After reading through about 1000 posts reguarding this pulsing issue I am having with my car, I have just plain confused myself .

Heres my case:
I start the car, it idles at 1500. I press down the gas, release- BAM pulsing idle. Only does it from 1500-1600. Now the car warms up- I get a 800 idle, well some of the time. The rest- its still pulsing.

What I have done.
Adjusted TPS with a DMM, replaced and re adjusted. Sits at 1ohm perfectly.
Cleaned whole assembly around TB to prevent sticking.
Adjusted the BAC to no avail.
Checked, double checked, and checked again for vacume leaks. Replaced 90% of all vacume hoses and used carb cleaner to find no such leaks.


Now heres 2 things. My bac control circuit in the ECU is fried I think- the connector, brittle from age crumbled, allowing the pins to touch. I can no longer adjust the bac, well- it does nothing.
The other thing- I had to remove the coolant lines running through the throttle body. The conenctors were so badly rusted from the last owner using NO antifreeze- that pin hole leaks were everywhere around them. Could this affect the thermo wax or what not?? Should I just remove this and do the throttle body mod?

Any input would be helpfull as this is stumping me.

 

I also know my injectors need to be cleaned, I kinda half assed it this weekend with a container of carb cleaner and a whole lotta free time.

The stuff that came out of them was just amazing- Mixture of 17 years of gas and crap in the fuel. All of the Orings and Rubber seals were in great shape- when I get them pro cleaned- Ill replace them then.

The car pulls alot harder in the bottom end with these "cleaned"- Ill report back how my other plague of hot start and flooding issues has been solved, if at all.

 

There could be a Bad gasket somewhere, either on one of your intakes or on your ACV or BAC or something..My car was doing this as well.. it stopped after i did a bunch of things, idles almost perfectly now.. Check for nipples that arent plugged on the intake

 

hey
Mine had somethign to do with mazdas little secret. The Sub zero start system. When the car starts cold, it injects coolant into the engine. When I replaced my system the pulse stopped. try adding coolant to the resovior 90/10 coolant-water mix. Or, just get a block off plate for where it attaches to the block.

 

Ive checked every vacume line I can find, and wasted a can of good carb cleaner.

I do need to replace my UIM gasket, I know that for a fact- its not leaking as any test I can do show, but with how many times Ive had to rip the UIM off- It needs it.

 

My car came from the factory without one?

 

Hey just an idea but here's what I did. Replace the check valve on the vacuum hose behind the intake manifold. Mine idled like **** until I replaced the check valve.

 

check your O2 wire and the O2 sensor(bad O2 can couse lots of issues)...and another source of bouncing idle is the thermo wax

 

Replaced O2, resoldered and crimped a new connector on the harness after origonal broke.

Im really leaning to the Thermowax- but im not sure how that whole assembly works .

Oh and I replaced that checkvalve and vac line.

 

The Spyder,

You'll probably end up needing to go through the ENTIRE intake, fuel, & exhuast system hunting down all vac leaks, replacing all gaskets, hoses, gromets, etc.. and fixing/replacing broken components.

Check this link:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/faq-idle-problems-286931/

I'm going through this with my A/C causing fluctuating idle, low 250 idle or dying when the engine's decelerating & under the A/C's load, etc...

Already cleaned & verified my BAC, ACV, and Air Pump fixing emission issues.

 

I thought so.

However- I warmed the car up with a nice LONG drive, adjusted the tps- and the idles down to 1300 no pulsing. It just went away??

Ill try starting it tommorow and see what happens after its cooled down.

 

I have a reman engine, and recently just put all metal gaskets in it to ensure no leaks there. My PowerFC needs to relearn the idle every time it loses battery voltage. i.e. pull the battery cable off. It just takes 10 minutes of idling with no load then 10 minutes of idling with load to get it back. The load could be A/C or lights. Good luck man.
Mike

 

Bumping this back up.

My idle is now a constant 1500 pulsing. Dosent settle down or anything. I have replaced ALL vacume lines, new UIM gasket, tested working TPS, and the carb cleaner trick does nothing.

The only thing I can think of is the fast idle assembly. I have a known good TB assembly I will switch onto this car and try.

Im going to try adjusting the tps again- I think the "good" replacment I have is bad. Because its range is from 1k-7k!!!! That would explain my high rpm hesitation, no?