Bambam7

OK, I have been dealing with some of these probs since I got my 7. New engine- no change. New TPS- no change! No emmisions- no change!
Multiple probs- don't know if the're related. I am at my wits end.

1-It misfires, gives a "thump" abaout once a second at 1000rpms, and frequency increases with RPM's, to about every half second at 3500 (revving in neutral)

2-VERY harsh from accell to decell. just touch the gas a TINY bit, and it gives a big bump, then accelerates. Same to decell. (just installed new TPS- the old one was shot, but no change, and I did reset the ECU) Very annoying while trying to cruise at a steady speed- feels like I'm being bumped from behind.

3-I can't get it to idle above 600 RPM's. The idle screw is all the way out. The only way to bring the idle up is to pop off a vacuum line. Idle also sounds like it's kindof working hard, like the timing is way too advanced, but it's fine. It changes tone every few seconds or so- like it has a mind of it's own.... compensating for something.... The timing jumps around a bit to.

4-When *partly* warmed up at idle it revs from 1000 to 1300 or so.... by itself.. up and down... (There are no obvious vacuum leaks- but that doesn't mean there isn't one!!... Isn't that what it usually is?) When I give it just a touch of gas- like to rev it to 1200 or so, it does the same thing, (Whuup, Whuup, Whuup) If I push the gas a little more, at sortof gives a little cough/stumble, then the revs shoot up instantly all the way up to 2500. It just won't run smoothly below 2500 rpms.

5-Will only run with the pressure sensor dissconnected- with it connected it misfires and hesitates so badly it will barely acelerate!

So basically- the car is drivable, it's damn fast, but it runs like ***.
There is definately a managment problem somewhere.....

Well- Your turn.... Please give me some ideas, I've been through the car and back again.... Because If I get rid of it, it would be too emotional to be on the forum..... And I'd miss you guys! Sniff.

RETed

This is normal.&nbsp Changing to new spark plugs/spark plug wires might minimize it.


Misadjusted TPS.


You're running too rich at idle.&nbsp If you're talking about your 90GXL mentioned in your .sig, there's no easy way to fix this.&nbsp Are you running a bigger fuel pump by any chance?


Part of the TPS problem...

Bad pressure sensor?&nbsp Do a error code check on the ECU yet?




-Ted

HAILERS

The pressure sensor. Have you tested it with a voltmeter to see if it is working right? I don't have a manual for your car but it is probably similar to the 88 on line at http://www.iluvmyrx7.com/Technical_I...ice_manual.htm in section 4a. It requires a vacuum to be put on it. A Mittyvac can be had for about thirty buck at Pep Boys. Or if you have a meter and can get on the output which should be a brown and red wire on the sensors plug we can compare what you read at a given rpm compared to what I read on my car. Not a preferred method but better than nothing. I have what is called a pill in the vac line to the pressure sensor , its really a orifice, and my car does not like to run without it. Some people claim that the nA don't get one . Both my na have one. Shove a wire through the vac lline to see if you have one in there.

Snrub

iTrader: (1)

Mine does something similar to that. After reading the haynes manual I though it might be afterburn. Anyone know how to decide if it's a miss or not?

Bambam7

OK- re-adjusted the TPS, and the idle hunting is gone, I used the lights method- the ohm and volt methods don't seem to work for me. It seems to work best when I adjust it from NO lights, to -just barely- when the first light comes on. The second light wont come on for another turn or two, but it's better the further away from the second light coming on as possible. The bump on off decell is still there however, not as bad, but annoyingly present. I don't recall that being normal.

So- If the misfire is normal (anyone else have it?) That leaves me with the idle prob, and the pressure sensor prob.

Well, all signs point to to rich. My emmisions test also indicated WAY rich.... (very high CO, VERY low NOx)
I tried getting the oriface for the pressure sensor. , and hooking the pressure sensor back up- same prob. It won't run with it hooked up, and it doesn't test bad!!
The old TPS was shot though, and the ECU has a funny habit of comparing sensor values, compensating and learning engine conditions. When I put in the good TPS it wouldn't run worth crap until I reset the ECU.
The pressure sensor only controls timing advance, but with the new TPS, the ECU may see the pressure sensor signal as being good now, instaed of defaulting to "failsafe" (crap).

Idle prob- Well, I havn't modified my fuel system, but I havn't checked my injectors either. I dropped a primary injector while assembling the new engine- broke the pintle off of it. I have had a sneaking suspicion that It way be locked open or cycling to fast or something..... I am getting TII injectors from Six rotors. I'll know if thats the prob.

Thanks so far guys, any more input or interpretations would be great....

supergoat

Mine thumped too a little bit. I changed spark plug wires. My idle is smooth as silk now. Power delivery down low is a lot better too as well as throttle responce. Try changing wires, for $12 it's not bad, you probably need them anyway.

HAILERS

Pressure sensor tests good but car won't run with it hooked up? Can't help but think the wiring is screwed to the sensor or the ECU is corrupt. Almost hate to mention it, but have you checked and made sure the ground wire on the pressure sensor is less than .1 ohm??? Have fun. Is there the slightest chance that someone put a pressure sensor for a turbo in your car? As in the wrong sensor in the wrong type of car???

jeff_oner

i have a 91 n/a and i get a thump in the exhaust while idleing, it still thumps after changing plugs and wires. and when i let off the gas it thumps rapidly. is this normal also?

mazdaspeed7

The problem with your car being really touchy on the gas on and off the gas sounds just like mine. I think it has to do with the TB. Have you done the TB mod? I think the lack of the dashpot could cause this. The nylon inserts to smooth out the 6 ports smoothed out my idle a bit, and made it less edgy on-off throttle. Generally, it made the whole powerband silky smooth.

On the idle, advance your timing some, it will bring your idle right up. I have the opposite problem on my car. I cant get it to go below 1300 rpm idling. I know I could get it back down by retarding the timing, but I dont want to lose the power from this.

Your pressure sensor sounds like its making your small problems even worse, But I dont really know what to tell you about it.

HAILERS

OOPS

Tim Benton

iTrader: (1)

I just the, dropped it on the ground and broke the pintle off one of the injectors. And you put it back in? If so then there is your problem, things pretty much wide open with no pintle to restrict flow. Replace now like you should have when you dropped it and broke it.

Tim Benton

pp13bnos

iTrader: (1)

Maybe its time to go to an aftermarket ecu. I know it cost some $$, but it seams that would be the next major mod to your car anyways. Not to mention, would probably pickup upto 25hp. (Best case) If i was'nt saving for a house, it would be my next mod.

My car has a hunting idle for about 15seconds after i first start it. Its porbably the tps, but i need to get off my butt and adjust it.

CJ

Bambam7

Yep, I have determined the hunting idle is the TPS- fixed.
I replaced the O2 sensor about 4 months ago too.. No Change.
It's funny, If I connect the pressure sensor, I get an engine code for it only under accell. It is funtional, IE- If the car is idling, and if I suck (yep!) on the hose to the sensor- the idle drops a bit (and gets even rougher) which isn't good becuase it's around 500 rpms then. Same thing if I plug it into manifold vacuum.
I really can't afford an aftermarket ECU, plus I have to pass emmisions once a year. But I think I will test all the wires at the ECU as per the Dave Gibson's website.I will also re-ground the ECU grounds, and run supplementary ground and power leads from the battery to chassis and alternator.

Mazdaspeed7- You said when you put in the flow directors you also fixed a vacuum leak- Wouldn't you attribute all of your newfound smoothness to that instead?
And no, I havn't done the TB mod. Winters are cold up here, and I need the choke funtion during warmup or it'l probably stall.

mazdaspeed7

First, you need to replace that pressure sensor. I have one Ill sell you for cheap if youre interested, or you could get a new one.

Actually, once I got the manifold all apart, I noticed the gasket was bad on one of my 6 port covers, but I dont think it was causing a vacuum leak. Replacing all of the gaskets didnt do anything for my idle. I adjusted the TPS, it was pretty far off, and that helped smooth out my idle, but its still not perfect, and I cannot get it to stay below 1300 rpm.

HAILERS

Ok. You've looked for vac leaks in the obvious places. Try the not so obvious. Take the two vac lines off the acv and put a hose on the nipples of the acv and see if you can pull a vacuum. If not then the diaphram is leaking and is causing a vac leak. Do the same with the egr valve. Use the line going from the egr solenoid to the egr. If you can't pull a vacuum the diaphram is shot and is causing a vac leak. What is the part number written on the top of the boost sensor, please?

Bambam7

I don't have an ACV anymore....
The boost sensor part says
N350
EIT12272

I don't think it's a turbo one by accident, becuase at no vaccum it is already at 12V... If you BLOW into the hose it doesn't change the value any- only sucking on it.
I don't believe I have a vacuum leak anymore....
I have a fuel delivery prob somwhere.
I hate the bump it gives from acell to decell, no matter how slow you push the gas pedal... once it touches a certain point it gives a jerk... then accelerates.
Oh well.. Im going to put in different injectors, then start testing everything electrical.