chris_g

iTrader: (29)

Issues I am having: Car will not idle below 1500. Seems to stumble when I have it idling at 1500 to try and make adjustments. I will post a video of the idle as I think it will help diagnose the issue. It seems to run…decent…but then it will have small ‘pop’ like noises causing a stumble in the idle. Header glows read on the front rotor (lean, ignition, or vacuum issue)

Car Details: 1984 GS
Header to straight pipes back. No muffler yet. I forget who made the exhaust. I remember buying it off a member on here years ago and people said it was high quality.
Rats nest removed
Sterling carb
Holley FPR at 2.5psi
Mr. Gasket generic Fuel pump
Stripped intake

Compression: Front Rotor: ~90psi
Rear Rotor: ~85psi

Ignition: Reinstalled distributor according to FSM. When using a timing light to align timing marks, the distributor needs to be fully retarded. Is it possibly off one tooth? This has me worried a bit as its not centered like it should be. I aligned the ‘pin’ and the small punch hole.

Both igniters were checked and replaced with ones that I know work from a good running car. This is to clarify so I know; Which igniter is leading? The one towards the radiator or the one towards the alternator?

Coils seem to be fine as the timing light is putting out a very consistent flash. I noticed a very strong arc ability with these things, too. Not used to that so much on any of our old Mopars. The coils on the RX7 were arcing from inside the hole to one of the electrical prongs on the coil for the wiring. Is there an issue, or is this normal?

Emissions: The previous owner of this car removed the rats nest. Whether it was done correctly, I am not sure. It ran fine 2 years ago which was the last time I had it on the road. Now I am slightly wiser, and checking it over. I have included pictures as to how everything is hooked up. What do you recommend for case ventilation? I noticed mine just loops from the oil tube to the intermediate housing.

Carburetor: Sterling carb purchased used from a member on these forums. Jets were cleaned out, but I will be cleaning them again to double check. USPS or Canada Mail dropped it and the throttle linkage was bent, but I straightened it out. Maybe an issue happened during the transition from Canada to NY.

It seems to be running rich, judging by the spark plugs and exhaust. The float bowl adjustment is perfect. I don’t think it is a fuel DELIVERY problem. It may rely in adjustments?

Intake: The intake manifold has been completely stripped. Excuse my terms here, I am not as educated as a lot of you on here yet. I took out the butterfly valve and closed the hole with jb weld and a plug. I purchased a block off plate from Racing Beat for the ACV. The Anti Afterburn hole was plugged with a (I know, bad.) rubber hose and bolt until I take the intake off again. The intake gasket is new.

Exhaust: It seems I may have a small leak somewhere by the header. It sounds like it may be coming from where the header bolts to the housing. I will check this again and retighten everything.

Vacuum Leaks: I checked over and over and could not find anything. I checked by hand, eyes, and starting fluid. I didn’t hear the engine do anything after the starting fluid.

Summary: The plugs make it seem as if the car is running rich, and so does the exhaust. The glowing header on the front rotor would make me believe its running lean (weird), or an ignition issue, or vacuum leak.

Any help would be awesome, and I apologize for the long read. I figured this would help to state what I have done so far.

bahlorm

Wow this seems a lot like the problem I am currently having. But after I rebuilt the carburetor the rpm is actually around 800-1000 on my car, but still stumbling. So I will be interested in checking back in on this one to see if you have found the problem and what others have to say. Unfortunately all I can say is good luck, and maybe you can get a few ideas from a post I had on here. Named rebuilt carburetor and still stumbling or something like that. There were many people that has told me several different things to look for and how to do it. Maybe one of the ways they have told me may help you out. If not then keep us posted on what you do find out, I definitely would be interested in finding out.

Also one thing I was told to test if you are concerned about your coil is to swap them around and see if it makes any difference. It only takes a minute to switch the coils and if one of them is operating differently than the other there should be some noticeable difference. Also for the ignitors the leading is the one pointing toward the radiator.

74RX4

iTrader: (10)

You've been busy.

First thing I would suggest is to check the bolt and hose capping the #2 anti-afterburn outlet on the intake manifold. Make sure it is still sealing and hasn't melted from the exhaust. Hard to get enough starter fluid down there to change the idle. Symptoms suggest a vacuum leak to me.

Your distributor is off by a tooth. Leading ignitor is towards radiator, trailing is towards alternator, Trailing coil is towards the front, leading coil is towards the rear. They should not be arcing. Usually due to old plug wires, not bad coils, but could be coils to.
Some one else can suggest alternative methods to hook up crankcase (we really don't have a crankcase) ventilation. I have mine hooked up in the stock configuration.
Here is the definitive Tutorial on removing the rats net so you can check the PO's work.
http://maz_tutorials.ten15.net/Tutorial_1.pdf

You can download 85 (same as 84) Factory Service manual with wiring diagram at
http://wright-here.net/cars/rx7/manuals.html
or here
http://foxed.ca/foxed/index.php?page=rx7manual

Kentetsu

I would start by re-verifying that the ignition is wired properly. The glowing header on the front rotor would indicate either a lean condition or very retarded timing (my bet). I think by the sound of things that you either don't have leading spark on the front rotor, or it is receiving it's signal from the wrong ignitor (incorrect routing of spark plug wires, or ignitors hooked up backwards?)

Basically, start by making sure that you have spark, and that it is happening at the correct time.

Good luck....



.

chris_g

iTrader: (29)

Well I have been working on it for a few hours today, and here is what I found so far.

My distributor is in fine, I reinstalled it about 30 times. The arrow on the rotor is pointing right, to the pick up closest to the firewall. I believe this is correct.

The coils are getting a resistance of about 1.6ohms, both leading and trailing.

The plug wires are fine.

Leading coil to L, L1 to lower plug closest to radiator. L2 to lower plug closest to firewall.

Trailing coil to T, T1 to top plug closest to radiator. T2 to top plug closest to firewall.

All plugs are getting a consistent spark and checked for spark with both a timing light and putting the plugs on the shock tower to visually inspect.

The plugs look a little darker, its not getting perfect combustion from what I can tell. That or there is a little carbon build up which would not surprise me. The plugs were cleaned before running and reinspecting.

Fuel pressure is a little higher than last time I checked. About 4psi. Too much?

Float bowls are perfect when running.

I have a leaking header where it bolts to the engine. Shouldnt cause an idle issue any ways.

And now where the issue may be

I tried this numerous times prior to this post, as its what the problem would seem like. I took ether and sprayed it at the hoses on the passenger side of the carb. No increase in RPMs.

Spraying it on the drivers side caused a decent increase in RPMs. It seems to be a line, or plug, near the firewall on the intake.

Ill replace those tonight or tomorrow and post back with what I have found.

StumpDrummer

Make sure there are no intake gasket leaks or carburetor gasket leaks
Dont run it except when necissary when the carburetor is that lean!!!youll toast it pretty quick
try screwing the idle adjustments in all the way .
then back them out 2.5-3.5 turns out then try to restart it .try 2.5 turns first ...worked great for my 390cfm.Then fine tune adjustment to lean untill slight miss then back to more untill miss is gone with air breather off .adjust both screws at the same time in .25 turns when finished put air breather/cleaner back on

I had the same problem on an old 82 model 7 years ago. local seven guy talked me through it on the phone and after it was done i didnt have to touch the carburetor for a year or 2

if they header starts to glow again try rebuilding the carburetor.

chris_g

iTrader: (29)

On the Sterling, I screwed both the idle air adjustment and the idle fuel adjustment in completely. Backed the IAA out 1/4 turn, and te IFA out about 2.5 I think.

I havent seen the header glow since those adjustments, but I havent really ran it for a while yet either.

I think I have an early FB sterling on a later FB intake judging by the IAA. Im not too sure.

chris_g

iTrader: (29)

Picture time!

Plugs, before cleaning:



Dizzy:



Plugged vacuum ports:



Intake:



Intake Manifold Gasket gap? Is this normal? The gap is on the other side, too.(The fluid is gas, all gone now.)



Carb Spacer. Does this look bad? I pulled it off and on the bottom where it attached to the intake there was fluid. should there be a gasket?



And this cap, which I have no idea what its for. So ill search.

chris_g

iTrader: (29)

All vacuum lines and plugs were replaced this morning. (Pictures 4, 5, 6)

Still not idling. Maybe Ill buy some freeze plugs and just replace the intake gasket...again.

I tried to tighten the header, but couldnt. Im not a fan of the huge exhaust leak buts its not my priority this moment.

StumpDrummer

Dang I wish you had a second carb you could bolt on to see if its in the carb or not.
have you taken the carb apart and cleaned it out just to see whats goin on inside the carb?
get a pipe cleaner to everything!!!!! or a thin wire !!

if you have help get someone to crank the car while you look in the carb to see if its getting gas through the venturies, not just the accelerator pump

GREG5656

My 79 RX7's Tac pointer would bounce up to 1000 rpm's to 1500 plus and down again in less than a second time interval. The problem was not my wiring, it was the Distributor "Points Plate" that was lifting upwards by a 1/4 inch. Remove the 2 screws holding the plate down, and lube the bearing under it, and the weights also. (My bearing were bad, I did not feel a smooth rotation of the plate after lubeing it)...This lifting of the plate, caused the trailing points rub block to touch the cam prematurly, making the points open too soon. Test this by lifting the plate with your fingers at one end and watch to see if your points open and close. . .This opening made my RPM gauge to be unreadable, and Yes my timing was not the best and it really was the timing issue that led me to shim the plate which gave me a steady timing dwell and consequently a Tac that now reads steady. I shimmed the "Point Plate" with a thicker washer at the hold down screw, to hold it downwards preventing the 1/4 inch upward lifting, but, remember the plate must have a gap under it for the vacuum advances of the Leading & Trailing to move freely. Greg5656

Kentetsu

This car should have electronic ignition, so no points involved. Thanks for the input though.

j9fd3s

iTrader: (3)

i had a similar problem a couple years ago, similar setup too, 12A with headers, no emissions and a sterling.

i put the manifold on, and then ran it with the stock carb, no problem. then i put the sterling on and no idle. it would run from like 1500ish up, but nothing below that. i could run it on brake cleaner just fine

basically the idle circuit didn't work, even though the passages were clear. i swapped in the metering block for the other sterling (which was all bent from ups), and it works.