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Hello Everyone, I have been looking at this forum for years and I finally got my email fixed so I can post. But before I get started I just was to thank everyone for what they have done in the Thunderbird community. ok here we go..........

Just to start out I have a 1994 Thunderbird and the check engine light has always been on. I haven't really put the time into turning it off because it seem to run ok.
Until lately. I know Iv had 1407 for the most part. I mean its been some years. Then a buddy of mine looked at it and found a vac leak. So I got ford to order the hole peace that goes from pcv all around to somewhere on the driver side. could be brake booster. anyways just that helped a lot. but light come back on so I was like whatever.

So a few weeks past...then it started running rough. I mean I could smell gas. I would have to put gas in every other day. So I did a scan and it was showing P0155 has something to do with heater circuit on bank 2 sen 1. so I replaced with Bosch # 15717 upstream. cleared code. ran little better. stayed off for about a day. well it come back on so I just drove it didn't think nothing else about it. well then it started burning more gas. and smelled really bad. I had black stuff poring out the pipes. it got really bad. I didn't even want to park in my drive way. so I come across someone posting about the computer going bad. so I found the exact same ECM and got it and plug it in. crank first time. no burning gas smell. actually runs really good now. but the check engine light is still on. I don't know why. I finally broke down and bought a scanner and I ran it and got 3 codes tonight. P1151 P1131 P0155

I know this is a lot to read I just hope somebody can help. for the people that skip all the reading I have pictures of my scanner. shows live view. maybe this can tell you something. But for the most part the car runs very good when you drive. but if im setting still, its just rough. I know I still burning gas but its not as bad. I thought about running all new wires to all 02 sens. they could be shorted to ground or something.






 

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first of all, welcome :)

now i just have to ask, why would you willingly run with a CEL for so long without fixing it. you probably could have gotten much better fuel economy and avoided possible power-train damage by keeping that light out. fuel economy is nothing to sneeze at nowadays too :facepalm:

since your car is indeed a 94, and they are know for PCMs burning up and hanging injectors open. you most likely did have a bad PCM if it was running so rich and smelly. if swapping that out solved the fuel issue good work. unfortunately you may have fouled your O2's and they may need replacing. i would definitely inspect the wiring first though. it runs up through the engine compartment by the main engine harness connector then down under the car.

i dont really like the look of that one O2 running at 0v so you probably have some wiring problems somewhere. hopefully everything it connected good and none of the pins got damaged in the ECM harness connectors during the swap. usually they still show some voltage when connected but failed. they just fluctuate from high to low voltage really sluggishly. the upstreams should be going from high to low really fast. rears should stay pretty constant at a midrange voltage.

also what have you done to the car since you owned it? fuel filter, MAF cleaning, plugs/wires, vacuum line replacement? i would start with these if you haven't.

http://www.mn12tech.com/vacuum-hose-replacement.php is very helpful for the vacuum lines, their hidden everywhere.
 

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Holy Fueltrim batman!

Look at those identical sky high fuel trim numbers on both banks! I would start by cleaning the MAF sensor ASAP before driving the car. Either that or a very massive vacuum leak (a bad rubber vac line in the engine compartment). O2 sensors are not bad, don't blame the watchman for the bad news! Those numbers represent EXTRA FUEL being added to compensate for something!!!!

A good scan tool would give more parameters (like BARO) and a definitive diag could be made. But I would start with cleaning the MAF and watching those numbers.
 

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yep, i wasn't quite sure about those since the motor wasn't warmed up, but i would hope for them to be a little lower :tongue: maybe i should go see what my scanner says for trims on a cold engine. iwasnt to say their supposed to be somewhere around 2%
 

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yeah, mine were running around + or - 2% at 90* so those are indeed crazy high :D

at the most mine would get to around +8%

so + is lean right? must be some crasy vacuum leaks somewhere if so, perhaps a toasted MAF or something
 

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yep, i wasn't quite sure about those since the motor wasn't warmed up, but i would hope for them to be a little lower :tongue: maybe i should go see what my scanner says for trims on a cold engine. iwasnt to say their supposed to be somewhere around 20%
LTFTs are part of the keep alive memory that gets reset when you pull the battery. They take about 5 minutes to relearn, and reflect past history. I think 25% is the Calibratable limit.

STFTs should NEVER be 40. His total trim at idle is 40+25 or 65% (lean/adding fuel). And being identical on both banks also says a lot.

Also, his coolant temp is 91C ~ 190ishF, getting close to the boiling point and definitely warmed up!

I would like to see his trims when he starts driving, they will definitely go down.
 

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whoops, didn't see the Celsius XD 90* fahrenheit is quite cold
 

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Do a snap throttle test, watch the MAF parameter (turn off scanning other parameters for speed) and see what the MAF sensor reads at higher RPMs.

It should reach up to 153 gm/sec. THere is a pattern to look for if you scanner can graph, it is like a pulse.

Otherwise clean the MAF with maf cleaner, reset the battery (tons of tutorials on the web) and see if there is any change in the trims.
 

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Discussion Starter #9
thanks for all the feedback. just more info on what I done over the years.
tune up 4years ago
MAF replaced 8 months ago
ECM/PCM replaced 4 days ago
PCV Vac hose that goes all the around to brake booster replaced with factor ford part
02 bank 2 sen 1 replaced 3 months ago
replaced only 1 coil pack same time tune up 4 years ago
replaced fuel filter about 2-3 years ago


im check for vac leaks. I just keep getting that P0155 code everytime. its the first thing to show up. im check wires hopefully I find something.
 

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Try an oem maf (even a used junkyard unit) instead of that aftermarket reman unit.
 

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definitely... those A1's even new are complete junk. i tried 3 of them and tons of other tune up things trying to figure out my run ability issues back in the day. turned out the remand rubbish was bad out of the box 3x and i needn't have done most of the other few hundred dollars worth of work... :rolleyes:

just head out to ford and get one from them, mines been working for nearly 6 years now with regular cleaning every filter change.

but yes, run through the vacuum lines as well. their ancient nowadays and most likely will melt in your hands like an Egyptian mummy.
 

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:p yeah, my browser kept jumping back up the loaded images as they were popping up. couldn't keep my screen scrolled to the bottom for the life of me. makes reading latest posts a pain :D
 

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Discussion Starter #15
Before I go spending money. I'm try swap 02 sen from driver to passenger. The only code I'm getting is the p0155. Heater circuit malfunction bank 2 sen 1.
 

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Bank 2 is driver's side, sensor 1 is the one before the cat.

Be sure to check the heater circuit voltage at the O2 socket.

And don't feel like you're crazy if swapping makes it just plain go away - it could even be oxidation in the plug and socket!

One thing you CAN try, if it reaches, is to swap the plugs only, leaving the O2s in their original position. Oh, it'll run not-right, but if that fixes it, or if it swaps the problem, you'll have a handle on it. And if it makes no difference, then you've also got a handle on it - it's either the socket/plug, or the wiring for the heater power on just that one circuit.

RwP
 

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Discussion Starter #17
Thanks for the info.

But we're can I find how to check heater circuit. I know there are 4 wires. 2 are for heater and 1 is signal and the other idk. Can you ohm the heater circuit? Or do I just turn key and check for 12v?
 

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Thanks for the info.

But we're can I find how to check heater circuit. I know there are 4 wires. 2 are for heater and 1 is signal and the other idk. Can you ohm the heater circuit? Or do I just turn key and check for 12v?
Yes and yes.

BTW - Heater +, Heater Ground, Signal, and Signal Ground - four wires.

You check voltage back towards the ECM, and resistance of the O2 sensor's heating element.

That said - I have no idea what the resistance SHOULD be, but it shouldn't be open!

RwP
 

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definitely... those A1's even new are complete junk. i tried 3 of them and tons of other tune up things trying to figure out my run ability issues back in the day. turned out the remand rubbish was bad out of the box 3x and i needn't have done most of the other few hundred dollars worth of work... :rolleyes:

just head out to ford and get one from them, mines been working for nearly 6 years now with regular cleaning every filter change.

but yes, run through the vacuum lines as well. their ancient nowadays and most likely will melt in your hands like an Egyptian mummy.
The MAF in the pic is definately a reman. His looks clean, but that don't mean it works!
You are right about the MAFs. I got some from Advance Auto that were giving me worse readings than the one I replaced. Unless you have a very good scan tool there is no way to know what is going on. The generic readers never give the BARO parameter, and they only way to verify the MAF is the snap throttle test on air flow. A generic scan tool is a waste unless you are the autozone guy telling people they need o2 sensors. Those scan tools can't read any EGR data either, so you can just guess.

You can get a used pro scanner on ebay (like a red brick) for under $200, and trust me it will more than pay for itself.

When you install the MAF, you have to do 3 near WOTs, and read the Baro parameter. It should read the actual Barometric pressure at your altitude (not the adjusted one from the weather report). The number is actually reported in Hz. Some scanners will convert to inHG. At sea level, you should have a baro of about 161ish Hz (about 30inHg). Denver may have a Baro in the 140s. If you see a under say 155 at sea level the MAF is probably bad (there are some other reasons - like a blocked cat that my throw the number off). Some cars come with a high altitude calibration and actually work better at higher altitudes. The MAF determines air density and can adjust fuel delivery with this information.


I agree with buying one from the dealer, or sometimes they sell them new from Hitachi (the OEM). I see there are motorcraft remans on rockauto for around $100.


The heater code could could be a problem in the wiring harness as well. Get a pinout diagram of the computer and check the wires/resistance of the heaters. Sometimes wires can melt and short out too.
 

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...I have no idea what the resistance SHOULD be, but it shouldn't be open!

RwP
Absolutely should not be open. :)

[email protected]=120W; it's not going to be below 60w...

It will be <5 ohm for sure; prob ~3.

AFAICR, the error means it's open, or a wire, or a connector.
 
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