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Warm up..Backfire, terrible idle...wont fire over..

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Old 12-04-09, 05:26 PM
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backfiring is usually unburned fuel igniting in the exhaust

if you are backfiring, you're getting fuel but it isn't being ignited or burning completely so i would check ignition...

Just because the plugs look good doesn't mean they are good and they don't have to be wet to be fouled. Put an inductive timing light on each wire. Or pull the plugs and test them off the engine, but grounded while cranking. Other than that you're going to have to ohm out your coils and wires and check for a signal.
Old 12-04-09, 06:06 PM
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Originally Posted by alexdimen
backfiring is usually unburned fuel igniting in the exhaust

if you are backfiring, you're getting fuel but it isn't being ignited or burning completely so i would check ignition...

Just because the plugs look good doesn't mean they are good and they don't have to be wet to be fouled. Put an inductive timing light on each wire. Or pull the plugs and test them off the engine, but grounded while cranking. Other than that you're going to have to ohm out your coils and wires and check for a signal.

alrighty.....That'll be next step after compression and testing plugs.. Thank you Alexdimen!!
Old 12-04-09, 07:41 PM
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You said you checked the plugs and they aren't fouled? I had a rough idle while cold for a while and once or twice while warming up one or two of the plugs fouled and then upon the next start up it flooded.

I'd say start with the basics which is what you seem to be doing. Check for vacuum leaks and the plugs and then move from there.
Old 12-05-09, 04:16 PM
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compression yeilded about 98-99 in the rear and 90-91 in the front. Plugs were way fouled.... i'll be getting new ones......
Old 12-05-09, 06:21 PM
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okay okay... Plugs were bad. They're NGK 6725.... race plugs... Should I just replace these plugs with something else.. et even says on Rx7.com's website that they foul easily on the street. But at the same time....i'm kind of afraid to put anything else in there..
Old 12-05-09, 06:28 PM
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Originally Posted by mannykiller
okay okay... Plugs were bad. They're NGK 6725.... race plugs... Should I just replace these plugs with something else.. et even says on Rx7.com's website that they foul easily on the street. But at the same time....i'm kind of afraid to put anything else in there..
I would glass bead blast them and spray them out with carb cleaner. Gets all the carbon or w/e is fouling them off. Compressed air and/or carb cleaner to get the glass beads off.
Old 12-05-09, 07:37 PM
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hmm never heard of glass bead blasting....how about sand blasting... I have access to one of those. But I'm still gonna get new plugs though.
Old 12-06-09, 12:11 PM
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When someone says sand blast they usually aren't literally using sand. Sand blasting can cause major health problems and usually the media used is glass bead, walnut shells or some kind of oxide. I'd bet that if this is a blasting cabinet that he's using glass beads.

It's your call, but I wouldn't buy $120 worth of spark plugs when I could fix the problem for free. The auto service industry routinely cleans plugs this way. The only trick is properly cleaning the beads off. Compressed air and carb cleaner.
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