QuestionBackfires on acceleration - My van backfires on acceleration. The problem is worse under engine load (like going uphill) and seems to be worse in cold weather, especially if there is a lot of moisture in the air (snowstorm).
Your help in identifying the problem is appreciated.
AnswerHi Harold,
There is one test you can do and one possible maintenance item to consider.
The test is to do a readout of the engine control module's memory to see if it has noticed anything wrong and stored a two-digit fault code number. To readout the memory use your igniton key: "on-off-on-off-on and leave on" doing this in an elapsed time of 5 seconds or less. The check engine light will remain "on" but then begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to verify the counts are correct. Then group the counts in pairs in the order of appearance to form the two-digit fault codes. Then either write back with the results and we can see what to do or check at www.allpar.com/fix/codes.html for a translation of the code numbers. The last code will always be 55 because it means "end of readout".
The possible cause, which won't be revealed by the readout, is that your catalytic converter is plugging up. That restricts the outflow of exhaust gas which then can cause backfiring when climbing and loss of power at highway speeds on the flats. Listen for any sounds of hissing from the exhaust system, and also a good independent exhaust shop (not a chain type operation) can check whether that might be your problem without pushing you to replace your entire exhaust system. But with 177,000 miles on the van, and if you still have the original converter, it could well mean that the honeycomb inside the can has shifted off-axis or plugged up so that exhaust gas cannot pass through it freely.
Let me know what you learn in any case and we can take it from there if it still isn't fixed. Also tell me which engine you have because ther are about 4 different ones that could be in the van.
Roland
