Good evening,

First post here for me and new to me (about two weeks) 1984 GSL-SE with low miles (odometer reads ~28k). Car starts and idles very good at 800 rpm. I have a problem with sputtering at 4,000 rpm and higher when accelerating. I can coax it a little higher if I really ease on the accelerator, but still sputters as it increases. So far i have replaced the following:

1) Both coils as one was testing bad and had melted a little on the top.
2) New NGK BR8EQ-14 plugs
3) Wix metal fuel filter
4) New battery
5) New air filter
6) new plug wires on order
7) distributor cap and points on order

Vehicle has stock intake and appears engine is stock as far as I can tell, aside from the exhaust. There is a custom 3” exhaust with headers (CATs removed). The 6-port vacuum pumps are disconnected with this exhaust. Air pump and emissions rats nest still in tact.
Edit to add: first week seemed to run ok, but sputtering now.

Corrected compression testing reading in the 120-132 range. I have verified the timing and checked the igniters based on guidance in FSM and Haynes manual. Double checked the wiring to the new coils according to FSM/Haynes manual. Checked the air flow meter according to FSM/Haynes and everything checks out.

List of things to do:
1) Verify fuel pressure reads according to FSM.
2) Replace plug wires, dizzy cap and points when parts arrive.
3) Service/check injectors?
4) Likely change exhaust to RB style with 6-port activation tube at some point.

I have posted some photos below and tried a video, but can’t seem to get it uploaded.

Any other recommendations or where to start in the FSM/Haynes for troubleshooting the sputtering?

Thank you,
Brandon

 

You're on the right path when you are thinking its likely a fuel problem. It wouldn't hurt to remove the two injectors and send them out for a cleaning and flow testing. Its not uncommon to have a lower mileage car with gummed up or sticky injectors. I would verify the fuel pressure at the fuel inlet as well. Just make sure you're within normal operating range.

When you're in there you can check the vacuum lines and replace as needed. You will also have to replace the dynamic chamber to intake manifold gasket. Ensure you get an oem gasket and ensure all of the old gasket and material are removed before installing the new gasket.

Having the 5th and 6th ports non functional is actually hurting the engine's performance. The dynamic chamber stores pressure and at higher rpm, the 5th and 6th port actuators open from exhaust backpressure, and this allows the store pressure in the dynamic chamber to be released and forced into the engine. Mazda called it a supercharging effect. Your best best is ro replace the exhaust with a full Racing Beat exhaust, which is specifically designed for the GSL-SE. Or if you like your exhaust, you can install a backpressure tube and a center presilencer.

Next up, at you next oil change, toss that Fram filter. Those have been known to not been the best quality for our cars. The oem Mazda filter is your best bet and it is readily available.

 

Thanks for confirming I am on the right path with investigating the fuel. Will report back on the fuel pressure findings tonight when I get off work. Will take your advice on shipping them off sooner than later and replacing the OEM gasket and vacuum lines.

Tracking the 5&6 ports and lack thereof due to my exhaust. I am not wedded to this exhaust and have previously years ago used RB and found they have high quality stuff. Likely to go that route with a full RB SE exhaust. Any recommendations on either the regular short or street port long versions? In either case I will go full exhaust and have to source the split air pipe from the exhaust to the ports, so any advice on sourcing of fabricating that would be greatly appreciated.

Great info on the Fram… forgot to mention, I do have oil and new OEM filter on hand as well.

thanks for the quick reply and assistance!
Brandon

 

Always get the RB streetport, its well worth the cost.

 

Yes, as the guys have mentioned, you're on the right track. I've been running the RB SE specific exhaust for 25 years and have zero complaints as they operate correctly functioning 6-ports as designed - as long as the port actuators are sealed properly and the gaskets are intact where they meet the Lower Intake Manifold. That said, the RB Presilencer which comes with the full exhaust is setup with very specific design facets to work with stock porting on a SE.

Continue down the route of Injector cleaning, though I don't suspect any problems with fuel or delivery if you're feeding it clean gas. Lots of threads on here about fuel tank decomposition, so maybe look into those. Also, your pictures are helpful to ID several other things you need to fix right away or you'll be chasing symptoms; you have 2 vacuum sensing tubes missing that attach to the intake manifold spider:

These need to connect to the Distributor vacuum advance for Leading and Trailing, and you seem to have them hooked up to the Fuel Pressure Regulator and Bypass Air Control Valve. Once you hook them up properly (*move the vacuum tubes from their current position on the spider to shift them to where they belong), this will likely fix your stutter at 4k RPM, as that's where vacuum advance on Leading would show the biggest differential. Trailing is an economy measure, but gets advanced as well to maintain timing.

Also, in this pic showing the Fusible Links;

Someone has replaced a Fusible Link with a section of wire (*unsure which one...). This may have been to fix a problem circuit, but leaving it there will certainly increase the risk of burningmsomething out downstream. Fusible Links are there to protect circuitry - which will be very hard to find as replacements in this day and age.

As with all things "SE", search on my Username and your question to get more info at your fingertips. I've been around here almost 25yrs now and there's a ton of information available using search that you,can read on your own, in the middle of the night, and not have to wait for replies from us. Also, make use of the "Related Topics" below this thread for good links that might help.

Good luck, and welcome aboard!

 

Sorry for poor pic quality; holding a flashlight, tablet and pushing a camera button is hard. Note blue silicone vacuum hose location. You'll also need to attach the other hoses to where they belong on the spider, as per this FSM diagram;

All of the spider ports and vacuum hoses need to be hooked up or pinched off, or you'll have vacuum leaks and never get it to idle properly. Also, throw away your Haynes manual. For an SE, there are so many significant differences that the FSM is the only way to go. I like the printed version, but the digital version is available for download on Foxed.ca.

 

Thank you for the additional information! Those two vacuum hoses are/were connected. Just didn’t have them connected when I took the photo. I will send a pic later tonight with them connected as they are.

The internals of the dizzy are pretty dirty and could use a cleaning. When I blow lightly on both vacuum ports, I can see the advance, but it only moves a very small amount, like maybe a 1/4”, is that normal? I will double check all the other vacuum lines as well.

Thanks for the intel on the fusible link… I thought that one looked odd. I will look into how to replace/remedy that situation.

Idle is good, just the sputtering at higher RPMs. For what it’s worth, when I changed out the fuel filter, all looked pretty clean under there.

Thanks again for the assistance and additional resources.

 

Got those advance vacuum lines back in place. Fuel pressure at main line reading 56psi so within FSM spec of 49.8-71.1. Time to dig into the injectors.

Also dug into those fusible links…
the makeshift red wire one was on the injector link. I rearranged what was there so the makeshift is down on the headlights and retractor. Green link in injector and brown for computer according to FSM. Thought that might be the sputtering, but nope, still sputtering.


New fusible links added to shopping list.

​​​​​​​

 

Roughly 1/4" of movement inside the Distributor is normal for vacuum advance, and it should be clean and lightly greased to be sure it doesn't hang up in operation.

Tell us some more about the sputtering at 4k RPM. Does it only happen under load, during hard or light acceleration? Does it happen all the time at the same RPM or intermittently? What you described before could be ignition related, but would have also been explained by the lack of vacuum advance on timing - which is why your picture stood out to me.

A new Distributor Cap and Rotor never hurts (*these cars don't have points). Also, the MSD Coils you have installed - are they the model designed to be run in horizontal configurations? Many are only designed to be run vertically and the oil runs out over time, leading to intermittent operation, especially at higher RPM. This is all speculation until we hear more about the symptoms,

 

Sputtering under load, doesn’t seem to happen when in neutral raving rpms up. During hard acceleration mostly, can coax it a bit higher if im lighter on the throttle, but still sputters out before reaching 5k. Normally happens at same RPMs around 3-4k. If I try to push through it and keep the accelerator down, it completely bogs down

Thanks for correction on points… have those parts on order. Broke down to injectors tonight and cleaned them up visibly. Orings and everything look pretty good. Still considering sending off of deep cleaning. Put back together and have a quick run… now seems to start sputtering a little higher RPMs, around 5-5.5k now similar to before under load and hard acceleration.

double checked all vacuum lines and they are connected according to FSM and nothing looks rotten or cracked.

on the ignition timing, I probably need to take a deeper look into that. The marks on the pulley are very hard to read, so I could be off some with that. The dizzy adjustment is sitting about in the center of that means anything. Idle is very smooth along with lower rpms.

The MSD coils are the high vibration coils, which I understand to be ok mounting horizontally.

 

Just a long shot .. maybe bad gas (or old gas)?

Try running the engine with the fuel pump drawing fresh gas from an external container.

 

I wouldn't touch timing until you get the Fuel issues solved, and this reads like fuel VOLUME delivery, likely due to a clogged Fuel Filter. The ones you need to check are the inlet screen filter (coarse) located in the rubber hose going from Tank to Fuel Pump, then the Fuel Filter downstream of the Pump, and lastly it might be worth draining some gas out of the bottom of the tank without disturbing it - as this is the lowest point of the tank, and sediment will come out with the drain removed as its right below the Fuel Pickup screen.

If you find any restrictions the 2 filters, that would explain loss of power at >4k RPM. When my Fuel Filter got clogged recently, the car would accelerate fine up to speed, cutting out occasionally, but would not accelerate past 65mph, no matter what I did (*downshifting made it worse). New Fuel Filter fixed it right up, and inspection of the fine screen filter on the input side of the Fuel Filter showed it was all clogged up with fine rust sediment. I had dumped stored fuel from my steel Eagle cans into the tank a few days prior...

Focus on fuel. Resist the urge to tinker!

 

Thanks for the feedback! Will continue to focus on the fuel… did replace the large metal main one already. Will look at the inlet filter and try to find the other downstream guy as well.

Got the new plug wires, dizzy cap and rotor today. Installed them and same sputtering result. Into the fuel filters I go!

thanks for the advice on draining from the tank to get rid of any sediment.

Will execute those tonight and tomorrow and report back.

Meanwhile, I will resist the urge to tinker, but it sure feels good to back under the hood of one of these. My last time was in the mid-90s on my 1981 12A RX7.

thanks again LongDuck and to the others!

 

not exactly related but you said your car has 28k on it?! it looks like its desert brown like mine, I would love to see some pics and find out where you got it!

 

When you drain fuel from the tank, catch it in a CLEAN white container. This will allow you to see whatever is in there and possibly determine what needs to be done. Reply back with pics,

 

Will do, won’t get to it until tomorrow.

 

I purchased it about two weeks ago, I am third owner. Original owner had it in New York from 1984 to 2021 accumulating about 27k miles where the second owner found it as a “barn find” and took it to Forida. Second owner apparently put a coat of factory paint and cleaned it up a bit and used it for shows mostly trailering it around. I don’t have any written docs other than carfax that aligns with this. It’s in very good shape with little rust and paint is decent, but not show quality by any means. Engine bay needs some detailing and cleaning, but compression is good. All stock except a custom 3” exhaust, which I will be replacing with RB. Interior is all original (carpet, dash, leather seats, etc) Few loose ends to tie up, but mostly everything is working properly.

 

Oh cool!! I saw this one on eBay I was tempted to put in a bid... it looked really nice and still does! any plans for it? a nice example for sure!

 

Drained some fuel into a container and posted pictures (it’s a 5 gallon bucket for size reference). Definitely some small bits of sediment hanging out in there. Is this something I can get cleared out in the filters and frequent changing or will it require draining, dropping, cleaning and resealing the tank?

Digging into the in line filters now to see how they look.

 

First cone inline filter at the fuel pump had a turd in it! Seems like it was dirt/dust compacted, nothing like metal/rust shavings.

 

Test drive was a success! RPMs ran smooth from idle all the way to redline buzzer. I will still keep an eye on the bits I got from the tank and consider dropping and cleaning the tank when it gets low.

 

FIXED! Also, those wheels get the "chef's kiss" from me. I would love to have those on my SE. 😎 Are they from a manufacturer that's still making them? Spacers? I gotta know...

Thanks for the pics and post back as you get further into the ownership experience. Be aware that EVERYTHING inside that interior is brittle. Be very careful when removing plastic parts, as they'll typically come off in pieces and replacements are NLA. Hope to see you around more on the boards,

 

The wheels don’t have and good markings except JWL and VIA on the fronts.

I tried looking them up and came up with some close matches. Circuit performance CP21 and Alzor 881 with the later being a much closer match. No spacers on them. I need to get out and take some measurements, but the tire sizes on them now are 215/40ZR16 in the rears and 205/40R16 in the front. Tires have good tread, no visible rotting, and installed in December last year, but are approaching 10 years old according to the date on tire. Researching new tires now….

Thanks for the additional tips on the interior. Definitely be posting up on the progress and questions.

Hijacking my own thread, but you don’t happen to have pictures of the 5/6 port split air pipe connections? I am going to get the RB exhaust with the SE connections for it, but have to find the pipe or come up with some way to connect it. Best I can see in diagrams is it is called a split air pipe and connects to the rubber hose at the passengers side near the port actuators and there is some type of one way valve in that line.