Ok guys all of a sudden last week my 3800 rpm hesitation turned on like a light switch. BOOM so anyway now my car starts bucking and back firing just before 4k making me look like an ******* everytime i pull out of a parking space. SO i checked the faq and it says:

"The dreaded 3800 RPM hesitation is cause 90% of the time by poor ground connections between the engine, the battery, and the car. Clean or replace all the under hood ground connections. On 86 model year cars , replacing/regrounding the pressure sensor's ground wire has helped (do not re-ground a 87 or later model year). If there is still a problem after that, look at cleaning the fuel injectors and (on a N/A) that your 5th/6th ports are operating correctly"

Now I would like to know if someone can identify to me the ground from/to the engine block. I have an 86, what pressure sensor ground are you talking about? The only one I can think of is the oil pressure sensor and there is only one wire coming from it.

 

engine block ground is on tranny bell housing. pressure sensor is in front of pass. side shock tower

 

I get the same hesitation on my T2 but its only slight. There's no bucking or backfiring whatsoever. Check out RotaryRessurection's DIY Ground Kit. It can't hurt.

Chris

 

i did have the same problem, what u might want to do is check ur secondary injectors see if they are working. Then try checking your fuel tank, check and see if ur fuel filter is dirty. Those were my 2 problems

 

I regrounded the EFI harness (under the UIM) basically cleaned it, and then attached another one from it to the firewall and it cleared up the trouble on my '87 T.

 

DESCRIPTION

If you encounter a 1986-87 RX-7 vehicle with a surge or stumble during acceleration at more than 2500 rpm, this may be due to an improper ground between the emission control unit and the air flow meter. Test for the symptom according to the procedure shown in this Service Bulletin. (Refer to Service Bulletin Category 4, No. 036/87.)

The ground circuit of the emission control unit has been improved since November 1, 1986.


Those are the words from the TSB

CHECKING PROCEDURE

Use an ohmmeter to check the resistance between the 2C terminal of the emission control unit and the boost sensor/(pressure sensor) ground terminal (BrB). If the resistance is not 0, proceed to the next step

Those words are from the TSB.

About five items on your ECU use a brown/black wire for a ground to pin 2C. They, Mazda, elected to tap the brown/black wire at the boost/pressure sensor instead of the brown/black wire at the AFM. It's easier to access is the why of it.

All the TSB are at ALLDATA.com It cost a small token to view them. Less than a half tank of gas.

 

Ok from what some said it seems more like the fuel filter than the electronics of it.
I just came back from a drive and it find that after driving a bit it allows me to go straight to 5k without a problem. Also bucking, backfiring and the absolute inability to pass 4k dont seem to fit under the term "hesitation".

I also havent changed my filter after cleaning my shitty rusty gastank.

Well ill try the fuel filter tomorrow and if it doesnt solve the problem im gonna pay someone with more time to reground everything. I pray its something simple.

 

And your water thermo temp sensor is working? Checked it out? Plug on. Approx .4-5vdc once the engine is warm on the input wire to the ECU?

Boost/Pressure sensor working? Measure the voltage at the ECU per the FSM to check it out.

 

I got a 86 N/A and wana reground my pressure sensor. Is there a step by step to do this? (And dont tell me to search i already looked for like and hour. Im not saying its not here i just cant find it lol)

 

so the water thermo sensor can cause a hesitation of some sort if so then i think i found my hesitation and cold start problem!

 

www.aaroncake.net has a guide to redo the grounds. Follow the links til you find it.

 

Resolder the ecu solder joints. After going throw it with a magnifier. If that's not it reground the grounds with sandpaper. Have the same problem, but I haven't fixed it yet. I'll keep you posted. First I want to read up on the thread that instructed me on this fix. Can't find that page.

 

Problem fixed! Here's a picture of my ecu. Can you see where the problem is?
<a href="http://s5.photobucket.com/albums/y190/iamxeddiex/?action=view&current=P1010093.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y190/iamxeddiex/P1010093.jpg" border="0" alt="Photobucket"></a>

<a href="http://s5.photobucket.com/albums/y190/iamxeddiex/?action=view&current=P1010091.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y190/iamxeddiex/P1010091.jpg" border="0" alt="Photobucket"></a>

 

So it's a resistor that needs to be replaced??

 

it read good, just broken joints.