Symptoms -

-Idles with a miss

-Very harsh 3800 hesitation when cold

-This evening when I was making a right onto the highway, the car started sputtering. I coasted it to the side of the road where it idle'd like usual, and tried to rev it. It wouldn't rev worth anything, would just hit a wall at about 1500 RPM. My A/F was reading anywhere from 17 to 20 while this was happening. After about a minute, it was running fine and I drove away. It was fine for the drive to and from dinner after this.


I have beefed up the tranny to firewall ground, and grounded the ECU to the floorpan. The car runs real strong when hot. I was told that the fuel system is all stock, but that the turbo has a port/polish. It has spiked up to 15 pounds of boost, and the A/F still reads in the low 12's at this point, so the engine is pretty healthy, just doesn't like to idle smooth or run when cold.

One thing I noted last week when I had the intake/throttle body off was that I never could find the engine harness ground on the engine. I looked all over for it, but never saw it.

 

Just thought that I would add in that when I said "idles with a miss," it's more of a stumble every now and then, not so much missing.

Also, I just went and checked over my TPS and everything. The car only wants to hold a solid idle when the TPS is set to 0 ohms. If I set it to 1K, it will hunt for the idle and run extremely rough, as if it is running way too rich.

I set the TPS to a dead-nuts 0K ohms, adjusted the idle screw, and tightened down the intercooler, then went for a test drive. In 2nd gear, I noticed a slight hesitation at 3800 and under 10 pounds it was running leaner than normal. In 3rd gear everything was good, no hesitation, pulled very hard, and registered a low-12 A/F under 12 pounds.


At this point, I am assuming that the ground I could never find is going to be my culprit..... but how am I going to fix something I can't find? Any list of the most likely places it should be? This is an 87 TII.

 

are you talking about the ECU ground ?

 

I believe so, yes.

 

I dont know what year your car is but if it is an S5 I think this link may help it shows a pic toward the bottom of where the ECU ground is located on an S4 and an S5

http://aaroncake.net/RX-7/grounding.htm

 

"S4 NAs and most TIIs have it on the solenoid rack under the intake near the BAC valve (drivers side, near oil filler neck)"


My BAC valve is on the......... passenger side?


I'm almost positive that the ground was not where either of those pictures shows, but I will poke around with a flashlight tomorrow when I get off work and see what I can find.

 

On a series four, the black, two wires for the ECU ground are supposed to be screwed down to the rear ROTOR housing just left of the centerline of the rotor housing. Throttle body/intake manifold have to come off to see it.

Still can't find it? In a lurch, go to the ECU. Pull the small plug off and the middle plug off. See the pure black gnd wires? Follow them up the harness. You have to remove the outer cover of the harness doing this. About six inches up the harness you will see where they are spliced together. Get a piece of new wire of 18-22 gauge. Solder that wire to the others. PUt a ring terminal on the other end of your new wire. Attach that terminal to one of the studs that hold the ECU bracked to the floor board. Done

 

I might just do that to save a lot of hunting. I already had to put that rear housing => throttle body water line back on once, not really wanting to do that again.

 

Got worse today -

I was coming home, got in the turn lane onto my road. When I got around the turn, the car started trying to shut off anytime I pushed the gas enough to open the secondary plates. It sounded like it was running on one rotor when it did run, and revved very rough. The A/F was reading very high again.


My guess right now is the injectors, because I imagine under the 10-15 pounds that it's been running at, the 550's are damn near 100% duty. Probably won't hurt to go ahead and replace all 4 and throw some 720's in the secondarys, but does any one have anymore input?

 

When it was wanting to die and you stepped on the gas was the car going anywhere or was it like it had lost all power to move ? If so I had that happen two diffrent times a while back I replaced a few things like the FPR and the Fuel filter . Could be your injectors I myself am not really sure .

 

It was barely moving at part throttle, and then when I pushed on it some more, it just completely shut off. I might order all new fuel parts when I get paid Friday and just go ahead and replace all that crap.

 

are your battery terminals and your alternator good ?

 

Ok, I feel like a complete retard right now, but I did make progress tonight.


The jerking issue thing? Yeah....... it's amazing what gas in the tank will do for a car. In my defense, the gas gauge barely works so I have no way of knowing to fill up other than my trip. Oh well, live and learn.

I grounded all the little ground wires to the floorpan at the ECU. Seems to idle and run better, but I will know more tomorrow. I will also check the alternator tomorrow.

 

LOL

 

is it hard to get to the ECU ? and grounds

 

It's just in the passenger side floorpan, under the carpet.


Well, got off work today and came out, started it up and the car ran like ****. Tried to drive it, but it started doing the exact same thing again, cutting out, stumbling, etc.

It will idle normally, but when you try to accelerate at anything over a snail's pace, or rev over 2K, it starts breaking up and will eventually shut off. Again, A/F is reading very high.

I guess I will replace the fuel filter first then the injectors or pump...... anyone else have any ideas?

 

did you double check your tps is still with in range.
did you check to see if your BACV is not messing with anything?
is it grounded correctly?
could you posibly have a bad injector?
is your MAS in stock upright, not tilted position?
did you do the vac line test with carb cleaner?
good luck!!!

 

-TPS is good to go
-BAC valve seems to be working normally, it doesn't have enough adjustment in it to make the car run this rough/shut off at over 1/4 throttle I wouldn't think anyway
-Bad injector is definitely a possibility
-MAF is fine
-Haven't heard of this

Both times that the car has done this to me is when I get off work, after it's been sitting out in near-100*F all day, and both times that it's done it, it has cleared itself up after running for 5-10 minutes.

I am thinking that I could've pumped the fuel filter full of rust/crap in the bottom of the tank when I was running it on fumes the past two days. I don't know how long this fuel filter has been on the car anyway, so it will get replaced this weekend. Other than that, injectors are my best guess at the moment.

 

Don't mean to hijack the thread, but does this fix really work? I think I have the same problem w/a bad ECU ground and this would be a lot easier than repairing the ground on the engine. I know it's probably not the "correct" way to fix the problem, but I'm not looking for a long term solution as I'm planning an engine swap within the next year.

 

Had another retarded moment.

The MAF WAS in sideways. Turned it the right way, and wow does it run better. Buttery smooth idle, and drove like a dream. I guess I will have to wait until tomorrow to see if it fixed my problem coming out of work, but it made a hell of a difference driving it just now.

 

Well I hope that solved your problem good luck . Also anyone got a pic of where the ECU is cuz I looked under the passenger seat under the carpet and didnt see where it would be . I have an 86 N/A I have a pretty good idea its located behind the center console behind the stereo atleast thats what the repair manual I have says ?

 

Go standalone with full rats nest/emissions removal. it's the end all problem fixer. worked for me.

 

Ask NZCONVERTIBLE. The answer is YES for me and the NZ and if I remember right a few others.

There is no guarantee. It's something that has worked for Some, not all.

It's more logical than someone saying "get your injectors cleaned" or get a stand alone bs.

Also a fellow named RXSTR in the archeives mentions it.

 

Sit in the passengers seat. Put the seat all the way fwd. Plant your feet on the floor where the floor slants upwards. It is under your feet right there. Carpet needs to be lifted up. It's intuitive on how to lift the carpet up.

 

Okay thanx man I'll check it out