Answer: Your Mass Air Flow Senor is operating below were is should. This condition gives you low power, replace to recheck system.

Question: 1998 Jaguar XK-8 miles: 76,000. Hi, I own a 1998 Jaguar XK-8 it has been a great car for years but now when I take my car out first thing in the morning it runs rough, seems low on power and sometimes backfires. When it warms up it seems ok. I have had all regular service work done at the dealer so I took it in. They charged me $122.00 to tell me they didn't know what was wrong. They scanned the computer but it didn't show anything and they couldn't get the car to duplicate it. What do I do now?

Answer:   This is a difficult problem to detect because the computer can not sense a malfunction, the vehicles computer system thinks everything is ok. In reality what is happening is the electrical component inside the MAF sensor becomes contaminated by air impurities. These containments imbed themselves to the electrical component that senses the air flow causing the sensor to be slightly off, but not enough to trigger the MIL (malfunction indicator lamp). Replace the MAF sensor with a new. NOTE: (Mass Air Flow MAF sensor or Air Intake Sensor AIS, depending on manufacturer. It does the same thing only with different names).

Question: 2002 Ford F-350 mileage: 110,000  Hello! Bob and Ken My truck runs well when cold, but hesitates when warm. I have changed the usual tune-up items: plugs, wires, dist cap, cleaned fuel injectors. I have also changed the coil, and driveline control computer. The Ford dealer has changed the Hall-effect pick-up (breakerless points), and ignition module. There are a few other symptoms, which may pinpoint the problem. The momentary hesitation/power loss (fraction of a second, just enough to take out and re-apply the driveline slack), that is most noticeable between 2300 and 2500 RPM (no-load or heavy-load) is accompanied by the Tachometer needle momentarily losing power, and falling towards zero. The needle generally falls only two to three hundred RPM, before it jumps back to a very slightly reduced indication. The ignition fail code appears when I do the diagnostic tests (with an Ohmmeter). I was thinking that the next place that I would look is, for a loose connection at the Tachometer, or the condenser at the coil. This problem has been with me for about 3 years, and before I dive under the hood again I thought that I would ask for your help. Cheers from Canada!

Answer: About the only thing left that we could think of based on the symptoms you described is the ignition switch, control relay as Fords had problems with them in the past. Another cause could be a poor electrical connection or a faulty ground.

Question: 2004 Mazda RX-8 mileage: 30,000.  I see that other people asking questions have had acceleration/power issues.  I'm not sure if my problem is different.  I bought the car new in Canada, and installed a Rotary Engineering high performance exhaust system.  I relocated to Connecticut and had to install a (new) stock exhaust again to pass emission testing.  I also had intake problems that seemed to be solved with a new shutter coasting valve, valve diaphragm, and fuel filter.  At the same time, I also replaced the clutch.  However, now I have no acceleration.  I can accelerate to redline in second gear without moving faster than 10 mph.  The shop that did the work (on everything except the exhaust) assures me that the clutch is fine, and they sounded like they were grasping at straws when they suggested a compression test, so I declined (besides, I was convinced they were bleeding me financially).  And if that wasn't enough, it is starting to drop oil - about a cup every 6 weeks (I'm not driving it, so it's easy to measure).  So I have 2 questions: 1.  Any ideas as to the problem?  2. Know any good rotary mechanics around or near Fairfield County in Connecticut (other than the ONE Mazda dealership)?

Answer: If the car is only going 10 mph in second gear and the engine rpm is close to redline, the clutch is slipping.

Question: 2004 Ford F-150 mileage: 37,000.  When you press the accelerator slightly, it hesitates, likes spits and sputters, or when doing 40 mph, when you keep your foot on the pedal slightly, it will shake and hesitate.  Does not matter whether it is hot or cold.  If you are in traffic, stop, and go, sometimes causes it to stall.  (When you accelerate then take your foot off the gas quickly).  Any ideas?  Changed fuel filter, plugs, air filter, oil and transmission filter.  Nothing changed.  Your help would be greatly appreciated, I would hate to take it to a dealer and be overcharged without having an idea of what it could be.

Answer:   Your car is equipped with a computer controlled engine management system.  It sounds like you have a vacuum leak or a IAC (idle air control) valve that is slow to respond. 

Question: 2002 Ford Explorer mileage: 68,000. When you apply pressure to the accelerator there is a hesitation, then jerks and then accelerates. I have replaced the spark plugs, plug wires, distributor cap, rotor button and fuel filter. Any ideas?

Answer: If the oxygen sensors have not been recently replaced, a new one should be installed. Also, perform a fuel pump pressure test. Clean fuel injection system including throttle bore, idle speed control motor and passages. If the problem still exists, scan the computer for trouble codes.

Question: 2003 Honda Accord mileage: 56,000. When the engine warms up to normal operating temperature, it will hesitate or surge when the throttle is depressed. It will do this when it is in drive or at idle. You can make the engine really stumble by moving the accelerator on the engine at the throttle body. No readable error codes in the computer at this time. When this happened before, the dealer replaced the mass airflow sensor, replaced the computer chip with an updated version and said the injectors were dirty, so they added some high strength cleaner to the gas. The hesitation stopped after that, but now it is back again. Any suggestions besides taking the car back to them. I have checked all the obvious things.

Answer: If a major tune-up has not been done recently, this could be the cause of your problem. Replace the spark plugs, plug wires, fuel filter and air filter, etc. Also, replace the oxygen sensor. In addition, service the fuel injection system. Clean the carbon deposits from the throttle bore and idle passages.

Question: 2002 Jeep Grand Cherokee mileage: 78,000. My Jeep Grand Cherokee was running great until a few months ago. Now when you are accelerating slowing from a dead stop the engine hesitates until you get up to 30 to 35 mph. Then it begins to accelerate smoothly. I have changed the distributor cap and rotor, the spark plugs, had the injectors cleaned all with no help. The fuel filter was changed; it helped for a few minutes and started doing the same thing again. Is there anything else I can do before I take it in to a shop? The engine only hesitates and surges at low speeds but it seems to be getting worse. Now if you accelerate very hard you do not notice it, but if you are accelerating normally, it is bad. Thank you for any help you can send my way..........

Answer: Lets perform a fuel pressure test under load, you will find that the fuel pump is letting you down when you need it most. Replace fuel pump to recheck system.

Question: 2000 Honda Accord mileage: 99,000. The problem is that when I accelerate with the pedal about One quarter on the way down to full throttle it will start to hesitate. Now this hesitation is like one of the cylinders is not firing. Which could be possibly true. But this does not happen all of the time. Which is becoming irritating. Sometimes it could do it when you startup and then for a while it wont do it. I have replaced the spark plus and wires. Have checked the fuel injectors with an ohm meter and they checked out o.k. Because all of them have the same reading. This is the weirdest thing that my dad has come a crossed too. He has been a mechanic for about twenty years. I have heard that it could be an EGR Valve problem, but I think I checked it out right and IT was fine. Another thing we checked was distributor cap and the rotor. Is there a temp gauge that could be bad? I don't know what else this could be. If you could be of any help, it would be great. Thank You

Answer: Your problem sounds like a faulty ignition distributor.