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Old 12-15-2010, 04:02 PM
lneidlinger lneidlinger is offline
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Default 1991 4.0 rough running

I bought a 1991 ford ranger a while back. Its a single cab, short bed, 2wd, A4LD with the 4.0 V6. So far, it has been running great. The exhaust system fell off before I got it, so right now it dumps out about under the passenger seat after the two cats. It's louder than most, but hasn't been too bad. The truck has 181,000 miles on it.

Anyways, I usually park it in the barn to keep it from getting super cold and to keep it out of the elements as the front end is in pretty good condition and I plan on keeping it that way. The bed is another story, but I had to park it outside one day so I could plow the driveway with the tractor. I was afraid we were going to get more snow in the morning so I left my truck outside so I could get the tractor out in the morning in case I needed to. Luckily I didn't, but my truck didn't like being in 10F all night, and the thermostat stuck close. On my way to school that day, it got hot, very hot. Almost into the red, but when I started to speed up and get more air flow over the engine it backed down to about 3/4 the way up the temp gauge. Luckily my commute is less than about 10 minutes. When I went home that day the thermostat unfroze itself and it never got further than about 1/4 the way up the temp gauge, like normal. I still replaced the thermostat and put new coolant in it. We had to jack it up to find the drain valve on the radiator, and when we jacked it up it seemed to flex the frame a little bit as the gap between the right side of the bumper and the headlight grew to about 1-1 1/2". We also had to take off part of the air intake tube that runs right on top of the fan, the flattened part that says "Caution: Fan"

Now, before I drove it into the shop, on the way from Napa to get a new thermostat (after I got out of school, after the overheating incident, after the thermostat unstuck itself), it started, drove, and sounded like it normally does. After we put it down, now it is acting weird. The engine is still as responsive as it was before, but in reverse or drive it shudders at lower speeds and sounds like it either has a huge exhaust leak on one bank, or is not running on all cylinders. The exhaust also smells bad, much different than it did before. When it is cold, the exhaust smells kind of gassy, but when its warmed up it smells almost like hot metal. I made special care to not unplug any electrical or vacuum lines around the thermostat area, and went over all other connections that I could see to make sure nothing else got unplugged. Its almost like we crushed or pinched whats left of the exhaust pipe and now it has a huge amount of back pressure, maybe before the cats so that might account for the different smell and increased noise.

Thanks for reading, appreciate any responses!

Last edited by lneidlinger; 12-15-2010 at 04:11 PM.
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