88MJofficer Posted April 16, 2008 Share Posted April 16, 2008 So my 88 backfires (more when its cold) inbetween shifting gears and when I left off the throttle. I just changed the plugs, but the wires, cap and rotor looked fine. What do I need to adjust or replace? Link to comment Share on other sites More sharing options...
Eagle Posted April 17, 2008 Share Posted April 17, 2008 How many miles are on the oxygen sensor? If it's old, it doesn't react as fast as it should to throttle changes, so if you're running rich to accelerate and then take your foot off the peddle, it still sends a rich mix to the engine but the engine doesn't need it -- so it dumps some unbruned gas down the exhaust and it backfires when that hits the catalytic converter. I'll bet your gas mileage is sub-standard, too. Replacing that O2 sensor should fix the backfire and improve the gas mileage. Link to comment Share on other sites More sharing options...
88MJofficer Posted April 17, 2008 Author Share Posted April 17, 2008 I just replaced the o2 censor about two or three weeks ago. It has better throttle response and got my mpg back up to around 17 so thats not it. Link to comment Share on other sites More sharing options...
jeepthing07 Posted April 17, 2008 Share Posted April 17, 2008 I herd somewhere a exhaust leak can cause it. mine backfires between gears if i get on it really hard. it leaks between the header and down pipe. just a thought... Link to comment Share on other sites More sharing options...
Wildman Posted April 17, 2008 Share Posted April 17, 2008 Which Plugs did you install??? You might want to re-view this- http://comancheclub.com/forums/viewtopi ... park+plugs Also change the distributor cap and rotor, and install new wires. You could have a 'mis-fire' in one cylinder causing the un-burned fuel going into the exhaust, causing the back fire. You could have a plug wire not tight on the plug. Good chance your only running on 5 cylinders. Link to comment Share on other sites More sharing options...
james750 Posted April 17, 2008 Share Posted April 17, 2008 Mine did that when i had a bad cat... u might want to check that. Link to comment Share on other sites More sharing options...
ifixit8 Posted April 18, 2008 Share Posted April 18, 2008 I don't mean to hijack, but my mj does the same thing. I figured it was because of the fact that I don't have a cat. I have new wires, cap, and rotor. my plugs were new untill i blew a head gasket. since that I haven't replaced them though. so maybe my issue could just be plugs? Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 18, 2008 Share Posted April 18, 2008 I don't mean to hijack, but my mj does the same thing. I figured it was because of the fact that I don't have a cat. I have new wires, cap, and rotor. my plugs were new untill i blew a head gasket. since that I haven't replaced them though. so maybe my issue could just be plugs? It's definitely not your cat or lack thereof. Below is the "cat" I've been running for years. There was a similar problem a member of the strokers forum was having with his 96 XJ. His problem turned out to be a bad fuel pressure regulator. Image Not Found Link to comment Share on other sites More sharing options...
88MJofficer Posted April 18, 2008 Author Share Posted April 18, 2008 I replaced crappy Bosch plugs that the previous owner had in there with just stock Champions. I heard they are the best to run and thats when it started backfiring. It does run alot better with better response, but its just a little pop...nothing really extreme I just want it fixed. I don't think the cat is bad, the only thing I can think of is the rotor. I cleaned the contacts on the distributor so I really don't know. Link to comment Share on other sites More sharing options...
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