Excessive Cranking/Transmission Issue

[MackAttack]

Hey guys, Mack again with more problems with his truck haha

I have a 2009 Chevy Suburban with 164,500 miles, and I’m having a couple of issues. Issue one I am having is with her cold starting. Every morning when I start her, she cranks like crazy for Atleast 8+ seconds, starts a tiny bit, then dies again, while shaking like hell. Rinse and repeat 2 times and we’re in business. After I start driving though, I could feel the car shaking back in forth as if it’s struggling for fuel for a little bit, then it’ll fix itself and it will start right up normally if you start it within an hour. Do you guys think it’s a fuel pump?

Second issue I am having is that when I am coming to a stop, I can feel something a little to the front of under me going “clank”/“clunk” paired with the car feeling like it was slightly rear ended. Sometimes I’ll just hear the clank with no shaking. In my honest opinion, it sounds like The transmission is downshifting too late. The reason for me thinking this is when I take my foot off the gas while driving, and put it back on, sometimes the car will Snap/Jult forward and snap your head back, I think it might be in a higher gear than it should be. I just serviced the trans fluid about 3K miles ago

Please help! Mack

 

[strutaeng]

On your first question: please purchase a fuel pressure gauge and hook it up to see what pressures are. It's the only way to determine if it's a fuel delivery problem.

The nicer gauges have a long hose you can tape to your windshield and see what the pressures are while driving and engine under load.

Sounds like you are starting to have transmission problems as well. :-(

 

[OR VietVet]

The first problem sounds like classic examples of fuel delivery problem. The long crank part sounds like a fuel bleed off, either by the pump or a leak somewhere, like an injector. Need to get a fuel pressure gauge attached and with a long enough hose, bring out the back of hood and tape to w/s and watch the pressure while driving.

The second problem does sound like a transmission problem but hopefully a transmission tech will chime in. @rockola1971 or @NickTransmissions .

Question, did both these problems start happening at the same time?

 

[MackAttack]

On your first question: please purchase a fuel pressure gauge and hook it up to see what pressures are. It's the only way to determine if it's a fuel delivery problem.

The nicer gauges have a long hose you can tape to your windshield and see what the pressures are while driving and engine under load.

Sounds like you are starting to have transmission problems as well. :-(

Alright awesome OMW to auto parts shop right now. Which brand do you recommend?

 

[MackAttack]

The first problem sounds like classic examples of fuel delivery problem. The long crank part sounds like a fuel bleed off, either by the pump or a leak somewhere, like an injector. Need to get a fuel pressure gauge attached and with a long enough hose, bring out the back of hood and tape to w/s and watch the pressure while driving.

The second problem does sound like a transmission problem but hopefully a transmission tech will chime in. @rockola1971 or @NickTransmissions .

Question, did both these problems start happening at the same time?

That was something Chevy told me a while back, but they wanted 350$ just to look at it, and god knows how much to fix it. The fuel pump issue started maybe 2 months ago. The transmission acting out was about around the same time, if not maybe a month older? When I first bought the truck from my father in February, I had complained that when I shift from P to D, the car jults sometimes. It has just gotten progressively worse, and now the issue that was concerning me was that it’s starting to act up while driving

 

[strutaeng]

Alright awesome OMW to auto parts shop right now. Which brand do you recommend?

I've had a few of the ones from the local parts store, but the short hose eventually deteriorates and leaks.

Last one I got was the HF Maddox brand with the longer hose. I haven't used it much, but seems decent. IIRC it's like $50. Money well spent for diagnostics.

 

[MackAttack]

I've had a few of the ones from the local parts store, but the short hose eventually deteriorates and leaks.

Last one I got was the HF Maddox brand with the longer hose. I haven't used it much, but seems decent. IIRC it's like $50. Money well spent for diagnostics.

Alright awesome I’ll grab that puppy. I’m a Atv mechanic hobbiest so I’m sure I can use it for my off roaders as well

 

[MackAttack]

About the tranny, how hard would that be to fix? I know transmissions are no joke to disassemble lol. I believe I have a 6L80 since that’s what came standard with these guys. I have a few friends that own shops, but I doubt any of them can do such complex things like transmissions

 

[iamdub]

No CEL? Does it have any modifications at all? K&N drop-in filter?

The problems could be related, and an electronic issue at that. A quick/free test would be to unplug the MAF sensor and see if there are any changes to the symptoms.

 

[MackAttack]

No CEL? Does it have any modifications at all? K&N drop-in filter?

The problems could be related, and an electronic issue at that. A quick/free test would be to unplug the MAF sensor and see if there are any changes to the symptoms.

as in modifications to the engine, there is nothing. I just replaced the water pump, thermostat, thermostat housing, radiator, all fluids, coolant temp sensor (which I have to replace again since it is freaking out on me). If you mean aftermarket, everything is about the same except for the inside of the truck. No check engine lights, Zero rust on any surface of the truck (California vehicle it’s whole life) not even a tire pressure light. I can ask my friends who work at orilleys which I’m about to go to to run a OBD2 Port scan

Edit: I meant to mention, I do have aftermarket electrical systems inside the truck but nothing aftermarket with any mechanical parts of it. I have a high end audio system with subs head units speakers amps but It has nothing to do with anything with the tranny or anything. Chevy refused to look at my truck when I brought it in for a whining sound lol. They’ll sell you a new truck but they won’t fix the current one haha

 

[iamdub]

as in modifications to the engine, there is nothing. I just replaced the water pump, thermostat, thermostat housing, radiator, all fluids, coolant temp sensor (which I have to replace again since it is freaking out on me). If you mean aftermarket, everything is about the same except for the inside of the truck. No check engine lights, Zero rust on any surface of the truck (California vehicle it’s whole life) not even a tire pressure light. I can ask my friends who work at orilleys which I’m about to go to to run a OBD2 Port scan

I was trying to connect the symptoms and the first that came to mind was the MAF sensor. If the PCM isn't properly reading the airflow, it would affect the fueling and also the shifting. Oiled air filters are known to coat the MAF wires, skewing their readings. But, the MAF could still be faulty. It may not be so much that the PCM sees it operating out of range, so no DTCs are set. You can check all the basics such as fuel pressure activities, codes, etc. But, I'm betting that it's likely gonna come down to using a scanner that shows live data to see what the sensors are reporting at key on/engine off, cranking, and idling.

Unplugging the MAF forces the PCM to default to a speed density map. While not ideal at all for normal operation, it could be better than trying to operate on grossly erroneous info from a faulty sensor. Like I said- just a quick/free test.

Chance are that, if the trans and cranking/drivability issues are related, it's an electronic problem. I'd go after the drivabilty issue and see if the trans acts right after that. The transmissions are known for their common faults, particularly the torque converter and sloppy tuning.

Next time it has sat for a while or overnight, when it should have an extended cranking, don't start it. Turn the key to on (all gauges on, right before the cranking position) for about 5 seconds. Turn it off for about 5, then back on for 5, then off for 5. Repeat the on/off cycle 3-4 times. Then, twist the key to crank as normal to see if it fires up any quicker than it has been doing.

 

[MackAttack]

I was trying to connect the symptoms and the first that came to mind was the MAF sensor. If the PCM isn't properly reading the airflow, it would affect the fueling and also the shifting. Oiled air filters are known to coat the MAF wires, skewing their readings. But, the MAF could still be faulty. It may not be so much that the PCM sees it operating out of range, so no DTCs are set. You can check all the basics such as fuel pressure activities, codes, etc. But, I'm betting that it's likely gonna come down to using a scanner that shows live data to see what the sensors are reporting at key on/engine off, cranking, and idling.

Unplugging the MAF forces the PCM to default to a speed density map. While not ideal at all for normal operation, it could be better than trying to operate on grossly erroneous info from a faulty sensor. Like I said- just a quick/free test.

Chance are that, if the trans and cranking/drivability issues are related, it's an electronic problem. I'd go after the drivabilty issue and see if the trans acts right after that. The transmissions are known for their common faults, particularly the torque converter and sloppy tuning.

Next time it has sat for a while or overnight, when it should have an extended cranking, don't start it. Turn the key to on (all gauges on, right before the cranking position) for about 5 seconds. Turn it off for about 5, then back on for 5, then off for 5. Repeat the on/off cycle 3-4 times. Then, twist the key to crank as normal to see if it fires up any quicker than it has been doing.

Alright ordered a pressure tester and I am picking it up today. Let me go try the turning key on and off trick. I have tried this a couple times, but only turned the key about twice. Let me try and update you

 

[MackAttack]

Alright I got into my truck, put the key in, turned it to the “On” position for 10 seconds, for 8 intervals on and off so 80 seconds of time for the fuel pump to prime. Turned it to the “run” position and same thing. Cranked like crazy, barely started, shook the truck, and died. I didn’t even try to keep starting it because I would have to do this 3 more times lol
Mack

Edit:does this make it a higher possibility that it is a fuel pump? I also am buying 8 new spark plugs even though the old ones were not bad

 

[avalonandl]

Yes sounds like a fuel pump

 

[iamdub]

Alright I got into my truck, put the key in, turned it to the “On” position for 10 seconds, for 8 intervals on and off so 80 seconds of time for the fuel pump to prime. Turned it to the “run” position and same thing. Cranked like crazy, barely started, shook the truck, and died. I didn’t even try to keep starting it because I would have to do this 3 more times lol
Mack

Edit:does this make it a higher possibility that it is a fuel pump? I also am buying 8 new spark plugs even though the old ones were not bad

Not necessarily. Checking the fuel pressure and the pressure's characteristics (Key on/engine off, key off with pressure over x time, etc.) will determine that. I wouldn't bother with replacing the plugs if the current ones are good. They'd have to be really bad to not spark. I feel it'd be wasted money. Also a risky move unless you know for sure your new plugs are genuine.

 

[MackAttack]

Not necessarily. Checking the fuel pressure and the pressure's characteristics (Key on/engine off, key off with pressure over x time, etc.) will determine that. I wouldn't bother with replacing the plugs if the current ones are good. They'd have to be really bad to not spark. I feel it'd be wasted money. Also a risky move unless you know for sure your new plugs are genuine.

Ahh ok. I’m testing the fuel pressure right now. Thank you guys so much for helping me with all this. The truck has so much value to me and everyone is telling me to sell it but I would never haha. I’ll get right back to you guys after I get the results from the pressure test
Mack

 

[mattbta]

Ever had the cam position sensor replaced?

 

[NickTransmissions]

About the tranny, how hard would that be to fix? I know transmissions are no joke to disassemble lol. I believe I have a 6L80 since that’s what came standard with these guys. I have a few friends that own shops, but I doubt any of them can do such complex things like transmissions

Check out my 6L80 Tear down video for a good understanding of the process (link is in my signature)...Assuming you acquire thr tools, ATSG manual and set aside the time to learn how to work on them, they're not terribly difficult...

 

[donjetman]

Sounds flooded to me. If you try to force more fuel in after gas pump clicks off the first time can ruin the vapor cannister purge valve on intake (AC Delco # 214-1680) and/or the rear charcoal cannister. Or leaky fuel injector(s).

Next time you go to start it put the gas pedal too the floor and crank it. Putting the pedal to the floor shuts off the fuel injectors.

 

[MackAttack]

Ever had the cam position sensor replaced?

No i never have. It would also make sense as sometimes, it won’t even crank it’ll start so fast after I did the 3 restarts of it not starting. Would it make it act like this too?