LTDMan's '87 Mercury Grand Marquis LS (Big Red) *DUW*

[Bowman85merc]

thats the same paint code as my merc, and same interior tirm too haha, its like my merc all sedan style haha
shine it up, and u will have one beautiful car mang, good luck

[LTDMan83]

Big Red Lives Again!

After installing only a new Duralast Battery & Positive Cable, Big Red fired right up on the first crank! The HO sounds great, and I can't hear any strange noises coming from the engine anywhere throughout the RPM range. Only problem now is that the engine will not idle, and will only stay running if you keep the throttle at least 800-1000rpm, which I suspect will be a bad TFI Module (which is what 87mercman also suggested). The next free day I get, I'm gonna change out the TFI module, and hopefully she will idle then, so I can take her for a short ride afterward.

Stay Tuned.

[marquisman]

that is really good to hear!

[87mercman]

I figured that's all she'd need to "wake up" lol

Keep us posted...

[LTDMan83]

Just replaced the TFI Module after work tonight, and now she will Idle, only very irregularly and will stall out eventually. Runs and sounds damn good though.

Slightly aggravated at this point about the idle issue, I was planning on ripping into everything full-force this upcoming weekend, and figuring it all out, when I logged into GMN tonight and noticed I had a PM from 87mercman. This is one of the benefits of staying in touch with the previous owner of a modified car.

One thing to note that your recent post just reminded me of, and that I thought I should definitely give you a heads up on so it doesn't worry you when you go for the first drive...

When I did the ECM swap out, part of the pin outs that you were supposed to add was one for the VSS since the HO mustang ECM typically came from a 5-speed. The one in Big Red is from a 5-speed, and I never was able to find the wire on the Speed Sensor that I needed to tap into for that set of data. The ECM works and manages everything just fine, except as I explain below for the occasional stall, especially right after disconnecting the battery.

What will happen is this, the first several runs after clearing the ROM on the ECM (ie disconnecting/replacing the battery cable) the car will idle weird and when you go to drive, she will drive fine until you start to slow down. When you get almost to a stop she will stall unless you keep feathering the gas. This is due to the ECM looking for a cue from the speed sensor as to the deceleration rate.

After you run for a few times the computer builds into its ROM that it should essentially not look for/ or ignore the "faults" from that data. This could easily be remedied by adding the pin to the ECM connector. If you need any assistance as to what this entails I still have all my research compiled and can send it your way.

Thank you, as I literally could have spent 100's of Hours, and Dollars, trying to figure this out, and probibly would have never thought to check if the ECM connector harness was missing the wire/pin for the VSS signal, lol.

[LTDMan83]

Big Red and I take our first Cruise together!

Today, I implemented a Temporary work-around for the weird idle/stalling issue. Was as simple as turning the Throttle Stop Screw on the TB, so that it holds the throttle open at about 800rpm. She idles as smooth as glass at that rpm, and will not stall at all even while driving. Again, this is just a Temporary work-around, until I can fix the actual problem.

Afterwards, I took her out for our 1st Cruise together. Now, I can tell you for sure that this a real HO engine, as Big Red has some Big Cojones. While driving, I can even feel the difference in the HO's Cam Profile vs the lopo that I've been driving for the past 5yrs. I can tell that it is running rich, and the stock restrictions on the Intake/Exhaust side of things are holding back some potential power. Even despite the Richness which is no doubt bogging the engine down somewhat, She still has an excellent Throttle Response, which is probibly because of the Mass Air.

I drove her for around 20 miles, and she didn't even miss a beat the entire time. Lots of squeaks and rattles coming from the inside of the Dash/Interior, and she still has a long way to go before she achieves that "Magic Carpet Ride" feel that my old '87 LTD had while gliding down the road, but I will get her there eventually. I'm just happy that I have a Box to drive again.


Now, the "Big Red" DD Project shall truly commence. The U-Pull-it guys are gonna be seeing me very soon, as she needs quite a few pieces which can't be found anywhere but the junkyard. Shloads of work ahead of me on this car, but she will be one Beautiful, Fun, and Reliable Beast to DD, once I am done.

Stay Tuned.

[87gtVIC]

Good to hear its running strong! And will be fixed up all perty

[85crownHPP]

have you tried messing with the IAC any??
I'd guess its an IAC problem if opening the throttle with the set screw helped...

[p71towny]

He said some of the pins on the computer were effed up tho.

[87mercman]

I always loved that HO feel...she had cajones before the MAF conversion, but the throttle response jumped after I got that installed and tuned.

Glad to hear that she is no longer comatose and is back on the road!

The pins of the EEC-IV are not effed up, as I stated in the email he posted, there was an extra pin that needed to be added to the harness that I was unaware of originally. This PIN lets the computer know when the car is in de-accel, so it can adjust the A/F ratios for braking. Without this the computer assumes constant throttle, and this can bog the engine down at idle and de-accel.

Manually adjusting the idle with the TB screw is a temp solution that makes sense as it will not allow the idle RPM to drop into the "red zone".

I am going to be sending all of my research documentation to LTDMan83 in the next couple days so he can figure out the next course of action.

[Lincolnmania]

excellent

[LTDMan83]

Yes, what 87mercman said.

The IAC was my next suspect, until I came on here and read the PM he sent me. Supposedly the Computer will eventually learn to ignore the lack of a VSS signal, and then will go back to Idling and de-accelerating normally, at that point I could then turn the Throttle stop screw back to normal, and let the IAC control the idle again. I would rather fix the actual problem though.

It looks as if the hardest part would be having to take apart the ECM Connector and add the Wire/Pin Out in the correct location, also locating the wire that carries the VSS Signal that I need to tap into.

Also, another solution would be to find a MAF computer from a 91+ mustang w/ an automatic, but supposedly they are hard to find, and expensive when they are found. So I'm not sure which route I will go, I will be keeping the current EFI system no matter what though.


More Updates to Big Red are coming very soon

[86VickyLX]

Why doesn't it have a VSS? Does the car have cruise? You should be able to tap into that for VSS signal. It's a green wire with a white stripe. There's a black wire running along with it.

[LTDMan83]

It has one, just the signal coming from it is not tapped into the ECM, which is something that the Mustang 5-Speed MAF ECM requires. Cruise has been mostly gutted from this car to my knowledge.

[p71towny]

Cant you just use a Mark7 Ecm and keep cruise as well??