Poor running 88 Ranger

[kswillie]

Not what I would call a classic truck but its getting there. It"s a 88 Ford ranger 2.9 V6, 5 speed, 123K, 4X4. Starts fine and goes to fast idle like it should but once the RPM starts to slow it starts to miss. The warmer it gets the worse it idles. It accelerates great. Stick your foot on the floor it takes off great. Slow down to a stop when it gets to operating temperature and the motor lopes and has a hard not dying. It has a smell not like the rotten egg smell catalytic converters make but more like a gun power smell. The exhaust has two small catalytic converters in line. Plugs have about 5K miles, Fuel filter is new and the air filter is new. Any guess that may point me in the right direction to what is wrong? Thanks

 

[ericlb]

are you sure the exhaust is free flowing? have somebody raise the engine rpm while you put your hand near the end of the pipe and make sure its not restricted, if the converters are not plugged, do you have a autozone store near you? they will hook up their diagnostic tool for free, and see what it says, you may be dealing with a bad sensor ect and it will take the diagnostic tool to find which one has things wacky

 

[ShadetreeRet]

Two thoughts, 1-A vacuum leak will cause a bad idle at times, 2-A bad EGR valve will cause a rough idle. I have an 86 F150 that started idling rough some years ago, asked a friend who was a mechanic, he said, Block off the EGR valve and see if that makes any difference. I cut a piece of aluminum flashing to match the shape of the EGR mount and blocked off the air flow through the EGR valve and it idled just fine. If that is the problem you have two choices, either replace the EGR valve or leave it blocked off. (Don't tell anyone I said so.)

 

[Bob]

Intake gaskets.