My 300 now has a mis-fire. It is only really apparent at tickover and lower revs, I have noticed that when the 2 connectors on the thingymaboppers on the front casing (PTU 's i think but am not sure) are moved around the engine note changes but the mis is still there. The plugs are new 5000 miles ago , there is no smoke even when doing 35-40 mph , i dont go any faster as i still have an oil leak to fix.

Any ideas guys , i think its electric but i dont have a ,manual yet.

 

Cheers John Crisp

Just a thought- have you cleaned the throttle bodies? When they're full of cr*p you get rough running at low revs / tickover.

 

The reference is on AndyP's page somewhere.

 

HTH - Gio

Mine was doing the same and was pretty sure it was the ptu, so bought one from Courtesy, fitted it and........wa-hey, no difference! next was plugs so new set of those. no difference.

Ended up being the throttle pos sensor and just disconnectiing it and putting it back on cured the mis-fire! the wiring to it was a bit dodgy tho, and have since had it properly done and runs sweet. I'd check that next on yours!

 

Good luck.

Hello John,

 

Check the coil pack connectors. Mine did exatcly the same and worked it self loose. The connectors are prone to breaking.

 

Vijay

thanks guys,

my car had the mis fire just after i bought it i removed the plugs to check them and they are fine, it cleared after i ran the car for a while, now it had returned to misfiring.

I have been told b4 about the throttle bodies so i think i need to look at them Gio and clean them out.

The PTU is on the drivers side James, right.......what is the other thing on the passenger side with 4 wires in it driven off a camshaft and when i push the wires in the engine note changes, maybee just a coincidence.

Vijay could u tell me where the coil pack connectors are (are they on top of the plugs.....i am a diesel mechanic and a bit thick at car designations of components hehe)..

 

Cheers again guys John Crisp

If you're looking at the engine from the front, PTU is l/h/s kind of under the left throttle body attached to the front of the black plastic cover, a corragated cigarrette size metal box. Throttle position sensor (and try this next) is attached to the r/h/s throttle body.

The round thing adjacent to the PTU is the crank angle sensor. This gives the signal to the ptu and ecu to fire the plugs and injectors... Try removing the connector and cleaning it. Have you tried the injector connectors? TPS is a strong possibility too as mentioned above. Throttle bodies should really be cleaned at regular intervals...

 

HTH

 

CheerZ,

 

Andy

 

PS John, did you get my mail???

Cheers Andy u have some mail mate.

 

Are there any diagnostics like checking resistances of the PTU or am i better waiting for a manual to go down that road....

 

Thanks guys for the reply's......TLC needed for my 300.. I have lots to go on, i just need some time to pull it to bits now.

 

Cheers John Crisp