Zipdrive 20

1985 GSL-SE 13B stock. Vert slight random stumble at idle but otherwise runs fine. I did search and everyone describes plug condition as slightly brown. My plugs are more grey in color.

I have tried various plugs but currently have NGK BR9EQ14 installed, which is reccomended plug. These plugs have about 5k miles with almost no highway driving. Does this color indicate any problem, possibly a lean condition? Thanks for any help.

j9fd3s

iTrader: (3)

looks good to me. have you tried adjusting the air fuel mixture screw? it controls fuel at idle

Banzai

iTrader: (13)

A lot of variables and schools of thought about plug reading. Basically whitish is lean, black is rich. Lean melts you down and blows you up, Rich causes excessive stumbling and loading up. Tan is just right. these don't look bad. The type of fuel and oil (rotarys burn a little of this too) also can affect the plugs color and texture of deposits.

Zipdrive 20

Yes, been everywhere following suggestions and service manual. Read all the idle posts I could and found many things wrong with the car, improving the idle along the way. Engine has 185k miles, idle smooths out if I set at 1K. Maybe that's just simpler than chasing the stumble at 800 RPM.


Fuel is regular with ethanol, that's about all we can buy in my area. One station sells premium ethanol free at a premium + price of about 30 cents a gallon. Oil is Valvoline 10-30 dino.

So this looks slightly lean but not enough to hurt the engine? I have adjusted the mixture per the manual, it's just hard for me to tell. You think I might have it slightly lean? Going a touch back rich can't hurt and I'll then monitor the plugs again.

RX-7 Chris

iTrader: (19)

The plugs look fine to me.

Have you replaced the vacuum lines? I fought my idle but now I'm good. I ended up replacing all the vacuum lines on the engine. The lines under the upper intake were the worst.

Also see int the tps is adjusted good.

Zipdrive 20

Thanks, the TPS is set, checked it several times over a few months. I replaced most of the vacuum lines while un-sticking the 5 and 6 ports. Only vacuum lines I did not replace were some of the longer ones to the vacuum switch, relief solenoid valve and switching solenoid valve on the passenger side. I will look at those this weekend.

Zipdrive 20

Every vacuum hose is replaced now EXCEPT 2 of the 4 on the spider under the intake manifold. Too cold outside now to spend that much time but will tackle this summer. Some were pretty bad. I think the idle changed slightly. Thanks for the tip.

Interestingly, the TPS now is set using a different method as well as the throttle stops. Reading manuals the throttle stop position is vague to me. Reading various posts it's important in the interaction with the BAC at idle. The stops appear to be fully closed at idle. (see attachments) The Standard clearance is when the secondaries start to open, not idle. Am I interpreting this correctly? If set incorrectly the secondaries could be slightly open at idle which probably would cause bad idle.

Here's what I did:

1) Disconnected the TPS and connected a meter reading ohms between the "top" pin and right pin holding the TPS connector with the single pin up. (see attachment)
2) Adjusted the throttle stop screw until the meter stopped moving. Doesn't really matter what the value is right now, when the meter stops moving the throttles must be fully closed. I adjusted back up slightly to show movement then back down. At this setting (fully warmed up engine and not on fast idle cam) the throttles must be fully closed.
3) Adjusted the value to 1K using the TPS.

By setting the TPS and throttle position this way the idle improved and mainly the idle with the AC on dramatically improved. Right or wrong it's better.

ONE QUESTION, and this may be the source of some of my idle problems. Using the "correct" method to set the TPS I only read 10 volts, never anywhere near 12. The attachment says "current flows to one of the voltmeters" and only further down the page indicates you need a 12 volt lamp to make a tester. Doesn't really say I should be reading 12 volts.

This may be normal to only read 10 volts or may indicate some electrical low voltage problem. Voltage in the car reads 12.5 volts. Anyone with GSL-SE knowledge know what voltage I should be reading?

j9fd3s

iTrader: (3)

i think you've got it about right. the primary throttle is set to a certain angle/clearance from the factory, by the throttle stop screw. once you've got that, then you can adjust the TPS.

i don't know about the 10v vs 12v question, i've always used the test lights. however you might want to check voltages around the engine, IE at the alternator, etc the alt should be 13.6-14v, and a drop to 10 sounds like a lot

bugman1973

you might want to try different plugs as well I've always used the BUR7EQ and the BUR9EQ plugs on my cars buy two of each they are trailing and leading sets on my car it seamed to even out the idle. and maybe do the block off kits as well for the emissions. that makes it so much easier to adjust the idle and maybe the air pump to the fifth and six port actuators mod. after that idle adjustments are so easy.

Zipdrive 20

Where do you find that angle / clearance? The one noted in the manual shows the primary throttles start fully closed, attain the 15 degree angle and the secondaries begin to open. The angle is adjusted by bending a tab, not adjusting the throttle stop screw. It looks to me like the throttle stop is only to keep the primary throttle from contacting the throttle body and "digging in" over time. It seems to be an important setting but not a crystal clear procedure to me.

Thanks for the suggestion, will check the voltage at the alternator.

I have these plugs and they idle much rougher than the stock plugs. Possibly this is pointing to something. They also burn very dark, which makes sense if they don't burn cleanly. Possibly there is a voltage problem in the car that I need to find. Thanks, will chase that now.

j9fd3s

iTrader: (3)

i thought there was a spec in the FSM for that? i know they tell you to leave it alone, and i usually do.

for spark plugs on a stock ignition i like the Rx8 leadings, and stock GSL-SE trailings.

bugman1973

you could also try the BUR7EQP AND BUR9EQP those burn much cleaner that the regular versions but i was always one to pay $10 a plug vs $15 a plug

Zipdrive 20

Thanks for helping, driving me crazy trying to find the info. Nothing in the FSM that I can find. Car was running very poorly and I have found a ton of things wrong. This one setting just is not clear to me.

Interesting comment on plugs, you don't use RX-8 trailing because the trailing doesn't do much? I'll try them.


I can try these also, don't mind buying plugs either. Thing is it should idle fine with stock plugs if I have everything right so somewhat chasing a ghost until that's right.

What would be most helpful if someone who knows the TPS setting procedure would put a DC meter on the connector where you set TPS (Don't change your setting for me, just check!) and see what voltage you read between the top pin and the bottom pins. One bottom pin should read voltage and one not, what voltage do you read? If it's 10 then I know what I have is normal and will stop chasing that down. If 12 then I have a problem.

j9fd3s

iTrader: (3)

the Rx8 trailings are actually a different length, so i don't like to use em for that reason.

the leadings make a nice difference though, and work really well on a GSL-SE.

bugman1973

its been so long since i have done that but i can look up the procedures. i know its on the archive somewhere

Zipdrive 20

Went shopping and the leading NGK (RE7C-L) Part No. 6700 are the longer ones at 21mm. They are heat range 7. NGK 6700 RE7CL Iridium Spark Plug

The trailing NGK (RE9B-T)Part No. 6701 is a 9 heat range and 19mm reach, which is the correct length. NGK 6701 RE9BT Iridium Spark Plug

Just checking, please confirm which ones you are running in the leading, the 7's or 9's? There may be room for the 21mm's but I am very cautious knowing it's 2 mm longer.

Zipdrive 20

Found a procedure here way down this article. Will try this, wanted you to know so you didn't go on a long search. Is this what you were looking for? Thanks for the effort!

Solving GSL-SE Idle Problems

"To adjust the throttle stop screw, first take note of it's current position. The object is to turn the throttle stop screw inward an eight of a turn each time--propping the throttle plates open more and more. When you get a linear response from the Air Adjust Screw, you are probably in the right place. The Standard Procedure for Adjusting Idle will also work properly. You will need to use it since changing the resting point for the throttles will put your TPS out of adjustment."

So having the throttle fully closed as I have it is wrong. I'll work on this today.

GB7

iTrader: (1)

Zipdrive, have you checked injector seals for leaks. They turn hard and brittle and can be a source for vacuum leak. Spray with carb cleaner to check. just on easy thing to eliminate

j9fd3s

iTrader: (3)

i run the leading Rx8 plugs, the 7's (you could get 6's too). same length as the Rx7 plugs

i just went and grabbed a trailing Rx8 plug and the trailing FD plug, and the Rx8 trailing plug is shorter. so i guess the Rx8 trailing will fit, but its further away from the chamber, which isn't ideal

Zipdrive 20

This is something I have been reluctant to tackle, but just because I haven't done it. I found plenty of hard brittle rubber so it's very possible. Let me look into buying replacement parts and give that a try. Going to take a while to do that but I will be sure to give feedback to your suggestion.

Zipdrive 20

OK, I'm convinced it won't cause a problem, just making sure there wasn't a typo. Odd thing is the specs for the RX8 leading is a 2mm longer reach than the FB leading and the RX8 trailing is the same reach, but actually is shorter.

Zipdrive 20

j9fd3s, this is in the top 3 pieces of advice I have been given on GSL-SE! Installing RX-8 plugs made such a difference. (I went whole hog and bought leading and trailing) Idle is very good now, throttle response is better especially in 4th and 5th gear. Bought at Advanced Auto using 20% off internet purchase pick up option plus $50 off $100 coupon for future purchase; I'll buy a better timing light. Looking at it this way they were not outrageously expensive. Over the last couple of days:

bugman1973 suggested BUR7EQP AND BUR9EQP, I had the non P versions from previous plug testing so I installed. They ran much better so my stock BR9EQ-14's are shot. But there was still a stumble and I realize it was not the P version he recommended.

If I was going to buy plugs it made sense to try the RX-8 even though they are expensive. What a difference even over the BUR7EQ AND BUR9EQ! I can't imagine a better plug.

Idle is almost factory smooth now with just a slight rumble every 30 seconds or so. Next step is to follow advice from GB7 and replace injector seals. Might wait for warmer weather now and will report back to those giving their time and advice. Much appreciated!

Zipdrive 20

Removed the injectors today to send off for cleaning. It looks like they are leaking and all the rubber parts are hard. Found many of the vacuum lines under the intake hard also and replaced all. The photo shows a missing grommet, I recovered it after taking the photo.

Looking down in the injector holes I see a plate with maybe 15 small holes. Can't tell if this stays in or is also removed for cleaning. Just asking, I think it stays in but wanted to know before I re-assemble.

As mentioned in the archives I read the connectors did break and I was being as careful as I could. Replacement looks pretty straight forward. One post mentioned to use butt splices and specifically not solder the connection. This goes against what I would normally do. Any comments on which method is preferable?

GB7

iTrader: (1)

Plate with holes stays in. [which connectors broke,injectors?] look in the junk yard for injector plug off another jap car and splice wiring in

Zipdrive 20

The injector connector that stays with the car, not the one on the injector.

Bought two of these.


GP Sorensen/Fuel Injector Wiring Connector (6414) | 1985 Mazda RX7 1.3L FI Rotary | AutoZone.com