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Suicide Bobb
11-30-2010, 03:19 AM
I don't want any "tl;dr", so here's the short:

When I shift and let out the clutch, then give it throttle immediately after, my car will hold the rpms for about one second or so, then accelerate. It almost seems like it didn't grab the gear, and then all of a sudden it's good to go. Power delivery also is not especially smooth, meaning when I hold a constant throttle, it feels akin to a gear in the transmission that has a few sheared teeth (but it is like this in every gear).

Also, when I do a cold start and continuing on until the car warms up, the rpms waver down a few hundred rpm, and then back up again, in what seems like a distinct pattern. It's similar to a vacuum leak, but the "up-down" intervals are more spaced out. Once it has warmed up enough, it stops.

I was told that the latter issue was the IAC, which controls the choke in order to properly warm up the car. This makes sense and hopefully will either totally disappear or get better after I clean the throttle body and the sensor.

While the former issue feels like a clutch issue, I have a strong feeling it isn't because it doesn't slip when going uphill, or when I am full throttling it and hit a rut in the road, and I would think that the issue itself would involve not a lag in the rpms, but a rise in the rpms and a lack of movement. A local mechanic thinks it's a clogged fuel filter, and told me to clean the injectors and throttle body, run a tank of gas through it, and then change the filter. He says that the lag is from the system building up enough pressure to where it gives in and operates normally again (not his exact words, but you get the point).

Do both of these diagnosis make sense, as well as the attack plans? I think I'm gunna hit it with some fuel injector cleaner and clean the TB/IAC tomorrow, but I want to know if the fuel delivery system is even a probable cause of my two issues.

Suicide Bobb
11-30-2010, 03:20 AM
Drat, that was too long. Best I could do...

06goat
11-30-2010, 03:28 AM
i think your cars tryin to tell you your gay

06goat
11-30-2010, 03:29 AM
but the lag problem seems like your transmission is sticking.. thats what I got from reading that. the IAC problem is most likely the problem with the inconsistent rpms, but you know cars, nothings ever that easy.

Suicide Bobb
11-30-2010, 03:32 AM
but the lag problem seems like your transmission is sticking.. thats what I got from reading that. the IAC problem is most likely the problem with the inconsistent rpms, but you know cars, nothings ever that easy.

Soooo true! I don't know how my transmission could be sticking though...it's a manual btw

stangman67
11-30-2010, 03:51 AM
Does it catch at all going into gear?? Certainly seems like the clutch isn't disengaging completely

Suicide Bobb
11-30-2010, 04:29 AM
What do you mean by "catch"?

stangman67
11-30-2010, 04:46 AM
Ie is it hard to put it into gear?

Bob Saget
11-30-2010, 04:53 AM
I don't want any "tl;dr", so here's the short:

When I shift and let out the clutch, then give it throttle immediately after, my car will hold the rpms for about one second or so, then accelerate. It almost seems like it didn't grab the gear, and then all of a sudden it's good to go. Power delivery also is not especially smooth, meaning when I hold a constant throttle, it feels akin to a gear in the transmission that has a few sheared teeth (but it is like this in every gear).

Also, when I do a cold start and continuing on until the car warms up, the rpms waver down a few hundred rpm, and then back up again, in what seems like a distinct pattern. It's similar to a vacuum leak, but the "up-down" intervals are more spaced out. Once it has warmed up enough, it stops.

I was told that the latter issue was the IAC, which controls the choke in order to properly warm up the car. This makes sense and hopefully will either totally disappear or get better after I clean the throttle body and the sensor.

While the former issue feels like a clutch issue, I have a strong feeling it isn't because it doesn't slip when going uphill, or when I am full throttling it and hit a rut in the road, and I would think that the issue itself would involve not a lag in the rpms, but a rise in the rpms and a lack of movement. A local mechanic thinks it's a clogged fuel filter, and told me to clean the injectors and throttle body, run a tank of gas through it, and then change the filter. He says that the lag is from the system building up enough pressure to where it gives in and operates normally again (not his exact words, but you get the point).

Do both of these diagnosis make sense, as well as the attack plans? I think I'm gunna hit it with some fuel injector cleaner and clean the TB/IAC tomorrow, but I want to know if the fuel delivery system is even a probable cause of my two issues.

IAC stands for intake air control, it controls the RPM of your vehicle when you're vehicle isn't moving. Engine temperature has nothing to do with it.

Remove it, as well as the throttle body & spray them down w/ a degreaser. (you gotta clean the hole in the t/b this sits in or it won't make a difference. Also, be careful not to twist/push on the IAC when you clean it....it will screw it up.

might be a good idea to disconnect the battery before you re-install it....that way the PCM resets & wipes out the ****** idle memory.

Bad4health
11-30-2010, 05:15 AM
but the lag problem seems like your transmission is sticking.. thats what I got from reading that. the IAC problem is most likely the problem with the inconsistent rpms, but you know cars, nothings ever that easy.

if it has wires, wheels or boobs its gunna give you problems

Suicide Bobb
11-30-2010, 01:44 PM
Ie is it hard to put it into gear?

Nope

Suicide Bobb
11-30-2010, 01:45 PM
IAC stands for intake air control, it controls the RPM of your vehicle when you're vehicle isn't moving. Engine temperature has nothing to do with it.

Remove it, as well as the throttle body & spray them down w/ a degreaser. (you gotta clean the hole in the t/b this sits in or it won't make a difference. Also, be careful not to twist/push on the IAC when you clean it....it will screw it up.

might be a good idea to disconnect the battery before you re-install it....that way the PCM resets & wipes out the ****** idle memory.

Thanks for the help!

roarzorz
11-30-2010, 02:01 PM
Sounds like you already got some good advice. My first line of attack would be to change the fuel filter, clean fuel injectors, and clean the tb and intake manifold. Seafoam that bish.

Slayerx
11-30-2010, 02:12 PM
Ya, looks like these guys gave you all the right advice. Man I miss carburetors....
I'm having a similar problem with the idle RPM's as well, does it whether its warmed up or not. I'm hoping its just the auto choke :confused:
Anyways, GL!

Suicide Bobb
11-30-2010, 02:19 PM
Sounds like you already got some good advice. My first line of attack would be to change the fuel filter, clean fuel injectors, and clean the tb and intake manifold. Seafoam that bish.

Well the reason you should replace the fuel filter last is that if you replace it, then knock all the crap off the injectors and what not, it's just going to clog up the new filter.

But yeah, seafoam wouldn't be a bad idea. I already seafoamed my engine internals (oil related stuff), and then my oil pump just so happened to decide to fail the next day...

Suicide Bobb
11-30-2010, 02:20 PM
Ya, looks like these guys gave you all the right advice. Man I miss carburetors....
I'm having a similar problem with the idle RPM's as well, does it whether its warmed up or not. I'm hoping its just the auto choke :confused:
Anyways, GL!

Sounds like a vacuum leak to me. Take it to a shop, ask them to smoke test your vacuum system for leaks. Should only be like $20. Or if you can hear the leak, then drip some soapy water around the area you think it's leaking, and it should bubble up. Replace the hose and enjoy!

Shinju
11-30-2010, 02:28 PM
It's an Audi...... is that year S4 turbocharged? My B5 did something similar when the Turbo sensor went **** up, also a bad o2 sensor will cause acceleration lag as well.

Audi's are expensive to own no matter what year they are, my 01 S4 was a money pit, 800 per Turbo sensor and 300 for a new o2 sensor mind you I had the bi-turbo so I had 2 o2 sensors.

Fast and fun but way to much on the pocketbook even for me when I was making bank. Felt my money was better spent else were so I sold the Audi and got my xB and never looked back.

roarzorz
11-30-2010, 04:45 PM
Well the reason you should replace the fuel filter last is that if you replace it, then knock all the crap off the injectors and what not, it's just going to clog up the new filter.


Fuel filter comes before the injectors. No way trash off the injectors will clog it up. Only trash out the tank can clog it up.

Bassin Buick
11-30-2010, 04:49 PM
Well the reason you should replace the fuel filter last is that if you replace it, then knock all the crap off the injectors and what not, it's just going to clog up the new filter.

But yeah, seafoam wouldn't be a bad idea. I already seafoamed my engine internals (oil related stuff), and then my oil pump just so happened to decide to fail the next day...

Same thing happened last week to my car , i seafoamed it then changed the oil , low and behold within 300 miles i had a rod knocking and i have only 100k on a gm 3800 series 2. not too many miles at all for that motor.

Shinju
11-30-2010, 05:13 PM
Same thing happened last week to my car , i seafoamed it then changed the oil , low and behold within 300 miles i had a rod knocking and i have only 100k on a gm 3800 series 2. not too many miles at all for that motor.

You probably had hidden issues that the Seafoam brought up by cleaning the bearings, Never heard of Seafoam its self causing rod knocks.

Tell you what though, Remember Motor Up? That stuff you add to your oil that if you ever ran the engine bone dry of its oil supply the engine will keep on going?

Well I put that to the test with out even knowing it was happening. I decided to try it I had a Shelby CSX 2.2l Turbo II and this stuff was great for Turbo's helped with keeping the turbo bearings coated with hight heat synthetic material, Anyway I was moving from Oregon to Wa state and I was driving the car 500 miles since I did not want to pull it behind the moving van.


I was pulling off in Olympia to get gas and food as I was parking I could smell burning oil and my stomach hit the floor I got out the car since it was not moving was smoking as if it was on fire I popped the hood and the smoke rolled out but didnt see anyt flames, After the smoke was gone I could see Oil spray all over the engine bay and noticed the Dipstick and holding tube was GONE broke off somehow! The Gas tendant was also a mechanic and they sold stuff like this at the station so I bought a dipstick just to see if there was any oil left, There wasnt even enough to show on the stick.

After all that drama we guestimated that I drive the car for roughly 300 miles with out any oil other then what was left circulating in the engine through pressure. Motor Up saved the day, got the car fixed a day later and a new oil change and drove it fort 4 years after never once had an engine issue.


Dylan take your car to the shop that did the work on it and let them know something is not right, Dont work on it yourself and risk messing up your warranty with them, infact dont say anything about checking it yourself to them at all, Put the ball in their court.