New discovery with my idle & fuel mixture problem

MalcolmV8 · Post by **MalcolmV8** » Fri Nov 17, 2006 9:49 pm

cgrey8 wrote:However I wouldn't expect yours to go quite that low with the smaller "clear" tube.

Are we using different metering tubes? I'm using the 19lb tube in a C&L 73mm mass air with stock Ford electronics. I have stock stang 19lb injectors too.

Malcolm

cgrey8 · Post by **cgrey8** » Fri Nov 17, 2006 10:07 pm

Yes, I'm using the tube meant for 24lb injectors (blue tube). But I'm not running 24lb injectors. See, my MAF was sold as a 19lb tube, but was delivered with the 24lb tube. The seller never resolved the problem and I didn't push it that hard since I have a TwEECer and can compensate. Without a tuner, this would be a big problem. However with a tuner, I simply modified the tune to include the actual curve of the MAF and tube I have so it'll work with my injectors.

See, the way changing the tube works without a tuner is it lies to the EEC, telling it that there is less air aspirating into the engine than actual, in an effort of lowering the pulse-width to the injectors. With larger injectors, this is exactly what you want...so you match the tube to the injectors you have installed which affects how badly you lie to the EEC about how much air is aspirating. It's a neat trick but it has a side-effect if you use injectors larger than about 24lbs. The EEC uses the MAF's calculation of aspirated air to determine how much load is on the engine. Based on calculated load, the EEC calculates fuel-unrelated things like Spark and EGR. So thus the worse you lie about how much air is coming in, the more skewed spark & EGR control gets.

In engines running 30lb injectors and up, people are not as interested in drivability as they are in WOT performance...so these details are not as big of a deal. There's also the fact that an engine that needs 30lb injectors has a MUCH better volumetric efficiency than a stock engine which means it aspirates more air. This additional air gets the LOAD calculations back up closer to where they would be with a stock engine running the stock MAF which corrects for some of the issues above, but certainly not all. With a tuner, you can compensate for most all the variables involved in the engine mods and in most cases, you can get near-stock drivability from a moderately modified engine.

MalcolmV8 · Post by **MalcolmV8** » Sat Nov 18, 2006 11:53 am

I seemed to recall this exact problem showed up last winter and cursed me for months, then went away over the summer and is now back. Sure enough I found my post from last year, Nov 3rd. About the same time when the weather was cooling down.

viewtopic.php?t=372

Since weather seems to play a roll and the only thing we've come up with is O2s getting cold I'm going to revisit that. Perhaps my 12v source that's heating them is going away? Will check into that today.

Thanks guys
Malcolm

MalcolmV8 · Post by **MalcolmV8** » Sat Nov 18, 2006 1:56 pm

OK in tracing wires I found my O2s have a very good source of 12v. Their own dedicated wire from the battery to their own relay (trigged by ignition in run) and their own circuit breaker. So clearly they are getting as much of 12v as they can.

In tracing grounds I broke out the wiring diagrams. The ECC has multiple grounds. Pins 60 and 40 seem to be shorted together and run wire circuit 60 BK/LG which seems to be common power ground that runs to the frame, battery, body etc.
Then there's pin 46 (sensor signal return) which runs circuit 359 BK/W appears to be a dedicated ground for sensors only. I imagine to get an accurate ground reference to all the sensors. The O2s don't use this circuit, instead they use the common ground listed above connecting to pins 60 & 40.

Now I discovered something new. While looking in my Ford EFI book I saw something by the EGOs (O2 sensors) that I'd not seen before. An orange wire with a ring terminal labeled HEGO ground and it goes to pin 49 on the ECC. WTF? So I look back at my wiring diagram and it's not there.
Upon further inspection on the wiring diagram I see pin 49 on the ECC is labeled as "fuel sensor ground" and shows the same orange wire running to the white ten pin connector going to the engine harness and then just stopping showing a ring terminal.

So I measured from the pin 49 on the ECC harness (ecc disconnected from harness) to ground to see if that ring terminal is just bolted to the motor and I got 12.4 mega ohms. So I guess now I'm confused. What is that pin 49 connection for? Also where should I expect to see it coming out of my harness? Do I need to pull off my upper intake or can I just spice into it by the 10 pin connector and ground it to the motor?

Thanks for any help
Malcolm

Blk87 · Post by **Blk87** » Sat Nov 18, 2006 4:06 pm

That wire is grounded to my firewall. It does have the ring and needs ground.

cjcnomor4 · Post by **cjcnomor4** » Sat Nov 18, 2006 4:39 pm

mine grounds at the right rear head

MalcolmV8 · Post by **MalcolmV8** » Sat Nov 18, 2006 5:49 pm

Turns out mine is grounded too. Not sure where (to tight in there), I had one lead of my DVM on pin 60's earth circuit which was disconnected from the battery at the time of testing. I discovered my error in testing and found it was indeed connected. So still haven't found my problem.

Thanks
Malcolm

Blk87 · Post by **Blk87** » Sat Nov 18, 2006 6:38 pm

Malcolm this is a reach but swap the ecm from the red truck to the blue and check your HEGO's again. Just a thought......

MalcolmV8 · Post by **MalcolmV8** » Sat Nov 18, 2006 8:26 pm

I gave it a shot. Some issue with the EGOs dropping to 0 volts at idle. Only the A9L doesn't handle it very well. Once you sit and idle like that for a while it starts to surge really bad where as the A9P just kinda stutters.

Blk87 · Post by **Blk87** » Wed Nov 22, 2006 8:03 am

Malcolm whats the power when it starts to fail. Input to the o2's Does the 12vdc change as well.

MalcolmV8 · Post by **MalcolmV8** » Wed Nov 22, 2006 6:38 pm

Nope, input power stays at a steady 14 ~ 14.5 volts or where ever it happens to be.

I asked this same question (about my idle condition) on eectuning.org to see if anyone had any ideas.

http://eectuning.org/forums/viewtopic.php?t=6781

I think I'm going to try and relocate my ACT sensor from the intake tube to the lower intake. This will require drilling and taping the explorer lower intake but the air down there should be a great deal hotter than in my air intake tube right behind the air filter. Since my problem is somewhat temperature related (goes away in the summer) it seems like a logical start.

I may also try and swap in a stock 55mm mass air meter instead of my 73mm unit and see if that helps. After that I'm out of ideas.

Later
Malcolm

cjcnomor4 · Post by **cjcnomor4** » Wed Nov 22, 2006 6:45 pm

the mustang pcm is set up to see the hotter iat temps in the lower intake. in the air inlet tube you may be hitting 110 or so on a summer day. even in the intake tube youll see a bit more than ambient temp. in the intake you'll run much hotter. hotter air is less dense. should lean out your mixture quite a bit. the right iat should be 1/2 pipe thread i think.

MalcolmV8 · Post by **MalcolmV8** » Wed Nov 22, 2006 6:56 pm

CJ,

Chris was telling me that while looking at the ACT in his tweecer it only allows the ECC to learn idle conditions if ACT is 100* or above.
As you say sitting in the air intake tube it won't be much hotter than ambient, this could be part of my problem.

I already have the tap from when I made my intake tube. All I need to do now is go get some gaskets.

Thanks man
Malcolm

MalcolmV8 · Post by **MalcolmV8** » Wed Nov 22, 2006 7:12 pm

Chris,

You had posted this picture showing where a stock Mustang ACT should go.

However I don't have that marking on my lower intake. Not on my truck or the spare explorer lower I have. Looks like it will be a bit of a job to get it in there.

I wonder if putting it in the upper intake as low as possible is just as good? Is a stock Mustang ACT in a runner tube right before the injector?

Thanks
Malcolm

MalcolmV8 · Post by **MalcolmV8** » Wed Nov 22, 2006 10:38 pm

MalcolmV8 wrote:Is a stock Mustang ACT in a runner tube right before the injector?

For anyone searching the archives someday, the ACT is in the number 5 runner of the lower intake. Thanks to CJ here are two pics below clearly showing it.

I then went and looked at my red truck since it has an Edelbrock performer lower and sure enough there's a provision in the number 5 intake runner with a pipe plug in it

. The ACT on the red truck is also in the intake tube. Maybe I will move that one too.

Drilling and taping the lower intake runner on the explorer motor will not be as easy. It does not have the thick casting hump on it so I will be going through a very thin wall which means the sensor will probably stick way into the runner restricting it some. I may have to aluminum weld on a square stub that gives it some body and helps keep the sensor from going so deep into the runner. It's just a very tight area to work in.

Malcolm