Engine Codes with HO conversion

[SirFoxx]

Hello once again!

So I just took my '86 tc around the block. I noticed that the idle is surging, especially when rolling up to a stop light. Along with the surging, when I roll up to a stoplight, the idle will drop, almost stall, then pick back up to a surge-y idle. I also feel like there is a dead cylinder, but its hard to tell with one open header (had to cut one side off, need to fix). Plus, it sometimes has a hard time starting without giving it some throttle. Out of curiosity, I ran the eec iv test, and got the following codes: 12, 21, 22, 16, 13.

Now, 12 and 13 both point to (Idle Speed Control motor or Air Bypass not controlling idle properly). Is that the motor thing on the backside of the TB? Before I did this swap, my TC would start and search for an idle for a few seconds before settling down to a nice smooth idle. Now it has a hard time idling.

21 -- Engine coolant temp out of range. Not sure whats going on there. The coolant temp worked previously, and is plugged in (at least, it should be). If it isnt, which plug is the coolant temp plug so I can check to be sure?

22 -- MAP (vacuum) or BARO signal out of range. Not sure what this means?

16 -- According to the list, this is only a 1.9, 2.3 and 2.5L engine code?

Before I forget, here is the part list that I have:

• '86 gt cam
• gt40 heads
• 1990 mk vii DX3 ecu
• 19lb explorer injectors
• lincoln logs w/ new o2 sensors
• ho upper intake
• explorer TB w/ bored egr spacer

With the newer computer, as soon as I got out of the car, I saw 4 flashes, and I completely forgot about that part of the test that requires user throttle input. Could that throw off the computer and put out false codes?

If you need to test voltages or other info, lmk and I will do my best to do so.

[gadget73]

12 and 13 mean either the IAC is unplugged, or its bad. Or maybe you have a big-ass vacuum leak somewhere.

21 - is the engine fully warmed up? You get this code if not. ECT is in the pipe heading back to the heater core, 2 wire sensor, kinda next to the AC compressor.

22 - is the vacuum line connected to the MAP sensor? Does it have a big hole in it?

16 - idle too low to perform HEGO (oxygen sensor) test. Related to 12 and 13. Fix the idle, this should go away.

I'm making the assumption these are all engine running tests, and not engine off tests since some of those don't exist as a stored code.

Maybe related, did you connect the orange ground wire to the back of the intake? It comes out of the oxygen sensor harness and is used by the ECM as the ground return for all of the sensors screwed into the motor. ECT, O2, and ACT sensor readings will be skewed if this isn't hooked up and that can make it do stupid stuff.

[SirFoxx]

12 and 13 mean either the IAC is unplugged, or its bad. Or maybe you have a big-ass vacuum leak somewhere.

21 - is the engine fully warmed up? You get this code if not. ECT is in the pipe heading back to the heater core, 2 wire sensor, kinda next to the AC compressor.

22 - is the vacuum line connected to the MAP sensor? Does it have a big hole in it?

16 - idle too low to perform HEGO (oxygen sensor) test. Related to 12 and 13. Fix the idle, this should go away.

I'm making the assumption these are all engine running tests, and not engine off tests since some of those don't exist as a stored code.

Maybe related, did you connect the orange ground wire to the back of the intake? It comes out of the oxygen sensor harness and is used by the ECM as the ground return for all of the sensors screwed into the motor. ECT, O2, and ACT sensor readings will be skewed if this isn't hooked up and that can make it do stupid stuff.

Ok. So I remembered that I plugged one of the lines coming off the plenum with a bolt. That line went to the MAP sensor. I had no idea what that thing was till now. Hooked it up, started it up, and all the idle issues went away! It also seems like it ran a bit better. Fixing this should hopefully make 16, 22, and maybe 12, 13 go away? When I started it, it did look for an idle briefly, then settled down, making me believe that the IAC is working correctly.

As for 21, no, it wasn't fully warmed up. It was warm enough the bring the needle up a bit, and that was it.

Also, when climbing on the motor to find the map vacuum line, I noticed that the back of the lower intake didnt seal, and is leaking oil. Looks like I will need to address that. >.<

[sly]

It may be coming from the PCV grommet too... check that first as a little ultra black under the lip of the grommet and shoving it back into the intake works wonders to stop that leak.

[SirFoxx]

It may be coming from the PCV grommet too... check that first as a little ultra black under the lip of the grommet and shoving it back into the intake works wonders to stop that leak.

I would hope its coming from there but my gut says otherwise. I ordered a new one from rock auto along with some sway bar end links. Hopefully that fixes the oil issue. If not, the lower isnt that bad to remove. We'll see!

[87gtVIC]

One trick is to put a think bead of silicone behind the rear of the lower intake seal. Helps prevent it from pushing out. I also strongly suggest using guide studs to install the lower. Cut the head off of four old lower intake bolts and cut a notch in them so you can use a flat head screw driver to remove them once you guide the lower intake into place. The guide studs in the four corners will help ensure the intake goes on straight and true so you dont accidentally push a gasket out of place.

The orange ground for the o2's spoken about above attach to a stud at the rear most drivers side lower intake bolt in case you need to know.

The replacement PCV grommets need a bit of silicone to seal. They just seem to come too small and just fit loose. I also find that the pcv valve itself kinda fits loose too. Common fix I head for that is some heat shrink around it to build up its girth.

If you convert the car to mass air (which may not be out of the question considering the larger heads you installed) you can then leave the map sensor unplugged from a vacuum source as it now becomes a baro sensor.

[gadget73]

I use the FelPro Permadry gaskets. Rubber end wall, tiny dab of RTV at the corners only. I'm not a big fan of sealant in general, gaskets and surfaces that aren't garbage should not need it.

Guide studs help a ton. Makes the intake gaskets stay in place too. Just make sure they are long enough to retrieve afterward. I once made a set short enough that I had to pull them out with a magnet. They only came up flush to the top of the intake and I couldn't grab them.

but yeah see if connecting the MAP clears the other codes. Engine has to be at least 160 I think for the ECT to read correctly.

[DerekTheGreat]

While most likely not related, I got code 21 for my ECT when the engine was cold. That and IAT out of range code too. Thought it was time to replace sensors but when I checked Ashley's old Town Car, she had the same codes, only the computer must ignore them for a period of time because it didn't set the CEL..

[gadget73]

Almost nothing sets that light, but the temperature sensors are very important with speed density for fuel mix reasons. Also if the coolant sensor never shows its warm, the oxygen sensors don't work and if the air sensor doesn't get warm it doesn't go into long term learning to correct it's habits.

I've actually seen the light twice on the Mark VII, once was a bad TPS, it had a dead spot at idle and the light would come on every time I let off the pedal, and once was a leaky EGR valve.

[DerekTheGreat]

Yeah, it's fairly odd. According to the shop manuals, the light should be set any time there is a code stored or generated. That is not the reality though.

[gadget73]

there is some failure number theshold that it has to cross though and some of them are such a high number that it basically never happens.

[DerekTheGreat]

Out of sight, out of mind??

[gadget73]

more or less. honestly I never bothered to check mine for codes unless it was doing something odd. When the TPS went, it had a distinct stumble. The EGR I found purely by accident. I was just curious if it even worked and found that it didn't hold. Swapped it with a spare and the CEL went away. I never actually read the codes or cleared them.

[86VickyLX]

If the problem is there the check engine light illuminates. If it's not there the light goes out. 86 doesn't have a check engine light. That didn't appear until 1989.

[gadget73]

which is why the 88- are better. Screw that stupid light.