BloodOfYasuke

Hello all. Since I bought my car (2003 Acura TL >123k miles) in March, I’ve had weird shuddering issues. If I slowly accelerate, the car will jerk a little bit or if I’m driving down a hill, I’ll be stuck at 40mph and around 2500rpm’s. I’ve also noticed that if I have the A/C on, the car will idle no problem but then sound like I stepped on the gas pedal and then relax again. Otherwise the car will idle no problem. Also, when I drive uphill, I’ve noticed the car shudders also.

the previous owner really neglected the car and I’ve been trying to fix everything and it’s been a bit overwhelming but I’m trying my best. I was working on the engine mount and I noticed a loose vacuum line near the front motor mount. I put a screw in it and zip tied it, but the issue has persisted.

any ideas? Hoping it isn’t a transmission issue. Thanks!

Jon M

Hi, I don't want to lead you down the wrong path but something about your description reminded of a problem I had. It may or may not be related to what you are experiencing. Do check your transmission fluid and change as needed. You will usually get error codes and D5 flashing when you have tranny problems. However as previously mentioned check this old thread to see if it is similar to your problems https://acurazine.com/forums/2g-tl-p...-ideas-991328/

whitetiger5

When you say shuddering, do you mean misfire? ignition coils can act up, causing misfire symptoms without any CEL's. they are easiest to feel when the car is in drive and stopped because the drop in output from the engine can be felt through the transmission/chassis more easily.

Jon M

You never mentioned if you had/have an error code. Have you checked? If the plugs/ coils were misfiring you should have an error code.

BloodOfYasuke

I haven’t had any warning lights come in when it happens. I did change my spark plugs months ago and the car has run smoother after that.

I’m not sure what an engine misfire feels like, but if I had to describe it, it’s like a dog shaking itself off after getting wet. I feel it in my engine first and then in my seat. It’s noticeable but I don’t think I’m gonna die or anything when it happens.

i was told maybe a loose vacuum line can explain it. Sometimes if I’m keeping a constant speed and I release the gas, the rpm’s will go up a little and then back down.

Jon M

To see what a misfire feels like, start the car and when idling nicely pull off one of the coil pack connectors. Sit in the car and see if it feels the same, slightly rev and release to increase the feel. If that is what it feels like for your problem you should check each of the coils for carbon trails on the tubes. I have had small micro holes in the tube and the spark arced causing a misfire.
Intermittent problems are the worst. You need to gather as much information as you can when it is happening. Things like RPM, Speed, temp, uphill, downhill, electrical conditions, does it happen when A/C on, heater on, etc. etc. This is to figure it out and to help recreate the problem. Once you can recreate the problem then it can be solved.

whitetiger5

I had a brand new, bad DENSO coil from RockAuto (it was one of six) that created what felt like misfiring (though we know technically it can be argued it wasn't a misfire if no CEL was thrown).

Because there was no CEL and I presumed all of my new coils were good coils...I ended up looking through so many other parts on the car before I started replacing each one by one with my old coils.

I am sure there are tools that can be used to detect without all the trouble, I would love to buy one if it were cost effective.

Jon M

Whitetiger5 The misfire has to be frequent enough to cause increased emissions on 2 consecutive trips in order to trigger the P0300 codes. So you can have some misfires and it won't trigger the DTC until it is more consistent.