S4 NA, rough running, slow revving, front plugs fouled
07-24-08, 12:07 AM
#1
S4 NA, rough running, slow revving, front plugs fouled
Ok, so I've been having problems with my S4 N/A since I got it. It idles high (~1200) and shakes around quite a bit at idle. When revved, it revs slowly and takes a long time to come back down to idle (video: http://www.youtube.com/watch?v=A4dE5IsPRV0 ). I only drove it about 30 miles and it was very low on power (I had to basically be at WOT all the time and redline it everywhere). I thought the problem had something to do with the injectors, so I decided to pull them out and send them out to be cleaned. As I was tearing everything down, I noticed wires going to 2 of the injector clips were so brittle they cracked, and all of the clips them selves were damaged too. When I puled off the exhaust manifold, the front exhaust port was a weird white color, like it wasn't running on that rotor at all (the rear port was black).
I got some new injector clips and soldered those on and reassembled everything with the cleaned injectors and all new gaskets, etc.
I finished everything yesterday, and when I started it up, it was doing the same damn thing. I haven't driven it yet (car is on jackstands atm), but the idle is still high and it revs at about the same speed. I pulled the spark plugs (brand new) the front plugs are dark and look like they are fouled, the rears are still shiny. I don't know what the hell is going on, anyone have any ideas? I think it's running on the rear rotor only. anything I can check for?
I got some new injector clips and soldered those on and reassembled everything with the cleaned injectors and all new gaskets, etc.
I finished everything yesterday, and when I started it up, it was doing the same damn thing. I haven't driven it yet (car is on jackstands atm), but the idle is still high and it revs at about the same speed. I pulled the spark plugs (brand new) the front plugs are dark and look like they are fouled, the rears are still shiny. I don't know what the hell is going on, anyone have any ideas? I think it's running on the rear rotor only. anything I can check for?
07-24-08, 12:14 AM
#2
Also, the car is stock except for a catless race pipe. I have removed air pump, ACV and rat's nest. The problem started before removal of rat's nest so I don't think that is a factor. When I put on the ACV block-off plate, I sealed the **** out of it with RTV too, so I don't think it's leaking. I'll get out there with some starter fluid tomorrow and see if there's any vacuum leaks.
I've done a compression test and the bounces are even. I don't remember the exact numbers, but I think they were in the 90's.
I've done a compression test and the bounces are even. I don't remember the exact numbers, but I think they were in the 90's.
Last edited by need RX7; 07-24-08 at 12:24 AM.
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07-25-08, 01:29 PM
#6
OK, both rotors are OK compression-wise, I'm getting spark to all 4 plugs (checked it). I'm thinking my resistor pack is bad. Where can I get another one? I couldn't find one on Mazdatrix, I guess I could find one at a junkyard or something, but I'd like to have a new one.
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07-25-08, 05:48 PM
#8
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if compression is good the motor just needs spark and fuel... should be smooth sailing to get her running well again.
if fuel pressure truly is low it would effect both rotors, not just one?? before replacing pump, maybe check your fuel filter first.
fwiw
if fuel pressure truly is low it would effect both rotors, not just one?? before replacing pump, maybe check your fuel filter first.
fwiw
07-25-08, 05:53 PM
#9
Yeah, I'm pretty sure the resistor pack is the problem, me and a friend tested it with a test light and some of the wires barely lit the bulb in the test light. We also tested the fuel pressure and it was a bit low, so I'm replacing it as well, just for good measure.
Last edited by need RX7; 07-25-08 at 05:59 PM.
03-20-12, 08:35 PM
#11
Whoa, a blast from the past 
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I ended up finding that the wiring to 2 of the 4 injectors was cracked due to age and heat, causing the car to run on one rotor. I soldered on new plugs and it ran the way it should from then on.
EDIT: I reread the thread and see that I claim that the problem still persisted after replacing the injector plugs, but I swear that fixed it. I seem to recall revving it on one rotor after replacing the injector plugs, getting a loud backfire then having it run normal.
So I'd check your wiring first, and if that doesn't help come back here I guess.
. I ended up finding that the wiring to 2 of the 4 injectors was cracked due to age and heat, causing the car to run on one rotor. I soldered on new plugs and it ran the way it should from then on.
EDIT: I reread the thread and see that I claim that the problem still persisted after replacing the injector plugs, but I swear that fixed it. I seem to recall revving it on one rotor after replacing the injector plugs, getting a loud backfire then having it run normal.
So I'd check your wiring first, and if that doesn't help come back here I guess.
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