Hi, thanks in advance for your help. I have a 1998 Ford Escort Sport with around 100000 miles on the engine. It runs fine except that on acceleration at lower rpms the car wants to jump a little. Once the rpms come up it goes away. It sort of seems like it's misfiring, but it's more of a random misfire. I've replaced the plugs and wires. Also, the PCV valve housing and hoses were melted so I replaced them. Could this be a mixture problem and if so, what would be the most likely cause?
Any codes given? Pcm sets the mixture, using all the inputs and designed programs, you can't reset it. If it is indeed misfiring, there should be a code given, any chance the check engine light flashes on and off?
August, 5, 2006 AT 10:54 AM
Nope, no lights or codes. I forgot to mention that the car has a manual transmission. I've also noticed that the car surges while accelerating and while at cruising speeds and rpm's.
August, 5, 2006 AT 12:25 PM
Plenty of issues that could cause surging, most are not diagnosaible by the average driveway mechanic. You sais you replaced the pcv system because it melted? What is that? Make sure it is hooked up correctly, check all electrical, vacuum, any connection you can see. Evap system could be causing issue also. On some of these cars, if you refuel while the cart is running, you can damage the evap system by drawing liquid into the system, it's rare though, but still is a concern.
August, 5, 2006 AT 3:11 PM
PCV - " Positive Crankcase Ventilation" It's a tube that runs from the crankcase up into a valve and into the intake. Sometimes they go from the valve cover to the intake. The original one was melted and since it runs into the intake it caused a vaccum leak. It is hooked up correctly. I Did not know that about re-fueling, I'll be sure to shut it down. I'll check all the evap stuff too.
August, 7, 2006 AT 10:38 AM
Ok, this weekend I checked all the vaccum hoses and couldn't find any problems anywhere. I took a water bottle and sprayed all the vaccum connections and could not hear any difference in idle speed. I also checked as much of the evap system as I could, I don't really know or understand a lot of it so I didn't really know what to look for other than loose hoses, no visible problems I could see. I also checked the air filter, it's good. What about the fuel filter? Got any other ideas?
August, 8, 2006 AT 4:59 PM
August, 8, 2006 AT 5:47 PM
Ford has had a problem with the Mass air flow sensors becoming dirty on these models that can cause the symptoms you describe. However, just by symptons I am not going to recommend you replacing a $150+ part.
I have heard of people having success by cleaning these sensors, but one mistake and you will have to buy a new one whether it was the problem or not.
If you decide to try and clean the sensor, you will want to use a electrical cleaning spray. It must be quick drying and non-residue. You do not want to blast this sensor. There will be 2 very tiny wires in the air stream of your intake. You only want to lightly spray these wires only. If you get the spray too close, it can break these wires and you are replacing the sensor. I would try and lightly spray these wires to try and dissolve the build up on them. The build up will be small, and the cleaning will be small also. Allow plenty of time for the chemicals to evaporate before attempting to start the car.
Usually you will get a too lean code latched in your computer, but maybe it hasnt gotten to a point inwhich the computer has picked up the fault.
Typically when I hear complaints such as yours, I think plug wire, or something in the ignitions system breaking down under a load. Another option you have is to buy one coil pack. Replace one of your coil packs and drive it. If not improvement, install the removed coil pack in another position. Continue until all coil packs have been tested. If after rotating them all thru the new coil pack, and the problem is not fixed, the only remaining ignition components are the PCM and the crank sensor. Both of which usually cause the car to just die and not start.
Good luck and if you dont have success, then you may have to take it to a mechanic and have them test it out on a diagnostic machine.
August, 8, 2006 AT 10:48 PM
Cool, thanks for your help! The electrical cleaner you talk about, would this be the same cleaner used to clean potentiometers and the like? Eg scratchy volume controls etc. BTW-already replaced plugs and wires.
Also, this thought came to me. Could it be a clogged catalytic converter?
August, 25, 2006 AT 5:13 PM
Update: Hi, here's what I've done since my last post.
Changed the coil. Did not help.
Cleaned the MAF. Did not help.
Double checked vaccum hoses, replaced a couple that were questionable. Did not help.
Looked everywhere for loose wiring. None found.
I am very puzzled as to what this could be. When accelerating, the car will push forward normally, and then stutter and then pick back up. It does this all through acceleration. It's not rythmic, I would say it's more variable. When you back off the accelerator and hold your speed/rpms it runs smooth. It sort of reminds me of back in the carberator days, when you'd have a clogged carb circuit and you'd push the pedal and the car would push forward on the fuel from the accelerator pump and would then fall on it's face as if it was running out of fuel. HELP!
August, 26, 2006 AT 12:41 PM
Well, have you had your injectors checked? I would turn to the fuel side and check the fuel pressure and injectors for proper operation.