seveninphilly

iTrader: (7)

Ok so I picked up an '86 gxl for my lil bro. It has a very bad 3800 hesitation(sp?).

What it does
1. car in neutral, step on gas feels free to bounce off the red line no hesitation at all

2. in any gear, driving it feels like you hit a wall at 3800

3. ease up on the peddel and it will accelerate just fine

I have delt with this before but not as severe my '88gtu had a minor hesitation, that was fixed with cleaning the 5/6 ports.

I have just for kicks changed the AFM, TPS(and set/the car idels great),

So has anyone had any luck with cleaning /checking the grounds? replacing the resistor for the injectors? or something entirely different.

thanks any input is good

osiris7

I highly recommend the hiper ground system or Circle Earth system by HKS..I have the HKS system and what it does is completely reground everything in the car..When i put it in i noticed immeadiatly that everything was alot brighter and my damn clock which never worked was working again..It also smoothed out my idle and alittle more power was felt..I personally again recommened it.

Relisys190

iTrader: (4)

i installed my own ground kit useing 4 4guage wires from the auto store, just install them in good places between the batt//engine//and chassis somewhere

ONLY one problem, i still have hesitation. but i am hoping that cleaning my 5th/6th ports should help

I dunno. i guess we'll see
-Mar (KUS)

guitarman68

Definitely something with the 5th and 6th port actuators... 3800 is when they open up.

Take them off, clean them up, make sure they can open up okay. I need to clean mine, normally it will give out a tiny bit when I hit 3800 then open up again.

Put a strip of grease on the rod and then put them back on (after you clean them up) and then take her out for a good run opening it all the way up and bringing it through the gears.

Take her home, check out the actuator (the little rod that you put the grease on) to see if the rod moved or not and if it went through the grease or not.

seveninphilly

iTrader: (7)

As far as the 5/6 ports go they open with a light touch of the finger. So i'm guessing that is not the problem

BTW the car is bone stock

HAILERS

Pulling the ECU plugs off and splicing in a ground to the pins 2R, 3G, 2C and 3A. Just spliced a ground, by soldering to the existing wires and terminating them with a ground lug and attaching that to the bolt that hold the ECU down. Thats on a series four, not a series five.

If I remove the ground lug and let it float in mid air...the car will hesitate when the secondarys come on under hard load at 3800 or there abouts. Put the lug back on...no hesitation/stumble.

See the thread by RXSTER in the archieves on this site.

I also spliced a ground to the brown/black ground wire for the boost/pressure sensor. Had/has, little to no effect.
https://www.rx7club.com/forum/attach...&postid=488879
https://www.rx7club.com/forum/attach...&postid=488875
https://www.rx7club.com/forum/attach...&postid=488871

seveninphilly

iTrader: (7)

So here is a ? for ya, do you think this could be a problem within the ECU its self such as burned out diode,resistor,capacitor or the common cold solder joint. Or is it independant of the ECU as in bad/broken wire in the harness, Or bad sensor/sensor connection on the engine.

A'PEXi 7

i got a new tps it was all good after that good after that


mike

seveninphilly

iTrader: (7)

ttt

I would love to figure this out
to find the true source of the problem

HAILERS

The hesitation I'm talking about happens at approx 3500/3800 rpm and only during hard acceleration. If your car will not hesitate in this range if you baby it through this range......then your problem is a bad ground, most likely.

If your car bucks a bit at other rpm/times, it's likely its another thing, like the tps.

Have you ever read the posts on this site where the fellow changed the engine or redid the harness under the intake and then his car did not start. Then later he finds he did not reattach the ground lug under the intake manifold? That's the grounds for the ECU. ECU likes to be grounded.

Look at the attached url. Look at the pressure sensor and how it has a wire that is BrB. Notice how the tps has a wire that is BrB, and the water thermo sensor has a wire that is BrB and the afm has a BrB wire. Notice how they all tie together? In real life they are indeed spliced into the same wire. Thats a ground wire. If you rip your harness apart b/t the crossover b/t the chassis and the engine, you will find a number of mechanical splices. That is a weak point. Some harness wern't made very good. Two out of three of my cars are good. One is a lemon, or was until I added the grounds noted in the earlier post.

On my car its not a matter of the engine itself not having a good ground. You can take a meter and you'll see 0.1 to 0.2 ohms b/t the battery negative terminal and any point on the engine. I don't need any extra ground straps b/t my engine/chassis/battery/coil. My coils are attached to the chassis and that is an excellent place to get a good ground for them. Don't need no stinking ground wire to my coil assy's to the battery. It's the ******* splices in my harness.

Other cars may differ.

Attachment: https://www.rx7club.com/forum/attach...&postid=601909

seveninphilly

iTrader: (7)

Hailers,

Thank you for taking the time to explain it. That makes alot more sense to me now than just running random grounds from this to that and hoping for results.

This weekend will be tooling time and I will post results

thanks again

seveninphilly

iTrader: (7)

One last ? in the diagram is this wire side facing me, or open end (that plugs into the ECU) facing me

Peruvianrx7

iTrader: (25)

is it true about greasing up the 5th and 6th ports? when i finished the rebuild i cleaned the hell out of them and they looked so shiny and perfect, but i didn't grease them i didnt grease the acv tiny arms that move the air cans on the ACV... could this be causing the 3800 hesitation? should i grease them? or is it even necessary? I will get the grounding kit first...

jinx22630

Ok. I did every single possible thing there was to do to my 88 N/A and nothing worked to cure this problem.
But here's what finally fixd it, and I think that it might be an overlooked solution.

After pulling out my scondaries the other day and cleaning them, I found that they were quite dirty, but, on the bench, they worked fine and sprayed. So, next step was to check the harness at the injectors and see what was going on at 3800 rpm. Everything was happening as it was supposed to. So I put the injectors back in, hoping that something would magically happen to fix it. Well it didn't.

So late the other night I decided to go out in the cold and pull them again. With flashlight in hand I shined the beam down the hole that the injectors went in. To my surprise, right under where the nozzle would be, there was a small disk with lots of tiny holes in it. So i figured what the hell. I got out some carb cleaner and a small piece of wire and cleaned out all the holes on the little discs. I reinstalled everything and fired her up. Of course she smoked a bit, but no biggie. I took her out for a spirited drive and all I can say is "Holy ****!!!!", it was like driving a brand new car. It pulled all the way to redline so fast that I buried the needle. I had power where I never had before.

Needless to say, after grounding, setting my tps, cleaning injectors, cleaning harnesses, soldering in new harnesses, cleaning 5th and 6th ports, trying new ecu's etc. I'm very happy to announce that this little accident has completely fixed my 3800 rpm hesitation.

If anyone is interested I'll try to take some pics, as I need to remove the injectors again to do some other things.

seveninphilly

iTrader: (7)

Sorry I have not got back on this post my brothers car is down for the winter for a clutch and some body work will get back in the spring for some updates.

Peruvianrx7

iTrader: (25)

sorry man i know exactly what u are talking about but i cleaned them both out when i rebuild the engine, and the hesitation was there. maybe their is different fixes for different cars. and by the way those things are called diffusers.

boosted1205

iTrader: (9)

It could just be bad grounding as Hailers said.
For a long time I was chasing tails trying to figure out a hesitation problem I've been having. It does almost exactly what you described. When I ease into it it's fine but once I floor it, it bogs. I THOUGHT it could be the secondaries but they were cleaned recently .
I thought to myself it can't be the grounds because I grounded new wires at the ECU and in the engine bay .
One ground wire at the ECU was not properly attached when I decided to re-do the wires .
When I was chasing tails, I must have pulled out a wire (there were a LOT of frustrations). The wires were all wrapped with electrical tape so I couldn't see it. **ONE** ground wire caused all sorts of havoc. **NOTE** solder *all* wires, no butt connectors. The single one that I didn't solder came loose.
It was more frustrating becase it didn't pull any error codes. Anyway, try the grounds. The MOST important one is the one below the throttle body attached via a ring connector . Good luck.

SevenGirl

jinx22630, pictures would be great.

jinx22630

ok. gotta wait till it gets above freezing here though!!!!!

SevenGirl

Oh heck, guess I gotta wait Blurrr... Might consider moving where it never gets that cold

TurboIISpiock

Doesnt those grounding systems usually depend of mod because i read somewere running a stock system could cause you to lose some ponies....... True?

Alias

Lose some from grounding? You won't gain anything from grounding, just get back what you lost in the first place.