Misfire under load!
 

Can someone help me get my sanity back!!!

To cut a long story short we cooked our disco and two engines later have sorted the temp problem but have a misfire problem.

No faults or anything coming up on testbook. new ht leads, new coil packs, new plugs, new alternator, new battery, new air flow meter. Still runs well along flat or downhill, but as soon as load is needed she farts like a trooper.

Something whcih we noticed yesterday - on cylinders 1,2, and 5 if we remove a ht lead while engine is hot and running the spark jumps about 25mm to an exhaust stud, a lovely strong spark. On the other cylinders we dont get the jump, but we can here it cracking nicely when practically touching the exhaust stud.

Are cylinders 1,2,5 exceptionaly strong spark and the others normal - or are 1,2,5 normal and the rest weak.

Can someone try their car for me or give some indication of what i should get.

Cheers guys this has been dogging me for about a year now.:confused:

Spark is equal to all cylinders.

ECU problem? Seems like something must control spark advance. See pix of a scanner monitoring real time data, that one at the bottom should change, as do many of the others, under changing loads. If you have or can borrow a scanner, have co pilot write down readings from several things while you hold the vehicle at various speeds and loads. Almost as dangerous as texting while driving. Might point to something, like sensor ECU uses to determine camshaft position, etc. Ignition items are covered in detail in the electrical troubleshooting guide of the RAVE.

BTW, how about sharing your info on overheating and slow roasting two engines over mequite coals?

Who's MAF are you using, did it have matching part numbers with the original one.
Do a compression test and get back to us with the numbers.