95 4.0L stalls randomly

It stalls idling crusing or accelerating, sometimes it will restart right away, othertimes it won't. Sometimes it goes days without dieing.

We were getting a cps code, so we replaced it with a new one from the dealer, (a mechanic friend suggested that saying he see's the ones from the parts store are junk all time). Problem is still there, and still give a cps code when it dies. Then we checked and when it would stall, there was no fuel pressure in the rail, we checked the pressure with a gauge, and it was low all across the board, so we replaced the fuel pump, problem still there but now it has fuel pressure when it stalls, but cps code still there.

Otherthings replaced because they were old
Plugs,
Cap and Rotor,
Wires.

We need some suggestions on which direction to go, and what to look at next.

Thanks
Scott

dyermullet said:

It stalls idling crusing or accelerating, sometimes it will restart right away, othertimes it won't. Sometimes it goes days without dieing.

We were getting a cps code, so we replaced it with a new one from the dealer, (a mechanic friend suggested that saying he see's the ones from the parts store are junk all time). Problem is still there, and still give a cps code when it dies. Then we checked and when it would stall, there was no fuel pressure in the rail, we checked the pressure with a gauge, and it was low all across the board, so we replaced the fuel pump, problem still there but now it has fuel pressure when it stalls, but cps code still there.

Otherthings replaced because they were old
Plugs,
Cap and Rotor,
Wires.

We need some suggestions on which direction to go, and what to look at next.

Thanks
Scott

Click to expand...

dyermullet said:

It stalls idling crusing or accelerating, sometimes it will restart right away, othertimes it won't. Sometimes it goes days without dieing.

We were getting a cps code, so we replaced it with a new one from the dealer, (a mechanic friend suggested that saying he see's the ones from the parts store are junk all time). Problem is still there, and still give a cps code when it dies. Then we checked and when it would stall, there was no fuel pressure in the rail, we checked the pressure with a gauge, and it was low all across the board, so we replaced the fuel pump, problem still there but now it has fuel pressure when it stalls, but cps code still there.

Otherthings replaced because they were old
Plugs,
Cap and Rotor,
Wires.

We need some suggestions on which direction to go, and what to look at next.

Thanks
Scott

Click to expand...

Many CPS sensors get replaced but quite often the true problem is simply the wiring/connectors in the 1st place. The sensor itself is a very simple low voltage coil and unless it becomes contaminated with moisture or get's physically damaged/misaligned it's gonna be fine.

CPS wiring/connector is another matter. At least on the older XJ's. Dunno much about the newer systems like yours but the next time it fails to start, give the connector a good excersize/wiggling. I finally just got rid of the connector and spliced the wire. Zero CPS problems since.

Be aware the fault could lie further up the harness so a diagram would be very helpful in order to follow & qualify CPS signal path to ECU. Of course make sure all the engine/chassis grounds are clean/solid and if the problem persists after qualifying the CPS signal path, you should know there's been a few cases of midly "shorting" starter motors fouling-up the CPS signal during cranking. One guy with a manual transmission finally noticed he could roll start his XJ but whenever he cranked it with the starter, it would never/rarely produce spark. That's a rare one but just to let you know in case you reach the end of your CPS rope.

Can you list where the chassis grounds are so I don't miss any?

dyermullet said:

Can you list where the chassis grounds are so I don't miss any?

Click to expand...

Sorry, I won't pretend to know 'em all so no list. But battery ground cable should be obvious. Also, on my '89 there's a braided ground from the firewall to the cylinder head and that should be clean/solid. Look under the dash for anything grounded to chassis and qualify those connections too. Also checkout the wiring around the ignition coil and any undressed wires that may touch metal with slight movement.