Zt190+2003-hesitation at low rpm.

[tonybusa1300r]

:shrug: Hi everyone,i recently bought my zt190+ and have sorted a few minor problems such as camshaft seals and a general tidy up in the engine bay.Every common thing that goes wrong on these cars has been done,ie-new cylinder heads,water pump,thermostat,cam belts,new looking idle controll valve,plugs,air filter,fuel pump and filter,orange clip,crank sensor,oil&filter,rear springs,and clutch with fly wheel and slave cylinder.My problem is hesitation at low rpm and difficult starting when hot as i have to use some throttle for it to start.However there are no problems when cold,also had it on t4 and it only showed inlet man valves but there is no rattle all nice and quiet and no loss of power.
If anyone has some ideas i would be very gratefull.
many thanks,
tony. P.S car has covered 62k

[COLVERT]

Worth checking the MAP sensor in the manifold.( Mass air pressure.)

[tonybusa1300r]

many thanks colvert, i take it that the map sensor dose not show up on t4 then.

[Mike Noc]

many thanks colvert, i take it that the map sensor dose not show up on t4 then.

It sure does.

Mike

[tonybusa1300r]

ok then that was not showing up, i could suspect o2 sensors what you think ?

[Mike Noc]

ok then that was not showing up, i could suspect o2 sensors what you think ?

Sorry I have a diesel so don't know much about the V6's. But the O2 sensor would also show up on T4. Generally speaking when you start the engine it runs open loop - that is to say it doesn't use the O2 sensor's input until everything is up to temperature. Then it reverts to closed loop running where it uses the O2 sensor's input to provide feedback to optimise performance. When up to temperature it will revert to open loop running on the overrun, as the injectors aren't injecting so the O2 sensor has nothing to measure.

Again as a general guide all sensors will show up on T4 so you may be looking for something mechanical - leaking manifold, fuel problem etc but as I said earlier I don't know these engines. If T4 flagged up the inlet manifold valves then they may need checking out.

Mike

[Tatts]

IIRC, hot starting problems = cam sensor.

Would a duff cam sensor also affect performance like the Op mentions?

[scouseeric]

Difficult starting when hot could be acam position sensor on the way out or just needs a clean.hth.



beat me to it Tatts!

[Mike Noc]

IIRC, hot starting problems = cam sensor.

Would a duff cam sensor also affect performance like the Op mentions?


Could give difficult starting but would not affect hesitation when the engine was running as the cam sensor is only used at start up to synchronise the camshaft to the crankshaft, as the camshaft rotates at half crankshaft speed the ECU has to know as number 1 piston rises is the camshaft on compression or exhaust so that it knows when to inject and provide the spark.

Once synchronised you can forget the cam sensor as ECU takes all its information from the crankshaft sensor for running the engine.

Mike

[scouseeric]

:shrug: Hi everyone,i recently bought my zt190+ and have sorted a few minor problems such as camshaft seals and a general tidy up in the engine bay.Every common thing that goes wrong on these cars has been done,ie-new cylinder heads,water pump,thermostat,cam belts,new looking idle controll valve,plugs,air filter,fuel pump and filter,orange clip,crank sensor,oil&filter,rear springs,and clutch with fly wheel and slave cylinder.My problem is hesitation at low rpm and difficult starting when hot as i have to use some throttle for it to start.However there are no problems when cold,also had it on t4 and it only showed inlet man valves but there is no rattle all nice and quiet and no loss of power.
If anyone has some ideas i would be very gratefull.
many thanks,
tony. P.S car has covered 62k

check your throttle cable for any slack.Easy to adjust and the difference in performance is amazing.Good luck!

[COLVERT]

Could give difficult starting but would not affect hesitation when the engine was running as the cam sensor is only used at start up to synchronise the camshaft to the crankshaft, as the camshaft rotates at half crankshaft speed the ECU has to know as number 1 piston rises is the camshaft on compression or exhaust so that it knows when to inject and provide the spark.

Once synchronised you can forget the cam sensor as ECU takes all its information from the crankshaft sensor for running the engine.

Mike
Agree. I mentioned MAP sensor due to the hesitation when ticking over.
There could be variations in manifold pressure at low revs enough to upset the ECU and fuel delivery.

[damienp]

new cylinder heads,water pump,thermostat,cam belts,new looking idle controll valve,plugs,air filter,fuel pump and filter,orange clip,crank sensor,oil&filter,rear springs,and clutch with fly wheel and slave cylinder.

Coil packs aren't on your list OP ?!!?

[tonybusa1300r]

Thanks for your input guys it only hesitats now and then, its this starting business thats most prominant, it wont start unless you give it a slight bit of throttle then if you turn off and re-start its ok but if you leave it for a few mins then you have to use the throttle:confused::confused::confused:

[damienp]

ok then that was not showing up, i could suspect o2 sensors what you think ?

I would have thought you would have got the yellow/check engine light on with this error. Is your coolant level still ok after having a new headgasket?

[tonybusa1300r]

Yes coolant is ok and dose not loose any, temp guage rock solid and warms up ok, t4 not showing any thing at mo, it just needs a bit of throttle to start when warm or hot. :confused: :confused: :confused:

[tonybusa1300r]

Went out this morning and it needed a bit of throttle from cold this time, am going for idle controll valve as all my probs seem to be between 650rpm and 1500 rpm and some times when i pull up to a stop say in a car park the idle speed start going up and down and then steady its self after 10 or 15 sec.

[damienp]

Went out this morning and it needed a bit of throttle from cold this time, am going for idle controll valve as all my probs seem to be between 650rpm and 1500 rpm and some times when i pull up to a stop say in a car park the idle speed start going up and down and then steady its self after 10 or 15 sec.

Shame you cant try someone else's coil packs first before you go spending. Good luck.