Misfire/hesitation under load

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Misfire/hesitation under load

Postby pesky164 » Thu Apr 17, 2014 7:39 pm

Cylinder 4
(854.49 KiB) Downloaded 238 times
Cylinder 3
(891.85 KiB) Downloaded 255 times
Cylinder 1
(858.92 KiB) Downloaded 227 times
Cylinder 2
(856.34 KiB) Downloaded 244 times

Hi, as stated in title, I have a misfire/hesitation under heavy load, feels like a plug/lead breaking down. I've checked the lambda - ok, also no fault codes, so thought I'd get the scope out. Attached are the four patterns, obtained by using the coil extension lead & HT pickup lead on channel A & channel B on the coil trigger. Not the pattern I was expecting on any cylinder but also worried about the interference on cylinder 3. I swopped coils & spark plugs but interference remained. I haven't checked the wiring back to the ECU & haven't checked the primaries with the scope yet, just thought I'd open up conversation now.

Vehicle: Fiat Marea 1800cc 16v 2001 Hitachi injection

Cheers in advance... :D

Paul :mrgreen:
Posts: 2
Joined: Thu Apr 17, 2014 7:18 pm

Re: Misfire/hesitation under load

Postby KimAndersen » Fri Apr 18, 2014 4:28 pm

Hi there

To start with I would use some basic diagnostic skills - such as whether the ignition coils are getting power and ground and finally I would see if the coil on plug are receiving a good trigger signal from the ECU.

A fairly easy way to check the functions of all the ignition coils in one simpel test - is to use a current clamp around the common feed supply to the coils. The ignition coils are getting power from the fuel relay - so if you can find this relay it shouldn´t be difficult to make this test.

Posts: 197
Joined: Fri Nov 30, 2012 4:53 pm
Location: Denmark

Re: Misfire/hesitation under load

Postby pesky164 » Sat Apr 19, 2014 6:50 pm

Cheers for the quick reply, I'll check current draw for each coil & let u know...

Having said that the fault seems to have temporarily disappeared.... :roll:
Posts: 2
Joined: Thu Apr 17, 2014 7:18 pm

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