13Beast REW

The FC is not doing too well. It wont idle regardless of what I throw at it. I've adjusted the idle, modified the timing, replaced the TPS, checked the injectors, checked the BAC and ACV, and verified fuel pressure. I was thinking that maybe the AFM was bad but when its unplugged the car wont even start. There are a few other things in the Mazda FC manual that I haven't tried yet like checking the water thermo sensor but I"m wondering if there is anything else I should be checking thats not in the manual?

hondahater

iTrader: (2)

did you check compression?

dcrews

iTrader: (2)

sounds like it could be a fairly large vacuum leak.....

Chuck

iTrader: (2)

I vote vacuum leak

motto

I had to replace the thermo sensor....

13Beast REW

Well... i replaced the vac hoses last night. Didnt run the car yet since I didnt get done until 3-4am.

This car is not in great condition, probably the only things right about it are that the engine runs well and the paint is a new looking in most areas. The interior is shot, I replaced the door locks last night and the pole for locking the drivers door from the inside is bent so i'm still trying to work that out. Atleast the passenger seat needs to be replaced since its been rained on atleast 50 times, the radio doesnt work, the antenna doesnt work, the fuel level sensor is going bad, the rear wiper is missing but the motor works, the window motors are goin bad, the TPS is a hack job, plus lot of other crap that I can't think of at the moment.

I'll post how she's idling or not idling some time today.

casio

it would idle better when warm than cold if it was the water thermo sensor. i've been there.
unplugging a sensor completely (like your AFM) doesn't verify anything. something can let an engine run if out of spec, but not let an engine run if its unplugged. it's not a proper test.

if i removed my rear wiper assembly, would you want to buy it? i don't have a switch on my car and haven't ever used the wiper in the 2 years i've owned the car. make any reasonable offer and i'll see how difficult it is to remove.

good luck with the car.
i would:
:volt/ohm test the TPS. make sure its hooked up right and reading correctly.
:make sure the AFM is sitting properly.
:open plates at idle a good amount (maybe just to help the car be closer to idle).
:make sure the water thermo sensor is plugged in. unplug it and check the contacts on the inside. one of mine was pushed back. this mainly affects cold engine since CEL fail-safe reads 176F at ecu. mine idled fine after a minute or so from cold start. so warm shouldnt affect much. (in my experiences)

13Beast REW

well... that didnt help at all but atleast it has fresh vac hoses now. i've already tested the TPS and its showing the correct voltage/resistance. The RPMs oscillate very heavily when trying to hold engine at a certain speed like 3000 RPM. I'm still suspecting some kind of air leak from somewhere though since when you build up pressure in the motor (like boosting on a turbo) and then let off at try to hold at 3000 RPM, the RPMs will actually hold steady for about 5 seconds then the oscillation will start back kind of gradually like the pressure is dissapating.

When the motor is cold the car will idle very roughly but as soon as it starts to warm up it (i'm guessing its as soon as the ecu comes out of closed loop) the motor bogs out. Now I know the idle is supposed to be just over 700 RPM but when the RPMs get below 1000 RPM even when trying to hold it there the motor bogs out like there is too much load on it (such as all accessories and lights are on and the computer isnt adjusting for the change in voltage). I'm trying to be as descriptive as possible so maybe someone will pick up on what it could be because now the situation is totally beyond the limits of my knowledge.

The only other thing I can think of in terms of the oscillation is that one or more of the solenoids are bad but even so, the car should still idle right?

13Beast REW

After searching a little bit and reading a little more I decided to clean the BAC, that didnt help either. Also, just to throw a little more info out there, the idle adjust screw is almost all the way out and it still wont idle. This just seems like a vac, solenoid, boost sensor, or TPS problem to me but I've checked all of those.

WAYNE88N/A

Vac leak....

The problems with vac leaks is that it makes you guys tweak on everything that was set right to begin with, which means when you finally find the actual problem, now you've got to reset all of your adjustments

The BAC and several other related idle items can be read from the ECU, key on, or car running, to verify each component...

Amur_

Might be an easier fix than you think.

https://www.rx7club.com/showpost.php...6&postcount=11

Amur_

How are you looking for vac leaks? My fav methods are to use either a garden hose or a butane refill... Water's free, but it doesn't reach everywhere.

13Beast REW

rather than check I just replaced them all. the only air hoses left that were on the car when i got it are the hoses connected to the air pump

13Beast REW

that and i think the CEL is blown or the wiring is bad. i thought wiring because i used to get an electical fire smell right around the firewall but i havent smelled it in a while

Amur_

There's more to check than hoses for vac leaks.

- fuel injector insulators/grommets (all four injectors)
- every joint in the manifolds where there is a gasket
- the water thermo valve on the BAC (often makes a whistling noise when it leaks)
- the snorkle from the AFM to the UIM

There're probably more things to check, but you'll have to ask someone who's more awake...

Even the idle adjust screw on top of the UIM can leak a little, but not enough to cause your current problem.

13Beast REW

i thought about the manifold. never got around to checking it which is strange since I had it off while i was changing the vac hoses. i guess i can check on that tomorrow or later this week. i'm just getting irritated because the car runs so well, lack of idle aside. Hell, it actually seems a little up on power considering its age and condition

13Beast REW

I'm about to go check out the manifold and gaskets, any other suggestions from anyone?

13Beast REW

I went out, drove the FC in the garage, held the rpms at 25K until I got got her all nice and warm, popped the hood, took a few pics, took a deep breath, said "damn thats more work than I feel like doin right now", back her out the garage and parked her. I'm naming tomorrow National Fix Atleast One of Your Damn Cars Day and wont be making an appearance at the JOB tomorrow. Hopefully it wont be a wasted holiday.

Prowla RX7

25k??? I'm sure that's a typo. 2.5K would be more realistic.

13Beast REW

yea you're right that was a typo. i meant 2.5K

13Beast REW

OK, checked the manifold and gaskets and they all seem to be in order. Granted the UIM has some old gasket crap on it, its still good enough to seal and I'll clean it once the damn car is damn idling damn it. On the other hand, the fuel injector craddle was totally clogged so I cleaned it. I also came to the realization that the hose from the air pump to the manifold on an S5 is not the same as the hose on an S4. So anyway, the car still isnt idling and i'm back to the drawing board yet again. Any ideas?

I took the liberty of taking a pic of the injector craddle inside the UIM.

Amur_

'Cradle' has one 'd.'


That's not a cradle - it's a diffuser. Cleaning it is good.


Dunno what to suggest. What part of the world are you in? Have you thought about posting in your regional forum and asking somebody with some experience to drop by and check things out with you?

13Beast REW

My friend actually posted that for me but he got the point across I guess. I have posted in the regional forum however not really any response. I'm back to thinking that the TPS is to blame. The TPS on this car has different color wiring (which may not mean anything) but I'm pretty sure its an S5 TPS and my car is an S4. I happened to have an S4 TPS but the wires on it are cut already so I'm guessing it may be bad also but I will try it. In the process of putting the manifold back on, one the injector o-ring was damaged so work on the car is suspended for the moment. I'm considering pulling the o-rings off my FD's injectors and seeing if its the same size.

The whole problem is strange though. Nothing I've done has had any effect on the idle at all. The idle adjust screw changes nothing, the voltages from the TPS read correctly, the BAC has been cleaned and shows proper electronic operation, all vacuum hoses have been replaced, the TPS has been adjust using the LED method, I've adjusted the timing, cleaned up the manifold, checked several related gaskets, brand new plugs and wires, fresh oil change and air filter, and I'm sure I've left something else out but atleast something should have had an effect on the hunting idle or the fact that the car stalls if the accelerator isnt pressed.

So as it stands right now, all I can think to do is clean the throttle body and test out this other TPS.

BlaCkPlaGUE

There is a adjustment screw for the throttle plates on the backside of an NA TB. If you twist it, it adjust the degree of how much the throttle plate stays open to allow air in at closed throttle. Have you tried adjusting this? it can be adjusted so that there is pretty much no air flow at all at that point, and if your BAC is sealed shut or you've removed emissions and plugged everything up, no air is gonna get in.

Amur_

He's saying that the engine is bogging out and dying when the rpm's under 1k. Bumping up the idle stop screw will only hide the problem, it won't fix it...