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I have a 2003 Silverado, 5.3, 4x4. I has 6in lift and 37in tires. Other than that it is stock. The truck is currently running sluggishly, not wanting to accelerate at times, rough idle, etc. Its not throwing any error codes. I have provided some readings. I am an amateur with hp tuners so if I did not provide the right data, please let me know. Thanks in advance for any help I get. Attachment 93874
Does it atleast have better than factory gear?
If not it's lugging the hell out of the engine if you have stock 3.42 or 3.73's. Needs 4.56's or 4.88's at a minimum.
The data log is missing a few key things. You need to log knock retard, burst knock, cylinder airmass, commanded AFR, injector pulse width avg for both banks.
Several times when you leaned into the throttle just enough to maintain or gain speed your timing advanced dropped like a rock to around 0 or negative timing. All of the power is going away because of that. The issue could be from knock or some other table like torque mngt pulling timing away. That is why some of that stuff needs to be logged.
You should also pull up the diagnostic trouble codes and see if you have a pending knock sensor code. That is a very common issue on these trucks. Any pending or current code will automatically yank whatever the maximum allowed timing in the calibration, typically that is around 8 degrees.
Thank you for your time and response. I am not 100 percent sure what gears are in it. I recently bought this truck and I can no longer get a hold of the guy I bought it from. I do plan to inspect the gears in the near future to see for sure what gears are in it. I recently got a quote on swapping them out and it was 2600 so it may be a couple months before I have the cash to do it. None the less I understand the strain it could be under if indeed it is 3.73 gears. That being said, it doesnt always run so crappy. Sometimes it seems to run much better. I have added those items to my data log and I will be doing another test run here shortly and will provide more data. There are no check engine lights on but I do find a transmission range sensor dtc stored in my vcm scanner. Thanks again for your help.Quote:
Originally Posted by 5FDP
This is the data from a drive this morning. I think I have provided all the PID's you've requested, if I am missing anything let me know. I will say that it did seem to run a little better this morning, not sure if the numbers confirm that. I am a novice to say the least lol. Thanks again.
why not do a hardware evaluation and rule out the basics? vacuum leak, poor ignition and so on. clearly you have an issue with torque management too
Well to be quite honest, my diagnostic experience is quite limited. I have been searching the web looking for advice and things to test/replace. That is what has brought me here. Looking for more advice to guidance on parts to test. I did replace the spark plugs 2 days ago and ordered an ignition tester as well to test the coils. The tester should be here today and I will test the coils. I have thought that a vacuum leak may be a possibility as well. I was under the impression that smoke machine was rather expensive, but I just came across a few on amazon for around 100 bucks. I plan to order one today, it should arrive at the beginning of the week. As far as a torque management issue I'm not really familiar with what exactly you're referring to. Would that be cause by the stock gears and over sized tires? Sorry if my lack of knowledge is frustrating, but that is why I'm here. I'm trying to learn and I thank you and anyone else who provides advice.Quote:
Originally Posted by eurowise
Just an update. I just got done testing the spark on all coils with and HEI spark tester. Seem to be getting good spark on all coils.
From the log it looks like you don't have a pending or current knock sensor code so that is good. If there was it would peg out at 8-10 degrees of knock and just stay there under the right conditions.
Fuel trims don't look that bad, nothing is exactly extreme one way or the other. There are a tad positive but I see that all the time. Possible a good MAF cleaning, throttle body cleaning and double checking that you have no problem exhaust manifold bolts would help the trims out.
What grade of fuel are you running? 87 octane is more prone to showing knock than 89+. Slightly better fuel could help over all running. I'd also check your motor mounts and transmission mount, if they are all worn out that would cause extra vibrations to be picked up by the computer and could pull power away.
The tune would also say what gears it is programmed for, that is under the gear/tire wizard in the edit tab. Otherwise you can just jack up the rear end real quick and check it the old fashion way with a piece of tape and counting driveshaft revolutions and tire revolutions.
Thanks again for the response. I have cleaned the MAF with cleaner. It doesnt appear to be in the newest condition, not sure how old it is. The throttle body I did replace as when I went to clean it I couldnt even hardly clean the junk off of it. I do think you may be on to something with the exhaust manifold. I did notice one broke head on one of the bolts. Also I think I've discovered a leak at the flange coming off the collector, which is right there before the o2 sensor. I would attempt to replace the manifold myself but I have read nightmares about those bolts and seeing one is already broken off, I think I will take it to the exhaust shop. I may just go with headers and new exhaust all the way back if I'm going to mess with it at all.Quote:
Originally Posted by 5FDP
I have been running 87. I will switch it up though and see if that helps some.
According to tire wizard I have the stock 3.73 gears. I used the wizard to adjust tire size for speedometer and now I'm getting random abs/check brake system lights.
Also, I will check for any busted motor or transmission mounts.
Something wigs out if you put a tire size over like 35in in the wizard. Likely why you are getting the ABS lights if you stuck in the number 37in.
Try creeping up on the number like try 34 or 35 first and see if it keeps the light off. The speedo will still be slightly off but no where near as bad if it had the stock tire size in there.
Cool, thanks. I'll give that a shot. Also this may sound ignorant but is there anything I can do to help out other than changing the gears? Would adding more power via headers and exhaust plus a good dyno tune help out at all?Quote:
Originally Posted by 5FDP
Adding power is good but there is still no way to gain back the mechanical advantage that is lost from the huge tires and lift kit.
Even if you added say 20-30hp or did a 6.0 swap to gain even more torque, it would still be fighting a losing battle down low in the rev range and speed because it just can't overcome the tall tires.
Gear swaps are pretty spendy if you can't do the work yourself. Other options would be finding already swapped diffs or finding a factory 4.10 front/rear diff to help out even though that's still kinda not enough gear for the tire size or swapping to smaller 35in tires to remove weight and rolling mass.
Roger that, thanks again for all your help. I just hear that it's a pretty tough "first time" thing to do without having someone knowledgeable to guide you threw the process. I'll take all that into consideration on deciding which route to take. I really wish I could do the gear swap myself. I would just hate to have to be that guy to get a truck towed to a mechanic with a mess of a gear swap. He would also hate me I'm sure.Quote:
Originally Posted by 5FDP