-term trim numbers.

celticwarlock

I have a scanner capable of this.

The next step will be replacing the downstream O2 sensor, and then monitoring the fuel trims as the car runs. I should be able to replace the sensor over the weekend, so I'll soon have more usable information.

Reality sucks

iTrader: (3)

I would have attempted to walk you through the diag on this, but you have changed so much now. My advice to you, Is to remove those injectors ASAP. The lower o-ring's will fail and hydro lock the engine.. Search my post's on this. You seem like a smart and capable person, but you may have just installed another problem. The injector typically is not the failure. Over the years with the side feed system, it's the o-rings that seep fuel into the cylinder past the injector in the rail it self... They always spec just fine. Send your oems off, have them cleaned, rebuilt and put back in is my best advice here with oem o-rings only.

Looking back at your photos, can you take a up close pic of each side of the connector, where your hand is in the photos.. what do they read ? .. if those are the ones you took out , they may be aftermarket trash already... Normally oem injectors with 128k on them, the red plastic of the injectors will look dry and faded in color.
The strong smell of gas is here is normal. If your going own a 4th gen understand the knock sensor is king.. you should have replaced it. That mis step has cost many on here a few sleepless nights, lost cash and hours of unnecessary diag.

celticwarlock

I don't think you have read my posts throughly.

All the injectors have been replaced with rebuilt ones from the recommended vendor on E-bay. The photos are of the old injector(s). I took no photos of the new ones, but they looked fantastic.

From the looks of it, the knock sensor can't be easily accessed anyway with only the UIM off. The lower one needs to come off also. This doesn't matter, though. I can still remove it with both manifolds in place.

You say that this sensor is 'king', but I don't know what that means in this case. I assume it helps the computer control spark and other engine functions, but your comment seems to indicate that the sensor is crucial in determining many critical parameters. I'd like to know what these parameters are.

celticwarlock

Wouldn't you know it....now there's a new problem.

After driving for a bit, the idle is now sticking at 1400 RPM when I put it in park. When I kill the engine and re-start it immediately, the problem goes away.

Lovely.

98 i30t 5spd

Did you clean the throttle body and the idle air control valve when you had the intake plenum removed? One of them could be sticking. Check your throttle cables as well.

celticwarlock

Those are the very first things I checked, and everything is in perfect order.

Having said that, it resets as soon as I kill the engjne and re-start it (without touching the gas pedal), so it wouldn't be the cables. The IACM, though it is clean, may have some kind of fault with it.

I successfully replaced the downstream O2 sensor (which went surprisingly well, thankfully....normally those things are stubborn as hell), so we'll see how/if the car behaves itself. It was the only remaining code, so I've met all the car's demands, at least according to the OBD 2 system.

celticwarlock

No CEL, no codes, but this random high idle thing is still happening.

I shut down the car and fire it up again right away, and it's gone.

WTF?

KP11520

TPS going wonky or needing to be reset? They don't always trow a code.

celticwarlock

I will have the live data scanner hooked up tonight when I drive the car home from work. If it freaks out again, I'll see what the data says about TPS activation. So far, it's not doing it during the day.....it only does it at night, so I figure it's probably temperature-related.

celticwarlock

Update:

It did this again, and the TPS was registering at .8% instead of zero when I was pulled over and idling. Here are some observations:

I quickly hit the throttle a few times, and I noticed a couple of things. First, the % didn't go up on the scanner screen when the throttle was pressed, but the RPM's went up. Second, the RPM's stuck on the way down at about 1400. Third, they eventually went down to about 800 by themselves after a minute or two. During all this, the TPS percentage stayed at .8%

After turning it off and immediately starting it back up without touching anything, the TPS percentage when back to zero, where it belongs at idle.

There seems to be a problem with the TPS signal. The computer isn't always getting an accurate picture of its position.

KP11520

Don't know if your year has an IAT sensor, but if it does, they don't throw codes when bad. And the ECU probably uses that reading to compensate air/fuel mix, or why else would it be there?

Some say it has no effect. Good Luck!

celticwarlock

I do have an IAT sensor, and the scanner isn't showing anything unusual with it. The temperature readings seem legitimate.

The real anomaly here is when the throttle is fully closed, yet the computer thinks it isn't (hence the raised idle).