Started up the car this morning, and a minute into running, engine started shaking like there is a misfire in one of the cylinders. The parking lot was also filled with gasoline smell from exhaust. Turned engine off and on, still no code, flashes 05 05 (which means everything is fine).

What should I do? Can I start the engine up again or is it not safe to do in case its a stuck open injector?

 

That does sound like an injector is stuck open. Does the engine oil smell like gas? If yes, then engine bearing damage can occur if you drive it. Even without gas in the oil, the raw gas into the exhaust will ruin the catalytic converter.

 

I'm gonna check the oil tomorrow. The engine ran with the misfire for only about 1.5 minutes in the garage total before I shut it off. The smell was a strong exhaust smell, and some smoke, smelled sorta like gasoline but not pure gasoline. Also I noticed some gasoline smell still lingering from under the hood. Gonna check the car more tomorrow.

I've had coil pack go out on me once, it was similar issue, engine shook but ran all the way home. Don't remember if exhaust odor was strong back then though.

 

That presents like the Pintle cap has broken off/disintegrated. and rather than spraying like an aerosol nozzle, is dumping plain gas into the cylinder rather than atomized.

OEM JECS rarely, if at all, break electrically. And truthfully, after at least 23 years old (brittle) with plastic pintle caps, are outstandingly reliable overall, but now the plastic is end of life. Overdue really. That's why Rebuilt JECS are the only real option rather than anything aftermarket (China).

If you are replacing one, do them all. And be done with it. $125 shipped for all six with matched flow rate at MotorMan Fuel Injectors on eBay! Get the six grommets as well at RockAuto. FelPro makes a quality set CHEAP.

And NO.... Don't run it like this. It will waste your Cat converter(s). Again, already at least 23 years old with how many miles?

Hope this helps!

 

Are you sure it's the injector and not something like spark plug or coil? Can't those things cause same symptoms?

 

Read the "Flashing CEL" thread.

 

Well I identified which cylinder is not working by unplugging each coil while engine was running... it cylinder #5. I swapped its spark plug and coil to new ones, and still not working. So I guess the other options are its injector or electric signal not going to the coil?

I noticed that when I unplugged each coil while engine was running, the gasoline smell got much strong from exhaust. So that means if there is no spark, the exhaust will smell like gas.

I got some CEL codes after I unplugged each coil one at a time while engine was running... P1320, and P0300.

P1320 is ignition signal, and P0300 is multiple cylinder misfire (which is prolly due to me unplugging the coils for testing). Only cylinder 5 seems to be misfiring though.

Is there a way to test if power is going to the coil, like using multimeter? Or what should my next step be?

 

I've read about something called a noid tester.
Supposedly tgey test for voltage to the coils.
I've seen these at harbor freight.

I'm foggy regarding what the facts really are.
I've given you a hint at least. Look it up.

 

(Rough/poor engine operation) + (fuel smell from exhaust) = failed/failing injector.

 

My max did the same thing about 2 weeks ago. CEL came on for a misfire (P1320), but the car was still running fine. After probably a week I went to start it up and it was shaking (misfire) and showing a code for a cylinder 2 misfire (P0302). Also there was a strong gas odor coming from the exhaust. A new coil pack later and she was back in business. No shake, no CEL, no gas smell. I got 286k on it so I'm sure the injectors are probably long overdue at this point but my problem seemed to simply be a bad coil pack. Ironically I lost my first coil pack probably 6 weeks ago and now this is my 3rd that I have changed since then. From what I understand the coil packs seem to have a domino affect once the first one goes.

 

Yes I changed some coil packs over the years as well, usually that would be the cause of misfires I've had. This is the first time a new coil pack did not fix it, nor did the spark plug.

Thanks for confirming that bad coil will cause gas odor from exhaust. I noticed the odor got much stronger when I disconnected a 2nd cylinder while searching for the bad one. I'm keeping my fingers crossed its not a bad injector.

 

Just unplug all six coilpacks, remove the plug from the questioned cylinder and hook up the coilpack. Have someone crank the engine for a few seconds and hold the plug tip near a solid ground. Spark, No more excuses. FUEL INJECTOR.

No tool needed. Just old fashioned common sense.

 

Is it a good idea to disconnect the electrical connector going to the injector of the faulty cylinder while I drive the car to the mechanic? I'm trying to avoid the gas going to the catalytic converter.

 

I don't think you can get to it under the UIM without removing the UIM.

 

Well it turned out to be injector on cylinder #5. Had mechanic replace it. Is the injector supposed to have a little plastic tip on the end? Because the broken one didn't. Mechanic said it was flooding with gasoline. He said exhaust was filled with gas and he kept it running for an hour after replacement to get the gasoline out... it was smoking a lot he said. Mechanic told me to drive the car for a couple days to clear out the system.

Well it's not misfiring anymore, but I got a CEL code 0509 after I got back from mechanic, which means O2 sensor. I'm getting rough idle I guess because of that.

Is this O2 sensor gonna fix itself after being flooded with gasoline or is gonna have to be replaced now too?

 

Tell me you did all 6 injectors while things were apart..... If one went, usually the others will start dropping. Paying the mechanic to do each as they go isn't a smart approach.

Six rebuilt OEM (JECS) and balanced cost $125 from MotorMan Fuel Injection on ebay. Pay the piper ONCE and be DONE with it.

If you have a bad O2 sensor or more, Find the right part numbers for your car and buy the NTK version wherever they are cheapest. NTK makes them for NISSAN and you will find prices 60 to 75% off for the same thing. There's a guy in California on eBay that beats everybody's prices.

Hopefully you didn't keep running it for a long time dumping gas. That really destroys the Cat Converters.

When I did my exhaust, I did all four O2 sensors new. (1999 Cali spec)

Doing things right with these cars always pays and cutting corners usually keeps beating you up. But it seems you have to learn the hard way despite getting all the good info you need to make the right decisions.

And your mechanic confirmed it was the Pintle cap, like I said in a post above. PINTLE CAP! You know.... At the end of the Fuel Injector. The plastic tip your mechanic discussed with you. Yeah, that Pintle Cap.

 

Unfortunately my mechanic does not install parts that I give to him, he only installs his own parts, so I can't give him my own injectors and I don't want to hassle with removing the intake manifold myself. Ya I forgot to ask him to at least install the other 2 rear injectors lol, will prolly have to pay $200 or $300 extra in the future to take the intake manifold off again... bummer.

How easy is it to replace the front injectors though? Can a newbie like me replace them? I saw it has electrical connection and 2 screws on each injector. Will the injector come right out if I remove those 2 screws? And new one pops right back in?

 

Do a search.

how to replace injectors on 1995-1999 Nissan maxima. Both on the web and you tube.

tge front 3 injectors are fairly easy to replace.
you will need a couple of L shaped Allen wrenches.

it's very important to put some engine oil on the O rings of the injector before installing it. I also rub some oil inside the hole it lives in. Failure to oil will rip the O ring and cause leaks.

it's unfortunate that the other two injectors under the manifold were not replaced. The others are likely to fail soon. Replace both when one of them leaks.

I replaced all my injectors as preventative maintenance when the intake manifold was removed for another reason. It's a given that the injectors will fail if you own the car a few years. Might as well fix them at your convenience. Otherwise the car will schedule maintenance at the worst possible time for you.

 

Before considering doing the injectors..... Find a better mechanic. If any Mechanic told me he had to use his own parts ONLY, I'd tell him AMF.... Adios Mother.......

They try to manipulate to make a lot of money sourcing parts and say they can't guarantee the job unless they buy the parts, and they aren't always the best or matched. Well... They can guarantee that the work has been done properly, as they should, but if the part(s) fail that you supplied, the cost of that labor to replace is on you. As it should be. Fuel Injectors definitely are something that should be matched and from a source that uses REAL OEM Injectors and parts, with an excellent reputation. There's way too much garbage being sold out there.

JvG is right....I learned how to pretty much do everything here on the countless threads and a few videos on YT to replace mine and do a Top Engine Refresh, making everything on the intake part of the engine as close to new as possible. Running so much smoother now and I'm still diving deeper to address everything to get another 227K reliable miles. Start searching, reading and watching videos on the maintenance (including preventive) your car needs. You will get confidence with subject matter knowledge and reinforcement through many validating places saying the same things. Buy some pumice Hand Cleaner. Time to get your hands dirty.... REAL DIRTY. LOL

 

In all fairness, mechanics not wanting to use parts they didnt source doesn’t necessarily mean they are trying to finesse you. They dont want to responsible for the parts you supply
them with being faulty, and then getting blamed for things not working. If you want specific parts, ask them to buy them on your behalf, as long as you are buying from a reputable source it really shouldnt be a problem. They just dont want to get caught up in a situation where they have to decide between losing more shop time to redo a job or having to risk losing reputation, all for a job that they wont even make as much money on in the first place. Be clear you want specific parts and if they wont work with you in that then yeah, find someone else able/willing to perform the job you need done.

Lots of shady mechanics out there but at the same time, there is even more bozos who think they know better than the guy who fixes cars for a living.

 

To Slamrod.....

Yes, I do agree with you.

If I were a shop mechanic, I'd have a customer who brings on their own parts sign waiver.

The waiver would state that the mechanic cannot warrant the quality of the parts. Only their installation.

The customer would state in their own handwriting that they understand they would pay the mechanic a second labor fee to replace the failed part.

Such a decision would make sense if the customer supplied an oem quality part. Also protects the mechanic from failure of a low quality part made of Chinesium.

 

In all fairness, Read what I wrote above AGAIN: They can guarantee that the work has been done properly, as they should, but if the part(s) fail that you supplied, the cost of that labor to replace is on you. As it should be. Written above plain as day. I don't understand the point like I'm being unreasonable? And I doubt they are more intimate with what works best on 4th Gens than the original owner for 23 years that has been all over the internet about his one 1999 Maxima. No other car to confuse things... or thousands.

There is no reason they can't enter into an agreement otherwise. Especially if the customer has done the research, work, knows what he is talking about and sourced the best parts for the job. Not just what the mechanics suppliers stock and can bring NOW!

I have several mechanics that have no problem with this. None have ever said no. And I live on the same small island as you! COMMUNICATION is the key that opens so many doors.

 

Had mechanic change the faulty O2 sensor, but car is still rough idling, although seems to be not as bad now. No codes coming up so far, but rough idle is still present.

He said maybe a valve is leaking somewhere that is causing this. Suggested I sell the car on Craigslist lol. What do you guys think, why would it be rough idling after faulty injector and O2 sensor replacements? The injector he put is OES he said. There is no misfires though.

 

Relax lol, I was adding to the discussion, I quoted your post just to give my reply context, not to direct it specifically at you or what you said. Just wanted to share my thoughts on why some mechanics have such policies, they just dont wanted to be bothered.

At the end of the day though youre right, given that its a perfectly reasonable request, if one mechanic says no to it, just find another one.

 

A leaking valve could cause a rough idle.
Yet he is just guessing until someone does a compression test and or a leak down test.
The problem would show as low compression in one or two cylinders. In addition one could connect compressed air into the low cylinder while it's at at the top of its stroke with both valves shut. The leaking air would come out of the throttle body or exhaust.

My guess is that mechanic might not know what's going on. He wants to get rid of his headache.
I would certainly want a compression test done.
either by that mechanic or another one.

 

HA! I am relaxed! Intense.... But Relaxed!

Like you said, lot of hacks out there. Maybe this can be a measuring tool to filter many out? I am always trying to find better ways to do everything! And most of all, reduce disappointment!

Now RITE's Mechanic told him to sell his Maxima cause he's clueless! LOL Or so it seems!

Maybe the mechanic, after replacing one injector, created a vacuum leak? So many possible points when taking so much apart! Even disturbing all those hoses and tubes (OLD) causes splits sometimes. Then there's cleaning the TB, IACV, MAF and EGR. that wasn't done either. But leak is where I'd start.

Now RITE will need to make (kidding) a Smoke Injector to find it like I did when I created a leak with mine! OUCH! (Idle Grief Thread) Speaking from experience.

Y'all be cool out there on the East End!

 

Agree with ya there lol. As for OP’s predicament, sounds like hes gotta decide if he wants to learn the ropes or if he wants to pick up some more overtime shifts to pay for Schrödinger's moneypit. Paying a mechanic to do a job is one thing, paying them to play detective is where the cost/benefit starts going south.

 

Well, there is an update lol. Took the car to another mechanic to figure out the cause of rough idle. In 5 minutes he said there is air leak, showed me by spraying brake cleaner on the intake manifold gasket, engine instantly reacted. 10 mins later as I was driving home, the engine became completely smooth... I have not seen it run this smooth in probably over 10 years... at red light smooth like butter and no vibration. I stopped by to get some groceries, but on the way back, I did start getting occasional vibration like a misfire from time to time. I got a code for cylinder 5 misfire, the same cylinder with the injector that was replaced. Mechanic said he put OES injector.

The car did run like brand new for 15 minutes, is the air leak something that will work itself out if I just keep driving? Maybe engine needs to run a while for the gasket to properly seal? If not, I will go back to the mechanic and request warranty to replace the gasket on the intake manifold (and ask to replace the other 2 rear injectors in the process).

I am annoyed that this mechanic that replaced the injector probably tried to bs me in order to not have to replace the gasket for free with warranty. This is the 2nd mechanic I been to in my life, and he is a bs-er like the first mechanic I went to. This guy also has 5 star review and most popular in my city.

 

Its very possible there is more than one leak, the replaced gasket isnt something that needs to be worn in. Maybe the new injector is faulty? Perhaps the output from the other two injectors on that bank is much different than the new injector on cylinder 5?

Just spitballing here (buckle up), but if the old injectors deliver X amount of fuel and the new injector delivers Y amount of fuel, that means cylinder 5 is getting a different amount of fuel than the other two. To my knowledge, the way the ECU learns long term fuel trims (aka, learned fuel adjustments) is on a per-bank basis, not a per-cylinder basis, as each bank has one oxygen sensor to monitor exhaust for air/fuel ratio (this is a V6 motor, meaning 6 cylinders, arranged in a V pattern with each ‘bank’ of the V containing 3 cylinders). In other words, the car over time teaches itself how much fuel needs to be added or removed from its factory programmed tuning, based on the live data it gets from the O2 sensors. It can add or remove fuel delivery from each bank of the motor based on the data it collects from the sensors, this happens on a short term basis every single time you drive (short term fuel trims), but when the same data happens under the same conditions across multiple driving cycles, the ECU is ‘smart’ enough to recognize a cause-and-effect relationship and that information is stored into long term fuel trims. So rather than it having to “think” about how much fuel to add or remove in real time and make drastic changes, it learns what to expect and makes that adjustment automatically going forward by adding it to its programming. The car is programmed to have the motor run at specific air/fuel ratios under certain parameters (engine speed, load, air ingestion measured by the MAF, etc). Since these parameters are practically never constant (ie; you could be going up a hill, the air might be colder thus more dense, gasoline quality, so on and so forth) the car must constantly measure data it collects (mainly from the O2 sensors and MAF) and make adjustments to fuel delivery with the goal of reaching the air/fuel ratio it is programmed to believe is optimal for motor performance - those adjustments are called short/long term fuel trims. This is what makes it possible for one car to function to factory specification across a multitude of environments, elevations, weather conditions - all without the driver ever needing to make manual adjustments to the car themselves. Very clever engineering common to modern vehicles that we all take for granted.

Back to the point - if your ECU has long term fuel trims its learned based on the amount of fuel your old injectors are delivering, and you replace one injector (AND assuming it so happens the new injector has a different flowrate than the old ones due to age, wear & tear, gunk buildup, etc - very likely if the old injectors are original), that would mean the cylinder with the new/different injector is being commanded to deliver either too much or too little fuel than what the ECU thinks it should be delivering. The ECU cant see how much that one injector is delivering, it cant see how much any one injector is delivering, it can only collect data from the oxygen sensor for that whole bank of 3 cylinders as an average of all 3 cylinders. In short, all three injectors on that bank need to be putting out the same flowrate of fuel or else the math the the ECU is doing is going to be wrong, because the ECU’s math is assuming that all 3 injectors are operating exactly the same as eachother. And if the ECU’s math is wrong, that would be the reason why the car is running like ****.

In this case, the ECU notices a change in O2 sensor readings due to the new injector and ‘thinks’, hmm, I need to adjust fuel delivery to compensate. But by doing so, its also adjusting the other two injectors in that bank (which technically didnt need to be adjusted, but the ECU has no way of knowing that, it can only assume all 3 injectors are the same). So now the O2 reading is even more skewed, and it makes more adjustments, which skew things even more, because the changes it is making is not creating the result it’s expecting based on its programming calculations. This goes on for a little bit up until the ECU realizes that no matter what adjustments it makes, the math is never adding up to where it should, and as a result, it basically throws its hands in the air and gives you a check engine light, with an error code that describes where it thinks the error in its math is occurring. For you, thats a misfire code on cylinder 5.

Perhaps you should replace the other two injectors on that bank with the same brand injectors? Or put the old injector back in since it seems it wasnt the root of the problem to begin with? Or, you could snoop around for other vacuum leaks, keep in mind these cars are old and the rubber hoses can be dryrotted and have leaks. Since youre getting a specific cylinder as a code though, I would focus on that one cylinder, but since its very likely that a brand new out the box injector flows different than an original, 2 decade old injector, I would assume thats what is causing the issue here.

(edited to make this wall of text a little more digestible for the less mechanically inclined readers among us)

 

The intake manifold gasket appears to be leaking.
It won't fix its self. It needs to be replaced.

Have him replace the other 2 injectors while he is in there anyway.

 

RITE, I'd go back to this second mechanic and have him take a good look at all the rubber hoses going to the intake manifold, and maybe just replace them all on principle to eliminate any other vacuum leaks. When the first mechanic pulled the upper intake manifold, he disturbed all those rubber hoses, and if he didn't replace any of the questionable hoses, they are probably leaking now.

Think about this. You had a vacuum leak, when it was fixed the car ran great for a short period of time. When that vacuum leak was fixed, manifold vacuum became stronger. Now the next weakest point in the system couldn't hold up to the stronger vacuum and it failed. Fix leak #2, and then you may cause leak #3. Whack-a-mole with vacuum leaks!

 

I agree with this.

Also have him replace the rear valve cover gasket while the intake manifold is off. The gasket will leak eventually. Fixing it involves removing tge intake manifold.

might as well replace the knock sensor as well.
super easy to do while tge manifold is off.
super difficult to replace if it's attached.

 

Thanks for you input everyone. That cylinder 5 misfire CEL went away, and I took the car back to the original mechanic. He said he is going to replace the gasket for free, and I will only pay 150$ for the 2 rear injectors.
He is working on the car right now, but he has been telling me suspicious things. He told me the gasket was fine and the 2nd mechanic must have sprayed something "strong" that is why engine reacted. Isn't that BS? I saw mechanic spray brake cleaner on the gasket and engine smoothed out for a few seconds, doesn't that confirm that there is a leak and gasket needs to be changed? He also told me he did not replace that gasket originally and just reused the old one. Is that a common thing to do, to reuse an old intake manifold gasket? That sounds like BS to me too. But then he tells me the engine runs good now but fuel trims are still off and he is investigating the MAF sensor.

It could be the SOB is telling me this BS because he is taking long time with repair and didn't replace anything yet. I hate mechanics.

 

Gasket would be fine, if it wasnt 2 decades old. Normally you could reuse the gasket as much as you like but with the rubber being that old, it needs to be replaced. Spraying something combustible to hunt for intake leaks is a tried and true trick so if that made the motor rev, its clear as day there was a leak.

If you hate dealing with mechanics, its never to late to learn to do things yourself ya know.. paying another man to work on your car is like paying a man to sleep with your wife, I tell you what.

 

One should always replace that gasket. It won't seal well a second time.

Thats why it leaked. The Something Strong comment is about Saving Face .

oh well. Look at tge bright side. You were able to get tgebother two injectors installed at no charge.

I suppose he did not replace the valve cover gasket?

Hopefully the old gasket won't leak soon.

I believe in Old Man Murphy.

" If something could fail, it will fail. And at the most inconvenient time."

 

FelPro Plenum (UIM) Gaskets are $2.99 at RockAuto.

 

Both valve cover gaskets were replayed 1.5 years ago.

 

It's stories like this (and my own) that made me learn to work on my own cars. Haven't needed a mechanic to fix anything in over 20 years now and counting. Your mechanic sucks.

 

Update: mechanic put new intake manifold gasket for free and 2 remaining rear injectors. I payed $150 for 2 injectors. He also said he replaced the MAP sensor, which parts and labor cost $180.

The car runs good now though atm, hopefully nothing breaks again. I will have to replace the front injectors next. He said parts and labor will cost $300. I'm not sure I would be able to do it myself, and save like $100.

 

The front injectors are a breeze. Do them yourself! When you're ready, let us know and we will guide you and provide tips etc.