hey guys im back... so the car is running extremely rich now and the back fire remains so im not driving my car anymore until i can get to the bottom of this, so i called golen today about my problem and my first proceedure was to change the oil imediatly and pull a spark plug to check it so i did and the plugs look fine to me brownish greyish i think whatever was causing my backfiring finally gave out any ideas?

 

Bad tune ? Who tuned it?

You may have a really bad misfire as well? Bad misfire will make the O2 read rich, which will in turn lean out the other cylinders ... Which is not good.

Are you sure your gettin spark on all cylinders? Injector pulse on all 8?

Correct fuel pressure?

How is it if you wind it out?

If you floor it does the problem go away? The PCM bypasses many of the sensors under WOT.

 

yea at WOT its gone but... seems like down on power also if i waited for the check engine like to come on car run better than it was but still minor backfire i only drove that way i would say 20min just so that i can get home from work it is soo rich to the point where is it unbearable..oh yea and PCMFORLESS did the tune for me

 

I just seen you had Bryan do your tune, so that should be fine. He does pretty good work.

With it running, spray some carb cleaner or brake clean, something like that, all around the intake manifold, throttle body, bellows ... A vacuum leak, unmetered air, causes a lean condition on that particular cylinder ( If it was a leak at one of the runners) and would make the O2's richen the rest, to compensate. There are too many little things that need checked first ...

How is your TPS reading? If it is past its critical voltage where it goes into power enrichment mode, you could be runing around all the time too rich because of it. You need to check alot of your sensors out and come back.

 

this really sucks without a scanmaster but everything is changed out exept that darn TPS when trying to slot it to .67 the mounts broke but we still got it down to .67 with only the screw washers holding it down should i replace it?, could that be very well my problem? maybe it moved over time who knows....

 

I had a bad o2, and it would sputter sometimes under acceleration, at WOT though it is bypassed.

If the problem is going away at WOT, I would be looking into testing some of the sensors. Get it on a scanner somewhere and have it checked out. I believe a bad MAP sensor can cause similar problems? If you know someone who can hook it up and get real time sensor readings, check out the 02's, MAP, MAF, TPS ...

The 02's should constantly fluctuate between 100-900mV. At WOT they should stick around 800-900mV.

With the engine off, key on, scanner on, slowly press the throttle pedal to the floor making sure the TPS is going "linear" on the scanner as you depress it. Also make sure it is reading 0% at idle. Actually, I think it can read up to 1 or 2% at idle. I forget. Hopefully someone with more experience than me can confirm this.

But before you get it on a scanner, do the basics and make sure you dont have burned plug wires or anything crazy and easy to miss like that. Make sure all the conectors are clipped in place securely and such. Try wiggling on the MAF, MAP, and maybe tapping the TPS with it running if you cant get it on a daignostic scanner. Wiggle on the wires going to the sensors as well to confirm there isnt a break in a wire. Just go over all the little stuff that is easy to over look.

Some guy today at work brought a Celica in that he had been trying to fix for 3 days. No start, no spark. He was going crazy testing stuff, only for me to point out that the coil wire was chewed ( Mice maybe? ) in half lol. So dont sweat the small stuff. You'll get it running sooner or later.

 

thanks alot bro youve been very helpful take it easy buddy ill keep ya updated

 

The other way around.... misfires cause the O2 sensors to read "lean" when they see the unburned air. That causes the engine to run rich on all cylinders on that bank.

Don't look at the TP% on a scan, and no, it shouldn't read anything but "0%" at idle. You look at the TPS voltage.... between 0.20-0.90V closed throttle. The PCM bases the TP% on the voltage.

 

Playa7970 ~ Let us know what you find asa you check it out.

Thanks Fred ...

I really couldnt remember about the TPS % ... I know on my Uncles Snap On Scanner He could moniter a bunch of sensors at once, and it would show TPS in both V and %. It was neat.

Hahah my bad on the 02 thing. I kept thinking raw unburned fuel smell, super rich ... I just worded it wrong ...

 

ok i checked the tps voltage is at .67 theres deff something wrong with the map sensor when i unplug is car ran fine for 3min then check engine came on and run with the same symptoms..... but plugged it back in started car again car ran fine for 3 min then back to running rich again ??? any way to read what the map is putting out without a scanner fred please help !

 

Sure. Measure the voltage across the green (signal) and black (ground) wires. There's a table of MAP voltage vs. "Hg and kPa in my online scanner guide.

http://members.aol.com/InjuneerZZ/ScanMast.htm

 

I know it may sound simple but check your maf sensor and your air filter. My air filter caused my maf to go out and my car was running way rich.

 

If you just put a K&N or similar ( oiled ) filter on your car, it can dirty the MAF, causing inaccurate readings.

If you unplugged the MAP sensor and it ran fine for a little while though, I would definatly look into that a little further.