97 TJ 4.0 runs rough after PCM replacement

No it needs to be totally disconnected and the feed to the starter motor linked. Some people say if the unit is left connected, the M&S unit corrupts the new ECU. Don’t know if that’s true. I didn’t take the chance.
what’s yours doing now?
 
I see. I just put in this ECU that I bourght from the USA. They reprogrammed it to match the Vin/Serial and mileage of my old ECU. I was hoping it would bypass the May and Scofield but obviously I still need to disable it with the fob.

Ive also read that even if you remove the M&S unit you still need the key fob to start the car?

My only real issue is that the keyfobs are totally unreliable and sometimes stop working even with new batteries. I had to pry the battery contacts in the fob to get more contact - which works for a few months.

Would you say it is a very difficult job to re wire the starter like that? I would love to know how you did it. I am good with electrical.

Thanks so much for your wisdom on this!
 
Just off out shopping, I'll try and contact you later. I could talk you through it on the phone if you'd like
 
The M&S unit is behind the dashboard cluster. It will need to be unplugged or removed.
The feed to the starter motor solenoid comes from the ignition switch and passes through the M&S unit, the Clutch peddle interlock switch and then onto the starter solenoid.
You can bypass the Clutch easily enough, as there is a factory service plug on the bulkhead.
You just need to find where the wires extend up to the M&S unit in a small piece of additional loom and link them out.
 
This is a similar item from the same seller that I got mine from. Just contact the seller with your VIN

eBay item number:
264228619747
 
Pat Goode said:
Just off out shopping, I'll try and contact you later. I could talk you through it on the phone if you'd like
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Hi Pat, I'm having the same issue with a TJ 4.0. Ordered new ECU from states, removed ms and skim but still not going. Manufactured end of 97. Right hand drive, just have two grey keys. Any help appreciated.
 
Tommy21 said:
Hi Pat, I'm having the same issue with a TJ 4.0. Ordered new ECU from states, removed ms and skim but still not going. Manufactured end of 97. Right hand drive, just have two grey keys. Any help appreciated.
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What ECU did you buy? To guarantee a non skim ECU for yours it ideally needs to be from a 97 TJ as from 98 onwards skim was fitted as an option.
I would avoid getting one from these companies that claim to programme the ECU for you. Better off getting one from a scrapped vehicle
 
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Bigeef said:
What ECU did you buy? To guarantee a non skim ECU for yours it ideally needs to be from a 97 TJ as from 98 onwards skim was fitted as an option.
I would avoid getting one from these companies that claim to programme the ECU for you. Better off getting one from a scrapped vehicle
Click to expand...
Thanks bigeef, I got it from @Wranglerfix, who has sorted lots of people that had ECU problems so I've no concerns about the unit. I took a look at it there and it's almost starting, I get hear the fuel pump going but no fuel is getting to the fuel line. So that couldn't be the immobiliser? Must be insufficient pressure coming from pump, there's plenty of fuel it. Need a new fuel pump?
 
Tommy21 said:
Thanks bigeef, I got it from @Wranglerfix, who has sorted lots of people that had ECU problems so I've no concerns about the unit. I took a look at it there and it's almost starting, I get hear the fuel pump going but no fuel is getting to the fuel line. So that couldn't be the immobiliser? Must be insufficient pressure coming from pump, there's plenty of fuel it. Need a new fuel pump?
Click to expand...
You could test that theory by trying some starting fluid down the throttle body. If it runs then you know there's a fuel delivery issue
 
Bigeef said:
You could test that theory by trying some starting fluid down the throttle body. If it runs then you know there's a fuel delivery issue
Click to expand...
Yep did that, ran for a second, which was great to hear. If it was the immobiliser it should run then cut out yes? So thinking crankshaft sensor or fuel pump possibly.
 
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