XM running odd

[Ropkeit]

My 2.0i 1990 XM runs 99% of the time very well but randomly the engine goes lazy. Sounds like she runs only on 3/4 cylinders. On idle, she goes off. Revs stay under 1300. Torque goes weak.

The car had been sleeping for 2 years, then I bought it and used it for 6 months, and in the last month, it started doing this thing. The car then was not used for 9 months due to lhm leak and no time and money to spend on it, tho I ran the engine almost weekly. Now she's running again, and Im planning to put her in use, but this fault will probably come back.

The lambda censor died btw and I guess somewhere after that, the problems started. I drove for some weeks, maybe the last month, without lambda. Could that have something to do with the problem? Now i've plugged the new lambda in and no warnings about that anymore.

If not, then could it have something to do with the coil/distributor etc? Should I clean it, change it, maybe change all the wires.....?

Thanks.

[aerodynamica]

Hi, It's hard to be sure without seeing it in person but one thing that can occur if the Lambda sensor is faulted is that the fuelling can be too rich (or weak) and it's possible that this caused something simple to happen such as spark plugs getting too much carbon build up. It's worth popping out the plugs and checking the gap and cleaning them with a wire brush to be sure about their condition. It's always best to check the easy things first!
I think your engine has Bosch Monopoint injection. I had Bosch multipoint 3.2 on my last XM, a 2.0 Turbo. I had a similar trouble to you but it was only after starting the engine and running for more than 5 minutes. It always started strongly and drove for 5 minutes completely fine. Then it began to go 'weak' inasmuch as it would cut off at stop signs or traffic lights, always started again but it would run weak for quite a while until about an hour where it ran fine. There was no loss in power as such it simply cut off when you de clutch to stop. It also jerked when you declutched to change gear as the short gap between gear changes was enough for the engine to almost cut. I read the fault codes on the ECU and the only 2 faults were: Turbo boost controller faulted (so I replaced it) and crank sensor faulted (so I replaced that too) I then replaced the Lambda sensor, checked the air flow sensor, the air inlet temp sensors and their connections, checked all of the termnals to the ECU, checked and cleaned every earth on the car , changed the air, fuel, oil filters and the thermostat, changed all the spark plugs and HT leads, fitted a new coil pack and it STILL had the problem..... So the only two items I didn't check were the engine 'knock sensor' as there was never a fault code for this, and the fuel pump itself. I considered that this would either work or not but that might have been my mistake! I now wonder if the fuel pressure was not high enough after the 5 minutes of running. There is also a fuel pressure regulator that is just a vucuum operated valve on the fuel rail. So these are all things to check! I also cleansed the fuel injectors and rewired the injector wiring loom but I don't think the XM 2.0i woud have that.

I don't know if this is of any help but it might be simple