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intermittent miss: fuel or ignition?


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My 1986 505 turbo developed a new problem over the past 2 weeks. It started when going over bumps, the car would sometimes miss. Now sometimes it misses on smooth roads, no difference if under load or not.

The car runs perfectly when cold, starts within a second. I only get an occasional miss and hesitation when car is warm. It can happen maybe 3 times in a 15 minute drive. Once, the engine stopped when I shifted gears from 3 to 4. I coasted to a stop and cranked it and it started right away. Once it stalled at warm idle after an unsteady idle, but restarted right away. And once it stalled when going into reverse (car warm) but took 5 attempts to restart. Sounded like engine was starving fuel.

The engine runs strong. Water pump replaced 2 weeks ago. Slight oil leak from turbo. No smoke. Plugs, wires, distributor cap and battery are relatively new. Good power, temperature gauge in normal range, turbo boost gauge does not work.

Not sure if it is a fuel issue or an ignition problem.

Unfortunately I am not very handy. I could do very basic things on my Volks Karmann Ghia (change oil, plugs, filters, wires etc...) (don't laugh!) but not sure of what I can do myself on the peugeot before I bring it to my mechanic...

Any suggestions are welcome...

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Disconnect the throttle microswitch (two terminal connector, not the three terminal one) and test drive to see if it goes away.

If that doesn't do it, disconnect the overboost sensor (on the intake elbow just before the throttle body)--make sure the wires aren't touching each other or anything else, then BRIEFLY test drive to see if it goes away.

A flaky microswitch or overboost sensor are not unheard of, and can produce something benign like a "hiccup" in power.

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Update:

Took the car for a drive today. Started fine, after less than 1 km, car started to hesitate and miss than died. Took 10 attempts and 10 minutes to restart the car, then drove back home.

Under the hood, the wiring coming from firewall to the coil looks terrible, insulation pretty much gone, not sure if that is the cause of the problem but that has to be fixed no matter what.

Trying to upload picture...

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joe -- in addition to a faulty component, as you suggest -- could it be a short or a loose connection somewhere? as bluebenz suggests, bad wiring or maybe a relay not seated properly (or something like that)? i only suggest this because of the intermittent nature of the problem...

andré

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Thank you both for your replies.

Before today's drive, I thought it was more a fuel problem.

But when the car would not restart today, I could clearly here the fuel pump when ignition turned on. I had only looked at distributor cap and plug wires before, but after seeing the condition of the wires going from Positive Battery junction connector to coil and then to left side of firewall (behind brake fluid receptacle) I think it is more an ignition problem. It almost looks as though a rodent chewed on the wires (possible because car had been sitting outside).

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Hello All,

Patrick emailed me on this and I asked him to check the crimping on the coil wires.

Whether this is what the problem was I believe the issue is fixed.

Happy motoring Poogoters

Graeme

The issue is not fixed yet. But yes, the wire running from PBJC to coil is in miserable shape, and the wires need to be crimped. Will attend to it next week, hopefully that fixes the problem, as it is dangerous to drive a car that hesitates and stalls in traffic!!!

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I'd also add the relays above the fuse box to check - it's almost always just a connection issue, so I always just pull the relays and check for corrosion, tighten up the connections in the plug, and use dielectric grease and pop them back in.

The coil wiring is likely the culprit from the sounds of it, but to keep the car reliable as possible and for preventative maintenance I'd do the same for any electrical connection you can find underhood, as well as ensuring battery grounds, and the grounding tree's on either side of the headlight are all cleaned and dielectric greased.

While you're at it - the TPS adjustment procedure in the tech section is highly recommended. I only recently did it on my 89 and was astounded at how well the car runs when you get it spot on.

Rabin

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Unless you're using a high end wire crimper with really nice sealed crimp connections, I'd recommend soldering new ends on and heat shrink tubing as the better fix. I cringe every time I see electrical repairs with cheap unsealed crimps.

I pretty much rely on proper soldered connections and heat shrink - the repairs to my cars are better than OEM. Eventual plan is to replace all connectors I can with nice sealed connections, and when the connector is off the wiring will be "snake skinned".

0000000015733_Def_2.jpg

Rabin

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If you're going to enjoy Peugeot ownership you should really roll up your sleeves and start tackling stuff like the TPC adjustment yourself. It's dead simple, and with your new multimeter you're all set!

Biggest pleasure I get from these cars is how easy they are to work on. Fix something and the feeling on the first drive is a amazing.

Rabin

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Well I cleaned all the 3 relays on top of fuse box with contact cleaner, a small metal brush and fine sand paper. Also cleaned 2 connectors. Then my mechanic crimped the wires at coil and changed a shabby looking wire that goes from coil to ignition module and so far, after a 40 km drive the car runs perfect. Did not miss a beat!

It was an intermittent problem, so hard to say if it is fixed for good, but so far so good!

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