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Shimell
Shimell, Nissan and ASE Master technician
Category: Nissan
Satisfied Customers: 363
Experience:  18 years with Nissan. Nissan and ASE master technician with advanced ASE certification.
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2001 Nissan frontier: liter..000 miles..service engine light..run fine

Customer Question

2001 Nissan frontier with 2.4 liter 4 cylinder engine with 225,000 miles. service engine light went on and wont pass inspection. Engine shakes a little at idle but seems to run fine. I think gas mileage is not as good as it use to be. Anyway I'm getting a code of po304 (pd)cylinder 4 misfiring. Research shows it may be the EGR. I tried to get it out but the bolts are too rusted and the pipe is too. So I removed the throttle body and the 4 Allen bolts in top of manifold.
Sprayed 2 cans of carb cleaner into it. From what I could see there was a lot of carbon in there. Checked the solenoid that sends vacuum to the egr and I don't think there's any vacuum going to it at all. The solenoid works. Thinking about changing the coil but then again I don't want to start changing parts for nothing. I realize the truck has a lot of miles on it. The body looks great but the underside and many parts are rusted out. I don't believe they make bolts that rust so bad. I'm still on the first clutch.
I drove all year since last inspection with check engine light on. Truck bucks a little for first 2 minutes when cold. A mechanic got it to pass last year and plugged up the egr, but right after that the light went back on. I feel I should just get another truck but I don't really have the money and I hate to rush into buying a new truck without time to research it. Any thoughts? After cleaning throttle body I got a code of all cylinders misfiring, I'm guessing it's from all the carb cleaner that had to burn off. Soon after that the same cylinder 4 misfire code came up. When this first started last year I changed plugs, wires, dist cap, rotor. Nothing helped.
Submitted: 3 years ago.
Category: Nissan
Expert:  Shimell replied 3 years ago.

you need to clean the EGR ports. there is an allen head plug in each intake runner, so there is 4 of them. they are in the intake manifold about an inch or two down the runner from the head. take out each plug and use a small screwdriver or round wire brush to punch through the carbon in the hole.

what is happening is your cyl #4 egr port is open, or slightly open and all the other ones are plugged. this makes all your egr gas go all into one cyl and makes it misfire. I have seen this problem many many times and am confident this should fix your problem.

if you have any further questions on this, please post them here.

Thanks!

Expert:  Shimell replied 3 years ago.

if you look in this picture here, this is the approximate location of each plug. this is marked with a red dot.

just a side note, each plug is an 8mm allen head. dont round them off. they are very tight to break loose.

graphic
Customer: replied 3 years ago.
Shimell
I did say that I removed the allen head plugs. and there was a thin layer of carbon in the hole that I scraped away and cleaned with carb cleaner. The only one I couldn't remove was the last one that's behind the egr, egr is in the way. When you say punch through the carbon, how deep do I go into the holes 1 or 2 inches? straight in ? up? down? Or just right at the plug which is what I did. I'm assuming I need to go a bit deeper than the surface.
thanks
Tony
Expert:  Shimell replied 3 years ago.

ok. what happens is the carbon builds up and it makes it look like there isn't a hole down in there, i bet you just scrapped away the top layer of the carbon. once you remove each plug, down inside the hole, there should be another hole about 1/4 to 1/2 the size of the bolt hole, if there is not, you need to take a small screwdriver into the center of each hole and push hard to puncture through the carbon. every time I have done this job, the hole was covered up so it doesn't even look like there was a hole there, there is a hole there, it is just filled with carbon. you need to puncture through it by pushing straight down into it...

Customer: replied 3 years ago.
Shimell
I did say that I removed the allen head plugs. and there was a thin layer of carbon in the hole that I scraped away and cleaned with carb cleaner. The only one I couldn't remove was the last one that's behind the egr, egr is in the way. When you say punch through the carbon, how deep do I go into the holes 1 or 2 inches? straight in ? up? down? Or just right at the plug which is what I did. I'm assuming I need to go a bit deeper than the surface.
thanks
Tony
OK What about the plug behind the egr valve? I can't get to it. Will it be OK if I just clean 3 of them? The egr is rusted in and there's no taking it out with out cutting it and the pipe that goes to the exhaust manifold. Could I get away with just the front 3 ports?
thanks
Tony
Expert:  Shimell replied 3 years ago.

you should at least clean as many as you can.

when you remove the plug, you are just gaining access to the tube that the egr flows down. at the bottom of the tube, inside each hole, in the center of each hole, there should be another small hole, if not, then it is plugged. then just take a small screwdriver and push straight down into the center of the hole at the very bottom. once you clear the hole, you will now have actually punched through to the intake manifold runner. so a small screwdriver should be able to go about 2 inches down into the hole. once you break through one you going to have one of those AHAH moments.

I hope im explaining this well enough. any more questions?

Customer: replied 3 years ago.
I'll try this in the morning and settle up with you after OK?
After I do this will the check engine light go off after driving for a while or do I erase it and then drive for some miles.
thanks man
Tony
Expert:  Shimell replied 3 years ago.

It would be best if you erased it. but, it will eventually go off after the problem is fixed.

just remember, after you get the plug out, at the very bottom of the opening, there should be a hole. just push through it with a screwdriver. it may be a little tough, but it should go through.

have a great evening.

Shimell, Nissan and ASE Master technician
Category: Nissan
Satisfied Customers: 363
Experience: 18 years with Nissan. Nissan and ASE master technician with advanced ASE certification.
Shimell and 9 other Nissan Specialists are ready to help you
Customer: replied 3 years ago.
Shimell
Hi, After doing what you said I thought it was fixed. I reset the code and drove about 75 miles. The light remained off, but I noticed the idle was a little low and a slight hesitating in startingas well. The next morning the light came back on and know the copde is p1402.
Which is what EGR again? It's getting harder to start and idle is worse too. Weird because it ran good after I cleadned those ports.
What now?
Expert:  Shimell replied 3 years ago.

code p1402 means there is egr flow when there should not be. so now we got the egr system flowing by clearing the ports. the next step is to get the computer back in control of when the egr system is allowed to flow.

since there is egr flow even when the computer says there shouldn't be, this could be due to a stuck open egr valve, or a stuck egr solenoid valve. or you could have the wrong vacuum hose hooked to the egr causing it to flow when it shouldn't.

reach underneath the egr valve and see if it is open, it should open "you will feel it lift" if the vehicle is warmed up and you rev the engine slightly just off idle. if you reach underneath it and push up on the egr bellow, and it is already up, this means it is open. remove the vacuum hose and see if it lowers.

let me know what you feel then we will move on.

Expert:  Shimell replied 3 years ago.
here is a picture of where you need to feel on your EGR valve.graphic
Customer: replied 3 years ago.
HI Shimell
I rev engine and EGR does not lift. It lifts manually. There's no vacuum at the valve. As a matter of fact I don't feel any vacuum at the sonenoid. The solonoid is working when power is applied but There's no vacuum going to it. Do you have a diagram of the vacuum line for me to double check that they're all in the right place.
thanks
Tony
Expert:  Shimell replied 3 years ago.

I will look for a diagram, but they are not very clear.

the odd thing is, this code is because there is egr flowing when there shouldn't be, not the other way around. also, the symptoms you had before suggested there was flow, but the flow was going all into on cyl. cyl #4. the one that wasn't clogged..

this would suggest the egr valve was stuck open, or you have the wrong vacuum lines hooked up and the egr valve was opening when it shouldn't be.

be back soon, going to look for a vacuum diagram

Expert:  Shimell replied 3 years ago.

here is the best diagrams available from the service manual.

graphicgraphic

Customer: replied 3 years ago.
the solenoid has a single hose on one side which I think is where the vacuum comes from.If this is correct then there is no vacuum. the side of solonoind that has two hose on goes to a port on throttle body which has vacuum. When I push up on egr engine wants to die while idling. egr is working fine, there's no vacuum to control it. I tested the solenoid with a battery lead and it clicks. I'm just a carpenter but I play with wrenches.
I don't know, I hope you do. I need my truck please help
Expert:  Shimell replied 3 years ago.
I have got very busy at work. I will look into this further tonight or tomorrow. Good information for me to go on.
Customer: replied 3 years ago.
ok thanks,
I'm going to double check now but all vacuum lines seem to be in place correctly.
Customer: replied 3 years ago.
Hi Shimell
I was playing around with truck go over everything that I could. Idle was low engine was shaking. while engine was running I reached in and moved the top of the EGR left and right. Imediately after that the engine smoothed out and idle went back up to where I think it used to be around 900 RPM. Took it for a ride on the highway and wow it ran like it used to again. It is running good now, so I pulled over and checked that the EGR was opening when throttle is opened. All is good, what happened was when I removed those plugs I had to slightly bend the egr to get to the forth plug behind it so I must have left it slightly out of line. Well enough of my bullshit you must be tired, get some rest and have a great evening!! thanks much
Expert:  Shimell replied 3 years ago.

well that would explain it then, the EGR valve was sticking...

good luck, and thank you!

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