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5.0 running rough with rich and lean O2 codes


Rembrant

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So at first blush I'd say if it has MAF it won't have MAP. But I really don't know that because you have the "upgraded" EEC-IV system with MAF and I don't have any documentation on that. Sorry.

As for the ICM, Ford was involved in a class-action lawsuit regarding distributor-mounted TFI modules. They never admitted that they had a problem, even though they did, but they did quit installing them on the distributor around 1991 on the F-Series trucks, which explains why your distributor has a place for it but it is actually mounted remotely.

I’m pretty sure it’s either MAP or MAF, not both.

Thank you gentlemen!

I had it my head that MAP was with speed density, and MAF with SEFI.

It was kind of funny, because I went to check it on the distributor (I was actually looking to see if the module was grey or black...I found several threads where people were saying to ONLY buy the black ones...whatever that means. Is it something like the Duraspark II modules with the different color grommets for the wire harness??). Anyway...when it wasn't there, I started looking around because I had to have an ignition module somewhere! Kinda neat learning these things...thanks again guys.

Rough running issues aside, the truck seems to be running even better than it was previously. I can't imagine an O2 sensor making that big a difference, but it could be in my head too;).

When the engine is first started, are these EFI systems running on closed loop or open during warm up/high idle. The high idle seems different...its not going quite as high and not staying high as long as it was previously...but again, maybe it's all in my head;).

 

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So at first blush I'd say if it has MAF it won't have MAP. But I really don't know that because you have the "upgraded" EEC-IV system with MAF and I don't have any documentation on that. Sorry.

As for the ICM, Ford was involved in a class-action lawsuit regarding distributor-mounted TFI modules. They never admitted that they had a problem, even though they did, but they did quit installing them on the distributor around 1991 on the F-Series trucks, which explains why your distributor has a place for it but it is actually mounted remotely.

I’m pretty sure it’s either MAP or MAF, not both.

Thank you gentlemen!

I had it my head that MAP was with speed density, and MAF with SEFI.

It was kind of funny, because I went to check it on the distributor (I was actually looking to see if the module was grey or black...I found several threads where people were saying to ONLY buy the black ones...whatever that means. Is it something like the Duraspark II modules with the different color grommets for the wire harness??). Anyway...when it wasn't there, I started looking around because I had to have an ignition module somewhere! Kinda neat learning these things...thanks again guys.

Rough running issues aside, the truck seems to be running even better than it was previously. I can't imagine an O2 sensor making that big a difference, but it could be in my head too;).

When the engine is first started, are these EFI systems running on closed loop or open during warm up/high idle. The high idle seems different...its not going quite as high and not staying high as long as it was previously...but again, maybe it's all in my head;).

They are open loop until the O2 sensor is hot enough to provide a signal, hence the heater in it.

FWIW, Ford did build some MAP sensor SEFI systems, I had one, a 1990 Lincoln Town Car, last year for the 5.0L engine, in 1991 the Lincolns received the new 4.6L engines, the Crown Victoria and Grand Marquis had to wait until 1992.

The change in warmup is probably due to the O2 sensor coming on-line earlier allowing the system to enter closed loop sooner.

The ICM was moved to the left inner fender starting in 1990 on trucks, big ugly (parts donor) had it there. As for the color of the ICM, the color denotes which version it is, gray is for push start, where the ICM "pushes" the dwell for a hotter cranking spark. The black ones are CCD which stands for Computer Controlled Dwell. There is one wire different, on a push start there is a red with blue stripe wire from the start circuit (branches from the wire to the relay) going to pin #4 on a CCD module it goes to the EEC.

TFI_5.bmp

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The change in warmup is probably due to the O2 sensor coming on-line earlier allowing the system to enter closed loop sooner.

Ahh yes, OK, understood. That makes perfect sense and explains why the high idle is a bit different. The change was subtle, but a change regardless. The high idle doesn't go quite as high as previous and it comes down much quicker.

I found a cracked spark plug boot tonight so I just ordered a new set of plugs and wires. I was going to do it over the winter, but might as well do it now while I can still road test the truck. I also noticed that it has Motorcraft Platinum plugs in it...not sure if that's good or bad, but I ordered a set of SP450 copper core plugs to replacement with. The emissions decal under the hood calls for ASF-42C as the correct originals, but I understand that the SP450's are direct replacements for them. It has ASF-42P's in it now. I was going to get Autolite 25's, but there were only 3 available on RockAuto.

IMG_3041.jpeg.e53416feaf93829217827b9c3ae0b6b1.jpeg

I don't know if the cracked plug boot makes much difference or not, but I do get some vibration sometimes. Somebody threw away all the plug wire separators and they're all intertwined with each other, so I ordered a couple packs of Dorman separators so I can get everything routed properly.

Thanks again for all the help folks. She'll be running perfectly before winter at this rate;).

 

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The change in warmup is probably due to the O2 sensor coming on-line earlier allowing the system to enter closed loop sooner.

Ahh yes, OK, understood. That makes perfect sense and explains why the high idle is a bit different. The change was subtle, but a change regardless. The high idle doesn't go quite as high as previous and it comes down much quicker.

I found a cracked spark plug boot tonight so I just ordered a new set of plugs and wires. I was going to do it over the winter, but might as well do it now while I can still road test the truck. I also noticed that it has Motorcraft Platinum plugs in it...not sure if that's good or bad, but I ordered a set of SP450 copper core plugs to replacement with. The emissions decal under the hood calls for ASF-42C as the correct originals, but I understand that the SP450's are direct replacements for them. It has ASF-42P's in it now. I was going to get Autolite 25's, but there were only 3 available on RockAuto.

I don't know if the cracked plug boot makes much difference or not, but I do get some vibration sometimes. Somebody threw away all the plug wire separators and they're all intertwined with each other, so I ordered a couple packs of Dorman separators so I can get everything routed properly.

Thanks again for all the help folks. She'll be running perfectly before winter at this rate;).

Wanted to tell you something I learned, it’s in the owners manual, when you cold start these the idle is up for a bit.

You can kick it off by tapping the pedal, like an automatic choke.

Found that interesting. And as I mentioned in another thread, I haven’t had my tester hooked up to this Bronco forever! Just working great!

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Wanted to tell you something I learned, it’s in the owners manual, when you cold start these the idle is up for a bit.

You can kick it off by tapping the pedal, like an automatic choke.

Found that interesting. And as I mentioned in another thread, I haven’t had my tester hooked up to this Bronco forever! Just working great!

I did not know that! I'll give it a try, but she's coming down pretty quickly now so not a big deal. It seemed like it was really too long though before the new O2 sensor.

 

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I had a similar issue, it actually ended up being the O2 sensor harness, I found it after my engine started smoking on a no crank. This was on a 1986 tbird sefi 302, there was a bare wire in the O2 sensor harness that rubbed on another wire, and apperently there was no fuse or fuseable links for the heated o2's in my 86, so it would short out and kill the computer. Was driving down a mountain pass, downshifted to accelerate, and the car just shut off. Fired right back up, with intermittent no starts until I saw smoke with the hood open.

You can also run an "engine cylinder balance test", not sure how well it works with batch fire, but on sefi, it revs the engine up and shuts off one injector at anytime and identifies bad/underperforming cylinders, I found a bad head gasket this way. You just run codes (I use a paper clip and a test light or analog volt meter), and within a minute I f the codes being reported, you just go WOT. You can run the test 3 consecutive times, passing two in a row is within spec.

The maf cars and trucks still have a map sensor, but it no longer reads vacuum, but atmospheric pressure and is now called a BAP sensor with no vacuum line. The map sensor was essentially your air to fuel mixture, if you have ever had the vacuum line fall off, I would get 6mpg instead of 20+. It uses the map sensor for instant vacuum readings for air fuel mixture, and then compares it to the O2 sensors and uses a table to calculate any fuel trim. Stock computer can only modify the fuel table by about 10%, and ethanol gas (e10 in my state) takes up 7%. The engine has to be in pretty good tune to not throw a check engine light, as you essentially only have 3% fuel trim for both elevation and wear and tear before the computer freaks out and throws a code.

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They are open loop until the O2 sensor is hot enough to provide a signal, hence the heater in it.

FWIW, Ford did build some MAP sensor SEFI systems, I had one, a 1990 Lincoln Town Car, last year for the 5.0L engine, in 1991 the Lincolns received the new 4.6L engines, the Crown Victoria and Grand Marquis had to wait until 1992.

The change in warmup is probably due to the O2 sensor coming on-line earlier allowing the system to enter closed loop sooner.

The ICM was moved to the left inner fender starting in 1990 on trucks, big ugly (parts donor) had it there. As for the color of the ICM, the color denotes which version it is, gray is for push start, where the ICM "pushes" the dwell for a hotter cranking spark. The black ones are CCD which stands for Computer Controlled Dwell. There is one wire different, on a push start there is a red with blue stripe wire from the start circuit (branches from the wire to the relay) going to pin #4 on a CCD module it goes to the EEC.

"85lebaront2"

They are open loop until the O2 sensor is hot enough to provide a signal, hence the heater in it.

I didn’t realize that, assumed it was timed since it was OBD1.

Interesting stuff here!

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The maf cars and trucks still have a map sensor, but it no longer reads vacuum, but atmospheric pressure and is now called a BAP sensor with no vacuum line. The map sensor was essentially your air to fuel mixture, if you have ever had the vacuum line fall off, I would get 6mpg instead of 20+. It uses the map sensor for instant vacuum readings for air fuel mixture, and then compares it to the O2 sensors and uses a table to calculate any fuel trim. Stock computer can only modify the fuel table by about 10%, and ethanol gas (e10 in my state) takes up 7%. The engine has to be in pretty good tune to not throw a check engine light, as you essentially only have 3% fuel trim for both elevation and wear and tear before the computer freaks out and throws a code.

Not all MAF trucks have MAP or BARO sensors, I challenge you to find one on a 1996 OBD-II system. GM and Volvos I have worked on have both and for two reasons (a) quicker response to sudden manifold pressure changes as you mentioned (b) better mixture control at low air flow rates (idle).

The EEC-IV systems can only be "adjusted" with a piggyback system, such as a TwEECer or Moates Quarterhorse. EEC-V systems can be completely reprogrammed with proper hardware and software (I use Binary Editor and a MongoosePro cable to do them).

I have two Flexes, a 2009 and a 2011, they have 4 O2 sensors, 2 at the manifolds and 2 at the catalyst outlets. The 2 at the manifolds are interesting in their function, they are a dual band, one narrow and one wide and provide the two separate signals to the EEC. The downstream ones are simply a catalyst monitor. These also have only an MAF sensor.

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