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[Idle/Starting Problem] 1986 Peugeot 505 S (1985 build)- XN6 2.0L, RWD

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I bought a 1986 Peugeot 505 S (Late 1985 chassis) and I can't get it to idle.

I was driving it down the highway while the battery light came on and it started hunting, lost acceleration power (I think went into limp mode with ECM), and then died. Alright so that is what happened but now this is what I have done to try and fix it. Vehicle has fuel pumping through the distributor with pressure to engine, it has a lot of spark, and it has air flow. Vehicle will crank and run for a bit then stop with "STOP" and "BATTERY LIGHT" coming on even when battery is fully charged.

Cleaned all grounds and connections, changed most light bulbs, checked crank sensor and few other sensors, checked relays, checked fuses, checked auxiliary air valve, tightened all hoses and checked for leaks, cleaned air system, checked distribution rotor by taking it entirely apart, looked at two spark plugs, checked vacuum systems, checked fuel system (replaced fuel pump and filter even). Replaced ECM with a 0280 800 056 recommended by RockAuto.com, OE: 0280 800 066 core (swapped both in and out multiple times testing). Engine is good with no white stuff inside the engine.

XN6 2.0L Inline 4 Cylinder, RWD, Bosch K-Jet Fuel Injected and 4 speed automatic, Peugeot 505S, Canadian/American version (LHD).

Recent Service
Here is all the last services performed by me and previous owner. I do not really want to put much more money into this vehicle and rather kinda sell or part now. I don't have mechanical experience.
Within 0KM (My work since died)

  • Bosch Fuel Pump with vibration rubber (upgrade) and Fuel Filter (NAPA GOLD)
  • Cleaned Air System and topped up oil level in it.
  • Brand new ignition coil. (DIDN'T CHANGE CONDENSER).
  • Topped up power steering levels.
  • Brand New Battery
  • ECM (OE: 0280800066 core - ECM: 0280800056) - Both are working and swapped both in and out to test it multiple times.
  • Thermo-lining Heat Shield and Sound Absorber
  • Light bulbs and head lamps all changed
  • Detailed and cleaned interior (Power polished, waxed, clay barred, and more).
  • Rubberized Spray entire Undercarriage and Engine Bay areas, and Exhaust Muffler Tip

Within Last 1000KM (Previous owner)

  • Alternator Upgraded from 80A from 70A
  • Water Pump
  • Thermostat
  • Belts
  • Oil Pressure Sensor
  • Cooling Fan Switch
  • Head Gasket
  • Valve Cover Gasket
  • Spark Plug Tube Seals
  • Spark Plugs & Wire
  • Oil and Filter
  • Fresh Coolant
  • Valve Timing
  • Engine Timing
  • Idle Set

Within the Last 5000KM (Previous owners work)

  • Rebuilt Rear Calipers, New Pads
  • Coolant Thermal-Time Switch and Auxiliary Air Valve
  • New Trunk Lock and Barrel
  • Central Locking Electronics Service

Within the Last 10,000KM (Previous owners work)

  • New Distributor Rotor (CAP)
  • Oxygen Sensor
  • Brand New Winter Tires

SOLUTION: 91 octane was in it instead of 87 octane. The timing was wrong.





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first, welcome to the group! and congratulations on your car, it looks great. i'd love to see more detail on the vibration rubber upgrade you did with your fuel pump, since that's what i'm working on with my car these days.

as for your problem, the one thing that comes to mind (that you haven't mentioned) is the tachymetric relay -- if it is dying (intermittent), your fuel pump is not getting power at times. i believe that the diagnostic for this is running a direct hot wire to the fuel pump...i'm sure others (more mechanically astute than i) can comment on this further.

there was a recent discussion on peugeot-l regarding an xn6 that wouldn't restart when hot, turned out to be a bad fuel accumulator. but that wouldn't explain all of the symptoms you mentioned.


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I cleaned all the relays and tested most to be working, and all fuses are working.

Mine would restart when hot and the battery light was on. When its cold starting even in +20C weather it won't run more than 2-6 seconds.

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The large intake hose between the throttle body and air flow sensor unit--check this very carefully. Make sure there are no splits; They can blend easily so it is best to remove the hose and thoroughly examine it. When reinstalling, it is very easy for it to slip off of the air flow sensor lip before the hose clamp has a chance to secure it properly. Don't overtighten those clamps either--they can split the hose.

Any air leak between the throttle body and that air flow sensor will cause the symptoms you describe.

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Seems like too many parts are being replaced here without knowing what the issue really is. For example I'd like to bet if the ECM and the fuel pump were changed back to the originals, the issue would still be the same as their failures are not likely to cause the type of issue described.. As mentioned above, all the air need to enter through the air flow sensor (are were talking CIS?) as unmetered air will make the engine run poorly. One combination is where the engine only runs on the 5th injector (aka cold start) and the engine will start and run only as long as the 5th injector runs is the same as the intake boot being split. That is not an ECM or fuel pump problem and the battery light will come on when the engine stops (as would be normal). This can be because there is such a large hole in the intake system that the air flow meter isn't being even asked to participate. With so many things going on in the front of the engine (water pump, T/stat, alternator, head gasket, etc, etc), damage can be created just by moving so many parts around.

Shot gun repairs will total a Peugeot very quickly. My experience with my two 505's is that the hard parts have rarely failed. Rubber, grounds and connections were usually where the fault lay.


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The XN6 has an ignition amplifier which is heat-sunk (sinked?) to the coil pack housing. They typically are pretty reliable. I have seen the inductive pickup within the distributor go bad, and normally it is heat related; The engine starts and run fine cold, but will fail to re-start when hot. This however is the result of having no spark.

The ECU on the XN6 is non-critical. While it can cause poor running, all it does is trim the A/F ratio via input from the O2 sensor. The air flow sensor and fuel distributor assembly do all the metering "heavy lifting"

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Welcome to the forum Animal - and another Western Canadian to boot! (Seems odd calling you that so feel free to post your name... :)

I'd have to agree with what's been discussed so far, the tachymetric relay will provide power to the fuel pump on start up, but if it doesn't sense ignition pulses then it cuts power and the engine dies. Run 12V direct to the main pump to make sure it's 100% powered all the time and give it another try.

Joe's suggestion that the air boot came off is another one that has stumped me - it wasn't until I felt all around the boot that I felt it fold in. Takes a fair bit of work to get them on right, and the clamp lined up and snugged down so take your time.

Only other suggestion is to check the oil bath air filter just in case.

BTW - I'm next province over in Regina SK, and I've got an XN6 car I'll be parting out. If there's anything you want to try let me know - Happy to help out. Hugh is another Albertan living outside of Medicine Hat - so he can also be of help if you're nearby.


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Hey, my name is Jonathan.

Ya I still can't find the problem and my mechanics given up on this vehicle. My dad is boggled as well and he's a airplane engineer. lollol. Fuel is good. It's an electrical problem. Replaced ignition coil and its not up to specifications still to get it running to diagnose the problems. Other one was cracked on bottom and really bad condition. Replaced ECM that didn't help either/Other ECM works still (swapped them multiple times).

Was told to try and sell it by my hired military mechanic. Just gonna make a down payment on a Jeep at dealer cost from my discount.

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Hi Jon,

Why don't you have your Dad call me and I can work with him to get it going. Have you considered taking it to Pioneer or Four Star to get it fixed?

I personally can't see you recovering much money at all due to the high cost of shipping and the limited parts of value on the car.

Your best bet if you don't want to do anything is to cut your losses and sell it for whatever you can, hell trade it in and try to get what you can.

If I were you I would spend the time and effort to try to repair it and get it running, then sell as a running car. Or better yet - drive it until you get some value out of it.

Parting it out will not only be a waste of more time, but you won't recover much money at all.


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I didn't do the tune up and most work on this vehicle. I bought it from a engineer who worked on his own cars and did majority of the workmanship.

Pioneer is an auto shop in Edmonton, Alberta or Jeep/Dodge dealership in Wetaskiwin? I have a control number on brand new vehicles for dealer cost at any dealership. Can't find Pioneer in Google Maps. I was thinking Sandy Lane Auto on south-east side, its pretty close and they have one guy who does Peugeot. The right automotive shop for Four Star Motors (south-side), you were talking about should be able to do it. They work on Audi from what google says on map.

I replaced the battery in the vehicle, that helped drastically for starting issues with the spark. Other 2013 battery was not covered by warranty because it didn't transfer over by ownership. Now I got it starting way better to even get it running 2-6 seconds. I swapped the ignition coil but not the condenser. Condenser works.

I found a huge problem. You guys we're talking about air flow a lot. I took off the air system to my surprise I found a lot of water that was in it. I took out all the fluid mixture (was water mostly) in the bottom pan with a entire roll of bounty paper towels; I had to remove the oil level screen in it, cleaned it all up really nice. Then I put the screen level back on, and added fresh engine oil back to the pan. Spray cleaned the air sensor and mesh air filter. Sealed it back up, and its now running for about 2-6 seconds off starting (from 5th injector mostly I am guessing? I am a noob). Then it's getting either too much oxygen or fuel (possibly wet gas? different octane?). I go to throttle body and try setting the idle speed. Just can't find a placement to get it idling continuously, online its suggested to do 2 turns out but that causes engine to shake. Under 1 (about 30-110 degrees) turn for mine it is running the best with no shake but even at 0 it has full fuel vacuum but dies out. After looking at another thread on here, I took off the O2 sensor near throttle body which still didn't help (Tried swapping ECM's back and forth as well). I read on a Bosch manual these engines like to have a lot of fuel to run.

I suggest this website for a checklist to others, it came in handy. PEUGEOT 505 XN6- Car Care: http://peugeot.mainspot.net/tips/505-XN6.shtml

****It turns out the car needs a static timing to line it up and then timing light when running fully on from youtube videos. Had no clue what set timing meant, thought was just a heading for everything below it on the car care website to do because it had no information. Gonna get on it right away when it stops raining. Also clean the point in the distribution rotor, may need to check gap. Kinda wish that XN6 care was more noob friendly, had no idea placement of distributor was to adjust the timing. Nor that fuel octane would cause the car to need a new timing, thought it would be electrically set by a knock sensor to advance or retard it. Thought the diaphragm screw was the timing... Didn't know what "timing cover" even was. :S

Vehicles sure have changed since the 80's. Getting to be a good learning experience. The military mechanic I hired didn't do any of this stuff even with the haynes manual for 505 I let him borrow, and he didn't know anything about it either. Wish the military mechanic I paid all the best in a war zone when theres no modern vehicle from his ignorance of not wanting to learn a old cars system to get evac to a green zone. He just gave up on my car then told me to go sell/donate it and something majorly wrong was with it... =( Was a waste to pay for his help, he didn't even swap any parts for me and my dad. I am gonna continue with that car care tips; I gotta redo most of the procedures after setting timing but I don't have all the tools or experience. I am learning vehicle definitions as I go along and reading manuals. This is the first time I've actually done anything with a car engine, and mostly doing it by myself now. I'll keep searching the internet for solutions as well.

I noticed a hose not connected on the AC, don't know where it would go to either because can't see any place from top angle, that it would connect too and my dad has my haynes manual for diagrams right now. Also unsure about another hose that wasn't connected to anything that might be the fuel pressure system (has 2 lines in from fuel distributor and its right beside the air system; quite possibly a air in/out-valve, is it not suppose to be connected to anything? Kinda thought it may be connected into the vacuum system but the car care says shock towers should have 1 place open for air at bottoms).

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