Help - Surging/Bucking/Jumping

[thomaswhite14]

Let me begin by apologizing if this does not go here. I'm a long-time lurker, but I just joined today. I do not have 10 posts yet.

Unfortunately, I have a severe anxiety disorder resulting from PTSD. Car worries and money are the number one triggers. I need help for my on piece of mind. I will say that I am taking the car to the dealer on Monday.

I have a 2014 Sonic LT 1.8L engine. During warmup and at the first couple of red lights, it bucks/jerks/surges. It's been doing this about 2 weeks. I've tried cutting the air off and putting it in neutral/park/manual. It continues to do it.

I've searched the forum and found many possibilities, but I figured it would be best to just ask. I'm terrified that my car is going to break. I rely on it for everything. Please, tell me if this sounds like I will need a new engine. Do you think it will be an expensive fix?

Note: Two months ago, I went slow over a speed bump. When I pressed the gas, nothing happened. No revving or anything. I turned the car off and turned it back on. Worked fine. Hasn't done it since. When I took it to get emissions done, it failed because of a code in the history. Check engine light never came on. Code was P0700 and U0073. Cleared the codes per mechanic's recommendation. Drove for a week. No new codes and passed emissions. The bumping started before the emissions fail.

Please, please help me. I'm a nervous wreck. I'm afraid that I will have to spend thousands.

 

[gnonne]

First thing to check is the air intake tube between the air filter box and the throttle body. These are known to crack prematurely and there is a TSB/warranty on them. Cracks here make it hard for the computer to control the fuel/air mix, which can cause issues like you report.

I've had three Sonics - replaced this part three or four times, twice before GM knew they were bad.

Could be something else, but that is the most common thing that comes to mind.

 

[thomaswhite14]

First thing to check is the air intake tube between the air filter box and the throttle body. These are known to crack prematurely and there is a TSB/warranty on them. Cracks here make it hard for the computer to control the fuel/air mix, which can cause issues like you report.

I've had three Sonics - replaced this part three or four times, twice before GM knew they were bad.

Could be something else, but that is the most common thing that comes to mind.

Hose is fine. I replaced it three years ago. A mobile mechanic that I trust looked at it. He suggested changing the air filter and spark plugs. Also suggested cleaning around valve cover and MAF sensor.

 

[thomaswhite14]

And fuel injector cleaner.

 

[Mike DZ]

...
I have a 2014 Sonic LT 1.8L engine. During warmup and at the first couple of red lights, it bucks/jerks/surges. It's been doing this about 2 weeks. I've tried cutting the air off and putting it in neutral/park/manual. It continues to do it.

...
.

IF the problem is only apparent during warmup and first couple of red light, but goes away after that, you do NOT need a new engine.

Cold engine (before it warms to operating temp) problems imply a sensor that is not providing accurate data to the engine control module (ECM). The ECM then sends the wrong signal to the injectors and you get the incorrect amount of fuel injected.

It could also be a MAP sensor, again providing bad data to the ECM etc etc.

This could happen without setting a check engine light. A tech can look at the live sensor data to see what they are reporting.

Since the problem appears to be related to a cold engine, you might need to leave it overnight to replicate the symptoms.

 

[thomaswhite14]

IF the problem is only apparent during warmup and first couple of red light, but goes away after that, you do NOT need a new engine.

Cold engine (before it warms to operating temp) problems imply a sensor that is not providing accurate data to the engine control module (ECM). The ECM then sends the wrong signal to the injectors and you get the incorrect amount of fuel injected.

It could also be a MAP sensor, again providing bad data to the ECM etc etc.

This could happen without setting a check engine light. A tech can look at the live sensor data to see what they are reporting.

Since the problem appears to be related to a cold engine, you might need to leave it overnight to replicate the symptoms.

OK, a mobile mechanic I know came over. He replaced the spark plugs, the valve cover gasket, and the engine filter. He added fuel system cleaner. He cleaned the MAF sensor.

Car is running with power I didn't even realize it had lost. I'm going to let it sit all night and try it again in the morning. Fingers crossed.

 

[Mike DZ]

Good to hear that you may have a fix. Best of luck to you.

 

[thomaswhite14]

Good to hear that you may have a fix. Best of luck to you.

Checked it out this morning. Seems to run well. Old issue is gone. When I turned it on, it revved up to 1500 rpm and gradually reduced down to 700 rpm at idle. Is this because of the new spark plugs?

 

[gnonne]

Could be due to the new plugs - not sure.

How many miles are on this car? Maybe a lot if the valve cover gasket was bad on a 1.8L...

 

[dannyg]

Checked it out this morning. Seems to run well. Old issue is gone. When I turned it on, it revved up to 1500 rpm and gradually reduced down to 700 rpm at idle. Is this because of the new spark plugs?

I take it the car didn't have a "high idle" and "low idle" before? My 2015 1.8L/5sp (45K miles) revs to about 1200 rpm initially when stone cold, then down to around 1000 after about a minute, then reduces to around 700-800 for low idle. 2014 might be set a bit higher, don't know.

 

[thomaswhite14]

I take it the car didn't have a "high idle" and "low idle" before? My 2015 1.8L/5sp (45K miles) revs to about 1200 rpm initially when stone cold, then down to around 1000 after about a minute, then reduces to around 700-800 for low idle. 2014 might be set a bit higher, don't know.

82,500. Idle issue hasn't repeated. It follows the same pattern as yours. Unfortunately, the hiccupping has returned. It stopped for a while after we cleaned the MAF sensor, so I'm thinking it's a bad MAF sensor. Thoughts?

 

[Mike DZ]

82,500. Idle issue hasn't repeated. It follows the same pattern as yours. Unfortunately, the hiccupping has returned. It stopped for a while after we cleaned the MAF sensor, so I'm thinking it's a bad MAF sensor. Thoughts?

The idle issue was probably the ECM relearning.

HIccuping? Can you be a little more descriptive in terms of engine or car performance?

A way to confirm that this particular sensor is at fault is to buy a can of MAF cleaner (it is a specific substance) and reclean it to see if returns to normal ops. I think the MAF is a $90 piece and the cleaner is $5-10. Or have the mobile mechanic back over.

 

[thomaswhite14]

The idle issue was probably the ECM relearning.

HIccuping? Can you be a little more descriptive in terms of engine or car performance?

A way to confirm that this particular sensor is at fault is to buy a can of MAF cleaner (it is a specific substance) and reclean it to see if returns to normal ops. I think the MAF is a $90 piece and the cleaner is $5-10. Or have the mobile mechanic back over.

Having him over tonight. Next test is the throttle body.

 

[thomaswhite14]

Having him over tonight. Next test is the throttle body.

I got frustrated and took it to the dealership. They sail it was a bad ignition coil. I'll pick it up later today and try it out. Not sold.

 

[Mike DZ]

I got frustrated and took it to the dealership. They sail it was a bad ignition coil. I'll pick it up later today and try it out. Not sold.

The good news is that they DIDN'T say "new engine".

 

[Davecntn]

My fix was changing the coil The plastic piece that holds the little Spring in gets cracked overtime and seems to set better once the car is warmed up replaced the ignitiin coil and the car hasn't had the problem since