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is200 auto misfire in neutral , low idle problems


mista_khan
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Hi

i have a is200 which was professionally converted to lpg in 2010 , its covered 45k miles since lpg installation and right now sits on 115k for a v reg thats not bad :)

anyway the car runs like a beauty on petrol and lpg until recently, few weeks ago i noticed while in neutral or in drive gear but stationary the revs would jump from 750 to 1000ish then come down, also around this time the idle speed in D and Neutral was lower then 750 , maybe around 600 making the engine sound like its going to turn off. But now its gotten worse, since the weekend it seems to stall on me on low revs i.e. start and stop traffic once its warmed up. Its turned off at me only when moving slowly and it just dies on me,

Ive checked it on petrol and the misfire is there, needle bounces between 500 and 700 revs in neutral and D while stationary , its obviously worse on lpg and thats where it stalls on lpg as any misfire on a car will be alot worse on lpg. once car is moving it doesnt stall or lack power etc.

Ive checked the engine code, just one code and its been present for over a year now and its a p0420 which is related to the catalytic converter. Its been there for the whole year but the misfire only started few weeks ago so i dont think its related.

any ideas what could be causing this? have iridium spark plugs since last year, had it service 2 months ago and had cambelt and water pump changed last month in march

 

cheers guys

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5 minutes ago, ColinBarber said:

I'd look at the throttle body, clean it including the idle control valve.

Thanks for your reply bro, can i get someone to rev the car so the butterfly valve opens in the TB and i spray in carb clean like wynns or do i need to take off complete TB as i dont think i can do the latter lol

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I'd try and clean as much as possible without the engine running first. Spray the carb cleaning on a rag and then wipe around the throttle body and butterfly (push it open). You can then try spraying into the body with the engine running at a fast speed to clean inside.

If there was a lot of dirt then the ECU may need to adjust the idle speed which can take some time. Once the engine is up to speed you need to come to a complete stop and take it out of gear and let it idle for 20 seconds, drive off and repeat. It will try and make a tiny adjustment each time so it takes a while to finally get to the correct idle speed.

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3 hours ago, ColinBarber said:

I'd try and clean as much as possible without the engine running first. Spray the carb cleaning on a rag and then wipe around the throttle body and butterfly (push it open). You can then try spraying into the body with the engine running at a fast speed to clean inside.

If there was a lot of dirt then the ECU may need to adjust the idle speed which can take some time. Once the engine is up to speed you need to come to a complete stop and take it out of gear and let it idle for 20 seconds, drive off and repeat. It will try and make a tiny adjustment each time so it takes a while to finally get to the correct idle speed.

Got it , will try this tommorow and get back to you 

thanks alot

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Done it thursday mate, wasnt that dirty tbh, the issue is still present although cleaning the tb has calmed it down slightly. One thing for sure is the misfire is present once engine is proper warm so after 30 mins of it being on ?

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It could be an injector playing up, or a coil pack, but these would normally trigger a fault code and you would typically notice when accelerating. May be worth trying a strong injector cleaner to see if that helps as a starting point.

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Yeah buddy, normally they would flash the engine codes. Which injector cleaner you recommend? So i can add it in my fuel and give it a blast on the motorway. I think it could be injector as i always use it on lpg so could be clogging up

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Right yesterday started car in morning, drove it for 15 mins, this is after giving it a 30 mile blast on petrol with stp injector cleaner on the day before! The trc and engine lights come on, with full loss of power, i barely made it onto the pavement. Turned car off , read codes, following codes came up:

p0120 

p0121 , both linked to throttle body? 

 

Can someone tell me the meanings of these codes as this seems to be causing the misfire issues!

i removed codes as i was in london and drove it back to birmingham, the misfire is still present when i put it in neutral and park.

 

thanks guys

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Probably best to get a mechanic to look at it. The sensor should be checked for alignment and possibly replaced if it isn't working correctly. The throttle motor should also be checked for correct operation.

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15 hours ago, ColinBarber said:

Probably best to get a mechanic to look at it. The sensor should be checked for alignment and possibly replaced if it isn't working correctly. The throttle motor should also be checked for correct operation.

Is it worth taking it to the mechanic and he can completely take off the tb, clean the tb and wd40 the sensor and put it back on to see if it makes a difference because i have a feeling due to it running on lpg its clogged from the insides?

 

 

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Hey colin, been messing about withmy car all day, i noticed one thing, i removed the airbox, removed the map sensor off airbox and the throttle bottle didnt make any damn difference to the engine sound, running or idle? The engine through up the code but didn get any rougher then it already was, is this normal? Or have we found our problem?

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You need to make sure you don't have any air leaks, e.g. a disconnected or split pipe. If you removed the map sensor did you block the vacuum pipe going to it? Potentially if the ECU is in limp mode it won't use the sensor reading anyway.

The TPS errors will need to be cleared first. This is a mechanical device, the map sensor won't affect the TPS errors. Either the TPS sensor isn't adjusted/working correctly or the throttle motor isn't working correctly.

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17 hours ago, ColinBarber said:

You need to make sure you don't have any air leaks, e.g. a disconnected or split pipe. If you removed the map sensor did you block the vacuum pipe going to it? Potentially if the ECU is in limp mode it won't use the sensor reading anyway.

The TPS errors will need to be cleared first. This is a mechanical device, the map sensor won't affect the TPS errors. Either the TPS sensor isn't adjusted/working correctly or the throttle motor isn't working correctly.

I carry a obd2 with me so tps codes were cleared on site, they havent came back since. When i removed the map sensor from airbox side, i left everything else as it is, so airbox was still over the engine, not sure what you mean by did i cover the vacum pipe?

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