Question-------------------------
Followup To
Question -
Hi, I have a 1993 Plymouth Grand Voyager. 3.3l Recently my van has started making popping noises under various parts of the body when i accelerate. Before the popping begins it starts to shake. It usually occurs around 45 and 55 mph. Since it began the popping noises have gotten louder. Th van was sitting for about 2 years, we got it running again by changing fuel pump. When it started up again it would shake while it accelerated as well, but mysteriously the problem went away. The mechanic who repaired the fuel pump truned out to be a crook, and we ended up correcting some of his mistakes when installing it. I'm thinking that this may be a fuel problem, or somewhere I heard that it may be the spark plugs? Any help would be much appreciated.
Answer -
Hi Reggie,
I suspect that there is some sort of engine malfunction that is causing unburned gases due to misfire in the engine to then ignite in the exhaust system and thus the popping sound. So first you need to solve the misfire issue.
Reading out the engine controller memory for fault codes is the first step. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
I have the troubleshooting manual for the 3.3L engines and we can look up the possibilities of what is wrong based upon what fault codes you show. There is also an essay on fault codes at the site:
http://www.allpar.com/fix/codes.html
which gives the meaning of the code numbers. But then you need to get specific info for what exactly might be the diagnostic tests or parts to replace to complete the repair. Let me know the codes and I can give you some direction.
Then after the engine runs better you can evaluate whether there are any leaks in the exhaust system that need attention.
Roland
Roland, I'm sorry I got some numbers wrong on the post before this one. the correct numbers are, (12-32-21-15-47-55). I apologize. Thanks again
AnswerHi Reggie,
12-the battery was disconnected in the past 50-100 key on-off cycles...nothing to worry about unless you actually didn't disconnect it which would suggest there is a loose connection to the battery or the powertrain controller
32-egr not responding properly. I would suspect that the exhaust gas recirculation valve is stuck open or shut or ajar. It is located right below the throttle body and the valve and its stem move horizontally, in and out. Look for a pipe coming from the rear exhaust manifold around to the air intake to the manifold area and you'll see it. The stem has a slot in it (this stem is inside a "saddle" that separates the valve body from the round vacuum actuator). Lever the slot back and forth to free it up and make sure that it moves easily against a spring tension in one direction. Spray some solvent of the stem where it enters the body of the valve to make sure it moves easily.
21-the oxygen sensor (mounted on the rear exhaust manifold) is not changing its output and unless the wires are bad it means the sensor itself needs to be replaced.
15-speed sensor for the trans output is not producing a signal to the engine controller (the speedo should not be working well if this were the case, and also the trans would not shift very appropriately). That sensor is on the side of the trans that faces the front of the car, at the extreme driver's end of the trans just to the right of the vertical gear shift post. These wear out and are easy to replace if you have those symptoms, but inspect the wires.
47-charging voltage is low; either the alternator is weak or the voltage regulator function of the engine controller or the control wire to the field of the alternator is open. You would expect a lower than 13.75V on the battery when the engine is running and the battery would run down.
So those are the probablilities. The egr and O2 sensor are probably causing the backfiring, but things will go better if you also deal with the sensor and the alternator circuit.
Roland
P.S. Those numbers should be read out in numerical order, so give it one more reading to be certain.
