Rough Idle / Backfiring through plenum
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Joined: Feb 2002
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From: Huntsville USA
Rough Idle / Backfiring through plenum
1996 Explorer, V-8, 90K miles, Original exhaust, plugs and wires and fuel filter about 20K miles old.
Recently started experiencing very rough idle, backfiring through plenum under acceleration/loading, temp seems to fluctuate 15-20 degrees during normal driving but never gets hot. Flashing check engine light.
Error Code 0402: Excessive exhaust gas recirculation.
Any thoughts? Clogged muffler/converter?
TIA
Patrick
Recently started experiencing very rough idle, backfiring through plenum under acceleration/loading, temp seems to fluctuate 15-20 degrees during normal driving but never gets hot. Flashing check engine light.
Error Code 0402: Excessive exhaust gas recirculation.
Any thoughts? Clogged muffler/converter?
TIA
Patrick
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Joined: Jan 2002
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From: Central Florida, USA
Rough Idle / Backfiring through plenum
That code indicates your EGR valve could be stuck open. You are correct, backfire exits up through the intake afterfire exits through the exhaust. In the pre EFI days incorrect timing was the primary cause of backfire. Now a host of things can cause this including the EGR valve. Sometimes you can whack the valve and free it up. Most of the time you will have to remove and clean it. The sensor is probably working correctly as the light is illuminated and you are getting a constant memory PO402, but make sure the vacuum line to the unit is not clogged or your do not have another vacuum leak. As timing could still be the cause the backfire (but not the PO402 or the light), check the timing with a light (spout disconnected) to be sure nothing there has changed. Reset as necessary.
The above has nothing to do with the temperature. 15°-20° sounds like the thermostat opening and closing around its design temperature. When you say it never gets hot do you mean overheat as in excess of 260°f? Or do you mean the engine nevers gets up to normal operating temperature of 194°f? If it's the former everything is normal. If it's the ladder replace the thermostat.
The above has nothing to do with the temperature. 15°-20° sounds like the thermostat opening and closing around its design temperature. When you say it never gets hot do you mean overheat as in excess of 260°f? Or do you mean the engine nevers gets up to normal operating temperature of 194°f? If it's the former everything is normal. If it's the ladder replace the thermostat.
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Rough Idle / Backfiring through plenum
Is the EGR valve the silver cylindrical unit mounted on the back of the air plenum?
The temp changing is actually occuring while driving down the road. I can watch the gauge fluctuate over a mile or two distance. It just started this when the other things started.
The temp changing is actually occuring while driving down the road. I can watch the gauge fluctuate over a mile or two distance. It just started this when the other things started.
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From: Central Florida, USA
Rough Idle / Backfiring through plenum
You still didn't answer the question about the engine temperature. Give us some numbers or where the needle points on the scale.
The EGR valve will have a gray (silverey) metal top with a plastic electrical connector (brown, I think) and a vacuum line connection (black?) The bottom of the valve is connected to the exhaust manifold and will usually be rusty red/brown and connected to the plenum with two rusty bolts.
The EGR valve will have a gray (silverey) metal top with a plastic electrical connector (brown, I think) and a vacuum line connection (black?) The bottom of the valve is connected to the exhaust manifold and will usually be rusty red/brown and connected to the plenum with two rusty bolts.
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Joined: Jan 2002
Posts: 185
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From: Central Florida, USA
Rough Idle / Backfiring through plenum
Sounds like you need to replace the thermostat. The correct temperature is important and yours is 194°. Use at least a 190° replacement thermostat. That should fix the needle problem and it should settle at about 1/2 travel on the guage. While the hoses are off go ahead and flush the system and replace the coolent. Make sure the heater is full hot during the flush so that gets cleaned out too.
Any news on the EGR?
Any news on the EGR?
