miss fire

[tol16v]

if anyone could help, i have a seat toledo 2.0 16v with abf engine which is the same as the golf mk3 16v. the problem i have is that at 2800 rev it has a slite miss fire. you can only feel it on the motorway at 2800 to 3500 revs have changed the lamber prob, ecu temp sender, ecu 30 relay, leads, plugs, dis cap, rotor arm, and some of the vacum pipes. it has been to local seat dealer and two other garages. has been on 1551, 1552 and 5051 code readers with no other faults showing up. car runs fine around town but on the motorway it has a slite missfire. am at a dead end wot to try next. any help please.

[Gambit]

is there a hall sender in the ABF distributor?

[Len]

Ya could try changing the Fuel Pump Relay.

[tol16v]

yes i think it has a hall sender, have read lots of people changing the fuel pump relay. would this cause a miss fire if not working correctly? which is the cheeper one the relay or the hall sender? 

[Len]

Fuel Relay cost me ?12. Dont know bout hall sender.

You can check the relay. Get the engine warm. Turn off and take out the relay, if its warm to touch, put it to your cheek is best, then its o.k. If its cold then change it.

[tol16v]

just phone local dealer, relay is ?18.00 +vat and they told me that you cant bye the hall sender on its own you have to buy a new distributer for ?90.00? +vat.

[Len]

U gotta a dear dealer.

Well try the trick with the relay, it could be that, a bit of back pressure in the system.

Tho i am surprised that none of the fault codes show anything if its in the timing.

[tol16v]

Going to try the relay later. Sorry did'nt under stand wot you mean about back pressure? I had to change the rubbers on the rear box about 2 months ago because they all split, but the miss fire was there before that. it has the origanale cat and centre box from new i think only the back box has been changed.

[Len]

If the fuel relay if faulty it could cause some back pressure in the fuel lines. With injection systems ya got return pipes to the tank. Stuff like that i was thinking.

[tol16v]

tested the relay, it was hot on all sides. have ordered new one anyway as the fault is very intermintent. going for the cheep options, looks like i am going to have to get a new distributor. new relay turning up on friday. thanks you all your replys. if i was going to clean the throttlebody is best to take it off or can you spray wd40 with intake pipe just removed.