# Car running rich?



## dschrier (May 6, 2002)

Only when it gets warm out, spring and summer, when I first start my car it bucks for a bit before it warms up. I've been told that this could be because it is running rich. Does a faulty O2 sensor cause the car to run rich? I get about 35-40mpg in the summer which would seem like my O2 sensor is fine. My car also pings even with 93 octance so I know there is something wrong with my EGR system. Could that be causing the bucking?


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## Myetball (Dec 15, 2002)

Have you checked your timing?


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## dschrier (May 6, 2002)

I haven't checked my timing myself, but I had the timing chain replaced about 20,000 miles ago, I have 155,000 right now. Would the mechanic have set the appropriate timing after changing the chain?


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## dschrier (May 6, 2002)

Would I be able to set the ecm to mode 1 while I am driving to see if the mixture is running lean or rich? I haven't really done anything with the ecm before, I am still learning.


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## Myetball (Dec 15, 2002)

What kind of car/engine do you have?


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## dschrier (May 6, 2002)

Oh sorry, 90 b12, Ga16i.


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## Myetball (Dec 15, 2002)

When was the last time you had the plugs changed?


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## dschrier (May 6, 2002)

I changed the plugs about 6,000 miles ago. I am using the bosch 4+4 platinums or whatever they are. I know that bosch suck for nissans, but could spark plugs cause pinging? Before I had just regular bosch platinums and the car ran the exact same way. I just got 38mpg with the last gas fill up. My PCV valve does need changing, but I can't get the thing off myself, I've tried with all my might and it won't budge. The O2 sensor has never been changed since I have owned the car(last 50,000 miles) The EGR diaphram moves fine when depressed and if depressed when the car is idling the engine cuts out so the valve itself seems to work.


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## blownb310 (Jun 10, 2002)

I wouldn't rule out that your egr system isn't functioning too, but the first thing to do is to check the timing. You see, when the old chain was still on the car and it was stretched, the cam [and therefore the ignition timing too] would be retarded a few degrees. At some point the ignition timing was probably advanced back to spec to make up for it. Now, when the new chain is in place, and the cam timing is back to normal, the ignition timing will be too far advanced.


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## Myetball (Dec 15, 2002)

These things are so hard to diagnose over the internet. I've only seen a couple guys fix their cars with performance problems. Heck, we had one guy pretty much rebuild his car and it still ran like crap  

Anyway, definately check the timing. Also check all your vacuum lines, you may have something cracked. Other things that come to mind...dirty filters..fuel, air.

Keep us posted.


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## dschrier (May 6, 2002)

I had the pinging with the old chain too. I just put 93 octane in my car and the pinging pretty much just goes away, except in the summer when it is really hot. I can't for the life of me figure out what is wrong. I have checked hoses but even the smallest hole could be hard to see by eye. I'll keep searchin, thanks guys.


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## blownb310 (Jun 10, 2002)

Well then, let's check the egr valve for operation. With the engine idling, reach a couple of fingers up underneath the egr valve and raise it off of its seat. The car should either stuble badly or stall instantly from the instant vacuum leak you have just created. If the idle doesn't change at all, your erg system is plugged solid with sludge.


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## dschrier (May 6, 2002)

Yeah, if I press the diaphram in while the engine is idling the engine almost dies. Does that mean the entire EGR system is functioning properly, or could something else still be wrong?


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## Myetball (Dec 15, 2002)

Here's a list of things from the handy dandy haynes manual.

- Engine stumbles on acceleration
-- Spark plugs fouled (not a problem)
-- Problem with fuel injection system
-- Fuel filter clogged
-- Incorrect ignition timing (still not ruled out unless you've slapped a light on it)
-- Intake manifold air leak 
-- Problem with emissions control system (EGR works so this is probably not the problem)

So that leaves fuel system, timing, and vacuum leak.

You can check for a leak by spraying carb cleaner on the various manifold connections. If the spray hits a leak idle should kick up or smooth out momentarily.


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## blownb310 (Jun 10, 2002)

dschrier said:


> *Yeah, if I press the diaphram in while the engine is idling the engine almost dies. Does that mean the entire EGR system is functioning properly, or could something else still be wrong? *


 ***** Yes something can still be wrong with the EGR system. You have just verified that the passages are not clogged and that the valve itself does work. That's good. But the valve still may not be operating if it doesn't see the proper vacuum signal from the BPT [back pressure transducer]. That's the round thing right next door to the EGR valve-with the foam ring around it. Are all of the vacuum hoses intact and leak free to and from the BPT and EGR valves? Quick test: while under the hood, rev engine somewhere between 2 and 3,000 rpm and hold it steady. Now reach under the EGR valve again and see if it is lifting off of its seat then. It should be. If it's not, it isn't getting the vacuum signal it should be to function while driving.


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## dschrier (May 6, 2002)

I'll check that next time I am out. Thanks for the help so far guys.


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## dschrier (May 6, 2002)

I just checked the EGR valve to see if it would open, and when the engine was reved it didn't move at all. How long does that speed need to be held at before the valve opens? Also, could there be something wrong with the BPT valve, can it get clogged or anything, or is a leaky hose the culprit definately.


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## blownb310 (Jun 10, 2002)

I would next suspect your vacuum source or the vacuum hoses. The valve should lift almost immediately during cruise [or simulating it the way you have].


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## Myetball (Dec 15, 2002)

The BPT valve and EGR valve both get vacuum from the EGR/Canister control selenoid valve. The control valve is connected to the throttle body and the hip bone's connected to the leg bone........


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## dschrier (May 6, 2002)

I just checked the ECU and got a 55 code so everything sensor wise is fine. All the hoses seem to be fine. So, one tube comes from the throttle body and goes to the BPT, what happens at the BPT that causes the hose running to the top of the EGR to open a vaccuum? Also, what does the hose from the bottom of the BPT valve running to the metal pipe away from the EGR do? My BPT valve looks like it had a foam piece around the center of the valve, but it was completely degraded and fell apart. Is this the problem?


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## phaedrus432 (May 5, 2003)

**BUMP**

Same problems here... Anyone care to answer dschrier's question? Thanks...


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## mattzmojo (Jul 2, 2004)

*did you find a solution?*



dschrier said:


> I just checked the EGR valve to see if it would open, and when the engine was reved it didn't move at all. How long does that speed need to be held at before the valve opens? Also, could there be something wrong with the BPT valve, can it get clogged or anything, or is a leaky hose the culprit definately.



Hello I was wondering if you found a solution to this problem? What I mean is , when you checked your egr valve for lifting at higher rpms and it failed, what might be/WAS the culprit? I have the exact problem, I have changed many of the vacuum lines going to and from the egr and bpt valves and checked the solenoid for continuity in the appropriate lines both passing. By the way what size wrench do I need to unthread the exhause nut on the EGR valve?(22m?) I have yet to clean it.
EGR FUNCTION IS THE BLOODY CODE....UGH!


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