2004 4.2 I6 What next?

[Cloudy79]

Hey everyone, I have had some issues with my TB in the three years of owning it. Besides the fact that it hauls ass at high rpm, I hate the lack of torque this engine has. Now it has started to act like the timing chain is stretched to the max and its time to decide which option would be best to continue with.

 

[BRomanJr]

Hey everyone, I have had some issues with my TB in the three years of owning it. Besides the fact that it hauls ass at high rpm, I hate the lack of torque this engine has. Now it has started to act like the timing chain is stretched to the max and its time to decide which option would be best to continue with.

The I6 has good torque when the Exhaust Cam Phaser is working properly, Do you or have you had any codes? Anything with "cam" in it might be affecting your torque.
Stretched chains are very rare, why do you think that? Could it be starting off in second gear? Do you get all 4 gears shifting in the trans?

What is your current mileage and maintenance history?

Welcome to the Forum.

 

[Cloudy79]

Heres what I am thinking. Let me know what makes sense or not. I have 20 years exp working on vehicles so I'm no stranger to it, but what I'd like to do is rid myself of the I6. Which of the either 5.3 or 6.0 would be the easier swap for this 4x4 ext? Since the timing chain requires so much work just to remove the valve cover, I would fully overhaul, but I hate this engine so not wanting to go that route.

 

[Cloudy79]

I had the trans rebuilt 15k miles ago. Only codes I get are from the bad gas cap and maybe another evap leak. Po 442 and 455 I think. Small and large leaks. No real problems except for the pcm being reflashed three times to finally fix the accelerator pedal or pcm fault for limping out into traffic and nearly causing an accident. Never had any codes for cams. The system does, every time its checked, say theres 6 or 7 things after reading the codes ex. Misfire, comp, fuel, etc... even if the cel is off. What I notice now is at low end when accelerating, it wants to buck and I can hear it in the exhaust as well as feel it. Not a severe buck yet as long as the ac isn't on. The harder I press the pedal, the more buck occurs. Same as my old stanza before the chain skipped teeth...

 

[Cloudy79]

173, 000 miles.

 

[BRomanJr]

Sounds like exhaust can timing is not correct at low RPMs, The intake/exhaust overlap is changed by the PCM by modulating the CPAS which then moves the cam Phaser and allows for low end torque, high end power and reduced emmisions by way of an "EGR" type scavenging.

I don't have experience with the I6, I would hope that others on here will report their experiences with low end torque issues.

From what I've read here and elsewhere, Most report that a dirty Throttle Body causes it's share of idle and low RPM issues, so removing and cleaning the backside of the TB is on top of the list of things to do.

Secondly I read about the CPAS issues, dirty, leaking, failed. (dirty/old oil is an issue with these too)

Lastly, the cam phaser itself causes a small number of issues.

 

[RayGumm]

I'm no expert, but I do have the I6 - and a clean throttle body and reset the PCM does improve performance and mileage. I would start there like Broman said. MAY03LT has a video on YouTube detailing the process, including the process to reset the PCM by removing 2 fuses (can't remember what numbers offhand, but both the PCM fuses) in the underhood fuse box for 20 minutes or so.

Plugs may be no good and/or not the right ACDelco replacements as well..

Good luck!

Welcome to the Nation!

 

[Cloudy79]

I'm no expert, but I do have the I6 - and a clean throttle body and reset the PCM does improve performance and mileage. I would start there like Broman said. MAY03LT has a video on YouTube detailing the process, including the process to reset the PCM by removing 2 fuses (can't remember what numbers offhand, but both the PCM fuses) in the underhood fuse box for 20 minutes or so.

Plugs may be no good and/or not the right ACDelco replacements as well..

Good luck!

Welcome to the Nation!

I believe I have seen this video during previous research for smaller issues I have had. It may very well be a dirty TB considering our fuel suppliers around here add the most ethynol and that adds up to trouble too. I will be replacing the plugs ASAP (saturday) and cleaning the TB. For starters.

 

[Cloudy79]

Secondly I read about the CPAS issues, dirty, leaking, failed. (dirty/old oil is an issue with these too)

Lastly, the cam phaser itself causes a small number of issues.

It is funny that you say this. I was in a pretty tight spot recently, so I allowed the oil to stay in for the full 10k. Although this is the only time I have EVER let that happen in any vehicle, that would be my luck! I use Mobil 1 synthetic if this makes you feel any better. lol BTW CPAS stands for Cam Position Actuator? Or am I mistaken?

 

[Cloudy79]

I also just realized this is in the non- technical threads.... Thanks tapatalk. lol They don't give enough options when starting a new thread through it. Should I start this over in the correct location or will it get all technical up in here?

 

[BRomanJr]

It is funny that you say this. I was in a pretty tight spot recently, so I allowed the oil to stay in for the full 10k. Although this is the only time I have EVER let that happen in any vehicle, that would be my luck! I use Mobil 1 synthetic if this makes you feel any better. lol BTW CPAS stands for Cam Position Actuator? Or am I mistaken?

Yes, CPAS = Cam Position Actuator Solenoid, The Cam Position Actuator (as it could also be called) is what I have been referring to as the Cam Phaser.

Usually Synthetic oil can go longer than the OLM dictates as the OLM is based on non-synthetic oil capabilities. The reason it is so high overall, (higher than other vehicles) is that the I6 holds 7 quarts, not the usual 4.5-5 quarts.

Oil analysis is the only way to know for sure if you waited too long.

 

[Cloudy79]

Here's an update on the TB. I did the plugs, fuel filter, and cleaned the throttle body yesterday. Dumb ass me, I never changed the plugs since I got it almost three years ago. But hey, it drove smooth until last week so. It must have been those age old plugs that were in it. It isn't wanting to buck anymore and it has more power now, but still seems weak with the AC running. Not too sure if that isn't just lower compression from age.

On another note, does anyone find it strange that the coil packs don't actually "click" onto the plugs???