Misfire/backfire

Tiny
CNGSTEVE
  • MEMBER
  • 1999 DODGE CARAVAN
  • 3.3L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Hello - I experience missing and sometimes "backfire" (like a popping that seems to come from the exhaust) mostly evident on sudden acceleration. My mechanic noted that P0300 code was present and he cleared it. He also found low fuel pressure and replaced fuel pump and filter with no change in the condition. In driving around to isolate the conditions when it occurs, I find that it will almost always miss and pop when I mash the throttle. However, if I accelerate steadily it can get up to 4,000+ rpm without a problem. Idling and low throttle driving is mostly perfectly smooth. Sometimes it will show up pulling away from a stop, but backing off and then slowly rolling on the throttle stops it. When I check for codes now on the odometer I only get 55, which I think is normal. Does these details help to point at a likely cause? - Steve
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Monday, April 18th, 2016 AT 7:57 AM

7 Replies

Tiny
HMAC300
  • EXPERT
If you got a code 300 originally that is a random misfire which can be anything like low fuel pressure, injector plugs/wire etc. The code 55 is no good so have it scanned at auto parts and get back to us. It may be a vacuum leak so check hoses off/cracked/broken etc.
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Monday, April 18th, 2016 AT 9:33 AM
Tiny
CNGSTEVE
  • MEMBER
No codes showing on the scanner. That 55 on the odometer from using the trip/reset buttons seems to be an artifact of the older 2-digit code system that could give the codes by flashing the check engine light. 55 simply signaled the end of the codes (per some Dodge forums). I don't see any problems with the vacuum hoses.
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Monday, April 18th, 2016 AT 7:57 PM
Tiny
HMAC300
  • EXPERT
Check compression and other basic checks like plug wires, coils, and plugs.
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Tuesday, April 19th, 2016 AT 5:59 AM
Tiny
GINA SIMMONDS
  • MEMBER
Going to throw this at ya my 1999 Dodge Grand Caravan started ro miss and pop through the Manifold after getting gas at 7-11 we have replaced so many parts still nothing - thinking there was water in the fuel tank my husband dropped it while waiting for me to go get fuel pump #2 and this is what he found either it is salt or sugar or sand he said it was sweet yes he tasted it hopefully once we put it back together it will be better Never would have guessed it Good Luck
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Sunday, May 28th, 2017 AT 12:57 PM
Tiny
HMAC300
  • EXPERT
What was fuel pressure reading?
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Sunday, May 28th, 2017 AT 4:46 PM
Tiny
GINA SIMMONDS
  • MEMBER
Fuel Pressure was reading 50 should have been 53+ new fuel pump is reading 53 cleaning rhe fuel injectors and adding new fuel
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Sunday, May 28th, 2017 AT 5:22 PM
Tiny
HMAC300
  • EXPERT
W pressure will give a misfire
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Monday, May 29th, 2017 AT 5:25 AM

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