JRX788

i just bought a 86 rx7 w/135000 and i replaced many parts but cant figure out why it is running lean. It is very noticable at idle because of the constantly jerking motor until u step on gas and also in its lack of performance. Any help would be much appreciated.

classicauto

iTrader: (3)

How do you know its lean?

Surging idle can be many things. Vac leaks, misadjusted/faulty TPS, bad BAC.......

JRX788

i took it to my former auto shop teacher and i adjusted my tps and my idle. It would stay running but not good you could tell the mixture was off but the motor just bouncing around at idle. We also hooked up at voltmeter to the O2 and the voltage reading stayed low so he told me it is most likely running lean.

i already did the tps , the timing, checked plugs , i tryed looking for leaks w/ the smoke machine, the car will run but with a big lack in performance. we think it may be running lean by the low o2 readings

if any one has any clue to what it could be please send me a pm or a reply with any details. i am also looking for any shops able to work on rx7s in the ct area

classicauto

iTrader: (3)

How did you "adjust your TPS and idle"?

Getting a voltage reading off the stock 02 sensor isn't going to tell you much. Also, if the sensor is actually reading lean (which should be a higher voltage, not lower) then its either innaccurate (most likely) or there's a major issue like a frozen injector. Any 2nd gen should be on the "rich" side of the stock narrowband sensor, even at idle for the most part.

You more then likely have a vac leak causing the surging at idle, don't bother worrying about AFR's at this point.

Also, some information such as model and modifications would be helpful.

HAILERS

What's the idle rpm?

What parts of the emissions have been removed?

What happens if you turn the variable resistor clockwise towards R? At idle only. Does not effect any other speed.

Bouncing idle can be too many things, including the vacuum hoses at the front of the dynamic chamber being swapped around.

Could be the grommets b/t the fuel injectors and the housing are leaking. Could be a lot of things.

If the emissons are still there, like the airpump and ACV, then the 02 reading will show lean even though the real mixture is rich. That's because of air being mixed with the exhaust gas prior to the 02 sensor location.

Could be a lotta stuff. Even timing.

Aaron Cake

iTrader: (1)

Check compression.

Also, has the car received a full tuneup?

The idle should need no adjustment under normal circumstances. It is electronically regulated by the ECU via the BAC.

The TPSs will need attention from time to time though, but there is a very specific procedure to adjust it. The car must be FULLY warm so that the thermowax has melted and the cold start cam is no longer holding the throttle plates open. The test light method can produce some mixed results, so adjusting by resistance is the best way in my opinion.

Running not good? That sentence made me die a little inside.

Measuring the voltage at the O2 sensor is not a reliable way to judge mixture. The sensor may cool off at idle. Also if the emissions system is working as designed, the sensor will be reading full lean at idle due to the air injected by the air pump.

Were the plugs and wires replaced, or just checked?

classicauto

iTrader: (3)

Doh, forgot about emissions. Been too long for me and that stuff

HAILERS

How can we forget the Clean Air Act???

Anyway, I flat forgot to mention the possibility of someone jacking with the AFM's internals. Do that and know not what your doing results in.........crummy performance, lean mixtures, rich mixtures, bogging and stuff. Thou shalt not jack with the afm.

JRX788

Alright here is all the info. The car is an 86 rx7 either and se or gxl not sure it is a 4 seater and the only two power items on the car is the sunroof and mirrors. the car is completely stock. there are no performance parts in the car i rather have a beautifully running stock rx7. i bought off a guy who was a mechanic and not a very good one at that. the two things that i know he deffinately replaced were the secondary fuel injectors cuz he gave me the old ones with the car. i noticed one of my secondary fuel injector seals or seats whatever they are called doesnt look properly seated. it looks like it wasnt pushed in all the way. when he had the car he told me it ran beautiful until normal operating temperature and it would die. so i bought the car so far i have put in the water thermo sensor on the thermostat, a new fuel pump cuz the old one was shot and looked original plus it was sitting in a tank with 8 month old gas. i drained the fuel line and replaced the fuel filter. i check all the plugs and the ignition timing was good also. i saw in the computer at school(which they have AllData) that there was a common problem with the temp switch in bottom corner of the radiator. i checked for power from the wires and it was there. the terminals looked a little corroded so i cleaned themup and reconnected them. i hooked up the emissions smoke machine to look for hopefully a leak in the dynamic chamber but i didnt see any. as far as the resistor goes i tryed adjusting that and it does affect the motor.i believe when i turned it towards lean it would die and when i turned it towards rich it would get a little better but still i take the car out for a ride and it has low power almost like i am trying to take off in second. i believe i had the DMM hooked up to the o2 correctly but the readings were in the negatives (positive to the o2 and the negative to the ground or battery). my teacher told me to check to see wat would happen to the o2 readings witha minor shot of starting fluid and the numbers were still in the negatives but they increased and came back down. The mass air was hooked up during that test.the nubers being in the negatives probably could have been the cheap DMM. Once again the car is completly stock the guy didnt try to hook it up with shitty performance parts he used it as a regular until it broke and he didnt want to deal with it. i dont know if any of this info helps but if any of this info sounds familiar please respond or send a pm thank you.

JRX788

I never screwed around with the air flow meter and to actually test it i took mine out and threw it into my friends 88 SE w/ 93000 miles and it worked fine in his but i did notice that the flapper would move a slight bit easier then his but i expected that since mine has about 30000 more miles.

JRX788

reposted same info accidently

JRX788

i adjusted the tps and idle how All Data told me to. first of all the car was warmed up and i built my own test light. plus i also double checked it with an ohmmeter and the reading at idle position was 1.02 which isnt much off from 1.00 ohms. and the idle was done by the idle screw on top of the throttle body with a jumper installed on the intial set coupler.

HAILERS

Look at the 02 reading while idling. Have someone pull the Blue plug off the Relief solenoid (this works on a NON turbo engine, not a Turbo)and once you do that the 02 reading should show quite rich because the air from the airpump should be dumped in the silencer in the right fender instead of the exhaust ports.

That's just something to do while awaiting someones answer as to why the car is running bad.

Did you say you checked the timing? Did you reply as to what the rpms are at idle?