M

Mick Freestyle

New Member
1997 V8 3.9

Had a misfire when under load tick over fine but when you put your foot down bad missing.
Changed spark plugs and rotor arm as arm was worn.
Test drive for a few miles all ok
Following day took it on motorway, it's a bit hesitant when accelerate from 3rd to 4th and then up to 5th
When at constant speed all ok, just when under load

Anyone out there with any ideas what it could be?
 
Ok will try it, also told that when I changed rotor arm I may of disturbed the weights and springs in distributor causing timing to be a bit out.
All starts ok, idles lovely and doesn't stall so hopefully it could be what you mentioned James
 
Well I have purchased a set of genuine leads, coil and rotor arm, fitting them tomorrow so fingers crossed all will be ok.
Failing that will have to start looking at other possibilities such as fuel filter and that sensor that sits behind the distributor which acts like a choke.
will be cleaning some if the breather pipes out and other parts which may get clogged up with ****e.
 
I would have done the free and cheap stuff (air filter etc) first b4 spending money on all the other bits...still.
 
An adjustable spark tester can often help narrow down the fault in just a couple of mins.

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temp sensor as said above, or slight head gasket leak or coolant into one of the cylinders .Dad the same with a 3.5EFi started and ran fine when cold, but as soon as the engine got up to temp it missed.
Replace the temp sensor first
 
Temp sensor may be the cause - have you bridged the connector with a paper clip to make the ecu think the engine is hot or in the alternative, check the resistance with a multi meter?

There are all sorts of things that might cause a mis-fire. Normally it is something simple bu tthe question you really need to answer is whether or not this is an ignition misfire or an injection misfire.

Ignition system is easiest to check so I would start there. Do a search, you will find lots about what you can check and what readings you should get and as said earlier in this thread with ignition parts always buy genuine replacements - pattern parts just die, sometimes in less than 5 minutes. Good luck.
 
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