irratic tickover after gearbox swap

30th January 2013, 00:45

recently swapped goosed gearbox on early saxo vtr. Dont know if its coincidence or not but when we started the car up for the first time afterwards, the motor reved for a short time and then the tickover went irratic. Ever since, It ticks over like its only firing once every fourth turn of the crank (like a big bang engine). its a bit better as the engine warms but not alot

Have swapped the plugs coz they were ready anyway and its no different. Have searched loads of internet sites but only thing I can find is its either coil pack or throttle position sensor...which I cant see Also,when the box was out, the thrust bearing was greased, could XS grease on the crank sensor be causing the problem and if so how the hell does it come out to clean it. the rubber gator seems to be imovable around the sensor

The lad that took the earth leads off couldnt remember where they came from so bolts both to a single point on the top of the gearbox. Is this the problem causer? should one be secured to the engine block and if so to where?

sorry for the the long post but wanted to supply as much info as possible. I was at work at the time the box was fitted so not able to sort things/ take mental pictures as it was swapped

thanks for any help
Paul

30th January 2013, 00:55

Quote:

Originally Posted by stigsdump

recently swapped goosed gearbox on early saxo vtr. Dont know if its coincidence or not but when we started the car up for the first time afterwards, the motor reved for a short time and then the tickover went irratic. Ever since, It ticks over like its only firing once every fourth turn of the crank (like a big bang engine). its a bit better as the engine warms but not alot

Have swapped the plugs coz they were ready anyway and its no different. Have searched loads of internet sites but only thing I can find is its either coil pack or throttle position sensor...which I cant see Also,when the box was out, the thrust bearing was greased, could XS grease on the crank sensor be causing the problem and if so how the hell does it come out to clean it. the rubber gator seems to be imovable around the sensor

The lad that took the earth leads off couldnt remember where they came from so bolts both to a single point on the top of the gearbox. Is this the problem causer? should one be secured to the engine block and if so to where?

sorry for the the long post but wanted to supply as much info as possible. I was at work at the time the box was fitted so not able to sort things/ take mental pictures as it was swapped

thanks for any help
Paul

Try the earths on the top of the box.

My VTS had a bitch fit when these werent on correctly.

30th January 2013, 09:38

Quote:

Originally Posted by robertlittler123

Try the earths on the top of the box.

My VTS had a bitch fit when these werent on correctly.

are they both supposed to fit to the single location on top of the box?

1st February 2013, 21:00

not had a chance to check the earths yet but have been reading up on the symptoms

tick over like a subaru...might be coil pack or injectors

How can I check injectors?

Coil pack...I have an inline sparker. If I can connect it in the HT lead somewhere it'll show if theres a spark on that lead...hopefully (assuming the HT leads are removeable from the pack or could fit at plug end using all 4 sparkers at the same time

1st February 2013, 21:24

Just a single bolt holding the crank sensor on,with a torx head iirc mate.

2nd February 2013, 18:50

OK..so bit of an update. Thoroughly checked earths and everything clean with good contact. Checked coil pack with sparker and all 4 supplies give regular good strong spark. The idle problem didnt change whilst doing the checks

Finally took off the idle sensor from the back of the inlet...looked OK. sprayed with contact cleaner and reassembled....no improvement

BUT
when I disconnect the wire to the idle sensor, the car tick over OK but with a higher tickover like the old fashioned choke. As soon as i reconnect the wire the subaru effect returns

so is this normal on other peoples....does the revs rise when you disconnect the wire.

I've managed to find a reasonable priced second hand sensor and am about to commit to purchase. The wiring where it attaches to the pug looks like it may have been bent a few times so am also thing on swapping out the plug for a replacement just to eliminate that option

Anyone else have any ideas of cause of subaru tickover?

thanks

2nd February 2013, 18:53

any ideas on how i'd check the injectors are all working OK?

3rd February 2013, 22:57

anyone???? do the revs rise to a fast idle when the wire is disconnected from the idle sensor?

4th February 2013, 11:26

Dumb question, you haven't knocked the crank sensor that lives down by the gearbox have you? They are pretty sensitive to how far away from the flywheel as they are a hall sensor (relys on magnetic variation to produce a reading).

The idle rising when the inlet sensor is disconnected will probably just be the ecu reverting to default map as it can't read the inlet flow properly, so it guesses the fueling based on the rpm. As it's more dangerous to run an engine lean than rich, it starts throwing more fuel. More fuel will = a slight rise in rpm for the same throttle position (just like an old fashioned choke in fact

).

4th February 2013, 17:01

Thanks for the confirmation. I have a replacemen throttle postion sensor on its way and have managed to get another connector plug this afternoon if it proved to be the connection

I'll have a closer look at the crank sensor next

7th February 2013, 21:53

OK, so fitted the replacement throttle position sensor and checked the wiring to the plug...no improvement

Removed the crank sensor and cleaned it up. Is there a small hole supposed to be in the end of the metalic pin....would it make a difference?. Cleaning it up failed to help tickover.

Removed ecu and checked none of the pins were bent, cleaned up many of the electrical block connectors from around the engine bay

If it helps, the tickover improves as the engine warms up.

Thinking of taking the car to local garage to see if the coils are firing when they should be. Local bloke used to have one of them sun diagnostic analysers and hes OK and helpful generally

running out of ideas now and hate being beaten.

Anyone know what to check next?

7th February 2013, 21:57

Try cleaning the throttle butterfly, sometimes will cause an erratic idle and stalling if theres a build up of crap behind the butterfly.

7th February 2013, 22:20

Quote:

Originally Posted by Jordysport

Try cleaning the throttle butterfly, sometimes will cause an erratic idle and stalling if theres a build up of crap behind the butterfly.

Thanks, already cleaned that up when i took it off to fit the throttle sensor (the screws are at the rear facing the bulkhead)