NA type running rich? (tuning?)

warrior · Post by **warrior** » Tue May 24, 2011 3:36 pm

I think my 1991 na is running rich. It has a very dirty (black) pipe and after any drive longer than 20-30 mins it leaves a black sooty film on the rear bumper. Also if I give it a go it will backfire a little when changing gear. The car runs very well and revs good but i,m sure it is running to rich.

What is the best way to solve this? Do I need to get it tuned or can I fix this myself. I dont want to put it in the garage unless I have to so I am happy to sort this out myself but am not sure where to start.

Anthug · Post by **Anthug** » Tue May 24, 2011 3:44 pm

Do you still have the catalytic converter?

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warrior · Post by **warrior** » Tue May 24, 2011 5:19 pm

Will check in the morning when the light is better....not to sure. Checked the plugs and they look ok to me , but i,m no expert. Running BOSCH PLATINUM FUSIONS FGR7DO1 Are they the correct plugs? Why do you ask about the converter?

Anthug · Post by **Anthug** » Tue May 24, 2011 6:07 pm

Usual symptoms of black around tail pipe when cat removed.

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brownie · Post by **brownie** » Wed May 25, 2011 9:46 pm

and goes without saying,your running 95 unleaded fuel,Cause the 91 is absolute shite and not designed for these cars,or ANY Jap import for that matter

aidwano · Post by **aidwano** » Wed May 25, 2011 10:21 pm

On a similar note mine has just started running lean.

I dont know why because it was fine up until a few days ago. I've got a feeling the fuel pump may be playing up as the car died at an intersection about the time it started to go lean. I've also got an rx7 AFM so i will check that is still calibrated as I set it up.

Any other suggestions for what it could be?

sprsta · Post by **sprsta** » Thu May 26, 2011 7:22 am

has anyone checked their o2 sensor?

warrior · Post by **warrior** » Thu May 26, 2011 2:56 pm

how do i check the o2 sensor?

WideOpenThrottle · Post by **WideOpenThrottle** » Thu May 26, 2011 4:29 pm

warrior wrote:how do i check the o2 sensor?

Pull it out & see if its burn't away!? I think there is some way to measure voltage but never done it!

Also & this is a wild guess... the heat shield around your air filter? restricting oxygen perhaps???

brownie · Post by **brownie** » Thu May 26, 2011 8:53 pm

That's something else crappy fuel will with stuff,O2 sensor.

sprsta · Post by **sprsta** » Fri May 27, 2011 7:16 am

warrior wrote:how do i check the o2 sensor?

heres some reading material

http://mr2.com/TEXT/O2_Sensor.html

0v is lean/broken
1v super rich

make sure the car is fully warmed up

also check for vacume leaks

Trevor · Post by **Trevor** » Fri May 27, 2011 12:07 pm

Briefly --- The mechanism in most sensors involves a chemical reaction which generates a variable voltage. The typical sensing element comprises a zirconium ceramic bulb, coated both sides with a thin layer of platinum. The outside of the bulb is presented to the hot exhaust gases, while the inside of the bulb is vented through the sensor body to the outside atmosphere.

A rich air/fuel mixture results in very little oxygen (O2) in the resultant exhaust gas and the difference in oxygen levels across the sensing element generates a relatively high voltage across the sensor's platinum electrodes, i.e. usually between 0.8 and 0.9 volts. Conversely a lean air/fuel mixture results in greater amount of oxygen in the exhaust gas and the output voltage runs relatively low at between 0.1 and 0.3 volts. When the air/fuel mixture is correct and combustion is complete, the output voltage runs at a mean of around 0.45 volts.

PLSEME · Post by **PLSEME** » Fri May 27, 2011 1:53 pm

Checked the plug leads

Keith Jones · Post by **Keith Jones** » Fri May 27, 2011 3:02 pm

If you want to check out whether it is the O2 sensor PM me, I have a spare one you can borrow to try.

dynofiend · Post by **dynofiend** » Sun May 29, 2011 10:27 pm

o2 isnt the only sensor it could be. Coolant temp sensor also has a direct effect on fueling, as does the MAF.

Incidentally, backfiring is usually a sign of the engine running lean, so it sounds a little like you have uneven fuelling, rather than just overfuelling.

aidwano · Post by **aidwano** » Mon May 30, 2011 6:31 pm

Checked my oxy, afm and ignition timing but they all seemed ok. Had a play with the throttle position sensor and it seems to have done the trick. Maybe you could check that?

dynofiend · Post by **dynofiend** » Mon Jun 06, 2011 4:39 pm

Odd, I was pretty sure the TPS in a 1.6 NA is binary. IE it only reads as either open or closed, as opposed to most cars where it is a constantly variable signal.

sprsta · Post by **sprsta** » Mon Jun 06, 2011 6:25 pm

may have been adjusted for the ecu to think it was open when it wasnt
i found mine was the same when i installed my link