* * * 94 V6 4x4 Engine bogging * * *

We had a really hard cold snap here in New England last month and when I went to start my truck one morning, it started and ran really rough for a sec until I depressed the accelerator which caused a ton of black smoke to spew out of the exhaust. It ran fine before this one cold morning. Never had any problems with it. I had a tune-up done to it because after the rough start it ran like crap, as if it was misfiring - in this case it was. So the mecahnic replaced the plugs, wires, rotor and cap. Things seem to run normal for a couple of days, however, now after getting progressively worse, the engine acts as if it's strainging. It bogs down when the accelerator is depressed and the temp gauge starts to rise. I can't drive it on the hwy, which I usually use to commute because it just doesn't have the power to maintain a high-speed, so I have to drive the back roads. It also Idols weird. The tachometer jolts up and down a couple RPMs and not so much like a vacuum line is off because I have seen that before. This is much more of a sharp transfer between RPMs. It will idol at 1500 and drastically drop well below and then resume the idol. It does it intermittently, unlike a vacuum line.

I was hoping that before I take it to the garage and spend at least another $400.00 - like the tune-up cost me, that I can get an answer or perhaps an idea of what this maybe and a ballpark figure on the cost.

Any help would be greatly appreciated.

-G

O.K. Here are a couple of suggestions:
- Did your mechanic install OEM plugs, wires, cap, etc? Using non-OEM parts could cause a decrease in performance. Also, check your ignition wires. A loose one may cause the symptoms you are describing.
- Step on your brakes while you are stopped. If the engine idle changes, you have a cracked, broken, or loose vacuum hose.
- It may need a new fuel filter. (I'm not sure where it's located. I haven't had to replace mine yet.)
- It may be a clogged EGR valve. It costs around $100, so cleaning it may be an option. It is located under the air cleaner and is about the size of a Silver Dollar, but 3 times as thick. It has one hose in the top and two in the bottom (If I remember correctly). It is removed by removing two bolts (10mm, I think). Take it off and tap it. If stuff comes out it is dirty. Cleaning it is only a temporary solution, replacing it will fix it.
These are only suggestions. It could be something else. Always try the least expensive option first. If that fixes it, you saved a lot of money. If it doesn't fix it, you're not out that much money.
I hope all goes well!