Help! A4 Avant 1.8T sport LPG running issues

[Insel Rowie Affe]

[h=2]Help! A4 Avant 1.8T sport LPG running issues[/h]

picked up last november a beauitful and well looked after audi A4 avant 1.8T sport with an LPG convo [1999/2000]


Up until the last month its been running fine, apart from a dodgy blower, which has been replaced


noticed some erratic idling, lower MPG and was sometimes funny to start again after using it breifly, had to wait a few mins and then it would fir up ok


so i took to my mech and we saw one black wire into the oxygen sensor was cut and tested the oxygen sensor which was faulty and replaced it [£100]

after doing this it ran like a bag of nails, found another fault with cam sensor which was replaced [£80 Bosch] and car was running back to normal, MPG was back up, idling smoothly, no flat spots or bumpy acceleration, drove like when i first got it on both LPG and petrol

and went home happy chappie

that was until the next day when i fired it up, back to the nails again, rough in the front and spitting out the back!



so puzzled about this we took to local audi specialist to get a throttle body reset and diagnostic in which they suggested another new sensor [spark something, will find out 100% what it is] for 160 quid

this i will see tomorrow

the specialist reset the throttle body for me and was purring nicely [MPG was stiill down tho] until i stopped at my mums and then next time i fired up was back to the very frustating running issues

seems to run ok after the computer is plugged in and [if any] codes are cleared

so before i start throwing more money at this and apply for food vouchers to eat i wanted to ask if anyone had any issues with the ECU reseting or changing with LPG or any similar sounding problems??

i noticed that LPG is 110 RON would using prem fuel be better in relation? [98 RON]


cheers


rich​

 

[Sandra]

Hi, Rich, welcome to audi-sport.net. Im sure you will get plenty of help and advice from the guys. Enjoy the forum. x

 

[Insel Rowie Affe]

Hi, Rich, welcome to audi-sport.net. Im sure you will get plenty of help and advice from the guys. Enjoy the forum. x

thx for the welcome, im a big audi fan yet not a fan of car electronics

hope someone can provide some past experience in this, i really dont want to sell her

want to remap her too, but seriously, not sure now

 

[A19quattro]

Have a look here; LPG Discussion Forum • Index page
Alternatively from my experience, does the running issue happen on both LPG and Petrol? Normally if you have a petrol problem it is amplified on LPG but if it's one or the other that kind of points the way to where the issue lies. If it's LPG mainly I would look for a good LPG machanic, they are not thet easy to come by but look for recommendations or there are some who post on the forum above, may be one in your area. If it's petrol issue, I would tend to switch off the LPG and take it to a normal Garage and try to get them to fix the petrol side, if sucessful you will probably find the LPG's cured too. You would be better to know as well when/if the LPG has been serviced, what system it is etc etc, hope this helps.

 

[Insel Rowie Affe]

Have a look here; LPG Discussion Forum • Index page
Alternatively from my experience, does the running issue happen on both LPG and Petrol? Normally if you have a petrol problem it is amplified on LPG but if it's one or the other that kind of points the way to where the issue lies. If it's LPG mainly I would look for a good LPG machanic, they are not thet easy to come by but look for recommendations or there are some who post on the forum above, may be one in your area. If it's petrol issue, I would tend to switch off the LPG and take it to a normal Garage and try to get them to fix the petrol side, if sucessful you will probably find the LPG's cured too. You would be better to know as well when/if the LPG has been serviced, what system it is etc etc, hope this helps.

MY mech is a LPG fitter and a friend so no worries there

have problems with both but LPG is amplified more yes, gunna get the LPG checked over a bit more tho

 

[aragorn]

Turn the LPG off and concentrate on getting it running right on petrol first.

Get some diagnostic kit on it and check the readings from the coolant temp sensor given its problematic at cold start.

You say it runs well after codes are cleared, why arent you reading the codes and dealing with them rather than just resetting them? The ECU could well be telling you whats wrong with it.

What your also missing is that resetting the codes resets the fuel trims. So if an Airleak, or faulty MAF or Lambda is causing the fuelling to be out, the ECU attempts to correct the erroneous readings, and often ends up with the engine running waay lean or waay rich. By resetting the ECU it puts everything back to defaults and it runs well again, until it readapts to the faulty readings...

 

[Insel Rowie Affe]

Turn the LPG off and concentrate on getting it running right on petrol first.

Get some diagnostic kit on it and check the readings from the coolant temp sensor given its problematic at cold start.

You say it runs well after codes are cleared, why arent you reading the codes and dealing with them rather than just resetting them? The ECU could well be telling you whats wrong with it.

What your also missing is that resetting the codes resets the fuel trims. So if an Airleak, or faulty MAF or Lambda is causing the fuelling to be out, the ECU attempts to correct the erroneous readings, and often ends up with the engine running waay lean or waay rich. By resetting the ECU it puts everything back to defaults and it runs well again, until it readapts to the faulty readings...

Hi thanx for the reply but i think u may have misunderstood my explanation of events

there were codes and they have been dealt with, there are no present codes showing but it just seems to work ok when we plug in the diagnostic computer!

the reason for the issue at cold starts was a faulty oxygen sensor which has been replaced and since then never had another starting issue just this running rough and low mpg

 

[A19quattro]

What LPG system is it?

 

[aragorn]

try unplugging the MAF and see if it runs any better?

 

[Insel Rowie Affe]

quick update

so the lovely specialists at AM in ilminster realized i didnt need to replace the sesnor they had ordered for me! savinbg a few bob there so i would highly recommend them, they were definetly more concerned weith my car than profits

found a code with the oxygen sensor so we had a fiddle with the wiring to the sensor and back to running perfectly again [like most times when i leave the workshop lol!]

will see 2moro when i start it up if any problems arise

 

[aragorn]

What was the EXACT code you had?

 

[Insel Rowie Affe]

What was the EXACT code you had?

not sure sorry, was an open circuit thats all i remember

martin my mech has quite a bit of experience with fitting LPG systems so he had a fiddle, seems like magic too me

im unsure of what model and make it is, i do know it injects directly into the heads on top of the engine is a small block with 4 gas injectors

will get some pics together soon

 

[Insel Rowie Affe]

so the oxygen sensor circiut is playing up, will get the whole wiring double checked

 

[A19quattro]

We has problems a few years ago with an Astra LPG, mechanic I use contacted teh Vauxhall factory installers and they advided there was a known wiring problem which invloved stripping back the loom to find the problem, fixing and sorting out the loom again. We bought it like that and I wonder how many LPG "specialists" looked at it and couldn't fix it before it got to that stage. I liked the fact our mechanic had the bottle to say I don't know, then phone people up who should and did know, sometimes I think experts are reluctant to ask questions because that's like admitting you don't know.