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6 port S4 won't run below 3000rpm

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Old 03-17-13, 12:46 AM
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6 port S4 won't run below 3000rpm

I just rebuilt my S4 NA 13B 6 Port engine and I can't get it to start on it's own (at least not yet, battery is charging again). We push started it with my friend's Sentra by popping the clutch at speed in 2nd gear and got it to rev up and kept it around 4000-5000 rpm. Once it dropped below 3000 rpm it wouldn't rev back up and died. To my knowledge I'm getting fuel and spark. The coils are definitely working (my left arm got a good zap), and I rewired my fuel pump to a switch and relay because it wasn't getting power so I now have a fuel cut off switch in case of flooding, or at the track. And I don't see any reason why I wouldn't be getting air.

Any help is appreciated
Old 03-17-13, 03:37 PM
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Had the same prob on an 86 I used to own. It would start, hit 3k and die. Couldn't rev it up at all. My prob was a bad ground by the trailing coil. May have been off main relay but it was a two wire plug that was round and white. I had tested it against a ground to the body but then checked it to the ground on the plug and got 0 reading.
Old 03-17-13, 04:36 PM
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I've had an issue before where it would rev and die regardless of what was done, but the issue I'm having is if I drop below 3000 rpm it dies, like a huge vacuum leak, and even giving throttle doesn't bring it back up. I'll check through the grounds again.

I did a vacuum spider delete and rerouted everything per the diagram and even have both check valves in as they would be in stock conditions. I've got the BAC and ACV and EGR block off plates in as well, and didn't have any issues before when I ran this setup. A/C, PS, and the Air Pump have all been removed as well.
Old 03-17-13, 04:50 PM
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And are you speaking of the ground just below the trailing coil with the capacitor R17G

Last edited by Shadowscreed; 03-17-13 at 05:08 PM.
Old 03-17-13, 05:24 PM
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AFM connected? Whenever this happens to me it's either AFM or BAC vacuum connection.. Also, put the BAC back on No reason to remove it.
Old 03-17-13, 05:50 PM
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bad AFM
large vacuum leak
faulty TPS
Old 03-17-13, 06:23 PM
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I deleted the emissions and bac. Worse idea I ever had was removing the BAC...put it back in. It only helps. Also, I hooked the orange solenoid up to the fuel pressure regulator.
Old 03-17-13, 06:25 PM
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Originally Posted by Shadowscreed
And are you speaking of the ground just below the trailing coil with the capacitor R17G
Not the ground to 'nowhere' on the back side of the shock tower. Pretty sure it was one of the main relay connectors.
Old 03-17-13, 06:40 PM
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Should be a link to pic if main relay. On cell phone might not work.

https://www.google.com/search?q=rx7+...nvtgvvsKJVM%3A
Old 03-18-13, 12:12 AM
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Originally Posted by RotaryEvolution
bad AFM
large vacuum leak
faulty TPS
Gonna try one of my spare TPS's, I checked all my vacuums and none were leaking and this is the same setup I ran before and it worked on my other GXL. And it worked a month ago before I had to pull it back apart to replace crappy aftermarket coolant seals. Only difference last time was that it had the vacuum spider in and I did the delete because everything fits better now.

Also to Derek, I ohm tested my AFM just in case when trying to figure out why my fuel pymp wasn't getting power, it tested fine.

And in case this may affect anything, this had an 86 harnes in it and is an 88 GXL like the other one I own, I swapped my 88 harness into it and am using the same N327 that was in it before, just swapped the engine harness to run my saturated injectors because I don't have any peak & hold injectors.
Thanks for bearing through this with me and all the help so far guys
Old 03-18-13, 12:31 AM
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Originally Posted by jharris2188
Should be a link to pic if main relay. On cell phone might not work.

https://www.google.com/search?q=rx7+...nvtgvvsKJVM%3A
The link worked fine and I thought if the main relay failed that nothing would work? I've changed one before just in case on my last GXL
Old 03-18-13, 02:15 PM
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Will update once I change out the TPS and get a good battery or a jump to crank it over, and I found Aaroncake's proper grounding write up, so I'm gonna go through and check and clean all grounds
Old 03-18-13, 08:54 PM
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Okay, so I cleaned all the body grounds in the engine bay, and also popped open all four of my ECU's, the N327 that was in the car has two blown capacitors ans several blackened solders, my other N327 has one blown capacitor and a couple blackened solders, and my N326 and N338 seem perfectly fine minus the bit of rust on the 338 and the one capacitor that is starting to turn color. So I now have the N326 in with my 88 harness and saturated injectors, I don't believe there should be any issues with the swap but I could be wrong. Icemark himself stated n32x was interchangeable.

And I'm pretty sure my battery isn't outputting the full 640CCA's that it's supposed to and my voltage keeps dropping to 8 volts from 12.6 when I go to crank it over. So I need to get autozone to replace it.
Old 03-18-13, 08:55 PM
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Check my facebook for recent updates to pics. I'll try to post a link or add to photobucket or something but for now my facebook is Curtis *******, yes that is my real name like Fokker lol :P
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