Why does my car have a surging when going down the road at any speed? Electrical?

1. Maruti Suzuki Ciaz SHVS Mileage - 28.09 kmpl
Tank capacity - 43 L
Range - 1208 km
Engine - Diesel SHVS, 1.3-litre, 90PS, 200 Nm, 5-speed Manual
2. Maruti Suzuki Celerio Mileage - 27.62 kmpl
Tank Capacity - 35 L
Range - 967 km
Engine - DDiS 125 Diesel, 0.8-litre, 47.60PS, 125 Nm, 5-speed Manual
3. Maruti Suzuki Baleno Mileage - 27.39 kmpl
Tank Capacity - 37 L
Range - 1013 km
Engine - 190 DDiS Diesel, 1.3-litre, 75PS, 190 Nm, 5-speed Manual
4. Honda Jazz Mileage - 27.30 kmpl
Tank Capacity - 40 L
Range - 1092 km
Engine - I-DTEC Diesel, 1.5-litre, 100PS, 200 Nm, 6-speed Manual
5. Tata Tiago Mileage - 27.28 kmpl
Tank Capacity - 35 L
Range - 955 km
Engine - RevoTorq 3-cylinder Diesel, 1.05-litre, 70PS, 140 Nm, 5-speed Manual

what country sold? lots of 405s' world wide and diffr.
engine performance ?(on an engine stand?)
or the driving wheels to road performance.?
please say exactly what you want or post symptoms. or?
engine codes are very hard to find here. (USA)
ah, but are here.
http://www.scribd.com/doc/25423642/Peugeot-Engine-Code-Reference-List
XU5 or XU9 something are the engine, codes.

wiki: ,see bold , I added.
The 405 was available as a 4-door only. Four-cylinder petrol engines included 65, 92, 110, 125, and 160 hp (48, 69, 82, 93, and 119 kW) units. A 1.8-litre diesel engine, with or without a turbo (70 and 90 hp (52 and 67 kW)) was added to the range during 1988 as was the 5-door estate.
the 405 ended in USA in 1991.
The 405 range included three petrol engines and two diesel engines, all four-cylinder with no 6-cylinder option, in a variety of states of tune and specification. The range was tailored to suit different export markets. The 1.6-litre saloon featured a low drag co-efficient of Cd=0.29, with other models varying up to Cd=0.33. The 1.4-litre (1,360 cc) engine was fitted with a four-speed manual gearbox. It produced 70 hp (52 kW) at 5600 rpm. The 1.6-litre (1,580 cc) engine was fitted with a five-speed manual gearbox and produced 92 hp (69 kW) at 6000 rpm. The 1.9-litre (1,905 cc) engine was available with a five speed manual gearbox, with an option of an automatic in the lower powered version.
The 8-valve version of the engine was available in two levels of tune; 110 hp (82 kW) or 125 hp (93 kW). A 16-valve version was available with the Mi16 model and this produced 160 hp (120 kW) at 6500 rpm and could reach a top speed of 220 km/h.[4]

probably cause by the a/c cutting in and out or running at idle . Fit an idle compensator to the system throttle or raise the idle speed 300rpm.

Did you bleed the fuel lines???

try checking the fuses even the ones on the inside

sometimes this is due to a bad harness wire, if there is any way you can get another wire to test it, that will be a first step.

try removing battery and cleaning all the ground under the battery tray and check main ground wire from battery to engine

Mine is fresh out of the shop for this very reason. First Ford shop could not find the issue. Second one found a spark plug wire that had melted against the engine (or exhaust) and it would short out, causing the engine to lope and surge.
Online, I found that it could also be caused by moisture in the Power Control Module, which many have resolved by coating the connector with silicone.

We had a similar problem and it was the connector that connects the ignition module (bottom of coil packs to the wiring harness. The technician spread the socket connectors and it solved the issue.

Hi. I have two Dynasty LE cars, (a 91 and a 93). Both have the 3.3 litre. The 1991 had almost the same problem as yours except it would only do it once the engine warmed up, (similar to your freeway issue, given distance and time for the engine to warm up to operating temp.) I had it in about three shops before the dealer found an intermittent fault with the cam and crank sensors. I replaced them and now it runs just fine. I hope this helps.