Main IndexAuto Repair Home Search Posts SEARCH
POSTS
Who's Online WHO'S
ONLINE
Log in LOG
IN






Backfire through intake when cold


Search for (search options)
 



hutchhash
New User

Jan 5, 2009, 4:10 AM

Post #1 of 2 (2014 views)
Backfire through intake when cold Sign In

1999 Jeep Wrangler 4.0L with 120,000 miles. Never had a tune up until last year (because it was running rough). Replaced all the ignition stuff (plugs, cap, rotor, wires). Runs much better now, but backfires through the intakake only when cold and only when accelerating. I assume it is a fuel mixture problem probably not related to the engine control chip. I'm thinking O2 sensor(s). Thoughts???


Loren Champlain Sr
Veteran / Moderator
Loren Champlain Sr profile image

Jan 5, 2009, 4:58 PM

Post #2 of 2 (2005 views)
Re: Backfire through intake when cold Sign In

Hutch; You are more than likely correct, that it is a fuel related issue. Backfiring, up through the intake, is 99% of the time due to a lean condition. The O2 sensors don't come into play on cold start up. Check the coolant temp sensor as it may not be telling the PCM that the engine is cold. Sometimes, it's just a poor connection at the sensor. Also note that a cold engine requires more fuel than a warm one. It could be due to partially plugged injectors..If you haven't had the injectors cleaned in the past 40K, I'd recommend you have that done, also.
Loren
SW Washington






 
 
 






Search for (options) Privacy Sitemap