Worn Injectors on '93 V-6 PU?

[cwilliamrose]

My truck has lately been starting very rich after warming up. Cold starts are fine. It smells of unburned fuel when starting warm and does not fire readily as it does cold. Beyond that it has lost mileage slowly over time. The truck has 135,000 miles. The injectors were "cleaned" at about 100K miles with no mileage change. Could this be worn injectors or some other cause? If the verdict is injectors, what's the best source and what should the cost be (ballpark).

Thanks...........Bill

[seang]

o2 sensor(s), MAF sensor, heavier right foot than when you first got the truck, worn, incorrect heat range, or incorrectly gapped spark plugs...

[Q451990]

Your situation certainly sounds like flooding for some reason or another. I had a similar issue on my first Q45 after replacing the injectors. It would start fine first thing in the morning, or after sitting for 4 or 5 hours, but let it sit for 15 minutes or so and it started rough and spewed a few puffs of black smoke.

After reviewing the service manual for a '94, which is the earliest model I can find online, it looks like your injectors are of a side-feed design - same as my Q. Long story short, the injectors typically don't fail partially open, so your problem is probably a failed lower o-ring. There are two o-rings and the fuel is forced around the sides of the injectors through the rail. If the lower o-ring leaks, it floods into the engine... if the upper one fails, you get a nice gas leak under the hood.

The best way to check for this is to pull the rails, but leave them hooked to the fuel lines. Turn the ignition switch on so that the pump primes and pressurizes the rail, and look for the leak. I have no idea how difficult it is to get to them on your truck... if you're lucky you can just replace the o-rings. Be sure to lubricate them and their mating surface in the rail with a smear of motor oil so that they seat properly and don't pinch.

Oh, and you might want to change your oil soon... the fuel that's not flooding your engine on a cold start has seeped past the piston rings into the crank case and into your oil...

Good luck and welcome to NICO!

Heath

[cwilliamrose]

o2 sensor(s), MAF sensor, heavier right foot than when you first got the truck, worn, incorrect heat range, or incorrectly gapped spark plugs...

I can see how those things would effect mileage but not so much hard starting when hot. I'll have to look at the service records but I know the O2 sensor was replaced at least once. Plugs are fairly recent but I should check them for gap, etc.

As for the heavy right foot, well, maybe. I have noticed times in the past when it seemed to have better power than other times so I am surely using more throttle when it's running "weakly" (which seems to be all the time now). But the mileage issue started long ago, before I had the truck extensively serviced 4-5 years ago and before the hard starting issue. And before I had a 330i to compare it to.

Thanks,

Bill

[cwilliamrose]

Your situation certainly sounds like flooding for some reason or another. I had a similar issue on my first Q45 after replacing the injectors. It would start fine first thing in the morning, or after sitting for 4 or 5 hours, but let it sit for 15 minutes or so and it started rough and spewed a few puffs of black smoke.

Yep, that's about what I seeing. It takes about 15-20 minutes after shutdown for this to become a problem.

After reviewing the service manual for a '94, which is the earliest model I can find online, it looks like your injectors are of a side-feed design - same as my Q. Long story short, the injectors typically don't fail partially open, so your problem is probably a failed lower o-ring. There are two o-rings and the fuel is forced around the sides of the injectors through the rail. If the lower o-ring leaks, it floods into the engine... if the upper one fails, you get a nice gas leak under the hood.

No leaks under the hood AFAIK. That lower o-ring could be the problem. The fuel in the rail heat soaks after shutdown, expands and leaks into the manifold. This takes a little bit of time to happen and a longer time to evaporate so you get a normal start. This problem came on fairly suddenly and a failed o-ring fits that better than a worn injector which would be very gradual.

Are the o-rings a standard size or are they available from Nissan?

The best way to check for this is to pull the rails, but leave them hooked to the fuel lines. Turn the ignition switch on so that the pump primes and pressurizes the rail, and look for the leak. I have no idea how difficult it is to get to them on your truck... if you're lucky you can just replace the o-rings. Be sure to lubricate them and their mating surface in the rail with a smear of motor oil so that they seat properly and don't pinch.

Oh, and you might want to change your oil soon... the fuel that's not flooding your engine on a cold start has seeped past the piston rings into the crank case and into your oil...

I'll try to do this test soon but I want to have the o-rings in hand first. No reason to take it apart twice!

So you're saying the fuel will get into the crankcase? If the injectors leak wouldn't it go into the intake manifold only or is there a path the to crankcase (like through the cylinders and past the rings)?

Good luck and welcome to NICO!

Heath

Thanks Heath. Very helpful reply and I appreciate the research too.........Bill
Modified by cwilliamrose at 10:04 AM 10/9/2009

[Q451990]

Are the o-rings a standard size or are they available from Nissan?

You should be able to buy the o-rings from Nissan. With a part that's so critical, and comes into contact with fuel, I wouldn't try to source them myself unless you have some pretty specific knowledge about o-ring materials and what they can withstand. We also have a sponsor here- http://www.deatschwerks.com - that is an excellent company. You could remove the rails and ship them to them for a full cleaning and test - and they would replace the o-rings as well. I think their service is about $20/ injector. My guess is that you would spend about $10/injector for the two o-rings each - so it's not a bad deal. If you're looking for an online parts supplier for OEM parts, the guys at http://www.everythingnissan.com are also great to work with. I couldn't find a price for the o-rings on the site, so you would want to call them for that. Probably not worth paying shipping for just the o-rings, but if you need other parts at the same time it's a great deal.

Quote »So you're saying the fuel will get into the crankcase? If the injectors leak wouldn't it go into the intake manifold only or is there a path the to crankcase (like through the cylinders and past the rings)?[/quote]I'm not sure on your particular engine, but on the Q and the 4 cylinder - the injectors sit south of the upper intake, feeding an intake runner that goes straight to the valves. So yes, the fuel leaks past the valves and into the cylinders and seeps past the rings into the crankcase.

Heath
Modified by Q451990 at 12:06 PM 10/9/2009

[cwilliamrose]

Thanks Heath,

I have the o-rings coming from the local dealer (no stock), should be here Tuesday. I think I found them on the EverythingNissan site -- they're called "injector insulators, pick-up, pathfinder, vg30e 91-94" $4.02 ea list price and $1 cheaper online but I'll get 'em quicker locally.

I'd love to send my parts to DeatschWerks but we're a no income family right now so hopefully this will do the job. I'll report back when I've done the deed..........Bill

[Q451990]

Just remember to lubricate the o-rings with a smear of motor oil after you install them on the injector, before you insert them into the rail. I know I said that earlier, but I can't stress that enough...

[cwilliamrose]

Will do, thanks......Bill

[cwilliamrose]

Quick question;

The service manual I have (Chilton's) says it's necessary to drain the coolant before you remove the plenum and fuel rail assembly. What's with that? It seems like you're working above the coolant system for this job...........Bill

[seang]

You can just drain it, its not even a big deal. The biggest thing is getting a length of hose to attach to the drain petcock on the bottom of the radiator. Beyond that it's a matter of having an empty milkjug or antifreeze bottle to catch the coolant as it drains. If the coolant is still nice and new, you can re-use it, just make sure the bottle you are using is clean. I like to use an electronics tester to measure the electrolytic properties of the antifreeze, ensuring knowledge. The stock radiator holds about a gallon, so you definitely won't fill two, one gallon jugs all the way.
Modified by seang at 7:08 PM 10/12/2009

[Q451990]

I would look at the FSM (Factory Service Manual) here.

It's under the Pathfinder, since they shared the same D21 Platform that year. The earliest online FSM is for 1994, but they should be very similar vehicles if not identical.

Heath

[cwilliamrose]

The '94 Pathfinder manual says the same thing -- drain the coolant at the block in both banks. PITA but apparently necessary. Thanks for the link!..........Bill

[Q451990]

I would skip those block drains!

Just make sure the coolant doesn't go into the intake somewhere and you should be fine. The block drains on Nissan engines are notoriously hard to remove, and on the Q45 at least, the block sometimes cracks there when they're removed. Supposedly they need to be removed while the engine is hot, but I just don't touch 'em.

My guess is that they're wanting you to drain it to get the coolant out of the throttle body - but draining the radiator should be more than sufficient.

Heath

[cwilliamrose]

Ah! Now it makes sense, the throttle body is part of the system. I'll use the radiator drain has you suggest and be careful with stray coolant. Thanks for the headzup on that Heath.....Bill

[cwilliamrose]

OK, it's update time.

First, the book lies. It's a bear getting the plenum off, mainly due to inaccessible hose clamps. I ended up getting the plenum loose at the front, tipping it up and removing all the stuff bolted to the bottom. There are still two hose clamps that I haven't gotten to. And because of all the hard, brittle old hoses, I want to replace all the hoses I can while I'm here.

The screws holding the injector caps on were very tight. I was able to loosen them with a cordless drill which allowed me to push hard on the screw without worrying about turning it too. Just get it straight, push hard and hit the trigger. I boogered one screw before I used the cordless and a ordered a couple of new ones. The boogered one came out by filing a notch the edge of the head and using a hammer and flat screw driver as an impact tool.

The manifold and plenum are full of oily dirty gunk. I have the plenum soaking in mineral spirits and I'll try to clean the manifold without removing it. It probably won't be as clean as I'd like.

There was an intake leak due to a failed hose (the small one going to the fuel canister). There may have been other leaks. BTW, hoses for this truck are expensive!

The o-rings for the injectors are just about impossible to find. The diagram the dealers have don't show them for the V6 and the local guys swear there are none. I solved this by sending the injectors to Deatschwerks when they offered to supply them (thanks Mark!). It's a good thing I did send them in, one had a bad coil and had to be replaced. I didn't want to do this originally because I was unemployed. That changed so I went for it.

I did run the pressure test Heath suggested and saw no leaks. That was disappointing but when the one injector tested bad I asked Mark if that could explain the symptoms I was seeing and he said it could be the problem. It certainly would account for the poor power and fuel mileage.

So, I'm waiting for parts, soaking the plenum and hoping I remember where all those tubes and electrical connectors go.....Bill

[seang]

The manifold and plenum are full of oily dirty gunk.

I don't like the sound of that. Is this normal? How full is it?

Is this caused by the EGR?

Is it caused by the PCV?

Do all engines do this?

I could understand a little varnish, but when it gets into the millimeter range, it's f***ing up airflow.

I was reading about how some Ford Taurus' have PCV systems that work too well and actually pull oil into the intake manifold. That is not supposed to be normal.

[cwilliamrose]

Maybe "full" wasn't the right word -- "completely coated" is probably better. And yes, it's my understanding that this is common and expected. The EGR valve and the crankcase ventilation both use the plenum. The byproducts collect there and in the entire induction system downstream of the butterfly valve.

I'd like to understand it better and also understand if a failure of some component in the system would make it worse. I have read it's a bad idea to defeat the EGR and PCV systems.

...........Bill

[seang]

Well, I Googled "gunk in intake manifold" and read alot of the results. I have come to the conclusion that as long as there is an EGR and a PCV functioning, that there will be gunk build-up in the manifold. I guess after a hundred-thousand miles of operation, I can see how some would be normal.

I read a thread from a 300C forum. An owner of a 2006 Chrysler 300C had reported a heavy build up of gunk in his intake manifold. He produced no pics, so IDK how "heavy" it was. But it is remarkable how a car that new could have such things going on.---------------------------------------------------------------------------------------------- I like the idea of the PCV. Using vacuum from the intake manifold, it pulls fresh air into the crankcase while pulling smokey blow-by gasses out. This keeps the oil cleaner for longer. Some of these gasses condense on the surface of the relatively cool intake tract.----------------------------------------------------------------------------------------------The EGR is to blame for some of the deposits. These deposits are mostly carbon with some hydrocarbons. The EGR cools down combustion temperatures, but having no EGR isn't going to raise combution temps to a harmful level. There is nitrous oxide available if you want to do that.

This system does reduce Nox emissions from the tailpipe, and so reduces the vehicles contribution to acid rain and other acidifying effects on the enviroment.

But you do realize that China is burning nasty coal at a far larger rate than your dinky little engine. Methane from livestock is also a larger contributor to the enviroment than all of our engines combined. There are alot of factors here. ----------------------------------------------------------------------------------------------Personally, I have defeated my EGR. My PCV is as Nissan had it.

Intake manifold gunk is a new realization for me, and cleaning it out might be part of my long-term-tune-up protocol depending on; the overall condition of the vehicle/engine, compression levels, and whether or not I love the car or plan on owning it for a long time.

[cwilliamrose]

We gave away our nitrous stuff last year. It was on a little airplane for a while -- until it backfired and bent the butterfly back on itself. You had choices between half throttle and full throttle......

[cwilliamrose]

Well, as of last weekend it's done,,,, finally!

Getting parts was a big PITA. The local dealer is of little help and the online dealers I used weren't much better. I did send my injectors in for cleaning and they found a bad one. This was likely my source of a number of symptoms, some of which I had forgotten about because I have lived with them so long.

I have only one day's running on it so far but it seems much improved. The hard starting when hot seems to be gone, fingers crossed! The truck used to knock fairly badly during acceleration and going up an incline. That doesn't seem to be the case anymore or at least it's much improved. It runs smoother -- it always seemed to have a vibration that was not shocks or tires or wheel balance issues. It seems to have better power -- maybe in part because I'm not backing off to deal with the pinging.

I don't know about mileage yet but I'm hopeful it will improve and get back most of the 10-15% it has lost over the years.

I did do one or two really dumb things on this job. I connected one of the electronic connectors to the wrong sensor and it was the one UNDER the plenum (of course). I thought I'd have to take a bunch of stuff off to get at it but I was able to remove the wrong one and install the correct one without any real disassembly. I noticed I had a loose connector when I was hooking up the spark plug wires. It had fallen behind the engine and wasn't very visible. I did an inventory of screws and hoses but not connectors. DUH!

And I missed hooking up one of the coolant lines to the plenum. It's amazing how much coolant comes out of a 1/4" fitting.

Anyway, thanks for all the help. The truck is much happier and so is the owner......Bill