Removing the ECU 35-pin plug from the ECU unit correctly

[Jennys280Z]

Hi all!

I'm new to this board and actually have spent several weeks here before signing up just reading/searching posts and trying to gain knowledge. A few years ago (July 2008 or so) I become the happy (well lately NOT happy) owner of a 280Z that was garaged and not-driven for many years. Well it's been an experience since then...lots to do!

It was running fine until a week or so ago when I started it and it began backfiring horribly, and idling rough, and running rough (no power:disappoin)

I realized the gas in the tank was a year old so I drained it and added 6 gallons of fresh 93 octane. The backfiring stopped but it is still running rough (though somewhat intermittently), still seems to have no power (like it's missing or not firing on all cylinders), and so I wonder what's wrong. I started to inspect the connectors all around the car (the famous ones as I've read about here and elsewhere) and the first one I started with (the EFI power connector from the battery), the brittle plastic clip that locks the connector shut broke as soon as I pressed it with my thumb!

SOOOO I realized before I start touching/fumbling with fragile/brittle connectors in ways they're not meant to be handled, I thought I better start asking professionals for some help on how to disconnect them the right way. It isn't clear to me intuitively how to take off connectors like the water temp and thermotime sensor, AFM connector, etc. I think I've got the fusible links, firewall ground, EFI ground, and EFI power connectors figured out though! But, I'm not even going to pull on those until I have some 'Electrical Contact Cleaner', and then I'm torn between getting some cheap CRC down at the Autozone or splurging on a little can of Deoxit, which I have to order online apparently and wait for shipping.

So to make things easier on myself (supposedly ) and on the car especially (haha) I unbolted the cover to my ECU as soon as I realized that all the circuits to all of the sensors/etc can be tested from the ECU (yaaaay!!!) BUT, I can't tell exactly how to remove the 35 pin plug from the ECU unit. I see there is a little metal clip to press and that releases the top end of the plug, and it comes out with a bit of pulling. But the bottom end of the plug seems stuck (there is a little plastic clip there on the bottom end of the plug, and it wraps around a little metal bar, like a hinge on a door). What I want to do is pull the plug straight off because I don't want to bend any pins but it only seems to want to swivel out from the top!

So how do I get this plug off? Do I just keep pulling at the top so it swivels at the top (pivots at the bottom hinge) and then lift it up and out after the plug clears the unit? Or should I use a slot screwdriver and press that plastic clip up so the bottom of the plug can pop out with the top? (Already tried that and it didn't budge ) So for now I just pushed the plug back in, and almost started throwing things, but cried instead.

Anyhoo, please be gentle with me! Yep I'm a newbie but that doesn't mean that I'm not just as passionate about my car (and smart in general) as you guys! Everyone has to start somewhere and I can't live on manuals forever (dying to troubleshoot my car!)

Thanks guys!

Jen

Edited January 30, 2010 by Jennys280Z
Issue resolved in this thread

[Z Tyler Z]

Anyhoo, please be gentle with me! Yep I'm a newbie but that doesn't mean that I'm not just as passionate about my car (and smart in general) as you guys! Everyone has to start somewhere and I can't live on manuals forever (dying to troubleshoot my car!)

Welcome to the forum, no worries about being new, everyone on this forum is friendly. I'm pretty new to Zs as well and to cars/driving in general compared to most people on this forum. (solid 2.5 years of driving experience )

So to make things easier on myself (supposedly ) and on the car especially (haha) I unbolted the cover to my ECU as soon as I realized that all the circuits to all of the sensors/etc can be tested from the ECU (yaaaay!!!) BUT, I can't tell exactly how to remove the 35 pin plug from the ECU unit. I see there is a little metal clip to press and that releases the top end of the plug, and it comes out with a bit of pulling. But the bottom end of the plug seems stuck (there is a little plastic clip there on the bottom end of the plug, and it wraps around a little metal bar, like a hinge on a door). What I want to do is pull the plug straight off because I don't want to bend any pins but it only seems to want to swivel out from the top!

I don't remember the ECU being that hard to pull out. There's a thread on here where I couldn't start my car for weeks and it turned out I accidentally unplugged the ECU when trying to get to the stock flashers (took off the ecu plate to try and get more room.)

I think you just undue to top latch and pull out and down. Really there isn't much to it. I doubt you'll mess up anything you can't easily fix.

It was running fine until a week or so ago when I started it and it began backfiring horribly, and idling rough, and running rough (no power)

I realized the gas in the tank was a year old so I drained it and added 6 gallons of fresh 93 octane. The backfiring stopped but it is still running rough (though somewhat intermittently), still seems to have no power (like it's missing or not firing on all cylinders), and so I wonder what's wrong. I started to inspect the connectors all around the car (the famous ones as I've read about here and elsewhere) and the first one I started with (the EFI power connector from the battery), the brittle plastic clip that locks the connector shut broke as soon as I pressed it with my thumb!

I'd also change the fuel filter if I were you, who knows what it could of sucked up. Have you checked basic stuff? Like spark plugs being fouled, cap and rotor wear, just basic things.You say there was year old gas in the car did you leave the car sitting for a year?

But, I'm not even going to pull on those until I have some 'Electrical Contact Cleaner', and then I'm torn between getting some cheap CRC down at the Autozone or splurging on a little can of Deoxit, which I have to order online apparently and wait for shipping.

I used the cheap stuff from Autozone and it seemed to work well think it was about 6 bucks for a can. Radioshack sells the Deoxit though.

[Zed Head]

You can get a big 5 oz. can (much bigger than the tiny Radio Shack package) of Deoxit at Guitar Center, if there is one in your neighborhood, for ~ $15.

It is the only canned sprayable liquid I've ever used that actually seems like magic. Quite often you can just spray it in to a corroded connection or switch and let it do its thing, without taking things completely apart. Very useful when working with old plastic.

Edit - Re the ECU plug - You have to pull some of the wiring harness down with the top of the plug to pivot at the bottom until the hook-like shape at the bottom of the plug clears the metal pin it is hooked on. It pivots down quite a ways before it comes free. It will feel like you're pulling too much harness out of the dash but that's how you work it out. On a 76 and 78 anyway.

Edited January 28, 2010 by Zed Head
More info.

[IdahoKidd]

Welcome Jen!

Perhaps an easier way on the ecu is to pull three screws out that physically hold the ecu to the side of the car. Everything becomes more flexible that way. Really quick and easy. Then you can just rotate the ecu instead of pulling against the wires to get room. The caps on the sensors have a small metal wire retainer on them. Look closely at the base of an injector and you can see it. It wraps around three sides and snaps into place. I just use a really small flat screw driver and loosen one side and then it simply comes out.

What year is your Z by the way. Slight differences in the electronics.

[FastWoman]

Compared to modern computer connectors, there's nothing at all delicate about the ECU connector. Just pull down the wiring harness as you rotate the connector around the bottom hinge point. Then unhook it from the bottom. That's how it's meant to be done.

[Jennys280Z]

Welcome to the forum, no worries about being new, everyone on this forum is friendly. I'm pretty new to Zs as well and to cars/driving in general compared to most people on this forum. (solid 2.5 years of driving experience )

I don't remember the ECU being that hard to pull out. There's a thread on here where I couldn't start my car for weeks and it turned out I accidentally unplugged the ECU when trying to get to the stock flashers (took off the ecu plate to try and get more room.)

I think you just undue to top latch and pull out and down. Really there isn't much to it. I doubt you'll mess up anything you can't easily fix.

I'd also change the fuel filter if I were you, who knows what it could of sucked up. Have you checked basic stuff? Like spark plugs being fouled, cap and rotor wear, just basic things.You say there was year old gas in the car did you leave the car sitting for a year?

I used the cheap stuff from Autozone and it seemed to work well think it was about 6 bucks for a can. Radioshack sells the Deoxit though.

Thanks Tyler!

I love this forum already. Even just randomly reading many threads for something I wasn't looking for can give me insight I didn't previously have.

Yup, the ECU plug has to be pulled out-and-down! It still seems scary to me to pull it like that. I don't know how I can do that without bending anything but I guess if the little pins are short enough...

Well I ddin't leave the car sitting for a year exactly. I drove it more often when the weather was warmer, and even then only for fun, but I filled the tank up about a year ago, and only used about 80+% of that tankful driving around for a year. I just didn't drive it very much but for little 5-mile jogs around town(I use my uber-reliable Toyota Camry for daily/groceries )

A friend inspected my cap and rotor a year ago and appear to be in great shape, I checked the condition/gaps on the plugs myself a year ago and they were also in great shape. I replaced the fuel filter too a year ago.

I almost got inside Autozone tonite to buy their CRC (probably good stuff because I read that Boeing authorized using it on their aircraft) but I wheeled into the parking lot on the way home at about 8:59 and the door was locked (they close at 9:00 ) so I just ordered some Deoxit from a vendor on Amazon who sells it for only $12.99 a can. I got a vacuum gauge too (yippee!) that I'm planning to hook up to the intake manifold in place of the brake booster...which leads me to probably the next question I needed help with...

http://www.amazon.com/CLEANERS-LUBRICANTS-CAIG-BRAND-SPRAY-Solution/dp/B00006LVEU/ref=sr_1_1?ie=UTF8&s=electronics&qid=1264741430&sr=8-1

http://www.amazon.com/Equus-3620-Vacuum-Gauge/dp/B000EW0KPY/ref=sr_1_2?ie=UTF8&s=automotive&qid=1264741453&sr=8-2-catcorr

I want to replace all the vacuum hoses in my hood but I don't know what size hoses to get. I would guess everything on here is metric sizes. I suppose there's a standard size hose that would be close enough to work but I dunno.

THANK you for your help!! :classic:

[Jennys280Z]

You can get a big 5 oz. can (much bigger than the tiny Radio Shack package) of Deoxit at Guitar Center, if there is one in your neighborhood, for ~ $15.

It is the only canned sprayable liquid I've ever used that actually seems like magic. Quite often you can just spray it in to a corroded connection or switch and let it do its thing, without taking things completely apart. Very useful when working with old plastic.

Edit - Re the ECU plug - You have to pull some of the wiring harness down with the top of the plug to pivot at the bottom until the hook-like shape at the bottom of the plug clears the metal pin it is hooked on. It pivots down quite a ways before it comes free. It will feel like you're pulling too much harness out of the dash but that's how you work it out. On a 76 and 78 anyway.

Hi Zed Head!

Yup, Guitar Center carries Deoxit D5. None of the Radio Shacks carried it though. They all had their own Radio Shack brand of contact cleaner instead. I ordered the D5 online, though I have to wait for shipping, I'll avoid a very long drive and save some money for my time. But so many people say so many good things about the Deoxit product, now including you, I decided to order and wait for the good stuff!

Thanks for helping me with the ECU connector. I still don't want to pull on it too hard but I'll look at it again this weekend. I understand though what you mean by having to pull on the harness. It was tight when I was trying to swivel it off, and that was another reason that caused me to think that it might come straight off instead. At this point I'm probably going to just take the whole ECU out so I don't have to pull on the harness. Hopefully doing that won't dumbfound me when I get under the dash and look at it again. I'm assuming that all the connections to the ECU are at the front (the harness plug) and there's nothing behind it that will keep it from coming out (other than bolts).

Again thanks for your answer. The way you worded it was easy for me to understand :)

[Jennys280Z]

Welcome Jen!

Perhaps an easier way on the ecu is to pull three screws out that physically hold the ecu to the side of the car. Everything becomes more flexible that way. Really quick and easy. Then you can just rotate the ecu instead of pulling against the wires to get room. The caps on the sensors have a small metal wire retainer on them. Look closely at the base of an injector and you can see it. It wraps around three sides and snaps into place. I just use a really small flat screw driver and loosen one side and then it simply comes out.

What year is your Z by the way. Slight differences in the electronics.

Thanks Idaho Kidd!

Yup I'm thinking that making it more flexible by pulling it off is best based on how tight it felt last night when I was pulling on it!

Aww I almost got lost thinking there were metal retainers on my ECU! Yes there are retainer clips there! I pulled them out with my little slot screwdriver tonight and the connectors slide right off! Thank you! I am SO glad I didn't just start pulling on them like a NOOB (I mean, like ME! )

Oh I am wondering why I didn't mention what year my Z is anywhere...it's a 1976, and on my little plate it says it was manufactured in 11/75

Thank you for your help! I love this site!

[Jennys280Z]

Compared to modern computer connectors, there's nothing at all delicate about the ECU connector. Just pull down the wiring harness as you rotate the connector around the bottom hinge point. Then unhook it from the bottom. That's how it's meant to be done.

Thanks so much FastWoman! Yup, y'all made a consensus on what to do and I'm confident on how to do it now! One of my issues is that I don't push or pull (or whatever) on things hard enough and it's NOT because I'm a girl it's because I just don't want to break it. :laugh:

[FastWoman]

That's probably a very good approach, Jenny! There are a lot of old, brittle parts that are easy to break, even if you're tugging/prying/twisting on them the CORRECT way! ;-)

[Jennys280Z]

ECU plug came off easily, and as described on this thread, when I removed the ECU unit itself. Thanks to everyone for their help here!