The Nissan Club banner

1 - 20 of 54 Posts

·
The Don.
Joined
·
6,151 Posts
Discussion Starter #1 (Edited)
Thought I'd add some troubleshooting tips for what is yet another source of fuel economy problems. This problem has recently plagued my car and it could (or not) be related to your fuel economy problems. There are other good threads that discuss other findings.

I have always been quite pleased with the gas mileage I get from my car. Typically I get about 27-30 mpg in the summertime and about 24-27 mpg in the wintertime. However, until very recently, my fuel mileage has been dropping quite badly. My fuel gauge isn't out of whack like many others so I rely on it often and check the 3/4, 1/2, and 1/4 markings against the trip odometer. For the passed two gas refills I confirmed there was a fuel economy issue.

I noticed the tach needle dipping every so often while idling. For me, that typically means it is time to do maintenance on the ignition system. But this time it didn't work. I swore the engine was randomly missing but it was barely detectable by simply listening to the engine. But listening to the exhaust coming out off the tailpipe confirmed the engine was randomly misfiring.


I did a number of checks,

1. Did a power balance test by disconnecting the injector(s) harness one at a time. No change detected.

2. Removed the fuel rail with the injectors attached and cranked the engine to see if all the injectors where firing. They all had a nice conical-shaped spray coming off it. Sprayed them down with fuel injector cleaner spray for safe measure.

3. Teed off a vacuum gauge to the fuel pressure regulator and viola! The vacuum was sitting around 15 in. Hg. My car typically sits around 20 or 21 in. Hg. That told me there is quite possibly a vacuum leak somewhere.

4. Confirmed a number of vacuum connections and didn't find anything loose or missing.

5. Checked the EGR system and confirmed a problem. Here is a very quick way to check the EGR system.

-- Warm up the engine to normal operating temperature.
-- Put your left-hand fingers underneath the EGR and feel the EGR diaphragm.
-- With your right-hand softly cycle the throttle open (about 2000 rpm) and closed.
-- You should feel the EGR diaphragm move up and down.
-- Pushed up on the EGR diaphragm and the car should idle poorly.

In my case, the EGR diaphragm didn't move up and down. That is because either the EGR/Canister control solenoid valve is not passing vacuum, it is bypassing air into the intake, or the ECU isn't controlling the solenoid properly. When I get another chance to work on the car, I will confirm it is not something easy like bad electrical connections before condemning and replacing the EGR control solenoid. So stay tune and I will keep you updated of the sure cause of my fuel economy issue once I find time to continue this ordeal.
 

·
Official Troll
Joined
·
7,780 Posts
I think we need to create one thread to be FAQ'ed for non-typical fuel economy solutions.
 

·
Registered
Joined
·
3,314 Posts
I thought I had a egr problem once, when I pressed up on the diaphragm the car wouldn't stall, turns out the hose from the carbon canister was completely disconnected. make sure all your hoses are connected or else your EGR won't function properly.
 

·
The Don.
Joined
·
6,151 Posts
Discussion Starter #4
Well, I promised an update on this thread and here is what I did which seemed to have fixed the problem because it hasn't occurred in about a week.

Disconnected the EGR control solenoid valve harness connector and tighten the female connectors of the harness so that it made for a tighter fit on the male terminals.

Disconnected the three hoses of the EGR control solenoid valve and sprayed carburetor cleaner inside each port of the valve.

Sprayed a good amount of carb cleaner down the hose from the solenoid valve that connects to the vacuum port of the throttle body. Reconnected all the hoses back to the solenoid valve.

Cranked the engine and got a good amount of smoke coming out of the tailpipe so I let the car warm up a little longer until the exhaust smoke cleared out. I took the baby for a spin and damn!!! the car's throttle reponse and idling was a whole lot better. That poor acceleration problem I use to have was gone as well.

My theory is that somehow the carb cleaner had cleared out gummy or carbon deposits from the throttle body and possibly other intake areas. This allows for better intake air flow. So my opinion is that if you get one of those fuel injection cleaning service like BG then make sure the air induction systems is taken care of as well. I believe that they all might be included in one price but definitely don't neglect getting the air intake system cleaned.

I am very pleased now. My car response and my gas mileage has recovered nicely.
 

·
Official Troll
Joined
·
7,780 Posts
Good stuff :bigok: Eventhough I don't think I'm experiencing the problems that you have, I'll inspect the EGR anyway.
 

·
The Don.
Joined
·
6,151 Posts
Discussion Starter #6
I have another update to this thread. After driving around for quite awhile my EGR problem came back to haunt me. The EGR/Canister control solenoid valve was indeed going bad when hot. When it failed and was giving me the same symptoms as mentioned at the start of this thread, I turned off the car and checked the resistance of the solenoid valve. Normally, the solenoid valve should read about 34 ohms. Mine was reading about 66 ohms, and was randomly varying, when it was hot. I sprayed some component cooler on the valve's housing to cool it off and the resistance dropped back down. Somehow heat was affecting it's operation. I just completely replace the EGR/Canister control solenoid valve which was like a three minute job, no kidding. Haven't had another occurence of this problem as of yet.

I just wanted to add another interesting piece to my fuel economy dilemma. I took off the oxygen sensor in my car, which was now about two years old, and noticed a few things. First off, the sensor came off extremely easily with the O2 socket, like if it wasn't even tighten down enough. I could see how the exhaust manifold heating and cooling effects would do this over time. I also checked the threads on the sensor and the manifold and they were covered with too much oxidation. So I used a wire brush to clean both threads. But most importantly, I noticed that the shield tip of the sensor was covered with hardened white deposits which means silicone poisoning. I have no idea what silicone gasket or material is causing this. So I did the following for the meantime, I cleaned the sensor shield tip with 2000 grit sandpaper and sprayed the sensor tip with a good amount of fuel injector cleaning spray which is O2 sensor safe. I put everything back in and tighten the O2 sensor nicely and have been driving the car for quite awhile. I have regained my normal 30 mpg performance but will keep tabs on this in case anything changes. I just wanted to add this because some of us have the one-wire or three-wire O2 sensor which has a grounded body and that might be a cause for fuel economy problem to some of you. Anyways, if anything changes then I will gladly post back here.
 

·
I keep em comin back.....
Joined
·
3,205 Posts
I've been wanting to change my O2 sensor but never gto around to it, I'll check this out today, thank jserrano!
 

·
Registered
Joined
·
3,314 Posts
JSerrano, since I sprayed that carb cleaner in the egr hoses, the car has been stalling out once in a while =\. I guess that means the system is flowing properly though. But I am still getting crappy milage, I have changed Coolant temp sensor, and o2 sensor. So I hooked up my car to a consult setup, What I've noticed is the temp is steady, the TPS and MAF seems to work okay .4-4.5v. but my timing is going pretty wild, 22 @ 750 rpm, to 11 @ 775rpm' everything else seems fine, coolant temp stays at 94C steady. I bought a brand new distributor, new wires same thing. You think it could be ignition coil? or knock sensor?

I pulled the plugs, pitch black, this is a 2k1 motor in a 93 chassis. please help =\
 

·
The Don.
Joined
·
6,151 Posts
Discussion Starter #9
rush0 said:
JSerrano, since I sprayed that carb cleaner in the egr hoses, the car has been stalling out once in a while =\. I guess that means the system is flowing properly though. But I am still getting crappy milage, I have changed Coolant temp sensor, and o2 sensor. So I hooked up my car to a consult setup, What I've noticed is the temp is steady, the TPS and MAF seems to work okay .4-4.5v. but my timing is going pretty wild, 22 @ 750 rpm, to 11 @ 775rpm' everything else seems fine, coolant temp stays at 94C steady. I bought a brand new distributor, new wires same thing. You think it could be ignition coil? or knock sensor?

I pulled the plugs, pitch black, this is a 2k1 motor in a 93 chassis. please help =\
I'm not sure the stalling was a result of the carb cleaner. You might actually have more than one problem. For whatever reason, this problem sounds to me more like an air flow, vacuum, or IACV issue. The rich mixture problem might be unrelated.

Give me the link for your thread on this problem so I can read up more and then I could post there anything that comes to mind.
 

·
Registered
Joined
·
3,314 Posts
I dont really have a thread, I guess I should go get a vacum gauge. The IACV screw adjusts the idle pretty well, i'm not sure as to how much of a test that is though.
 

·
Rockin the Le Bra
Joined
·
1,016 Posts
i should give my egr a check because i swear i thought i saw one of the hoses on the canister completely disconnected from the canister. i did some all highway driving the past 5 days and only got 22mpg going about 75mph most of the time. city driving is even worse...16mpg :(
 

·
Registered
Joined
·
606 Posts
wow you guys are getting a ton more mileage than i am i'm getting around 15 to 17 mpg city with barely getting on it.. I've noticed that my tach needle drops pretty low when i'm idling does that normally mean that i should check the ignition system. I'm coming up on 100k miles and i'm about to go get my fuel system cleaned at a garage around here they are having a special and its only 60 bucks as opposed to like 120. What all should i check to try and increase my mileage its starting to drive me absolutely insane.

Thanks for your help
 

·
The Don.
Joined
·
6,151 Posts
Discussion Starter #13 (Edited)
There are a number of things to check. Maybe start with the basic tuneup and then check the operation of the,

1. Fuel System
2. Ignition System
3. Oxygen Sensor
4. Engine Coolant Temperature Sensor
5. MAF
6. Idle Speed

...also remembered, 7. EGR System (the subject of this thread)
 

·
Registered
Joined
·
28,959 Posts
Update: After seeing 26 MPG occasionally after swapping out the cooland temperature sensor and getting my intake manifold gasket replaced, my fuel economy is starting to dip again. Idle is rough again, though not as rough as before. It *sounds* like I have another leak at the intake manifold gasket again but I guess it wouldn't jurt to check the EGR system.
 

·
Hopes and dreams
Joined
·
1,031 Posts
this has to be my problem, my accel used to kick harder, now its like a slow ass vtec system waiting to kick in
 

·
Hopes and dreams
Joined
·
1,031 Posts
my rpms never climb its liiek ...1.,...2....3...jumps to 4 and above
unless i punch it then it runs to 5k
 
1 - 20 of 54 Posts
Top