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Gary, ASE Certified Technician
Category: Audi
Satisfied Customers: 1052
Experience:  Senior Technician
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Hesitation from low RPMs to 4k RPMs. This occurs in each

Customer Question

Hesitation from low RPMs to 4k RPMs. This occurs in each gear, I have already replaced the Mass Air Flow sensor, and made sure it is not the clutch.
JA: How many miles are on the clutch? Has it been slipping or sticking?
Customer: Ckutch is fine, pulled the plates and checked it.
JA: What is the model/year of your Audi?
Customer: 1996 Audi A4 Quattro 2.8 249,000
JA: Are you fixing your A4 quattro yourself? What have you tried so far?
Customer: Problem only occurs after the engine reaches operating temp. When it is cold it is smooth as silk
JA: Anything else you want the mechanic to know before I connect you?
Customer: It has been a combo of me and a Mechanic. The system throws a MAF code. which is why I replaced that. I am thinking it is due for a tune up anyway so I am going to do plugs, wires, cap ETC.
Submitted: 4 months ago.
Category: Audi
Expert:  Gary replied 4 months ago.

Hello! My name is Gary.
Welcome to JustAnswer.
At 249000 miles, I would say it is potentially due for an engine rebuild.

But the first things to do is check and replace timing belt as necessary, and a top end carbon clean.

A worn stretched timing belt gives sluggish performance and can log MAF codes on many cars.


Customer: replied 4 months ago.
I have replaced the timing belt, waterpump and thermostat religiously currently there is less than 18k on the service. The compression is solid, does not burn a drop or leak at all. There was a Cam seal that was wet about 6 months ago and I had that replaced and as far as I know there are no other signs needing an engine rebuild.I was hoping that you would know which vacuum line to check or maybe another sensor
Customer: replied 4 months ago.
The other thing that would rule out the engine rebuild is taking it to the redline the car pulls as strong as ever. The problem only occurs at low RPMs. Also, fuel filter was replaced in the last 90 days ( I replace the fuel filter every year due to the price of the fuel pump)
Expert:  Gary replied 4 months ago.

Have you ever performed an upper cylinder clean on this engine?

With Sea foam, Subaru upper engine cleaner, or AC Delco etc.

Makes a surprising difference to the throttle response etc from decoking the cylinder head this way.

I you are confident the timing belt is correct, that is the main thing.

What code was set for the MAF sensor?


Customer: replied 4 months ago.
Throttle response is not an issue at all, I replaced the valve cover gasket and there was no buildup anywhere. The problem just began to occur seemingly out of nowhere so I am assuming if the timing jumped it would have bent my valves and ruined the engine how timing belts do to Audis when they snap. When I replaced the MAF the problem was better but not 100% the new part reduced the severity of the hesitation by 30%.. It threw the code again and I havent run it again. I will pull it again and read it out.
Customer: replied 4 months ago.
Since 60k, I have kept the maintenance records on point, Never has there been fuel below 91 Octane, seldom is the fuel not from Chevron. There is a corrugated hose that connects the MAF housing to the intake. Even though the hose looks intact if there were small leaks would that cause the issue? Or would it be the other two smaller hoses that run from the MAF sensor housing? Do you think that Plugs and wires could be a culprit at this point? Also, what Bosch plugs should I stick to for a 2.8L ? Do you think that if I change to double iridium or Platinum plugs that it could create any issues?
Expert:  Gary replied 4 months ago.

The carbon buildup I'm talking about is in the combustion chamber.

Starts at the back of the intake valve.

You could have an unmeasured air leak, post MAF, crack in airflow duct etc.

So lets see what code you had please.

Either of those spark plugs should be ok for you.

Is your intake, airbox etc all factory?


Customer: replied 4 months ago.
When, I pulled the head and it still shows the original honing marks crystal clear.
The airbox is all factory with a K&N filter, I did not do the filter charger kit.
Expert:  Gary replied 4 months ago.

MAFs don't like oil from air filters.

I don't run k&n on any of mine now.

I run AEM Dryflow.

I'm happy you are still running factory airbox.

Have a look at the duct you have mentioned especially hose clamp points wear the duct could gather.

The convoluted duct could be split.


Customer: replied 4 months ago.
It is 3 AM here so I will pull the codes tomorrow. Shockingly enough there have been very few issues with the car, for about 7 years I drove it 1100 miles every weekend, all freeway setting the cruise control at 85ish adjusting for mountain roads. For the hours on the road the engine was spinning about 3200 RPMs for 6 hours with very little around town driving when I would get to my destination. Then all week I would drive a company car. Every Mechanic that sees the car is blown away by the odometer and how spectacular the engine looks and runs. Smooth, no valve clatter (typical Audi characteristic) which is why this problem is very annoying.
Expert:  Gary replied 4 months ago.

Yes ok, that's fine, just come back when you are ready.

Sounds like you a well looked after example.

I can understand your slight frustration.

Good night for now.


Customer: replied 4 months ago.
Both connection points that the hose slides over are both cast aluminum, I cleaned both points well and I tightened them as much as possible. The hose i am talking about is after the MAF to the engine. I know I looked back and mis spoke and said intake. If there is a pinhole leak in that location could it cause the issue? I also do not know what the other two hoses are that are much smaller in diameter. The corrugated one is 4" and 10" long. The other two are 3/4" and about 3-4' in length, Are you familiar with the 2.8l engine enough that you know which hoses I am talking about and if they could cause this issue? Is there a chance on the plugs and wires? ( I have a toddler who is Autistic that keeps me up all night)
Expert:  Gary replied 4 months ago.

The large hose is how the engine breathes, MAF to throttle body.

The two smaller hoses are from valve covers, crankcase breather hoses.

I'll let you sleep now.

It is only 8.15pm for me.

Talk tomorrow


Customer: replied 4 months ago.
could they be potential culprits? Or Plugs & Wires?
Expert:  Gary replied 4 months ago.

For how well the car goes at the top end, it won't be a spark plug or lead.

I would say the difference between cold and hot has a bearing on the outcome.

I have a Scangauge on one of my cars, that shows me any data I care to look at.

Yours could have a faulty coolant temp sensor, or a split in a air duct.

Analysis of engine data on a screen, which means a passenger with a scan tool logging data for post roadtest, would help here.

I have done this many times with workmates.

Saves just guessing.


Expert:  Gary replied 4 months ago.

Hello again,

Do you need any further help?

I hope my advice has been of assistance to you.

Kind regards


Customer: replied 3 months ago.
No, I was called out of town for work and this is not closed
Expert:  Gary replied 3 months ago.

Are you about to look at your car again soon?

Your problem is a hesitation flat spot on acceleration, or surging under 4000 rpm?

Maybe there might be an ECM reflash update available from AUDI.