rapid fire plugs?
Thread Starter
Intermediate
Joined: Oct 2014
Posts: 33
Likes: 0
rapid fire plugs?
Ok so I just installed new plugs in my 85. I used ac Delco rapid fire gap at .035 and now it backfires through the intake when warming up if you pat the gas. Anyone have any idea what may be going on.
Melting Slicks
Joined: Mar 2001
Posts: 2,174
Likes: 56
From: Clarence N.Y.
If it didn't have that issue before the plug change,wonder if
a ignition wire became crossed or a plug gap got closed up
when it was installed. Both have been know to happen,just
a thought.
Jimmy
a ignition wire became crossed or a plug gap got closed up
when it was installed. Both have been know to happen,just
a thought.
Jimmy
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
Plugs shouldn't do that unless you moved the distributor or something while you were there. Only other thing I can think of is you broke a wire or something. When I took my MAP sensor off, it ran like crap.
Drifting
Joined: May 2007
Posts: 1,552
Likes: 324
From: Mid Ohio
You might check for a vacuum leak. Maybe a hose got bumped and cracked or came off. Sometimes this can be a real pain to track down as the crack can be on the unseen side. And.. an 85 is past due for vacuum hose replacement too. 
Thread Starter
Intermediate
Joined: Oct 2014
Posts: 33
Likes: 0
Ok so it has gotten a lot worse now at wide open throttle it stumbles really bad and will not clear out I exchanged the plug for Denso iridium parts store said the rapid fires were junk and theses were better. Anyways still no luck I have been reading a lot on here and think it may be the fuel pressure regulator the car has been sitting sine 2011 is it possible the diaphragm has dried out and cracked any help is greatly appreciated as I am Incredibly lost and aggravated now
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Verdad Gallardo
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
What specific plug did you get? The '85 should use Rapid Fire #1 and the gap should be .045. There are a number of Rapid Fire plugs (by number) and it's important to select the correct plug.
As far as the chain store parts guy and his "opinion", he's just trying to up-sell another plug and most likely has absolutely no idea what will be best in a specific engine. What Denso plug did he sell you?
If you think the fuel pressure regulator is bad, then get a fuel pressure gauge and attach it to the Schrader valve on the fule rail and let us know what pressures you see. Go to the local AutoZone and they will have "free rentals". If the line on the gauge is long enough, attach it and tape the gauge to the base of the windshield so you can check the pressure under different driving conditions.
As far as the chain store parts guy and his "opinion", he's just trying to up-sell another plug and most likely has absolutely no idea what will be best in a specific engine. What Denso plug did he sell you?
If you think the fuel pressure regulator is bad, then get a fuel pressure gauge and attach it to the Schrader valve on the fule rail and let us know what pressures you see. Go to the local AutoZone and they will have "free rentals". If the line on the gauge is long enough, attach it and tape the gauge to the base of the windshield so you can check the pressure under different driving conditions.
Thread Starter
Intermediate
Joined: Oct 2014
Posts: 33
Likes: 0
Thanks for all of the help unfortunately I have returned the car to the shop where I bought it n got my money back they think the tank is clogged up they said they would check it out and if they can fix it I can come back in a few days and check it out n get it back thanks again and I will post what happens