Sterling

The car:

Recently acquired 89 Vert.
Bone stock.
5 spd w/ 143K miles on clock.
Super clean Cali car.


The problem:

Starts right up, runs great, pulls pretty good up to about 5500-6000 RPM, even on hills. But it won't go past 7K RPM. -At all! (I've heard the buzzer only once, and that was in the driveway.)


What I've done so far:

• Changed the fuel filter. -No change.
• Go for a drive without the air filter. -No change.
• Apply my experience of simple carbed FB engines and just assume it was clogged cats, and post a "Help Me!" thread here. (I'm OK with carbs, but I feel like an idiot in here.)
• Checked out my plugs yesterday to find them caked with carbon and very white, complete with worn electrodes. the electrode on the #1 Leading plug is GONE! Replaced them with old ES7s I had, which will probably melt on the way to Napa. (-They gotta be better than what was in there.) -No change.
• Cursed and threw tools. -No change.
• Did a LOT of forum searching. There seems to be a very small percentage of threads dedicated to unmolested bone stock 89+ FCs with my problem. Tells me either my problem is very complicated, or very simple. (...please be simple, please be simple...)
• Did a code check and the CEL stays on for well over 2 seconds and that's it. (That's a #10, right?) According to the Bansai Racing site, that's the "Intake Air Thermosensor (AFM) Open or Short Circuit"
• The car is red. Was gonna check the redinator, but I dunno where it is. (Ehh. That's about how ******* lost I am. lol)

I don't have a FSM for this thing yet (just got her), so I'm working solely off my 12a rotary experience and this forum. I also have never trouble-shot a fulie before.
I checked the timing and the trailing seems intermittent. At one point it seemed like my #2 leading wasn't firing at all. My light could be fuct for all I know.
A minute later they're all firing correctly. (...wtf?) Plugs sure indicate they've been firing.
I have yet to chase this AFM thing up in the on-line FSM (-don't even know where it is...), but before I embark on an electrical wild goose chase, could somebody please just list through the causes of leaning out so badly high in the range in the order of probability? At least then I'll have a checklist I can hit one by one.

Car is damned sweet, though. Zippy as hell at 4-5K, and the handling is to die for compared to my old Sterling Nikki test rabbit FB! Friends are gasping in surprise that I'm driving around in a FI rotary after a decade of tuning carbys. LOL

Rob XX 7

iTrader: (8)

I would do a decarb treatment with some ATF or MMO, run it with those old plugs until it clears up, then when it cools down install the proper NGK plugs, bur9eq bur7eq. See how it goes from there.
Regardless of what the tach says, how does the car feel? You say its zippy, maybe think about checking if the tach is reading properly

Hazard15301

iTrader: (5)

FSM

I would get your injectors serviced by one of the reputable sources (Witchhunter, InjectorRehab). Also I would check the voltage to the fuel pump. It definitely sounds fuel related. Have you checked your secondary injectors?

Rob XX 7

iTrader: (8)

one time I had purchased a automatic RX7 to flip, it had bad ujoints so the car just drove like crap. First I fixed the ujoints, but the car had no power and would not rev that high.
That was the first time I tried the MMO decarb trick at the advice of a very well known rotary mechanics, this was back in 1993 or so. I could not believe the difference it made in that car, it was like you had added a turbo charger to this car.
Since then I have had many rx7s that did not receive the proper care, always start with the basics- they respond well

wrankin

Hmm, I interested in what you find out. I had a very similar experience with my FC track car - power just fell on its face at around 6300 RPM. We tried a lot of things - plugs, removing the MSD box I had, and nothing worked. Then, after three sessions on the track, it cleared up and just got all better. I felt the same behavior briefly this past year, but it cleared up within 10 minutes on the track.

I'll try and go find my old thread, but it may be of limited use.

-bill

Edit - looks like we may have some new insight into the problem - think secondary injectors. Here is the old thread:

https://www.rx7club.com/showthread.p...ght=ecu&page=2

nycgps

iTrader: (4)

I wonder which works better, MMO or the Zoom Zoom cleaner from Mazda.

arghx

iTrader: (3)

Put brand new BUR7EQ and BUR9EQ plugs in there. In my experience with nonturbo FC's, they are pretty sensitive to plugs. Even one bad flood and they won't run the same until you put brand new plugs in there. Also, if your aux ports are stuck it may really struggle to rev high. Make sure the aux ports and VDI are working.

Ha, you should see me struggle with a carburetor. But try working on an FD. Now that's complicated. As for the timing, you need to check the timing by jumpering the "initial set" diagnostic connector so that the idle and timing are stabilized. Firing order at idle is L1/L2 (wastespark), T1, L1/L2, T2 .

You know you've been driving 12A's for too long when you think a stock 'vert is "zippy"

Also, if you really are getting a code for the intake air thermosensor in the Airflow Meter you may want to change out your AFM.

pauli311

iTrader: (2)

I hate using most forums' search function, so what do I do?

Use google (toolbar, website, etc)

before your search, input site:www.rx7club.com and learn to use quotes properly. When you can search like a human thinks, you will find everything.

example - site:www.rx7club.com "Idle Timing" - would be a full search term.

I use this feature religiously, and it will cause you to gain seconds or minutes of your life back.

Sterling

I don't think I wanna try any treatment just yet. I've resurrected a few rotaries and I know the value of the MMO/Seafoam/ATF/Bug Snot/Walrus **** treatment. I don't want to compound my problem and make it even harder to diagnose when the engine dumps it's load into my cats. The cats have always been the first thing I've removed, so I don't really know what to expect.
As mentioned, getting the new plugs in is at the top of my priority list right now. The ones in there now are used, not up to the task, and will quickly degrade, especially due to the lean condition. Not too many test runs left in them.
I had checked the 5/6 port actuator system before. They seemed to be working properly. I just removed the pots and double checked. They move freely, as do the valve shafts.
I think my idle could be too rich. It does skip & fart a bit. I dunno; I can't imagine I wouldn't have noticed that before, and maybe it's just the plugs. How it ran with the other plugs at all, let alone better is beyond me, so... -Plus that would account for heavy carbon deposits on the plugs but scorched. It was a city car for at least the last 10K miles.
While I rechecked the 5/6 port actuators I noticed the connector for the O2 sensor has a braided ground wire hanging out of the harness sleeve. The other sheathed wire is connected to the plug, but that braided wire looked like it had broken off at the end. I couldn't see what it might have n=been connected to, and there was nothing obvious on the plug. So I jumped it to the perch that the plug is on (grounded to the engine).
Took a spin. No difference.
I have to get back to work, but I'll try to read the plugs later on.
Thanks for everyones help so far. Lots more reading to do!
I would really like to know how to check if my secondary injectors are coming on.

j9fd3s

iTrader: (3)

i agree with the plugs first. i also like to check the wires, the FSM spec is its bad if they are more than 16ohms/foot, and experience bears this out. new NGK wires are all you need.

2. you NEED to make sure the 6 port and VDI systems are not stuck.

the CEL when jumped, should turn on for 15ish seconds, and with no codes, will turn off. with a code it will turn on, turn off, and then flash the code.

if the secondary injectors are electrically not working, it will trigger a code, and a limp home. they could physically be stuck and the ecu would never know however.

the braided wire on the o2 sensor, is the shield, it is grounded by the ecu, and should not be grounded by the sensor. shield wires generally only get grounded at one end.

the VDI system makes the s5's more tolerant of exhaust backpressure it seems, and the EFI helps the cats last much longer, it is possible to have a plugged exhaust, but its not as common as it is on the 1st gens.

wrankin

if it won't get much above 6k, it's not the VDI system and it's not 5/6 port. both reduce power, but on a level road, neither are enough to prevent you from getting to 7k.

I agree about the plugs.

I don't know if you are seeing the same issues I experienced. The car would pull strong to 5k, get to 6k and then fall on its face. My plugs were whitish indicating a possible lean condition, which would be consistent with injector problems. I did not get any ECU codes when this happened. In my case, it was very intermittent.

From the link to Chris Ludwigs dyno charts in the other thread, the issue went away when a new ECU was installed. I wonder if it could be an injector driver problem in the ECU? (just a SWAG).

Good luck,

-bill

Sterling

Thanks, everyone.
According to you, j9fd3s, there is no error code.
I think the next step is to check the coils with an Ohm meter. Got a new one tonight.
Then, because it's probably simplest, check that the secondary injectors aren't physically stuck.
...Then I guess it's time to start messing around with the ECU.
There are no signs that anyone has ever messed with this engine, and it's very clean. I was disturbed by the sight of a lot of condensation inside the car on a few mornings, though. Never a good thing for electrical stuff.
wrankin, I'll have to hit that thread again after I familiarize myself with the FSM. I don't understand some of the things that are talked about in it.

IF it's the coil(s), would bum trailing coils do this? Wouldn't a bum trailing coil make the tach jumpy?
How much should I expect to pay for another coil?
Wouldn't the burned up plugs rule the coils out?
If it's the ECU, are they repairable, and if not, how much should I pay? Which one should I get? (I noticed a few different types for sale in the classifieds.)

Thanks all.