Misfire Related To Worn Camshaft

I'm having a hard time finding the cause of an intermittent misfire in cylinder one of my 2004 Jeep Laredo with a 4.0-liter engine. The vehicle has 77,102 miles on it. So far, my mechanic has replaced the spark plugs twice. He has swapped the ignition coils, installed new coils, cleaned and replaced the fuel injectors and replaced the crankshaft and cam sensors. He also has cleaned the fuel tank, replaced the fuel filters and checked the fuel pump pressure and volume. None of this work resolved the misfire.

The misfire occurs intermittently. I can be driving along with the engine operating without a fault when suddenly it begins to misfire. As I continue to drive, the misfire disappears and the engine returns to normal. After driving a little further, the misfire comes back and the process repeats.

Can you help?

K.N., Email

I'll do my best. Your technician has done a lot of work and must be just as frustrated as you. Ask your technician to consider a check for vacuum leaks, a loose ground connection in the fuel injection circuit and a check of the valve system. It is possible a valve is sticking. It is also possible a lifter or even the camshaft has a fault.

While it is unusual for a valve lifter or lobes on a camshaft to suffer from excessive wear at 77,000, in the past few years, changes in the chemical recipe of lubricating oil due to environmental concerns has increased camshaft lobe wear that also affects valve lifters. Let us hope something simple such as a loose ground is the cause of the trouble. If the camshaft and lifters need replacement, repair cost will take a big chunk out of your budget.

Recently, the transmission in my 1993 Dodge D250 needed an overhaul. The truck has a 6-cylinder diesel engine. Right after the repair, the air conditioner and speedometer quit working.

I took the truck to a local shop to have these problems addressed. The mechanic found that his diagnostic tool does not communicate with the engine computer. He replaced the computer but the problems continued. He wants to keep the truck for a few days to determine the cause of the trouble.

Do you have any suggestions??

D.L., Email

The fact that your troubles began right after the transmission repair is suspicious. Perhaps in the process of the repair, wiring became loose or damaged. Ask your technician to check the wiring near the transmission. He may find a pinched or damaged wire that is causing problems with the engine control module. If he finds a pinched wire or other damage, consider taking the vehicle back to the shop that repaired the transmission to have the repair performed at no charge.

I'm in the process of installing new brakes on my daughter's 1998 Chevrolet Cavalier. I found a crack in the hose at the right rear wheel so I replaced it along with the wheel cylinders at both rear wheels.

After installing the new parts, I went to bleed the system but no fluid came out. Several times, I have tried without success. I even had a mechanic friend help but he could not get fluid and air to bleed from the rear lines. Fluid does bleed from the front brakes so I am at a loss. What should I do next?

H.L., Email

Buy your daughter a new car and you will be a hero. All kidding aside, do not despair. You will fix this problem and be a hero without the cost of a new car purchase. It is possible the brake hydraulic system has a proportioning valve that regulates fluid to the rear brakes. If so, it may have a fault and needs replacement.

If the system does not have a proportioning valve, more than likely the trouble is caused by a fault in the brake master cylinder. To check the master cylinder crack open the brake lines on the master to the rear brakes and you might find that the master cylinder is not pumping fluid pressure to the rear brakes. If so, replacement should cure the trouble.

The 1.6-liter engine in my 2002 Mini Cooper overheats. The first time it overheated, I was stopped at a light when I heard a bang under the hood and saw smoke. It almost scared me to death! I shut off the engine and found that the coolant tank had exploded and antifreeze was everywhere. I had the car towed to a shop where a mechanic replaced the cylinder headgasket, thermostat and coolant tank. After this, the car was fine until it overheated again about 1,400 miles later.

Now when sitting at a light or stuck in traffic the temperature gauge creeps up to the hot side. I don't think it overheats but it gets very close. As soon as I start moving, the temperature goes down to normal.

I checked the level in the tank and it is full. Also, the radiator fan is working. What could be wrong?

E.S., Email

You have spent a ton of money. Consider returning to the repair shop that performed repairs to the cylinder head. There likely is a malfunction of the cooling system fans. The circuit might have a fault. The fans may not be functioning as designed and need replacement or perhaps a sensor is not performing normally. The encountered trouble might be the root cause of the headgasket failure. Do not wait. You do not want the engine to suffer severe damage from overheating.

The temperature gauge in my 2000 Nissan Frontier quit working. The engine does not overheat and it runs fine. In addition, the cooling system is full so I don't think there are any problems with the engine. Is the gauge bad?

L.O., Email

It is possible that the temperature sensor has a fault. Perhaps the temperature gauge circuit has a loose or corroded connection. It is possible that the circuit between the engine control module and gauge has a fault. Maybe the there is a fault in the instrument cluster.

If you are an avid do-it- yourselfer and have test equipment to check the circuits you might find the fault. You could replace parts until the trouble is repaired, but this can be expensive. Consider asking a qualified technician to troubleshoot the circuit. More than likely, he will find that the gauge has a fault. If this turns out to be true, it is likely the instrument cluster needs replacement.

Intermittently, when slowing to a normal stop the antilock brakes in my 2003 Buick Rendezvous activate. It does not occur all the time, but when it does, the brake pedal pulsates and it feels like the car will not stop. The trouble is very nerve-racking.

I spoke to mechanics at a couple of repair shops that said it would be difficult to find the trouble if it does not occur while the car is at their shop. What do you suggest I do? D.R., email

K.E., E-mail

It is time for a new car. Of course, I am kidding. The problem may not be as difficult to determine as suggested. The antilock brake system can be checked for diagnostic trouble codes that should point a technician in the direction of a lasting repair.

From your description of the trouble, it is more than likely that a wheel sensor or the circuit to a wheel sensor has a fault. Repair depends upon what a technician finds but sometimes cleaning the sensor mount corrects symptoms such as you describe.

Until this is fixed, time stops. Also, increase the interval between you and all objects ahead of you. When the antilock brake system activates, it is common for the stopping distance to increase.