Car bucks hard during accel, No CEL

[Sprode]

Hey guys,

I was away on business for a couple weeks, and when I got back I had a big problem with the car. Whenever I try to give it enough gas that it has to downshift or accelerate hard, the car will buck, hard, and then the revs will climb like ti for a half second or so like it was taken out of gear. Then the throttle remains unresponsibe for several seconds. Then it is fine again until I have to try to merge onto a highway or something. It was bad enough that the first time it happened I thought I blew my transmission (tiptronic). It does it pretty reliably. No CEL.

I took it to the dealer and they say it was "boost cut" but can't talk to the ECU because it is chipped (I have a friend on the inside so they are not giving me any nonsense about the chip). I was thinking maybe fuel cut? Does this mean its time for a new HPFP. Car is stage 2 with HFC. I have changed the cam follower and it didnt look that bad, but I am not sure if that is enough to rule out the fuel pump.

Car has about 38k miles. 07 S-line. Has the new coils from the recall.

If this is not a good enough explanation I will try to get a video on my droid and post it up.

PS I searched, couldn't find anyone having this problem.

I am on my way to the dealer now to get it from them. We will see how it goes. It is fine to drive unless I go over about 25% throttle

[jimrobbington]

hmmm, sounds interesting. I don't know what would cause the RPMs to climp like crazy without any power to the wheels, though....

[ECS Tuning-Audi]

I just worked through a nearly identical problem with another Stage 2+ car. He originally thought it was the follower but after he replaced the pump and filter as well he still had the problem. It ended up being spark plug gap. His car ran just like this until he gap'd down to .02 from .028 and it evened right out. While I think this is a bit much, try stepping down on a new set of spark plugs. .028, .026, .024, .022 and then .020 until you get something that works. You may want to try fresh bkr7e's and a proper gap.

Click here for spark plug options. I'd personally do the plugs first since they are less work and money than a HPFP.

[Sprode]

Jim,

Its as if you don't lift your foot off the accelerator immediately as you push in the clutch.

Chris,

So this is a missing ignition problem? It does seem to happen right as boost starts to come on. Dealer recommended I unflash so the ecu would talk to them. Guess ill try plugs first then idk where ill go from there. Thanks for the advice

[jimrobbington]

Ok, then I could see how it could be an ignition problem also. I would definately check that. Have you gotten a new tank of gas since you got back to your car? Maybe a little moisture got in it or something, causing spark to be more difficult?

[72mako]

This may sound dumb, but check your airbox and MAF sensor. I had the exact same issue, thought I was going to stall out on the Tappanzee Bridge during morning rush hour. Got to the dealer, they removed my new rev DV and said the problem was fixed. Dropped off my loaner, picked up my car and 15 min later was on my way back to pick up the loaner, exact same issue. At this point I was pissed because they put in a diaphram DV instead of the piston type that I had put in on my own. Next day they call and say there was a mouse nest in my airbox and one of the pieces of paper snuck past my air filter and was flapping in front of the MAF sensor. That got cleaned and I haven't had the issue since. I've since learned to check my airbox a little more regularly. I felt like I was on a bucking bronco at any speed when this was happening. Not sure that's your cause, but it is a cheap and easy fix if it was.

Nick

edit: They didn't check the airbox the first day because they were also doing a 75k service and I told them not to replace my filter as it is a K&N.

[Jaki]

I am having the same issue, but stage 1 revo. Only thing I have is a K&N, revo 93, and forge dv. It started happening only sometimes when I got into boost, and then it started happening all the time. One time I didn't take my foot off the gas and the check engine light came on for a few seconds and went off. I have the select switch, so I switched back to stock map and took it to the dealer about 2 weeks later. The funny thing is, this only happens when I'm running the 93 map. When I switch it to stock, it runs perfectly fine. The dealer had the car for 4 days, and said they couldn't replicate the problem (I gave it to them with the stock map loaded) and they couldn't find anything wrong. They did however find the CEL that was stored in the ecu. They said it was a random misfire code. Since they couldn't figure out what was wrong and couldn't replicate it, they didn't charge me for it. When I got my car back, my service advisor told me "even though your car is chipped, we're not charging you because we don't think the issue is related to the chip."

I changed out the spark plugs, and the issue went away... for about 2 weeks. Then it came right back, and again, it only happens when I run the 93 map.

[ECS Tuning-Audi]

I am having the same issue, but stage 1 revo. Only thing I have is a K&N, revo 93, and forge dv. It started happening only sometimes when I got into boost, and then it started happening all the time. One time I didn't take my foot off the gas and the check engine light came on for a few seconds and went off. I have the select switch, so I switched back to stock map and took it to the dealer about 2 weeks later. The funny thing is, this only happens when I'm running the 93 map. When I switch it to stock, it runs perfectly fine. The dealer had the car for 4 days, and said they couldn't replicate the problem (I gave it to them with the stock map loaded) and they couldn't find anything wrong. They did however find the CEL that was stored in the ecu. They said it was a random misfire code. Since they couldn't figure out what was wrong and couldn't replicate it, they didn't charge me for it. When I got my car back, my service advisor told me "even though your car is chipped, we're not charging you because we don't think the issue is related to the chip."

I changed out the spark plugs, and the issue went away... for about 2 weeks. Then it came right back, and again, it only happens when I run the 93 map.

What is your gap at?

[Jaki]

What is your gap at?

I use BKR7EIX with factory gap.

[ECS Tuning-Audi]

Oh my, try .032, .03 or .028. Never ever go by the factory gap.

[Tusin]

Yeah what Chris said. When I picked up my BKR7EIX, they were all pretty damn far off out of the box.

[Jaki]

Thanks, I'll try that. The first time I changed the plugs, I had no issues. It was during the second and third sets that the issues started, never immediately, but gradually.

[rnp614]

Jaki, I had that experience with a bad coilpack. Only bucked under a tuned map. Stock was fine. Maybe check that.

[Jaki]

Jaki, I had that experience with a bad coilpack. Only bucked under a tuned map. Stock was fine. Maybe check that.

Thanks, I'll take a look at that too. Come to think of it, I blew 3 coilpacks 2 days after getting flashed. One coil pack blew, I took it to the dealer, they replaced it, and a second one blew on the way out of the dealership. They replace the second one, I make it 2 miles from the dealer, and a third coilpack blows. I came back and they replaced the blown one and the 4th one as well. I'm going to the dealer for a oil change next week, and I have the recall letter for the coil pack, so I'll have them take a look at it. I'll also replace the plugs and gap them this time.

[CBRmatt600]

I will add one more note to check your gap!

I have been having constant, intermittent bucking problems under hard acceleration. From a low RPM, high gear pull at WOT my car would buck like a maniac. I also replaced stock plugs with the NGK's a while back, which fixed the problem for about a week, and it came right back. Pulled the plugs this weekend (which are supposed to be gapped at 0.28 from the factory), and found they were off by a decent amount. A couple were at 0.32, a couple at 0.30. I brought them all down to 0.28 and the car runs like a champ. Gap your plugs properly!

[EuroA4]

Factory gap is .032 I beleive. If you are chipped you should try .028 instead.

[coolguy32]

i've been having this issue.......but i'm not chipped, would it still be a spark plug issue?

[a4b7]

im having similar bucking problems...mine all checked out to be 0.28 from factory. I was flashed with revo...but havent had the program (disconnected battery) put back on for a while now. Should I still leave it at 0.28?

[ECS Tuning-Audi]

.028 might be overkill for a non chipped car, you may want to go back to .032. If you are stock it could indeed still be a spark plug issue, BTW.
You may want to try new spark plug . I like to start with plugs when diagnosing hesitation, especially if its been a while since your changed them (or perhaps haven't).

[coolguy32]

.028 might be overkill for a non chipped car, you may want to go back to .032. If you are stock it could indeed still be a spark plug issue, BTW.
You may want to try new spark plug . I like to start with plugs when diagnosing hesitation, especially if its been a while since your changed them (or perhaps haven't).

i'll look into chagning them.......thanks chief.

[ItsThat2.0T]

This just happened to me; I'm furious.

My CEL came on and went off.

If I disconnect the battery with it get rid of my REVO chip?! (Before I go to the dealer I need to remove the chip somehow).

[ItsThat2.0T]

Double Post

[Sprode]

Resurrection!

After *6* weeks and 3 attempted returns of my car to me by the dealer, they essentially turned the car back to me telling me there was a Diverter valve fault, but they did not think that was the cause of the problem. They also wouldn't replace the DV because it was a forge, even though I wanted them to just put it back to audi.

So I bought the stupid part from them, and 3 hrs later, ALL better. I truly did not expect the diverter valve to be the issue, but it was.

The bitch bolt wasnt even that hard to get. I didn't even need a wobble socket. The hardest part was realizing audi actually made an electronically actuated turbo bypass valve. Never seen one of those before, always vacuum powered like the forge.

Anyway, with the 490 dollars I saved by doing this myself, I'm gonna buy me the manual and a vagcom license, because I clearly can't rely on the dealer. Hurray.

EDIT: Looking over the old forge DV, There was definitely a slit in one of the vacuum tubes right off the nipple. That was likely the source of my problem. No more of that to worry about...

[72mako]

Thanks for the update, I was wondering what ever happened to this. Glad the car is running better now!

Nick

[Sprode]

Re-resurrection. The next day after making this post it started happening again. I just about went insane.

I ordered the Vag-com kit from ross-tech and plugged it in. DV issue again! I get under the car to find the electrical connector itself had come loose and was disconnected. This explains my errors, which I cleared.

Went driving again. STILL HITS A WALL. NO CODES this time. I limped home and rested on it.

Finally, against my own judgement, I listened to the first advice I got from Chris at ECS. (he also had the chance to sell me much more expensive stuff, but continued to recommend the cheapest solutions first)

After having done everything suggested in this thread and more, would you guys believe it was the fucking spark plugs? VW plugs were pretty dark, but I've pulled plugs out of my supra that looked like black holes. Either way, no codes before, no codes after, but now the car runs great.

Run the right plug everyone! BKR7EIX at .28 was necessary on my NON-CHIPPED car to make it run right. Now to get rechipped...

[Sprode]

Yeah what Chris said. When I picked up my BKR7EIX, they were all pretty damn far off out of the box.

Worth mentioning that YES YOU HAVE TO REGAP YOUR PLUGS OUT OF THE BOX! I saw someone posting while I was looking around for other things saying that bkr7eix came at .028 right out of the box and to just throw them in. That is not true, and a bad idea!

Trust but verify!

[ultimatetaba8]

I seem to have the same problem in my A3. It's the 2.0T DSG, chipped. At times it shifts smooth, many times, it's jerky upon shifting. I'm like...WTF?! But this may possibly be the answer to my problems..who knows.

Might sound like a dumb question...how do you regap these spark plugs? Would I use these same BKR7EIX on my application?

[ECS Tuning-Audi]

I seem to have the same problem in my A3. It's the 2.0T DSG, chipped. At times it shifts smooth, many times, it's jerky upon shifting. I'm like...WTF?! But this may possibly be the answer to my problems..who knows.

Might sound like a dumb question...how do you regap these spark plugs? Would I use these same BKR7EIX on my application?

Yes you absolutely can. If you have similar issues check your plugs out first! If yours are pretty well worn, we have them available here - click for BKR7EIX plugs. To check the gap, or adjust it, most tools stores like Sears will have ring dials that you can insert in to the gap and expand it or shrink it down, also they should have inserts that are spec'd to .028 .030 etc. and they work in a similar fashion. Both should be about 2 - 5 bucks.

[Sprode]

Yes you absolutely can. If you have similar issues check your plugs out first! If yours are pretty well worn, we have them available here - click for BKR7EIX plugs. To check the gap, or adjust it, most tools stores like Sears will have ring dials that you can insert in to the gap and expand it or shrink it down, also they should have inserts that are spec'd to .028 .030 etc. and they work in a similar fashion. Both should be about 2 - 5 bucks.

I couldn't find my plug gapper when I did mine so I picked one up at autozone. 99c +tax. Be aware that in order to decrease the gap, you will have to tap the end with a hammer or something (gently!) to get the gap to come down to the thickness of the gapper. This will make more sense when you are holding them in your hand. I doubt you will get a good plug out of the box gapped below .028