ORX705

i never had the problem with the stock ECU, but i have recently installed a programable management and come across the same problem. it also happens with my brother's microtech equiped rotor. we've tried tuning it out, but have had no luck.

can you add in an extra earth on each injector (splice in a wire attached to engine)?

NZConvertible

The injectors aren't "grounded" as such, so no you can't. They have a constant 12V feed and an ECU-switched ground.

Parastie

Is it difficult to replace the ECU with standalone units?

Amur_

And here goes me.

I have had the hesitation since the day I got the car.

She's an 86 NA.


I added all the recommended ground wires except the boost ground. Hesitation continued.


Eventually grounded the boost wire

https://www.rx7club.com/showthread.p...threadid=34026

which worked for a while, but the stumble returned.


Sent my injectors off to be cleaned and balanced. Finally put them back in yesterday. Sometimes she hesitates, sometimes she doesn't. I believe that it is reasonable to say that cleaning the injectors is not a 100% fix.


I'm planning on having an 'electrical day' in the next week or two where I'll pull and replace the major power lines in the car; the positive loop from battery to starter to alternator, redo my past 4-gauge grounds and review and redo all other grounds (when I first installed them I didn't solder them.)

I'll check back after that. I'm hoping that completing it all will mark the end of the hesitation prob. I've got an S-AFC installed and I refuse to tune it 'til things are running perfectly.



What series 7, please?

ORX705

thanks NZ
i knew that

astrochild7

iTrader: (3)

the only fool proof way is to do a full rewire so you have the peace of mind. that it was you not a bozo...

Scott 89t2

that isn't a hesitation.... that is a malfuntion. your injectors probably aren't even turning on. check the plugs.

Scott 89t2

that isn't a hesitation.... that is a malfuntion. your injectors probably aren't even turning on. check the plugs.

GUITARJUNKIE28

that happened to me once.

i'm surprised nobody has brought up the fuel pressure drop when the secondaries kick on.

i've fixed this problem in 5 fc's
3 were grounding issues
2 were fuel issues

specifics:
2 were the ground on the motor itself (the ring---there's a tech service bullitin in mitchell on demand)
1 was the grounding on the ecu (i scraped some paint off from underneath the bracket to cure it)
1 was the fuel pump itself (guy had 720's and they were sucking up too much fuel--warlboro fixed that one)
and the last one was the secondaries themselves being plugged up (i used my brake cleaner/air compressor trick on them)

it seems like this problem has no preference as to turbo or n/a cars.

NZConvertible

There shouldn't be one. When the secondaries kick in all four injectors fire at half the pulsewidth that the primaries were previously firing at. There is no change in total fuel flow as a result of the changeover so there should be no drop in pressure.

adamlewis

When I was running the stock ECU, I had the sputter every now and then. I grounded the ECU wire and it when away. One morning, it came back. I checked the ground and it had come loose. Made the connection tighter and it never happened again.

Now I have a Haltech so......

HAILERS

*********What series 7, please? ************

Series four, of course. The good series.

And the crimp splices on the secondary injectors, that I mentioned in the earlier post....... was where the previous owner replace the injector plugs and had crimped the wires on. I suspect there had been a fire there at one time seeing as how the bonnet liner was charred.

HAILERS

*******

HAILERS

Troniclow.......can you drive that car gently above four grand??? Just not be hard on the pedal but gradually accelerater above four grand????

Are you possibly hitting fuel cut???? Let's say you get above four grand, say five, and then stomp the pedal. Hit a brick wall? Do you have a fuel cut defender? What kind of exaust do you have? A downpipe and presilencer?

Eternal_Gamer

iTrader: (10)

I heard some say the stock wastegate is too small

GUITARJUNKIE28

emphasise "shouldn't".
then use a fuel pressure gauge and watch it...you may be surprised at what you see.

Canadian Rotary Man

Ok, here's my take on the whole thing. When the ECU hits ~3800rpm it changes duty cycles. from primary injectors to primary + secondary injectors. If your car's fuel mixture isn't set right(allong with the TPS) the ECU will run too rich for a split second when the secondaries engage causing the hesitation.

I recently rebuilt my throttle body to fix my car's idle problems. As soon as I got the TPS to hold a proper setting with the fuel and idle mixtures set properly the 3800rpm hesitation went away and power increased noticably.

On NA S4 RX-7s the cold idle system is done with vaccum lines and cams. When the idle cam sticks it thows the TPS out. It's a real finicky system. But it's EASY to fix. Helps your fuel mileage and emissions readings a lot when set right.

Do this before regrounding stuff. It's a lot easier. Also, clean off the ground from the top of the intake to the firewall with some steel wool if it's really bad.

GUITARJUNKIE28

actually you're backwards on that. on the fc's, the injectors have a constant ground and the ecu provides the power.

it's backwards from the way most cars work-where the ecu would provide the ground.

Icemark

No you are backwards/wrong!

If you look at the schematics (as well as in the car itself), there is a Black/Yellow wire and a LightGreen wire (or light green with a strip) at every injector (or Browns with strips and greens with stripes if you have a 86-87.5)

The black/yellow is 12V+ from the Main relay and is 12volts. If you have browns, then it is still 12volts, but through the resister setup but again then to the main relay for 12volts.

The Light green wires are switched ground wires from the ECU.

If you don't belive me or hailers, go out to the car, unplug any injector, put a digital multi meter on the Black/yellow (or brown w/stripe again if you have a 86-87.5) wire and turn the key on (without starting the car). You will see 12+ volts.

NZConvertible

Where did you get that idea from?

HAILERS

GUITARJUNKIE28........you're getting confused b/t your RX-7 and your YUGO. humor, please. IceMark and NZ be right on, bro.

Being a natural born attack dog (maybe just a dog?), I think I'll challange the bit about the fuel pressure dropping when the secondaries come on line. I drove around with a fuel gauge attached to my windshield wipers for at least a week and never saw that. What I did see ......was when stomping on the pedal and reaching 3500 rpm, was the fuel pressure rise up from approx 28psi to almost fifty when I maxed out on boost (sorry, low booster here, only 10psi). The only time I saw fuel pressure drop was when I got off the boost.

Believe it or not, I'm not ragging on you. Just what I've seen with my car. Actually the boost started rising prior to the 3500 rpm. It starts to rise as soon as I get into boost. Folks are tooooo sensitive around this site. Damn, the tv's on and the radical left is on C=SPAN again. Rabid dogs.

wpgrexx

On my 87 sport had bad hesitiation at 3800

I added a gorund to the boost sensor, nothing changed

I added extra batterry and chassis grounds, nothing changed

I chenged to clean injector, nothing changed

I changed the secondary injector relay thing at the MAF snsor, nothing changed


I added all new grounds at the ecu to each ground pin, no more hesitation. PROBLEM SOLVED

NZConvertible

So tell us what you saw. Is the fuel pressure changing significantly or is it just a momentary blip? Unless you're using mismatched, upgraded injectors with poor (or no) tuning, there shouldn't be anything more than momentary blip in fuel pressure at changeover, if anything at all. Any more than that and I'd be looking for problems.

GUITARJUNKIE28

from the schematic. where else?

HAILERS

Attached is a schematic for my 87. Others similar. The 12v comes from the green dots (it's an old jpg and the dots are there for some reason I don't remember) and goes to one side of the injectors. The ground comes from the ECU pins 3E, 3F, 3C, 3H.

If someone grounds out the brown/white wire on any of the sensors, then you won't get a ground pulse at the injectors to feed fuel to the injectors. Keep that in mind if you ever wonder why a car does not start and everything else SEEMS to have been checked out.

If you trace the Black/Yellow wire back to it's source, you'll find it passes thru the MAIN RELAY and then to the source....the forty amp fuse in the engine bay. This is a 86-87. Other models similar...just not as good.