Hey guys,
thanks for taking time to read this. I have been looking to answers to this for a while now. I usually come here to find answers, so figured i would post.

I have a 98' A4 quattro 1.8t.

A couple of weeks ago i started having a really unstable idle. Sometimes dropping low and then going high. Then one day it started bucking and jumping when i would take off. The whole time, witnessing the horrors of people yelling "hell son! learn to drive a stick before you get on the highway!"

So, first off i did a throttle body alignment, and it was ok for a day, then it came back.

i then re-alligned the throttle body replaced the air filter (with a K&N.. now i'm wondering if that was a mistake after reading some posts.) It ran fine for a day, then started doing it again.

I cleaned the throttle body and cleaned the MAF. It ran great for like 2 days.. then back to same old thing.. hesitating, almost dying at a stop, and lurching while giving it gas. I could maintain a speed, but it still acted like it was missing out. It then threw a P1127 and P1129 code (i believe they are bank 1 and bank 2 fuel too rich). I cleared the codes, and re-alligned throttle body.. a day later,, same thing.. but only a P1127 code this time.

I swear i am about to drive this into the side of a bridge.

so the information i have gathered is:

possible vaccuum leak - didn't find any
possible bad maf - don't want to replace if it isn't the problem
bad o2 sensor - hell may just replace to see
coil packs? - but it runs fine for a day or two at a time

It seems to steadily be getting worse.

Any thoughts guys? before i just start replacing parts? My bank account will hate that.

After a day or so, it starts doing it, then I disconnect battery, and hold brake.. then reconnect and perform throttle body alignment.. it works fine.

I figure it has to be a sensor or something electronic. right?

thanks for the help in advance,

My audi and i have a love hate relationship. I love it, and it hates me.

Jim

 

Sounds like what happened when my suction pump seperated. I don't know 98s have one but try checking that out. Look at my thread called car dying.

 

I see where I have a ?check valve? like in your picture, but I don't see that other piece from your picture.. So I guess the 98 doesn't have one.

It did renew my effort of looking for a vaccuum leak. Still nothing though.

Thanks for suggesting it though.

 

Every time your car worked fine, even for 1 day, you did something to the throttle body, so this is the best place to start looking for your problems.
There might be a MAF issue also, so do a wide open throttle log on the MAF, in 3rd gear, up to the redline, and post it here.
One more thing, there should be a field in VAG-COM showing how much the gas pedal is being pushed, so check if it shows IDLE at idle and see if the value increases as you push the pedal, in both easy and fast pushings.

 

I'll try that tonight, thanks. I'm a Vag-Com newb, so I will have to figure out where to find that info.

 

well don't know if this will help, but i couldn't get to a point where i could drive it in 3rd at wide open. I will try to do that tomorrow.

here is a log of it idling when it was having trouble..

i did rev it up a bit there at the end to see if it would hesitate,, but it didn't seem to.

I'm not entirely sure all of what i am looking at on that sheet, so let me know if there is something i need to do different. i'm still learning. Thanks

 

I finally got it logged while it was acting crazy

ok so I didn't know which part to cut out.. so the log file starts out with me taking off 1st, 2nd, 3rd, 4th.. then down to second when I turned off the highway,, held it in 2nd and it cut out for a sec, till I let up on the gas a bit, then it took back off.. I put it in third and let off the gas to go around a corner then floored it. and right then it started cutting out,, I held the gas all the way down, and it didn't want to move at all. I let up on the gas a bit, and it started to take back off, then I floored it again, and it started cutting out again. then I let up on the gas, and it speed back up and I drove the other half a mile home.

sorry, I just wanted to make sure everyone had the full story.

see attachment

throttle position sensor?

thanks guys,
Jim

 

I took a look at the log and it looks like the MAF shows 120 g/s around 4000 something RPM. This looks like a good value, is your car stock, do you have the standard 150 hp?

Please do another log exactly like this: get on the highway and find a place where you can floor it. Then start logging only on channel 2 so that we can have a more accurate log. Start moving and when you switch into 3rd gear floor the pedal and don't take it off even a little bit until you get to 5000 RPM at least. When you get to 5000 RPM let the car in idle mode and pull to the right in order to stop the logging. If you move your foot on the pedal while in 3rd gear you will have to do the log again. Also, try doing the log when the engine temperature reaches 90.
This log is for the MAF. Take a look at channel 31 you should see the Lambda Values, standard and learned. Take a log only on that channel in the same way as you take the log on MAF.
Also go on channel 10 and see if "Throttle valve angle" is "Idle" at idle and the value increases while you push the pedal. Also check the maximum value when the pedal is floored.
Let's see the results for these tests first and if we find nothing we will try to make new logs.