Backfire under boost. Help! please
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Joined: Apr 2003
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Backfire under boost. Help! please
I have a 97' A4 1.8TQ with an APR 1bar chip among other things.
Here are the following symptoms:
1) Gas mileage went from 30 to 25 on the highway
2) At low RPMs if floor it in a high gear it will surge really bad and backfire out the intake.
3) The voltage for the pre-cat is fluctuating lower then normal (.1 to .7), which is common for a O2 sensor 95k miles old. That will make the mixture too rich on average.
4) The car seems to surge under boost much worse then this summer or even a few months ago.
I'm getting the follow engine code from my VAG tool:
17963 - Charge Pressure: Maximum Limit Exceeded
P1555 - 35-10 - - - Intermittent
What do you think is wrong given the symptoms?
I think either the wastegate valve is shot OR the front O2 sensor is getting old and making it run rich. Then when I boost at low RPMs it is too rich and it backfires with too much gas. Possible?
Thanks,
Chris
Here are the following symptoms:
1) Gas mileage went from 30 to 25 on the highway
2) At low RPMs if floor it in a high gear it will surge really bad and backfire out the intake.
3) The voltage for the pre-cat is fluctuating lower then normal (.1 to .7), which is common for a O2 sensor 95k miles old. That will make the mixture too rich on average.
4) The car seems to surge under boost much worse then this summer or even a few months ago.
I'm getting the follow engine code from my VAG tool:
17963 - Charge Pressure: Maximum Limit Exceeded
P1555 - 35-10 - - - Intermittent
What do you think is wrong given the symptoms?
I think either the wastegate valve is shot OR the front O2 sensor is getting old and making it run rich. Then when I boost at low RPMs it is too rich and it backfires with too much gas. Possible?
Thanks,
Chris
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Joined: Aug 2003
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check vac hoses your turbo is overboosting and going into limp mode...
most likely the culprit is the "L" shaped hose that runs from the intake manifold back towards the firewall. That or another leak could trip the DTC. You can also use an ohm meter to check your n75 valve. Bad 02s would give differnt DTC. Youc na also check your plug gap and replace if necessary for running rich. Either way go easy on the car/turbo until you get things figured out.
Thread Starter
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Joined: Apr 2003
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L-shaped hose
Am I just looking for a leak in the hose? I've looked at the host and I don't see anything.
Also, what are the ohm values for the N75 valve and i assume i can check it off of the car?
What's your thoughts on why my gas mileage fall through the floor too? It seems like I'm running rich and the plug gaps look fine, but I could replace them and re-gap the new ones.
Chris
Also, what are the ohm values for the N75 valve and i assume i can check it off of the car?
What's your thoughts on why my gas mileage fall through the floor too? It seems like I'm running rich and the plug gaps look fine, but I could replace them and re-gap the new ones.
Chris
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On the L-shaped hose run your hand along it or just squeeze it to see if any
tear show. Did you check the rest of your vac hoses? There's a diagraph in my pic post. What does your exhaust look like? Once warmed up put your hand or cloth over the tail pipes to check or do you have excessive soot on the rear bumper? I think 25-30ish is the normal ohm range for the n75. Also what plugs are you running, what gap and how long have they been in the car?
Thread Starter
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Re: On the L-shaped hose run your hand along it or just squeeze it to see if any
I just noticed something else that could be nothing, but i thought it was different before.
On measuring block #60 it shows throttle angle and a description, idle, partial throttle and WOT.
When I have the gas all the way to the floor it only rears 86.4 degrees and displays "partial throttle" when it is floored.
I was pretty sure before it said 90 degrees and WOT.
The plugs are about 8 months old. They are copper core and I'll go out now and check the numbers on them.
Also the cars been running about 7/8 the temp it normally does when warm. It used to get up to 1/2 way on the temp gauge, but now it's about 2 notches before half way on the gauge. I can use my vag to find out what temp now.
Chris
On measuring block #60 it shows throttle angle and a description, idle, partial throttle and WOT.
When I have the gas all the way to the floor it only rears 86.4 degrees and displays "partial throttle" when it is floored.
I was pretty sure before it said 90 degrees and WOT.
The plugs are about 8 months old. They are copper core and I'll go out now and check the numbers on them.
Also the cars been running about 7/8 the temp it normally does when warm. It used to get up to 1/2 way on the temp gauge, but now it's about 2 notches before half way on the gauge. I can use my vag to find out what temp now.
Chris
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Thread Starter
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No backfiring out of intake - for now
I just went to purchase 4 new BKR6E's and I couldn't get it to backfire out of the intake under heavy load at a higher gear. It did it's normal surging, but no backfire. The surging seemed less and the max PSI seemed less too.
This whole backfire out the exhaust and overboosting all start when it got cold outside. It did it all last week, which was in the 20s and now it is 43 outside and it is not doing it.
Could the colder weather be causing it to overboost or shoud the APR chip handle that?
Chris
This whole backfire out the exhaust and overboosting all start when it got cold outside. It did it all last week, which was in the 20s and now it is 43 outside and it is not doing it.
Could the colder weather be causing it to overboost or shoud the APR chip handle that?
Chris