96 altima miss fire


bracketshark
07-27-2006, 03:29 PM
My car had a missfire, I got advice from fuel injectors, distributor, intake gasket plugs and wires, I even replaced the throttle body and thought it was fixed until I found the EGR hose was left off after installing the new throttle body. When I hooked it back up the missfire is back. I'm running the car with the EGR unhooked now. I removed the valve it was clean and appeared to in good shape, vac. held. What could make it open prematurely and cause this problem? Thanks :banghead:

JustSayGo
07-27-2006, 09:47 PM
The EGR valve should be closed at idle. You have already proved that you EGR valve opens and doesn't leak. There is a hose from the throttle body that should not have vacuum at idle. As the throttle body opens this ported vacuum begins to pull vacuum. Make sure there is no vacuum at idle. This ported vacuum is used as a signal to open the EGR solenoid. The EGR solenoid then connects manifold vacuum (which is much stronger than ported vacuum) to the EGR valve. The EGR solenoid has a wire connected to it. When there is power to the wire the solenoid opens and allows manifold vacuum to open the EGR valve. At idle there should not be any vacuum drawn through the solenoid. The solenoid may not be blocking the vacuum at idle because it leaks, or because there is a ported vacuum signal or electrical power to the solenoid. Which hose was disconnected? The hose connected to the EGR valve or the hose connected to the throttle body?

bracketshark
07-27-2006, 10:02 PM
The vacuum suply from the TB dosn't have vac. at idle but just a blip of the throttle and its there. The EGR has manifold vac. about the same time there is ported vac. at the switch. So what tells the switch when to allow the EGR to operate? Also what is the sending unit between #3 & 4 clyinders on the intake? It has 2 wires coming out of it going to a connector. My book might be telling me this sending unit controls the vac switch, its not clear to me. Thanks for the reply, and any other advise.

JustSayGo
07-27-2006, 10:11 PM
I think you are describing the EGR temp switch with two wires. The switch prevents the EGR solenoid from opening until the engine is warm. Connect the hose to the EGR valve and disconnect the hose to the throttle body. If the engine runs rough, the solenoid must be leaking and is the cause of the problem.

bracketshark
07-28-2006, 06:58 AM
The EGR is connected and the throttle body is unplugged, it runs good no skipping, as soon as the ported vac. is hooked up is when I have the problem. The miss is not at idle, its just off idle form 1200 rpm to about 1700 after that the miss isn't appearant, one other thing it doesn't do it until operating temp is achieved. What tells the switch when to open? The ECM? Thanks

JustSayGo
07-29-2006, 02:45 PM
You are describing correct operation of an EGR system. The remaining component of the EGR system is the Back Pressure Transducer. The BPT compensates for increased exhaust pressure by controlling a vacuum leak to the EGR valve to reduce EGR flow. The hose between the EGR valve and the transducer could be restricted or the BPT is not sensing any exhaust pressure possibly causing your engine to receive too much EGR flow.

Increasing exhaust temperature tells the EGR switch to close, connecting electrical power through the switch to the solenoid. The purpose of EGR is to lower combustion temperatures. Combustion temperatures are already lower when the engine is below operating temp, or under extremely low intake air temp conditions, so the switch blocks EGR until combustion temperature raises exhaust temperature at the switch. The blue/red wire to the EGR temp switch gets power from the ECM for diagnostic purposes rather than controlling power on and off.

Does the engine run strong otherwise? Is there any possibility that the ignition timing is not set correctly?

bracketshark
07-29-2006, 08:36 PM
The engine runs good and strong once it gets through the 1200 to 1800 rpm range. The timing is correct (I even bought a new distributor, same results with both) I'm guessing your in statement "The hose between the EGR valve and the transducer could be restricted or the BPT is not sensing any exhaust pressure possibly causing your engine to receive too much EGR flow. " the second posibility is most likely my problem. Its kind of obvious I'm getting too much vacuum to the egr valve or at least at the wrong time. I will check this BPT out and let you know what happens. Thanks so much for your help in this matter. bracketshark :banghead:

Jrf96
09-05-2009, 12:31 PM
The engine runs good and strong once it gets through the 1200 to 1800 rpm range. The timing is correct (I even bought a new distributor, same results with both) I'm guessing your in statement "The hose between the EGR valve and the transducer could be restricted or the BPT is not sensing any exhaust pressure possibly causing your engine to receive too much EGR flow. " the second posibility is most likely my problem. Its kind of obvious I'm getting too much vacuum to the egr valve or at least at the wrong time. I will check this BPT out and let you know what happens. Thanks so much for your help in this matter. bracketshark :banghead:
Hello, I'm new to the forum, hope you can provide me with some help.
I saw this very old thread regarding the missfire on altima 96 and was wondering if you corrected the problem and how.
It happens I now have exactly the same problem and went through the same process.
Any help will be appreciated.
JRF96

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