Engine missing and running rough?

Hi:

If the problem started after it was services, my guess is they bumped and disconnected or damaged a vacuum hose. Check for vacuum leaks. Also, is the check engine light on? here are guides to help us fix it.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

and

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

and

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down these guides and report back. Joe

When you first start the car and put it in drive it bucks and jumps. Never tries to go dead but it runs very erratic. When it fianally warms up it runs fine. What does it sound like it needs?

check fuel pressure. check motor mounts. check idle control valve. check coolant sensor.
check mass air flow, if equipped

Roy

Could be misfiring from the engine or harsh shift of transmission. Start by checking for trouble codes.

Hi guys.

My car has been starting extremely rough-on the third try usuallly and only if I press the gas while turning the key. It also died at stop lights and once and a while while I was going slow. I took it in a month ago and the shop cleaned the mass air flow sensors, gave it a tune-up, and new plug wires. A month prior to that we replaced the 02 sensor.

The day after I got it home from the shop (last month) the engine light went on again and it started on the 3rd try...really rough. I took it back and they kept it for a week. Finally,they said they couldn't tell what was wrong so they just gave it back to me. It's only gotten worse since then. Unless I give it gass while I try to start it, it won't start. All the lights go on (engine, battery, oil, etc.) and it just sits there. I can turn the key and try to start it for 10 seconds straight and this is all that happens. I turn it off, push the gas, and then it starts. However, when I am driving it, it feels like it is struggling to shift in gears while I am driving. It has not stalled while I am stopped lately (it used to do that all the time). Now it sometimes dies while I am driving. The steering will lock up and the lights will go on. It just stops running so I have to turn it off and restart it.

What are your thoughts? My uncle is a mecahnic (several states away) and he suggested it might be the idle control valve. I hate to waste another $400 to get nowhere.

THANK YOU!

Lisa

if it drives fine at normal speed, and your only problem is at idle, then I would make an educated guess that your fuel system is fine. Low fuel pressure or flow would generally be more apparent at higher speeds (more fuel demand).

Is your check engine light on? That will narrow it down. Take it to autozone or some other parts store, they usually will read your code for free. Post what the code says. If it a problem with you air system a code may narrow it down.

I have just changed plugs, plug wires, and fuel filter.
I thought I needed to tune up my car, but it"s still running very rough and shutting off.
what could it be?

Clean out the idle air control valve, EGR and PCV valves and test throttle position sensor and clean the MAF sensor with an electronic cleaner.

Thank You for your quick response.I appreciate your fast professional advice.
Thanks Again!!

on start up engine will run rough for about 2-5 min

It is probably the Idle Air Control Valve, IACV, which keeps the idle steady when cold or under engine load. It is located on the intake manifold near the throttle body. It may need to be replaced or you can check the ports that it opens and closes for carbon deposits to see if you can just clean out the manifold and throttle body ports.

Taurus Idle Problem:

2000 Ford Taurus SEL, V6, 3.0L (182 CID); DOHC, automatic, 125,000mi.

When engine is ‘COLD’ (morning startup and afternoon startup), engine starts immediately then comes to normal idle speed. Within a few seconds engine begins to idle roughly even while idle speed is constant. About one half of the time, the condition is not sever enough to cause stalling, so I can get the car in gear and drive until the engine warms up enough for the problem to go away. The engine runs like the day I bought it when it is hot. The other half of the time, after the engine begins to idle roughly, the RPMs drop and the engine stalls. After several restarts, and running the engine speed up to 2000 RPM for a minute or two I have been able to prevent the stalling and drive until warm-up. When the engine is idling roughly it is enough to shake the car, sometimes it make what I call a loping sound but the RPMs are constant.

About a month ago I bought an OBD II tester and have consistently gotten a DTCs P0171 System Too Lean (Bank 1), and DTC P0174 System Too Lean (Bank 2), and I have also gotten engine misfire codes, (somewhat inconsistently), everything from P0300 (random misfire) to misfire on specific cylinders.

So far I have: (1) changed the gas filter, (2) changed the spark plugs, (3) change all of the ignition coils where I have gotten a misfire DTC for a specific cylinder (three total), (3) replaced the upper intake manifold gaskets (since I had to remove this to get to the spark plugs), (4) changed the EGR gasket (since I had to remove this to get to the spark plugs), (4) checked for obvious vacuum leaks (visually and by touch), (5) tested both key-on and engine-on fuel injector rail pressure, (6) listened for fuel injector valve clicking, and (6) tested the PCV valve by applying a vacuum to the connecting hose.

Changing the fuel filter and spark plugs gave the engine more power (that I had not noticed was lost) but it did not correct the problem. Changing the coil for the first DTC code (P0306) that I received, eliminated an annoying little misfire that I would notice when the engine was hot and at idle, but it did not correct the cold engine problem. Changing the other 3 coils did nothing. I was never able to find any obvious vacuum leaks, all of the injectors seemed to be clicking (so I assume none are sticking) and the fuel pressure test was within spec. Finally, while the PCV valve did move in response to applied vacuum, however it is 12 years old and did not have the crisp clicking noise as it snapped back into place, but it did move freely and go back into position. Why did Ford make this valve so hard to get to on my engine?

I can send one of the diagnostic reports from Innova if I can figure out how to do this.

Help would be appreciated.

I love this site :-) it has helped me many times

The two things that need to be focused on are vacuum leaks and the IAC.

Can you be more specific? I failed to mention this in my initial question but I did several other tests. Regarding the IAC, I pulled the connector with the engine running, both when it was running smoothly and when it was acting up (running rough). In each case the engine either stalled or the idle became rougher.

Can you provide specific test procedures?

Also, why is when the engine is hot (been running for 10 minutes or so) it idles smooth at silk? I would assume if vacuum is an issue it would be an issue whether the engine is hot or cold.

Can you tell me if I am showing up as an "Upgraded Question" customer? I have tried twice to donate through Paypal, but it does not seem to be working. It completely bombed the first time(something with Paypale site)and the second time it seemed to work but I have received no confirmation. My Paypal account is showing no activity. Is there a way to check this?

I experienced a cold start roughness and found it to be the upper intake needed re-torqued. A vaccuum leak was there until the engine warmed up and expanded the metal, which sealed the leak until it cooled again.

Justdon, really good point about the expansion and subsequent sealing due to material expansion.

I purchased a 0-250in-lb torque wrench to reinstall the upper intake manafold when I replaced the spark plugs, and also replaced the seals before the reinstall. I realize this could still be an issue if I didn't get the bolts installed properly even though the torque may be correct.

Also it is possible that the manafold is cracked (mine is plastic) or that the lower manafold is leaking. I am going to try a test I read about, i.e. using carburator cleaner to spray near the manafold and other vacuum lines to check for leaks. If the engine accelerates then the cleaner is getin in due to a leak. The safer route to this test is to use pressurized smoke generator, but these machines are $1300 and I can't afford one.

Thanks for the suggestion.

Ahhh..good old plastic. Hope it didn't warp on you. Just curious, are you loosing any coolant? If so, maybe a quick pressure test and a check for combustion gasses in coolant may be warranted to eliminate intake or head gasket trouble.

As for the smoke machine. That's number one on my wish list.

My nephew has a 2000 taurus V6 DOHC. The car starts up fine and idles fine. Then when you give it gas it hesitates and spits and sputters and its especially bad or worse when trying to drive it. It will only go about 5 - 10 mph and if you keep your foot on the gas it will just stall out, but if you stop and put it in park it will smooth right back out when idling. Any ideas what this could be. It has new plugs, air filter and the main computer was replaced about a year ago with a brand new one.

Have you checked fuel pump pressure? Fuel filter?

Carb. cleaner is a good way to detect vacuum leaks. I use starting fluid. (just a preference)

no because it was idling fine and starting fine so I figured it was getting fuel. you can almost hear air when given gas but all vacuum hoses were connected sounded like it was coming from next to the fire wall kind of where the wire harness runs across from the egr valve.

You should change the lower intake gaskets as well. It has been known in this car for the lower intake gaskets to become smashed and lose its seal until the engine is warm and the gaskets expand

I would still check the fuel pressure. Also, check to make sure there is vacuum to the EGR and it isn't leaking.

I've recently noticed that the engine gets 'louder' as I step on the gas. I can actually feel the vibration through the gas pedal. it gets louder as my speed increases and practically disappears when I'm stopped. Just today, I stepped on the gas & it felt like the car was not going to pick up speed. Before I take it in, could you please give me some idea what it could be? I did not have a tune up at 100,000 miles. And my fuel gauge hasn't worked for a couple years (money).

Ok this is hard to say as it could be a number of things. It could be a mass air flow unit or a throttle position sensor or coolant temp sensor and O2 sensor etc. Now I do have ask is the engine light on?

No engine light is on. I took it in over lunch and they said it was a wheel hub bearing that needs to be replaced. Does this make sense?

Yes it could be a hub assembly. Does it get louder if you turn one direction and quieter if turn the other?

No, just as it picks up speed. They were able to correct the problem and all is working well. :) Thanks for your input & I'm excited because I found a great new mechanic! Thanks again!

Well great glad to hear it. Thank your mechanic for doing a great job that helps the rest of too as it builds trust.

runs bad cold OK ehen warm

Check the tune up parts first, then if the check engine light is on, check the ECT(engine coolant temp) sensor. It acts as the choke for your car, cost is about 20.00 dollars. Replace when engine is COLD!

when running engine runs rough,but when engine is going at speed engine runs fine, check engine light just came on ,also engine just runs rougher and then just stalls

What code numbers are listed? Knowing these may radially reduce the troubleshooting.

also post: What liter engine and the 8th digit of the VIN.

Other info that may help:


Has there been any recent performance repairs done or amintnence such as plugs or wires for example.

Is this worse when it's damp?

After reducing speed does the runnibilty problem return?

i have a 2001 taurus with a 3.0l 12v auto with 75000 miles.i have a problem with my o2 sensors it shows them as working lazy i replaced them twice already and no change on the scanner as soon as i give it gas its drops to zero it is the bank one sensor one that is doing it.it also has an occasional misfire on cylinder one and six, i replaced fuel injectors, spark plug wires,spark plugs, ignition coil, fuel filter no change what do you suggest i check next.any info would be helpful thanks hopefully you can help me

was this a flood recovered vehicle if so you'll have alot of problems with the electrical system mainly corrosion inside the computer. if not than you probably have a pretty simple fix. your coolent temp. sensor that relays information to the computer(not the dummy light or fan control sensor) regulates the air fuel mixture according to engine temp. If this is not working it will show the vehicle as running cold all the time and will create a rich burn and will trigger a o2 sensor problem code, more so will actually burn out the o2 sensors one after the other. also this problem is typical for dropping fuel economy

is the code saying lean bank one. lazy switching or something to that affect. if so look the motor over real close for vaccum leaks. scanner will always set bank one code that sensor is closest to the intake maniflod again look for vaccum leaks (NOS) 8)ps there is usualy a vaccum line that goes to the PCV valve and it will suck in and get a hole in it nad just make the 02's go hay wire. and there to expencive to keep replaceing