This is a '94 940T wagon. 350,000 km.
I have owned and mechanically maintained it very well for 14 years and normally runs like a swiss watch.
Lately it has been misfiring, randomly, when accelerating. Makes the same sputtering/missing noise as when you are running out of fuel. I have 3 of these, so access to lots of spares. Here is the skinny.
- There are no codes.
- I have a smell of gas outside the car particularly around the back end and back sides. Replaced all the hose clamps on the lines coming/going to the fuel tank (Some were rotted off) and tightened the big ring on the tank, Still smells.
- Trying to flag a parallel event related to this problem, the only thing I have is the mysterious gas smell.
-At idle, Fuel pressure 33psig with vac hose connected 44 with it off. This matches spec. Changed the FPR anyway, same result and same problem.
-With the pressure gauge connected on a long hose and gauge taped to the windshield I drove around until the misfire occurred. Fuel pressure was constant at 33'ish PSIG throughout. NOTE: Pressure didnt rise to 44 when I had opened the throttle and showed zero vacuum. (I have a real IPD vac gauge)
- Removed vacuum hose to FPR and drove around. Pressure was steady at 44'ish PSIG, same problem.
-Thought it was only after turning a corner, but now it seems to be everywhere.
-Read about the possibility of Crank sensor problem so changed it out. No difference.
- When this happens, I can fix it by taking my foot of the gas, and trying again. Sometimes it is OK the first time, sometimes it takes a second remove/replace to get it working.
- TPS replaced and adjusted.
-AMM cleaned at a distance by the spray method, and months ago before this happened.
- There is no change in the revs according to the tach when this happens. (I was looking for an electrical,sensor issue)
- Plugs, leads, distributor cap, rotor renewed.
- Plugs are very light brown colored, look perfect to me. Gas mileage has never been great and struggle to get 20 mpg despite perfect looking plugs. (Probably my right foot weight)
- When I kick down hard on the highway to pass a bugatti veyron, I get knock on full boost and then it goes away which I assume is the ECU richening the mixture as it is programmed to do.
- ECU input voltage for the Block temperature is good.

My forte is mechanical and shipbuilding so if there is anything electrical you think I should check please give good instructions.
I have spare ECUs etc. and another 94 sitting in the driveway, so can swap anything out without mortgaging my border collies to buy stuff (the kids have left already)

Thanks for the help
John