4age 20v help! runs terrible once hot

[whatcamber]

Hey guys at a dead end with my sprinter atm all opinions welcome!

Engine: 20v 4age BT, stock ecu, stock rebuild, standard cams ect.

Problem: runs like shit when hot

OK so the story goes start the car in the morning drive out my driveaway down a few streets engine is perfect! Then the engine starts to play up, at first its like a small hesistation or loss of power around the mid range. Once the car has reached full operating temp it runs like shit. Hesitates hard at about 2500rpm almost like it hits a wall missfiring and carrying on, i can barely get up hills. The car has no power at all it does however idle ok (doesnt stall or cut out at idle or when trying to drive). No back firing or black smoke out the back. Revs fine when not underload!

So things i have replaced:

Spark Plugs
Spark plug leads
Fuel pump

Things i have checked:

Benchtested ignition coil
Benchtest Coolant temperature switch (ecu)
Pulled apart dizzy
Played around with ign timing
Played around with spark plug gaps
Checked ecu with scan tool - found nothing..

I have had this problem for awhile not this bad however. The car has been down on power since before matsuri and has slowly gotten worse.

Any ideas?

[LittleRedSpirit]

Possibly a faulty temp sensor.

Possibly associated wiring.

[whatcamber]

I was certain it was that however i tested mine out of the car with my multimeter and it seems fine.. I havent check the wiring though..

[whatcamber]

Also if it was the CTS id expect it to be overfueling hard, the car runs alittle on the rich side but its not shooting out black smoke. It seems to me like a spark/ ecu issue.

[slide86]

put a clamp on the fuel return line and drive it and see if it improves........ie fuel reg stuck open so no pressure in the rail under load

[Matt]

I've had this in fwd cars and after replacing the knock sensor the problem went away on one.

The other turned out to be shit earths, tighten them to be sure. Do you have the check engine light connected because it should flash on when bogging down. Also check you have constant power connected to your ecu because codes can't be retained if you don't.

In factory configuration there is an earth from the engine lift bracket to the ignitor, adding this helps heaps.

[Slimer86]

I agree with knock sensor being faulty or coolant temp sensor.

[whatcamber]

Thanks ill give it a try this weekend

[Sam-Q]

check the caps in your ecu

[whatcamber]

I've had this in fwd cars and after replacing the knock sensor the problem went away on one.

The other turned out to be shit earths, tighten them to be sure. Do you have the check engine light connected because it should flash on when bogging down. Also check you have constant power connected to your ecu because codes can't be retained if you don't.

In factory configuration there is an earth from the engine lift bracket to the ignitor, adding this helps heaps.

Added a quick earth from the ignitor to the body and the car drives 80% better! Will grab some thicker wire and proper terminals from work tomorrow. Still has a small miss but car is definately driveable/ driftable!

Thanks for all the help

[swcustoms]

if you can afford to spend a bit of extra cash those earthing kits do make a difference i think they retail for about 100 dollars and you basically earth out across the whole motor

heres a link if youd like to chek them out .

http://www.nengun.com/greddy/ground-wiring-kit

[Matt]

You'll probably find that it also fires allot faster when starting and that your ecu will now retain codes, assuming it is wired correctly.

Leaky ecu caps will cause hesitation, though it is pretty easy to tell if you rip the lid off the ecu. If you are handy with a soldering iron, they aren't overly difficult to replace or you could always offer the local nerd at jay car $50 if he does it for you.