tomshark

my 85 euro runs great cold or warm when it rains. the same can not be said about dry and cold( back fires when warming up) any ideas? now this year in n.c. the weather has been perfect for great running but eventually it will dry up.

pcar928fan

Slight cam timing miscue... maybe a tooth or two off on one cam... others with more knowledge are bound to jump in here quickly with better ideas. Maybe a knock sensor that is broken.

Mrmerlin

first thing to check is the timing of the twin distributor, remove the caps and then set the timing marks to TDC, both of the rotors should match up with each respective housing hash mark, also inspect the coil end and distributor end of the coil wire for corroded ends and then run the car in the dark and look for fireflies

tomshark

i have done the timing rotors all are dead on .
what is at issue is electrity conducts better wet.
the wiring on all 80 "s germans cars is terrible . and i have step by step replaced rewired contectors
that were so brittle they break or have fallen apart to nothing.

what is a wiring issue that would lead to rough running, backfiring when cold and dry?

if it were timing or inproper rotor position or loose belt it would do it all the time not once heated up .

i replaced maf with known good one.

danglerb

I doubt the wiring connection, cars run differently when the air is damp. Have you checked the timing while the car is acting up?

atb

Does the twin dizzy have a green wire?

Randy V

Odd.

tailpipe

check the multi plug next to the jump post on pass side front make sure all connections are clean and tight it sounds like a dirty connection that workes better when wet could also be a ground strap for the motor thats come loose it definatly sounds electrical to me

danglerb

All but the dist is basically the same as US 85 with a crank sensor.

John Speake

Has it been federalised ? How many miles on the car ?

tomshark

1. no i have not checked timing when acting up . after warming up backfire goes away .
2.no green wire.
3.the multiplug and all ground wires cleaned and tight even the ground point behind multi plug that was tough to get at.
4. car has 85,000 miles . it has a cat, and ox sensor but leads to that go nowhere. i have not seen any control box ( aftermarket ) near fuse panel .. what else should have or could have been altered that i should look for.

John Speake

Usually an additional box if it has been federalised. Backfire will be due to fuel uiburnt in a cylinder being ignited by hot exhaust gasses in the exhaust system.

Souds like an igntion problem, or an injector flowing badly, which would give a weak mixture too weak to be ignited in a cylinder.

tomshark

and this situation only comes before it has warmed up.
and the front of the car are the ignition modules correct? and when it rains they are the first things to get wet.
i have cleaned the conections but how can i check to see if one or both are bad or will the car just not run if they are bad .
just to note i have change the temp 2 and it is running in spec.