grotto107

1984 GSLSE .Purchased in Feb. 2019. Ran perfectly until a month ago. I did adjust idling circuit in March to get it to idle when cold. 179,000 miles Daily driver..Stock other than shown below:

RB Exhaust system with presilencer (may be 2 of them, I don't remember) . No cats.
Air pump removed
Ford 2-speed radiator fan with Volvo 2-stage fan relay block and VW 2 stage thermoswitch (Why didn't prev owner just buy another Mazda clutch fan?)
100 amp alternator probably a GM

Starts finely and idles properly at 850 rpm.
When driving will stutter and surge at 2500-3000 rpm in all gears. Will also miss at 3000 rpms or so when reved and sitting still. Doesn't seem to be temperature related. Does it cold or when temp gauge is just above first mark(which is as high as it ever goes with this fan set-up.). Feels like someone cut off the fuel. If you let it fall to 2000-2500 rpms, it will run finely with no skips. After driving it 20 minutes or so, I can finally coax the throttle above 3000 rpms and it runs well all the way up to 8 grand except it will miss at 5500 rpm in all gears. Seems to be almost fixed until I start it the next day. The temp gauge is no higher when it runs well than it is when it is missing and surging. Voltage gauge is at about 1 o'clock and doesn't move when the car breaks up.

I thought it was a fuel issue, then an ignition issue, and now I don't know which it is. Here's what I have done , which has been no help whatsoever.
Jacked up rear of car to check fuel system. Fuel flows freely from gas tank.
Fuel filter (Wix) is about a month old and you can blow freely through it.
The little screen in the fuel pump intake line is clear.

Both ignitors test good
Tps is adjusted properly
Air cleaner is clean
new set of NGK plug wires
New NGK BR8EQ-14 plugs
Cleaned all coil connections
Both coils show 1.2 ohms at terminals
Both coils have a good ground
Distributor cap looks good inside and out. I did plug that vent hole in the dizzy because I lost the rubber vent plug and would get missfires from moisture when rinsing under the hood.
Rotor button shows a little wear but not much.

Where do I go from here?
Thanks

GSLSEforme

Read thru your post. Couple questions:
What do you mean by the coils have a good ground,nether terminal should be grounded...original wiring? Did you test secondary side of coil?Just as important as primary side reading.
Can you outline how igniters were tested? Do they have thermal paste on mounting surface?
Can you describe how you adjusted TPS?How did you adjust idle speed(800 rpm is spec),using idle air bypass screw?
You say voltmeter in car is at 1:00..can you put a voltmeter on battery terminal while car is running and get an exact reading?
Your statement about plugging the vent in dist cap from having water get in there and causing misfires is a clue. The vent is there for a reason. The misfires caused by water inside cap could be the source of your driveability issue. Depending on how long it was run like this and it doesn't take long...
In this case misfires are caused by condensation creating secondary paths for voltage to jump to another terminal inside cap,and/or to ground. I suppose you dried out cap somehow. What can happen is where that voltage was jumping around inside cap creates little carbon tracks that look like jagged lines up and down inside of cap and between adjacent terminals and coil terminals,like someone drew them there with a pencil. There's a term for this known as carbon tracking,not just a rotary thing,any engine with cap and rotor ignition system is susceptible to this.
You can have voltage bled off by a carbon track feeding a trailing plug from a leading plug firing event or the other way around or have voltage bled off to ground to pickup coil shield or distributor housing where the plug fires but not as strong as carbon track sapped a percentage of spark energy away.
They are not immediately obvious,need a very bright light to see them,if you don't know what you're looking for you may not see them. Why it idles fine is because it takes very little spark energy to fire a plug at low rpm under no load compared to what it takes accelerating the engine making power. If you can duplicate this condition while car is sitting still,hook up a timing light and bring rpms up to where misfires occur and watch timing mark to see if timing seems to flutter at same time as misfire,check both leading and trailing.

Have you actually checked base timing,leading and trailing,centrifugal advance and vacuum advance? These last two devices can further aggravate a driveability complaint if not operating correctly.
Replace the cap and rotor-did not see this in your list of replaced parts. Don't skimp on quality. While they're available aftermarket,i use aftermarket parts in some places on car,but this is not one of them. Do this and post back results good or bad,it will help future readers of your thread.This is not wasted money,it is maintenance.
I can give you more specific things to check if necessary. You will have established a baseline of known good parts that you know aren't contributing to the complaint and can be ruled out to focus elsewhere.

P.S.not a fan of washing/rinsing engines in vehicles,garden hose or pressure washer. It has a way of getting moisture where it doesn't belong. The majority of connectors on the car have seals to keep moisture out-not water under pressure. If you HAVE to wash down an engine compartment,follow up by drying with air at relatively low pressure for same reason,take distributor cap off and blow dry,before you start the car,keeping a finger on carbon rotor button so it doesn't get blown out accidentally.A slightly dusty/dirty engine is a happy engine.

grotto107

Thanks for your reply. I was hoping that you would see my post.I'll give you some quick answers now and then do some more inspection on the car.

1 .I've read posts here on the board saying that the coils are grounded to the chassis or fender through the bracket that holds the coils touching the fender. Read that rust between the bracket and fender can break the ground and cause ignition problems. I checked continuity between the outside coil body and a ground (master cylinder) and both coils checked good.

2. I checked the coil resistance (both coils) between the two terminals on either side of the ignition coil wire hole. The FSM said it should be 1.35 ohms plus or minus 10%.. Minus 10% is 1.215. I'm a little low at 1.2%. The FSM didn't show any more tests. How do I check the primary and secondary sides of the coil?

3. All wiring is original except where a previous owner rigged up that fancy cooling fan. None of wiring has been changed since I bought the car, and it ran great for 6 months.

4. I checked the igniters with a harness and 12v light that I made from the archives here on the board. I think it was designed by Ray Green(?). I got 3 used ignitors with the car and tested them before I tested the ones on the car. Two were good and one was bad, so I assume that my tester works. Both of the ignitors on my car tested good .My ignitors had no thermal paste on them. I put a light coat of thermal paste on them before I reinstalled them.

5. I adjusted the tps with 2 test lights per the FAQ section here."Solving gslse idle problems" by David Lane. Two test light leads(one from each test light) to the "mouth" of the green connector and one pointed end of each tester to the left and the other to the right "eye" of the green test harness. I turned the tps screw on the car until I had only one test light lit.

6. Yes I used the idle air bypass screw to adjust the idle. I also adjusted the thermowax pellet and the rich/lean screw on the passenger side of the engine and every other adjustment outlined in Lane's article. When I first got the car it would not idle until it warmed up. Would start and then die unless I kept my foot on the accelerator. I also adjusted the idle stop screw.
After 3 days I got the car to idle, and it has idled finely since. I did all of this back in February and the car ran great until a week ago So I don't think that my current problem that just appeared had anything to do with the idle adjustments 6 months ago. Just my opinion.

7. I will put a voltmeter on the battery with the car running tonight and report back to you.

8. I didn't see any carbon tracking in the dizzy cap, but I could have missed it. Will order a new cap and rotor button and report back.

9. I don't have a timing light here.Will have to get one and report.

!0. I last rinsed the engine compartment about 2 months ago. Had a missfire for about 3 minutes and it cleared up. Car ran great for 2 months afterwards until last week.
I understand your advice about rinsing engines. I live on the beach and keep a car cover on my car, but in spite of hell I get beach sand on the sheet metal where the hood hinges and around the shock towers and along the cowl. My previous 85 gslse rusted badly in those places. So about every month or so I rinse the areas around the engine to wash out the corrosive sand. I don't rinse the engine itself. I plugged the vent hole with dumdum to prevent any moisture from getting into the dizzy again. This won't be a problem in the future because I'm ordering a new cap with the rubber vent included.

11. After my initial post, I read here on the board the the AFM flap can bind and cause all kind of problems. I will check it's operation tonight. I'm wondering if it can be binding and after I drive the car for 20 minutes or so, it frees up and the car runs until the next morning when it's cold and binds up again. Will report on this tomorrow.

Many thanks for your advice. We are indeed lucky to have you here and we all benefit from your experience, knowledge, and advice.

GSLSEforme

The coils are bolted to the car but they're not grounded. If you had them hanging from the wires in midair they would work the same as being bolted in the car.If they were grounded the car would not run. The negative terminal on the coil is not ground it's the signal wire coming back from igniter to fire the ignition coil. Disconnect all wires from ignition coil,remove coil wire from hi tension tower. Multimeter on low ohms scale touch leads to each primary stud on coil. Always isolate coil from everything for testing. Primary readings will be about same as what you observed. Secondary testing,set meter to 20k ohm scale,put one lead on either primary stud and other down hi tension tower to contact in bottom. Should see readings between 5k-8k ohms.

TPS adjustments will have been negated by adjusting throttle stop screw-this is really not an adjustment point,there will be something else wrong with throttle body or a vacuum leak causing the no/low idle. Adjusting throttle stop screw is addressing symptoms not the cause.
Likewise adjusting the variable resistor on fenderwell is not meant to get the car to idle. Its original intent(i wish they had not put them in such an accessible place) was for fine adjustments after an engine repair or replacement. Whatever is determined to be the real cause of the idle problem,emissions are sure to be wacky from adjusting this. Refrain from"adjusting" this,they were delicate when new,after all these years they are frail and used replacements are few.


The fact that engine starts and runs indicates to me AFM is working,until such time diagnostics need to focus on it,no need to do anything with it or to it. This is another calibrated,delicate part that has been proven to be reliable even after all these years. Hands off.

Take a video and post here of cold startup idle,warm idle and missing at 3k rpm for all engine compartment to hear engine and back of car to hear exhaust. Using idle air screw,adjust warm idle to 800 rpm.You'll have to have someone in car to hold throttle at 3k while you video or other way around.
How many miles are on car?

grotto107

I apparently got some erroneous information about the coil body grounding here on the board. I will retest the coils per your instructions later today or tomorrow. I have a doctor's appointment in another town today and don't know how much RX7 time that I'll have.

I reset the TPS after I adjusted the throttle stop screw in February and checked it again yesterday, so I hope that's not the cause of my problem

I'll leave the AFM alone

I checked the battery voltage with the engine running last night. Battery shows 14.3 volts and my gauge reads about 13.8 volts.

Car has 179,000 miles

Will post a video today or tomorrow.

GSLSEforme

The coils should test ok,very rarely see a bad one even now. They’re much better made than what you can buy today,even”high performance” coils.
Never say never,i’d Be surprised if these were source of your problems.

Charge voltage is good. Normal.5 volt drop at dash gauge due to age/resistance.

Miles on engine not a concern. These regularly go 250k miles and more. I have a customer that has 292k on an SE currently and runs well.

Will watch for your videos.

grotto107

Coil test with no wires connected. Coil #1 (closest to radiator) shows 1.2 ohms between terminals and 8.5 kohms through tower. Coil #2 shows 1.1 ohms and 8.4 kohms respectively.

New dizzy cap and rotor on order

Videos to follow today

grotto107

Sent you video via email on board here. will try to post here.
Another video to follow

grotto107

Had to enter a message here in order to delete post

grotto107

PLEASE DISREGARD THESE VIDEOS. i'LL TRY TO ERASE THEM. WE pulled the dizzy cap and one of the terminals was bent. We must have done it yesterday when we reinstalled it. Was not like that before. Will take more videos when new cap and button arrives. Sorry

grotto107

I deleted the videos

grotto107

Here are the correct videos taken with a new Duralast dizzy cap (oem is still on order) and the existing rotor button (oem on order)

cold startup

cold running

cold running #2

hot running

Although the videos show worse performance hot than cold, when driving it runs the same -hot or cold

GSLSEforme

No fast idle when cold,previous SE owner? You know you have to depress and release throttle to set fast idle cam...is there a problem with wax thermostat? Sounds like there's an air leak when idle settles down,hard to hear engine over those chirping drive belts,old,need to be changed. Spritz some WD 40 on them while idling to quiet them,let car cool and video cold start again.

Take intake air boot off at throttle body,take very closeup pic of interior of throttle body,another with throttle @1/3rd open,another with throttle wot.
Take bypass hose off intake boot/dynamic chamber and closeup pic of metal tubes hose goes on.

Check ignition timing to see if correct and movement when "events"occur.Rent one at Autozone or some other parts store,need to do this before looking elsewhere for problem(s). Take plugs out,keep in order,post closeup pic of business end.

It sounds like an ignition misfire. It doesn't sound that bad? Video,really audio of driving car when it occurs,lay the phone on passenger seat and drive to recreate problem.

grotto107

1/3 open

think this one wqs closed. Pete may have cracked throttle

closed. Pete may have had throttle cracked


closed no throttle
Throttle body pix

grotto107

I think these are all the TB pix. Captions below them may not be accurate. I've been fooling with my phone camera and laptop trying to download these in order, but can't do it. Look at them and tell me if you need more.

grotto107

Pix of dynamic chamber hose to bac

grotto107

BOTTOM REAR

TOP REAR

BOTTOM FRONT


TOP FRONT
SPARK PLUGS

DESCRIPTION OF LOCATION IS LOOKING AT ENGINE FROM DRIVER'S SIDE FENDER

grotto107

Cold startup with fast idle cam set (never knew about that). And wd-40 on belts.


Shows startup about 1 second after firing (camera wasn't on quickly enough)

1. No timing lights anywhere near me to rent. Called 7 or 8 auto parts store. Ordered one from Amazon with 1 day shipping. Should be in Tuesday.

2. My buddy, Pete who is helping me, and is a decent shade tree mechanic,turned the variable resistor about 1/2 turn to lean.I had it almost all the way to rich from february to get the engine to idle. No problems from february to a week or so ago, so I don't think it could have made much difference. We wd-40'd the belts,

3.And he sprayed these 2 cans(don't know what they are) near the exhaust with wd-40. pictures at beginning of post (computer wouldn't load them below)

4. That's all we did. Took the car for a test drive to record a video of it breaking up, and it ran perfectly. Go figger?

5. After we ran the car for 20 minutes or so, it would break up about every other time at about 5500 rpms. Not as bad as before..

I'm baffled. Before it would limp down the road at 30 or 40 mph and die if you gave it more gas. I will try it tomorrow and report.

GSLSEforme

Plugs look like rear rotor a bit richer than front,fronts look more normal. Plugs look like they have miles on them,how many?

REALLY need to leave variable resistor be,i don't think you understand how delicate they are. They break very easily and your car won't run...very difficult to find a used replacement,there are no new to be had.

The "cans" are 5th and 6th port actuators,think of them as low pressure air motors. They are fed by pressure from exhaust system by tube that used to be on original cat converter and now fed by air tube on presilencers.

What you have done presented in your last post is not enough to "fix" anything.. Variable resistor only affects low rpm,no affect on anything over that. I didn't hear anything more than a burble in exhaust at any rpm in your videos that i listened to several times.

I submit that you have an intermittent problem,can be caused by many things. I didn't hear anything in videos to support how poorly you stated engine was running. Car has a lot of miles,you know they don't fix themselves. The issue will return,when is unknown.

No audio of driving car,no pics of inside throttle body...

grotto107

the plugs have less than 10 miles on them.

I didn't post the driving video because the car, out of the blue, ran perfectly for the first time in 2 weeks. Here's the video


I'll have to remove some more of the intake , and will get you pix of the throttle body.

I do indeed apparently have an intermittent problem. I'll drive it again tomorrow. Will get you an audio when it starts to act up again.

Thanks for your patience and help.

GSLSEforme

Just remove sir intake tube from throttle body.
2 12 mm nuts

LongDuck

GSLSEforme - do you think it could have been a sticking 6-port actuator that they lubed and is now working (more) correctly? This could also explain the difference in plug coloring between front and rear rotor, and given the ports are actuated by exhaust backpressure of 4-6psi in volume, it doesn't take much to make them hang up and stop working. One open with the other closed - above 3800rpm - would be my guess.

Something OP and his shade tree buddy did helped to mask the symptom. All they did was shoot video, pics, and spray lube on a few intake parts,...

grotto107

I did that and posted 4 pictures here.

GSLSEforme

For some reason,the throttle body pics didn’t show up til now. I’ Look at them in a bit.

grotto107

Drove car this morning. Back to breaking up again. Ran almost perfectly yesterday. Good news is that I have a video of it breaking up and surging. I have a couple more if you need to see them