[OneGreatGuy]

I have issues with my MAP and AFM circuits. My stock boost gauge is pegging whenever my ignition is on, cranking, or the car is running. It also feels like the car is hitting fuel cut all the time. I tested my AFM with the instructions in the BGB, and everything came out normal, so I don't think it is an issue with the AFM. I then tested the voltage coming out of the VC pin on the ECU, and was reading 5 volts, and checked the VC pin on the MAP sensor connector and read 5 volts, all good signs. I checked continuity to ground through ecu of the brown wire at the MAP sensor harness, and everything seemed fine. Then I tested the voltage at the PIN pin at the MAP sensor harness and was surprised to see 5.5 volts. This seems very wrong, as I believe PIN is the MAP sensors output, and should be within 2.5-5.5 volts. I then completely cut the PIN wire at the ECU connector(I initially thought that the issue was the wire being frayed and picking up a bad signal from some other wire. My car has had some chewed wires due to mice, as well as faulty electrical repair before I got it) and tested voltage coming purely from the ECU at PIN. I was measuring 5.8 volts, which is very concerning. Car cranks, and starts, but does not idle. after starting, the engine spikes to 2200 rpm, then smoothly dies. The car does have spark throughout the entire process, so I believe it is cutting fuel, which would align with what I am seeing in the AFM and MAP sensor circuits.

Any Help is greatly appreciated

 

[Strokercharged95GT]

Have you looked at the capacitors on the ECU?

 

[OneGreatGuy]

Have you looked at the capacitors on the ECU?

nope, I've been a little scared to open it up. Would a faulty capacitor cause this?

 

[Strokercharged95GT]

Faulty capacitors on 90s ECU are causing havoc on everything right now... All sorts of weird issues are creeping up. About 5 years ago, I had to replace them on my 90s A9L out of my Mustang. On Supraforums, once a month, someone has a faulty ECU causing issues. Open the ECU up and look for capacitors taking a literal **** on the board.

 

[OneGreatGuy]

Faulty capacitors on 90s ECU are causing havoc on everything right now... All sorts of weird issues are creeping up. About 5 years ago, I had to replace them on my 90s A9L out of my Mustang. On Supraforums, once a month, someone has a faulty ECU causing issues. Open the ECU up and look for capacitors taking a literal **** on the board.

I'll have to take a look tonight. Thank you! Any words of wisdom, mistakes I should avoid? I'm new to electrical work.

 

[Strokercharged95GT]

Should be able to open it up and look at it without hurting anything. Just google leaking capacitors ECU and you should be able to find pics of what you should look for. There is a place called Relentless Motorsports in TX that specializes in fixing these things. If your ECU looks normal, it could just be the chewed wiring causing everything...

 

[OneGreatGuy]

Should be able to open it up and look at it without hurting anything. Just google leaking capacitors ECU and you should be able to find pics of what you should look for.

Perfect. Thank you kindly

 

[xxxboosted2xxx]

Sometimes faulty capacitors DONT look any different. Some leak, some swell, but my tach ones LOOKED fine.
But they were not.

Have you soldered before? It's not hard, dont be too worried, just take your time brother!

 

[OneGreatGuy]

Sometimes faulty capacitors DONT look any different. Some leak, some swell, but my tach ones LOOKED fine.
But they were not.

Have you soldered before? It's not hard, dont be too worried, just take your time brother!

What should I look for in terms of faulty caps then? Is there a test or should I just replace them all. I did some more research, seems they are known to go bad pretty quick. I've done some basic soldering, but never messed with capacitors. I'm worried about residual charge left in the capacitors. Should I discharge all the capacitors before replacing them?
Thanks!

 

[BlueDragon]

Go stand alone. It's just going to break again and the AFM is always suspect they are terrible.

 

[OneGreatGuy]

Go stand alone. It's just going to break again and the AFM is always suspect they are terrible.

I really want to go stand alone, but funds won't allow it atm.

 

[1950884]

I would just replace all of the capacitors while you are there. They are very inexpensive & this will save you trouble in the future.
You should be able to find instructions on disassembly (start to finish) and repair on this message board.
Here is an example: ECU capacitor replacement "how to" guide

 

[BlueDragon]

If a 91 turbo ecu will work I could send you one to use. Might have to move a wire or two not sure sometimes its even easier.

 

[OneGreatGuy]

If a 91 turbo ecu will work I could send you one to use. Might have to move a wire or two not sure sometimes its even easier.

I'll keep that in mind. I think the path I'll head down is replacing the caps in my current ecu, and see if that does it. If not, I'll have to decide between buying your 91 OEM ecu or going stand alone...

 

[BlueDragon]

I can send it to you for free pay me maybe if you have to keep it. I don't need it I have multiple. If it helps you save for the right option. I don't know if you plan to keep the car or what but if you do I don't mind helping you out till you can get it done right.

 

[benckj]

Replacing the caps is not as straight forward as you think. You really need to know what you are doing or else you risk forming cold solder joints that don’t work properly.

To be honest I d look at getting an aftermarket PNP carputer and replacing your old 70’s design technology. There are so many advantages to running aftermarket you would be silly to overlook that option. If you can’t afford look into buying less expensive performance models or even 2nd hand. I picked up one recently for $50!

 

[BlueDragon]

Megasquirt PNP is probably one of your cheapest options new I think. Link and ECUMaster are a little more.

 

[T3HKMAN]

I've successfully replaced both ecu capacitors and tachometer capacitors but I've also soldered professionally. Soldering is something every DIYer should learn to do. I'm sure there are some helpful guides out there.

 

[mr2fastforu]

Id go with a fueltech and their diy custom harness, i did all the wiring in a couple days...Fueltech is not common on mr2s but i highly suggest it because its a very user friendly software to tune and they have very detailed instructions on how to wire everything...also fueltech is just a phone call away and they will answer everything!!!

Option 2 put another ecu/harness

Option 3 fix the harness since its chewed n solder the capcitors.

Goodluck!

 

[skutz]

My 93 start running and cutting out at times for a short while. Hard to find a replacement so I had mine repaired. Stated it was a capasitor. No problem since.