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Alright team - I'm about at wit's end on this one. I have an 83na that idles kinda rough and bogs down (usually dies - today's the first time I've had it backfire instead) when you give it gas. I put a smoke tester on the vac lines before I started digging into it and the entire bay was pluming. Everything else seems fine afaict. This is what I've done so far:
replaced all of the vacuum lines
checked pressure at rail (~40psi)
checked pressure at each cylinder (all ~149psi)
checked spark and plugs for each cylinder
reconditioned and tested injectors
swapped out 3 different DMEs (1 from F9T) and the relay
goose04 wrote: Fri Oct 22, 2021 5:47 pm
Alright team - I'm about at wit's end on this one. I have an 83na that idles kinda rough and bogs down (usually dies - today's the first time I've had it backfire instead) when you give it gas. I put a smoke tester on the vac lines before I started digging into it and the entire bay was pluming. Everything else seems fine afaict. This is what I've done so far:
replaced all of the vacuum lines
checked pressure at rail (~40psi)
checked pressure at each cylinder (all ~149psi)
checked spark and plugs for each cylinder
reconditioned and tested injectors
swapped out 3 different DMEs (1 from F9T) and the relay
That sounds awful, sorry. Is that squealing sound air getting in where it's not supposed to? Could still be a vacuum leak, especially if something (aos?) is plumbed wrong. What's the vacuum at idle? Any fuel smell in the fuel pressure regulator vacuum line? How did you refurbish the injectors?? How did you try a MAF on an AFM car? How old are the ignition parts--cap, rotor, plugs, wires? And what do the plugs look like? Air filter ok? Have you watched the fuel pressure as you give it gas? Hard to tell just listening to an internet video, but if the ignition is solid, my guess is the AFR is going out of whack when you give it gas -- either from vacuum leak or fuel delivery. You might try pulling one spark plug lead at a time to confirm each cylinder is contributing as much as the others. Try spraying starter fluid into intake as you open throttle. If that helps, then could be fuel delivery issues (38 y.o. Fuel filter?). Did this start out of the blue or get worse over time? Sorry for 20 question, but all clues might help.
Thanks for the reply Tom - no worries about the questions. There are a million different troubleshooting steps for anything, so feel free to ask away. Here's where I'm at with those you just asked:
not sure where the squealing is coming from as it happens fairly rarely; i've assumed belt, but can't rule anything out yet
i'll double-check the aos plumbing by this weekend, but it matches what it was before i swapped hoses (could be part of the problem)
not sure on the vac at idle - i just used a smoke tester. i can snag a pressure gauge and throw it on there
i didn't do a full refurb on the injectors - i replaced the seals and filters then ran cleaner through them
i have an F9T DME with a RT performance chip from that runs MAF instead of AFM
cap, rotor, plugs, and wire are all new - plugs looked fine a few weeks ago, but i can check again
air filter is brand new
just noticed my fuel pressure doesn't change much (if at all) with throttle - will run with relief
i swapped plug wires with the oem ones (had heavier wires on) and that seemed to smooth out the idle a little in the vid
i'll try pulling plugs by the weekend
when i first ran into the issue, i want to say starter fluid helped, but i honestly can't remember. i'll check again
fuel filter+pump are brand new
when i bought it this summer, the squeal was present occasionally on startup, but otherwise sounded fine. had it loaded on a truck and shipped out to me from AZ and drove it off the trailer. the issues started when i swapped the DME and AFM for the F9T DME and AFM, so i swapped them back but the issues stayed. the only other thing i can remember touching is the alternator when i rewired the headlights
goose04 wrote: Tue Oct 26, 2021 12:28 am
.... the issues started when i swapped the DME and AFM for the F9T DME and AFM, so i swapped them back but the issues stayed. the only other thing i can remember touching is the alternator when i rewired the headlights
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You said F9T and AFM -- did you mean FT9 (fTech9 DME and Rouge Tuning MAF chip board)? So, if I'm following, the car ran fine when you got it, with the bone stock DME and chip. Then you installed the FT9 DME with Rogue MAF and chip board, and the car started running like in the video. Then you reinstalled the stock DME and chip that came with the car, but it continued to run poorly?
If so, I'd retrace all steps involved in installing the AFM to make sure all plumbing is hooked up correctly. Also, try the starter fluid again, both in the intake when rev'ing and around the intake plumbing when idling -- if there is a biggish leak, the starter fluid can help flush it out. If I had to guess, you have a biggish vacuum leak somewhere and the motor is going too lean to rev, but that's truly just a guess based on how common that is. I'd also check how much vacuum you have at idle, and check if it is idling faster than normal, both of which can point to leaks. These cars are old too, so just removing everything and reinstalling could have cracked a wire connection or hose somewhere. If it happened right after changing swapping DME's and AFM's, it's most likely something that got disturbed in the process, based on the age-old 'what's the last thing you touched' principle....
(p.s., if you post to youtube and link here, the video will play within the post....)
I had a similar issue, for me it was a combo of clogged fuel system, chaffed harness where it lays on the head, vac leaks, a “new” distributor cap that was warped, and a coil that would fail the secondary winding once it got hot. Only difference is that mine would only start doing it once the car got to open loop tuning “temp”
