Rough idle / pouring smoke / misfire problem

[HighestStorm]

Hello I have a 2005 GMC Yukon 1500 4x4 and I'm having engine issues. Just had to replace my flex plate and starter because of a loud rattling noise, got a new battery because mine failed, replaced knock sensors and intake gasket and all eight spark plugs because of a corroded rear knock sensor and misfire. Right now it shakes and tries the pull like a drag car at idle, like when I'm pulling up to a stop it lurches forward like it wants to keep going, it's pouring smoke and check engine light flashing. I am currently troubleshooting the fuel injectors, I haven't checked the spark plug wires or cables yet but the smoke is more blueish and smells like gasoline. Whatever I went to AutoZone to get the code scan the only code that came up was my radiator fan relay circuit issue which is something else that I'm dealing with but shouldn't make the engine run bad how it is. Any advice would be greatly appreciated. Last advice I got from this website ended up being the flex plate which I just replaced so hopefully this will help me pinpoint what this problem is if anybody has answers.

 

[Bill 1960]

I’d start with a fuel pressure leakdown test to see if there’s a fuel injector stuck open.

And I wouldn’t spend any more money on it before a compression test. You don’t want to spend a bunch on peripherals just to discover it needs a teardown or replacement.

 

[swathdiver]

Hello I have a 2005 GMC Yukon 1500 4x4 and I'm having engine issues. Just had to replace my flex plate and starter because of a loud rattling noise, got a new battery because mine failed, replaced knock sensors and intake gasket and all eight spark plugs because of a corroded rear knock sensor and misfire. Right now it shakes and tries the pull like a drag car at idle, like when I'm pulling up to a stop it lurches forward like it wants to keep going, it's pouring smoke and check engine light flashing. I am currently troubleshooting the fuel injectors, I haven't checked the spark plug wires or cables yet but the smoke is more blueish and smells like gasoline. Whatever I went to AutoZone to get the code scan the only code that came up was my radiator fan relay circuit issue which is something else that I'm dealing with but shouldn't make the engine run bad how it is. Any advice would be greatly appreciated. Last advice I got from this website ended up being the flex plate which I just replaced so hopefully this will help me pinpoint what this problem is if anybody has answers.

I agree with Bill and will also add that a racing motor as you describe could be an idle air control issue (throttle body) or massive vacuum leak. You really need to put a scan tool on it that can talk to the computer system and run tests, along with looking for a leaky injector. Pull the plugs first and inspect them. Smell your dipstick, see if fuel is getting into the crankcase.

 

[treehan77]

You did t forget to reconnecting of the main connectors for the coils did you? I forgot that once, started it up and it ran like **** on only 4 cylinders lol

 

[rockola1971]

Did it ever run correctly after you did all the maintenance that you listed?
Did it run like crap before you started all this maintenance?

 

[HighestStorm]

And you're like no I got there sometimes I have a update on the condition and from what I'm experiencing could be a problem. The only time that it coming to a stop and just leaving from a stop and the only time it pours smoke is whenever it's low on gas, or if I have gas and it's started on a hill so does that maybe have something to do with the fuel pump? Every time I try to get the code scanned at AutoZone it's not acting up so the only code that comes up is my fan electronic issue which like I stated before should not be causing it to feel like it's going to die at a stop. It seems like a fuel delivery issue possibly? I'm not the most experienced with vehicles but I know the basics of how the engines run and basic mechanic work

 

[HighestStorm]

You did t forget to reconnecting of the main connectors for the coils did you? I forgot that once, started it up and it ran like **** on only 4 cylinders lol

Yes all of the coils and spark plugs are connected but the coils are $220,000 Miles old but look at my previous comment that I just posted maybe that will help pinpoint it more if you know about these engines I would appreciate the advice.

 

[HighestStorm]

I agree with Bill and will also add that a racing motor as you describe could be an idle air control issue (throttle body) or massive vacuum leak. You really need to put a scan tool on it that can talk to the computer system and run tests, along with looking for a leaky injector. Pull the plugs first and inspect them. Smell your dipstick, see if fuel is getting into the crankcase.

I don't have a scanner tool like that but I know people that do, I will check with them to see if they can run the tests but look at my previous comment that I just posted, the only time that it runs like this it seems like at least is whenever it's either low on gas or it started on a steep hill. At least that's how it seems because if I started with at least a half a tank of gas not on a hill it runs fine but if there's a quarter tank of gas or less and it started on a hill that's when the problems occur.

 

[HighestStorm]

Did it ever run correctly after you did all the maintenance that you listed?
Did it run like crap before you started all this maintenance?

The initial reasoning for the maintenance that I have done so far was because of the flexplate being cracked but I didn't fix it and I continued to run it with the flex plate issue, see attached images, for about 2 months I ran it. During those two months it progressively got worse, some of the codes that pulled through the AutoZone scanner in those two months were O2 sensor bank 1 and knock sensor. After getting the flex plate and new starter put in it ran good for half a day. Next day, it was shaking and smoking a little bit. Because of that and because I waited so long already to get the work at that point done I stopped using it and bought the knock sensors for it, a full tune up minus a fuel filter because I forgot to get that, the intake manifold gasket because to get to the knock sensor is you have to take off the intake manifold. First two or three days after fixing the knock sensors, again see attached images, it ran like a charm. The only code that came up was my radiator fan relay circuit issue which now I've replaced all three relays and that issue is starting to get under control but after a couple of days it started shaking at idle heavily and smoking like a train. But it only shakes aggressively if I start it on a hill with low gas, or after it's been running for a few hours. It's so hard to describe 50% of the time it runs fine but then the other 50% it almost seems like the engine is about to die. But to round up that lengthy explanation, it ran perfect when I bought it at $214,000 mi now it's at 220,000 miles and I ran it for a little over a thousand miles the flex plate problem was occurring and I think the flex plate issue may have caused these other issues to pop up or the fact that it's just that old of an engine and all these parts that I'm replacing are original. It's hard to describe, but whenever it smokes it reeks of gasoline not burning oil. Any theories? Thinking it has something to do with the fuel delivery possibly a fuel pump, I also saw one recommendation from somebody on another website that said to check the catalytic converter but that's one of the most expensive options it could be so I hope it's not but the person who recommended that to me also said that the broken flex plate issue that I was having might have been the catalytic converter but as soon as I fixed the flex plate that issue stopped but not before these other issues started because my theory is that I ran it too long with that issue and it caused damage elsewhere, or if I'm lucky maybe it's just the fuel filter is clogged. Any theories?
For reference, the picture of the knock sensors; far left is original not corroded and middle is original rear that was corroded and far Right is the new one that I installed and yes I installed both front and rear just to get it all done at once while it was open. And the second image is the broken flex plate that I was running for a little over a thousand miles. The idle shake and serious smoking issue didn't start until about 7 to 800 miles running it with the broken flex plate. My friend who helped me install the knocks on series has the same vehicle and worked on it for four or five years he thinks that possibly it could be a valve or timing issue worst case scenario.

 

[HighestStorm]

I agree with Bill and will also add that a racing motor as you describe could be an idle air control issue (throttle body) or massive vacuum leak. You really need to put a scan tool on it that can talk to the computer system and run tests, along with looking for a leaky injector. Pull the plugs first and inspect them. Smell your dipstick, see if fuel is getting into the crankcase.

I pulled the spark plugs the first sign of this issue. The codes for knock sensor and misfire and O2 sensors codes were all bank one codes. And if I'm right that's is the driver side banks (again I'm fairly knowledgeable on basic engine maintenance for most repairs outside of the internal block and trans issues, but still learning) When I checked the plugs the only bad plug was the cylinders closest too the firewall and on driver side, so I think it is cycling 7? And the corroded knock sensor in the picture is the one closest to the firewall. I did a basic ridiculously of the injectors by disconnecting power to the one I suspected to be the culprit (cylinder 7? Rear cylinder on driver's side same cylinder as the fouled out plug) and I know that's not a real test but I also have been told that is a simple way to troubleshoot them as a poor man with intermediate/basic experience and no proper tools or money. It didn't seem to make a difference in any way. The only thing that so far has helped temporarily and feels like I'm putting a Band-Aid on a broken arm, is when I have more gas in the tank it runs better for about 3 hours of operation. Like for example two times this week I started it on a steep incline, about 30° incline, with low gas it starts fine but after 15 minutes of being started with low gas in the tank it starts this issue of smoking and idle trying to jump up and down and check engine light flashing when I pull into a stop and take off but then check engine light and smoking and shaking turning off when I get up to speed. But two times this week whenever it really started acting up and shaking and smoking I pulled into gas stations to try to troubleshoot because I also had to fill up on gas put a little bit more than a half a tank in started it and it ran fine for a day or two until the gas level lowered again, I don't understand it. Unfortunately I kind of just have to keep running it as I do not have a spare vehicle and me and my fiance both have to get to work 6 days a week. Please send help lol all advice helps me learn.

 

[HighestStorm]

Here's a link to a video I found on YouTube of another person troubleshooting what maybe the same issue as me if you have the time to look at this video and have experienced this issue please let me know.

 

[Fless]

Looks like some basic tests would help narrow down the cause. A vacuum test, checking the IAC (Idle Air Control) function as @swathdiver mentioned, clean the throttle body, and make sure that the fuel rails are both properly grounded. Need to put an advanced scan tool on it to see what, if any, other codes might be generated.

 

[swathdiver]

...the only time that it runs like this it seems like at least is whenever it's either low on gas or it started on a steep hill. At least that's how it seems because if I started with at least a half a tank of gas not on a hill it runs fine but if there's a quarter tank of gas or less and it started on a hill that's when the problems occur.

That's almost always a fuel pump problem. You have several unrelated issues going on at once, they are not all interwoven.

You need access to a bi-directional scan tool, not a code reader but something akin to a Tech-2.

 

[rockola1971]

Smells like gas and white smoke...You are running rich. That rules out anything to do with knock sensors, starter and flexplate. Flashing check engine light is a warning of active detonation (spark preignition/ aka spark knock). 2 things I would look for while troubleshooting this. The easy one is first. Look for missing spark. Id check the spark plug wire and its coil at #7 which is the one you said was fouled. Turn the lights out (GO outside at night) and raise hood and start engine. See if you see any flashes of light around spark plug wires and ignition coils. Listen for a snapping noise which may also sound alot like a tick. A cracked igniton coil or bad spark plug wire (cracked, broken off) will cause the symptom you have. Second thing to check is the Bank 1 and 2 Pre cat O2 sensors. Compare them and see if they are similar in value AND switching values. They will immediately start showing readings once engine is started. Their values are ignored until engine is in closed loop. Third is a bad fuel injector or its associated wiring. It would be sticking open intermittently or possibly all the time. Check your oil dipstick for smell of gas in your oil. Change oil if you smell gas in it!

 

[Mudsport96]

Is this a flex fuel vehicle. What is the 8th digit of the vin number? If the fuel compensation sensor is bad and thinking you are running e85 when you have regular fuel in there, it will cause issues. Way too much fuel and it will advance the timing too.