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Smoking Tailpipe: Mazda 2.0L and 2.2LPosted 9/7/1999By Tom Anderson
Smoking from the tailpipe has been a problem with the Mazda 626, MX-6, B2000 and B2200 with FE and F2 engines. These engines have a timing belt driving the camshaft. The problem is not often seen in the chain driven 2.0L engines. The customer's complaint is smoke from the tailpipe after starting a cold engine. This has been a problem since this engine came out on the 1983 Mazda 626. The smoke may be blue or white and it clearly smells like oil. The condition usually happens after exceeding 100,000 miles, but has been experienced with as little as 70,000 miles. The latter can usually be attributed to poor oil and filter maintenance. After the engine has run a few minutes, the smoke usually dissipates. As the engine warms, the oil rings do a better job of sealing. Add a warm catalytic converter cleaning up what gets past, and very little smoke is then seen coming from the tail pipe. The actual amount of oil consumed is usually very low with this problem. The problem is with the oil control rings. Either they become stuck in the groove or, more commonly, the ring is so badly worn that it won't seal well enough to keep the oil off the cylinder wall. If the oil rings are stuck because they are packed with carbon, the owner needs to do a better job of maintenance. In the case of the worn ring, it's still a re-ring job because the oil rings lost the friction battle with the block. The cylinder block has a very high nickel and carbon content, which makes the cylinder walls very hard, so there is little wear on the cylinder. Rarely will you see a ring ridge or any taper to the cylinder. The honing marks may still be visible. In some cases, the oil control rings have been found to be worn so much that the oil control ring spacer/expander has been wearing on the cylinder wall. To repair, clean the ring grooves (a used broken compression ring works great for this), deglaze the cylinders, clean and reassemble. You may want to replace the valve stem seals and do a valve job, if needed. Since the guides for the valves are bronze inserts, there is little wear. Smoking on start-up doesn't always mean valve seals ... in fact, these days it's almost always rings.
Trailer Hitching on Light AccelerationPosted 9/7/1999By Jeff Knowlen
Vehicle: 1992 through 1997 Jeep/Dodge Pickup Trucks Engine: 3.9, 5.2, 5.9 Magnum (MPI) System: Emissions/PCM/Fuel Symptom: Trailer hitching on light acceleration Background: It can be very hard to put your finger on the cause of this condition. The customer complaint may be misfire or bucking at highway speeds or on very light throttle opening. When I first encountered this problem, it felt like an ignition miss but I couldn't see anything unusual on the scope. I checked cylinder balance and fuel pressure - both were OK. I tried adding fuel when the condition occurred, but that didn't help either. Next, I checked to see if the distributor was positioned correctly in the engine. Ignition timing is not adjustable but the distributor can still be rotated as though you were adjusting timing. Ignition timing is triggered from the crank sensor. There is a position sensor inside the distributor too, but it is primarily for synchronizing the sequential fuel injection timing, not ignition timing. This means when ignition takes place the distributor may or may not be in the correct position. If the rotor tip is too far away from the distributor cap terminal when spark occurs, the spark may jump back to the previous distributor cap terminal or may not have enough energy left to properly fire the correct spark plug. The misfire or bucking condition is only felt in this particular driving range because that's the maximum timing advance range. A scan tool will most likely show advance in excess of 30 degrees. This is when the rotor tip is the greatest distance away from the distributor cap terminal. To position the distributor properly, first use the mark on the hall effect sensor plate to line up the rotor at TDC. Then find the V8 mark (or V6 mark if working on a 3.9L V6) on the harmonic balancer and line it up with the zero degree mark on the timing cover. The V8 mark is usually hard to see - it is about 17 degrees after TDC. Clean the area with a wire brush to improve visibility. Now use the switch input of the hall effect pick-up plate to find the correct distributor position: Backprobe the 5-volt reference wire with a DVOM (gray wire on 1992 and 1993; tan/yellow wire on 1994-1997). Rotate the distributor a few degrees back and forth to the point where the 5-volt reference switches to zero volts. In locating the switching point, it is not important if the reference switches from 5 to zero or from zero to 5. Lock the distributor in place with the hold down bolt. Note: It is possible to set sync with a scan tool on all 1994 and later V8 engines.
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Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
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