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Engine bay electrical interference


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Hi there, diagnostics man says that there is still a lot of electrical interference around my engine bay that he cant pin point. For example the graph for the sweep of the tps was fairly smooth with the engine off and ignition on. With the engine on, the graph had massive spikes all through the range. There were some spikes on the injector pulse waves as well although not as evident.


Tried a search on google but can only come up with ideas about the radio suppression relay, ht leads routing, radio antennae and exposed power cables. How important is the layout of the ht leads? I know the original ford ones came with a plastic casing box to keep the wires relatively straight. Should i be transferring this over to my new ones?


Thinking that the problem might just be from a faulty tps, i disconnected it leaving all other sensors plugged in and i actually felt the seat pushing into my back for the first time in aaaages. There was however about 4-5 misfires between 2-3k rpm on full throttle but this didnt happen everytime. Im assuming i need a new one now. Not very accurate information i know but i'd like to know if anyone else has had any similar experiences with this sort of thing. Search results just brought up an old post by me!

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Electrical faults can be a total pain in the arse to diagnose and trace back.. Really you need to get it to an electrician who specialises in this kinda stuff so they can scope it out (eg, find out if the noise coincides with sparks or injectors firing etc...) and then try and trace the cause back...


Anyway.. most likely being caused by an earth problem, perhaps the supressor on the coilpack or perhaps just a bad loom.. it really is a need in a haystack.

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never simple eh?! ill check all the earth points and general things i can do myself. Cant keep going to the diagnostics man to look at his screen so do you know of an affordable (£100ish or less) oscilliscope that i can plug into my laptop and start doing these tests myself from now on? Voltmeters just arnt fast enough to display the relevant data and no graphs etc. Not sure if i need one for odb II (assuming thats what ive got) or a general one which harnesses onto the feed and return wires for different sensors/injectors etc. I think he was using some software called Peco or Piko?


Ill do the check on the coil pack that haynes mentions when it stops raining but i think this is the only test i can do with it for now.

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