At my Wits End!!

[Impala2]

I'm not sure that Wits have an end, but if they do, I'm at the end of mine! Having issues with our underused K11 micra, 1.0 coilpack version.

Here is the story so far for those bored or technically mined enough to read it...

Due to non-start and general running issues.

Symptoms - Occasional starting issues - usually when hot, misfire from suspected overfueling when under load, or heavy acceleration. The car would usually start with the coolant sensor unplugged, but exhibited the same symptoms when driven. (Very occasionally - when driving at speed, it would throw a "system lean - bank 1" code, cleared and would be fine for weeks)

Replaced (for the 2nd time) coolant sensor with a Delphi item. Same result.

Replaced Coil packs and Camshaft position sensor. Same result!

Removed the entire throttle body and cleaned everything, cleaned the MAF sensor hot wire.

Ran car with MAF sensor unplugged, symptoms exactly the same, so MAF assumed OK.

Checked throttle position sensor, lubricated; this seems fine.

Removed the idle control valve, cleaned with carb cleaner and re-assembled. Idling fine, revs increase as expected when high load electrical circuits opened so assume OK.

(replaced throttle body using DIY cardboard gasket, as old one was shot, and not available seperately for Bosch throttle bodies - must locate and fit one!!)

Replaced all 4 spark plugs.

Replaced (with used items) the fuel rail, fuel pressure regulator and fuel injectors. Changed the fuel filter and replaced all fuel lines after the filter with new items, as the old ones had “crusting” on the insides. (suspected issues caused by E5 fuel sitting in lines unused for 3 years)

Long cranking time resulted in a start. Very smooth tickover, easy revving at standstill. No fuel leaks, no rich smell at the exhaust.

Test drive confirms issues still exist. Runs fine at light throttle, but struggles when demand is put on the engine. Deeper pedal results in backfiring, holding back, and poor acceleration. Starting is often after a long crank and “chugging” to stall, then the 2nd try starts immediately and revs freely. Really smooth tickover with no hunting.

Any ideas? I'm fed up of getting excited when I change a part, only for it to be doing the same when I drive it. No fault codes, so no issue as far as the car is concerned.

Any help or advice appreciated. I used to sell K11's when they were new in 1994, and loved them then. I know that this car has so much more to give, but is holding back, it's like it wants to go, but it can't.

Please help it!

 

[FinnishCoffee]

Have you checked the fuel pump and its filter sock inside the fuel tank? The filler neck tends to rust, which then get sucked into the filter sock clogging it.

That will cause low fuel pressure, which the car can attempt to compensate for by firing the injectors for a longer period. (Unplugging the coolant sensor makes the computer think the engine is cold and it enriches the mixture like this)

The fuel pressure will probably fluctuate with fuel flow, more fuel needed -> more flow -> more debris getting sucked into filter sock. If the fuel pressure fluctuates, that can make the engine swing from lean to rich and back again.

 

[Micra Paul]

Have you checked the fuel pump and its filter sock inside the fuel tank? The filler neck tends to rust, which then get sucked into the filter sock clogging it.

That will cause low fuel pressure, which the car can attempt to compensate for by firing the injectors for a longer period. (Unplugging the coolant sensor makes the computer think the engine is cold and it enriches the mixture like this)

The fuel pressure will probably fluctuate with fuel flow, more fuel needed -> more flow -> more debris getting sucked into filter sock. If the fuel pressure fluctuates, that can make the engine swing from lean to rich and back again.

I'm not sure that Wits have an end, but if they do, I'm at the end of mine! Having issues with our underused K11 micra, 1.0 coilpack version.

Here is the story so far for those bored or technically mined enough to read it...

Due to non-start and general running issues.

Symptoms - Occasional starting issues - usually when hot, misfire from suspected overfueling when under load, or heavy acceleration. The car would usually start with the coolant sensor unplugged, but exhibited the same symptoms when driven. (Very occasionally - when driving at speed, it would throw a "system lean - bank 1" code, cleared and would be fine for weeks)

Replaced (for the 2nd time) coolant sensor with a Delphi item. Same result.

Replaced Coil packs and Camshaft position sensor. Same result!

Removed the entire throttle body and cleaned everything, cleaned the MAF sensor hot wire.

Ran car with MAF sensor unplugged, symptoms exactly the same, so MAF assumed OK.

Checked throttle position sensor, lubricated; this seems fine.

Removed the idle control valve, cleaned with carb cleaner and re-assembled. Idling fine, revs increase as expected when high load electrical circuits opened so assume OK.

(replaced throttle body using DIY cardboard gasket, as old one was shot, and not available seperately for Bosch throttle bodies - must locate and fit one!!)

Replaced all 4 spark plugs.

Replaced (with used items) the fuel rail, fuel pressure regulator and fuel injectors. Changed the fuel filter and replaced all fuel lines after the filter with new items, as the old ones had “crusting” on the insides. (suspected issues caused by E5 fuel sitting in lines unused for 3 years)

Long cranking time resulted in a start. Very smooth tickover, easy revving at standstill. No fuel leaks, no rich smell at the exhaust.

Test drive confirms issues still exist. Runs fine at light throttle, but struggles when demand is put on the engine. Deeper pedal results in backfiring, holding back, and poor acceleration. Starting is often after a long crank and “chugging” to stall, then the 2nd try starts immediately and revs freely. Really smooth tickover with no hunting.

Any ideas? I'm fed up of getting excited when I change a part, only for it to be doing the same when I drive it. No fault codes, so no issue as far as the car is concerned.

Any help or advice appreciated. I used to sell K11's when they were new in 1994, and loved them then. I know that this car has so much more to give, but is holding back, it's like it wants to go, but it can't.

Please help it!

With what & how did you clean the TB & mass air flow & air temp. sensors?

 

[Micra Paul]

Have you checked the fuel pump and its filter sock inside the fuel tank? The filler neck tends to rust, which then get sucked into the filter sock clogging it.

That will cause low fuel pressure, which the car can attempt to compensate for by firing the injectors for a longer period. (Unplugging the coolant sensor makes the computer think the engine is cold and it enriches the mixture like this)

The fuel pressure will probably fluctuate with fuel flow, more fuel needed -> more flow -> more debris getting sucked into filter sock. If the fuel pressure fluctuates, that can make the engine swing from lean to rich and back again.

If you suspect fuel pressure, may I suggest that It will be quicker, easier & more efficient to measure the fuel pressure throughout the rev range at the injectors /pressure regulator fuel distribution manifold?

Pressure Gauge Prices: Petrol fuel injection Pressure gauge at DuckDuckGo

 

[Impala2]

With what & how did you clean the TB & mass air flow & air temp. sensors?

I used a MAF specific spray cleaner.

 

[Impala2]

Have you checked the fuel pump and its filter sock inside the fuel tank? The filler neck tends to rust, which then get sucked into the filter sock clogging it.

That will cause low fuel pressure, which the car can attempt to compensate for by firing the injectors for a longer period. (Unplugging the coolant sensor makes the computer think the engine is cold and it enriches the mixture like this)

The fuel pressure will probably fluctuate with fuel flow, more fuel needed -> more flow -> more debris getting sucked into filter sock. If the fuel pressure fluctuates, that can make the engine swing from lean to rich and back again.

So, if I check that and find it to be the issue, is it time for a new fuel pump or just to clean/replace the sock? And if the filler neck is rusting, I guess that would need replacing, too. And how would I clean the tank to avoid it happening again?

 

[FinnishCoffee]

So, if I check that and find it to be the issue, is it time for a new fuel pump or just to clean/replace the sock? And if the filler neck is rusting, I guess that would need replacing, too. And how would I clean the tank to avoid it happening again?

You should be able to just clean the sock well enough. The tank is plastic so it should be able to be rinsed with water, the only major rust source is the filler neck.