01 denali wont cooperate!

[tswore]

Hey all, Im looking for some brilliance here. I have an 01 denali with the 6.0 in it that is givin me some fits. My wife called me the other day as she left work and said there was something wrong withe the transmission, it was all she could do to get the rig up to speed. She brought it by my work so I could look at it, and sure enough it seemed like the trans was effed up. The next day i tried to move it, and it ran good for about 2 minutes, then the same thing, seems like the trans was bad. So as i was diagnosing it it would run fine in park, but as soon as I put it in gear it would die. if I revved it then dropped it in gear it would move a little. By now I had ruled out the trans being a problem. Now (3 weeks later just letting it sit) when I start it it will run for like 5 seconds then die. It will do that 3 or 4 times then not start again for a few hours. I have swapped the MAF sensor with the one on my truck-no help, swapped the crank position sensor-no help, new o2 sensors on the upflow-no help (and ouch! $140) and unplugged the downflow ones-no help either. I am kinda at a loss here, dont know what else to try. I am about ready to take it to a mechanic to have them check it out, but dont really want to. If anybody has any input, please fire away, I am all ears!

[Manbearpig]

Any codes?

Is it AWD?

[tswore]

Originally Posted by Manbearpig

Any codes?

Is it AWD?

it is a AWD, and it did throw the 02 sensor codes, both bank one and bank 2, but i dont remember if it was sensor 1 or 2 (it was like 3 weeks ago). it also threw a "bank one too lean" code. now it wont run long enough to throw a code.

[Manbearpig]

Hmm You might try checking your fuel pressure

[bighaas79]

Hate to say it but now you've messed with so many things you'd be better off starting from scratch. First when you changed the crank sensor did you do crank position relearn on it? Second what were the readings from the O2 sensors before u changed them? Third when U replaced the O2 sensors did you reset fuel trim adaptives? Like wise with unhooking the downstream O2 sensors did you reset fuel trim adaptives after unhooking them. And by unhooking them in the first place you would have thrown pcm out of whack neway. Have you checked for vacuum leaks, is egr if so equipped working properly? Is there any codes set in any of the other modules, Before u messed with any of this stuff what were the fuel trims at to be setting the lean codes? Is your fuel pressure (regulated and unregulated) correct is your fuel volume ok? How much airflow are you seeing thru the maf? Is there any knock retard? Are your O2 sensors even responding correctly based on throttle angle and load? How much ac ripple are you getting from the alternator? What are the coolant temp and intake airflow readings? Are there any misfires?

Not to be a downer but I see this all the time customers will bring in their vehicles, and have already spent tons of money cause they wanted to save money and not have to take it to a mechanic. The fact of the matter is that vehicles have gotten complicated enuf that if you dont have the equipment or knowledge to know how everthing works and intergrates you will just be spinnin your wheels. To be honest with you i believe you wasted the money on the O2 sensors. Your lean codes would lead me more to believe you have a fuel airflow correlation problem. Stemming from most likely a weak pump, restricted or plugged fuel line or filter, possibly dirty injectors, vacuum leak, maf either incorrect or dirty, (and just because you switched with another one out of another truck if you didnt reset fuel tims you may not get an imediate response.) Its also possible that you could have a timing retard issue, or tps throttle angle issue. A bad coolant temp sensor reading an overly warm engine can cut fuel back so far as to not make it run.

Don't take this as jumpin down yuor throat tyrade or any thing I would just simply like to get across that it literally could be tons of things wrong, and without this information anyone here is taking nothing more than a complete stab in the dark with a response to your question. You may be better off to find a competent tech in your area and let them fully check over your vehicle and get you fixxed up. To me it comes down to having to ask yourself can I legitimately correct the problem myself without wasting money based on the available tools, knowledge and information available with out also losing time without my vehicle, (not to mention the frustration). Just as an example the $140 you spent on sensors would have given you almost 3 hours in the shop i work at ussually more than enuf time to have already found your problem.

In a world where everyone is lookin to save money trying to diagnose your own car without knowing what your looking for could waste way more then u save.
Just an opinion and ill step down off the soapbox now! lol

[tswore]

Ok, got it fixed! bad fuel pump. Finally broke down and took it to a mechanic to have him diagnose it. I had pulled the fuel filter out before, and it was pumping, but not enough pressure. pretty easy change, probably one of the easier I have changed. No problems Bighass79, no offense taken, and thanks for the reply. I am one that likes to figure out and fix things on my own. Normally I can whip this stuff pretty good, but the way it was acting I just didnt think it was the fuel pump. Oh well, never stop learnin, right? The important part is its fixed now, and mamas happy

[bighaas79]

Glad ya got it fixed. And no with as fast as they change the technologies in these cars nowdays you never stop learning! And believe me theres no way anyone can know everything on these things.

[Manbearpig]

Awesome! Glad you got it fixed!

Sounded like a fueling problem to me

[99-2door]

Fuel pressure should be one of the 1st 3 things you check on a running issue.