99 Sierra 4.8 driveability issues no codes

dtnel78 · June 19, 2019

I didn't say you're being lazy. I was saying slow the train down and develop a method. I have the same problem of diagnostic approach at times. I'm still a rookie at 46 soon to be 47yrs old but I've learned to settle down some. Only problem is I settle down to much and then not give a crap and just like my daughters fuel tank that's been out of her car for over a month and I didn't even start until I had all the parts.

I got it apart then other things came up. Just the way things are. I coach fastpitch softball for my daughters team, deal with depression, anxiety and severe back pain so I try to work around things.

I have so many more projects to do this summer including adding on a 3rd stall garage which I have yet to break ground for.

I've got my work cut out. I do have my son, some of his and my friends lined up for the concrete work along with the aluminum panels for the footings and forms so getting electric relocated away from where I have to dig is a thing I have to make sure is done then digging will commence.

I figure food, beer, a little cash for time will get things done in regards to helping me get the underground work for concrete and the flatwork done and save a lot of $$$ at the same time.

After that I just have to get it framed, insulated, sided, sheetrocked, gas blower heater hung and hooked up myself before winter hits.

Once I get that done I can add the car hoist in the winter. With the added space and hoist I should finally be able to regain my 2 original garage stalls and have all my tools moved to the new larger side and do my work from there with TV and all. I procrastinate much because I like my TV shows. Need to have both in garage and I'll be good.

That'll be happy wife and happy life as they say it.

Dogluvr · June 20, 2019

Oh I know you didn't say it but I did cuz it's true. I know better and I know a lot more that I could have done before getting online looking for a quick suggestion that will be a quick easy fix. Sometimes it works but not this time.

Another question... Something new happened today. I got MIL illumination which hasn't happened in a while. Code P0440. Haven't even looked into it yet. But what I noticed is on the freeze frame data for throttle position sensor it reads "no data" ...hmmm. The truck was idling so throttle was closed but shouldn't it read zero?? "No data" definitely sounds wrong.

sefiroxx · June 21, 2019

Back to fuel trims, o2 and injectors.

O2 signal should fluctuate around .5. Fuel trims should fluctuate around 0 ( or 128 if using old system).

You stated fuel trims were normal at 0-9. This would indicate the computer is adding fuel to make up for about lean condition. Lean due to vacuum leak, clogged/failed injector, failing o2 sensor, MAF (replaced already), dirty throttle body.

Just a mechanics stethoscope to verify each injector is opening, and an not lite to verify the computer signal is reaching reach injector

Dogluvr · June 21, 2019

Well I'm a little embarrassed but very happy with the results. I've had so many car projects going since I bought this truck for hauling stuff just over three years ago that I didn't realize how little I've done to this truck. It was running good when I got it and all I remember doing is water pump and fuel pump. So anyway I get into it and realize I haven't changed the plugs and wires. I thought for sure I had but I've worked so much on my other vehicles I couldn't remember. Whoever did the previous tune-up gave up when they got to number 8, the one that's a little tight in the back. It had 7 Bosch and one old AC Delco in number 8!! LOL you gotta be a special kind of lazy to change 7 of 8 plugs!! I've dealt with much harder tight spots than that!! Are you kidding me? These plugs are a breeze.

All injectors measured identical 13.6 ohms, and none appear to leak as I lifted them out to watch them under pressure and saw nothing.

All cylinders measured between 155-160 compression so that was good.

One wire broke pretty easy upon removal. I gripped the right spot to pull it off but the metal end inside snapped and stayed with the plug.

At least 3 of the plugs were hand loose when I got to them and one of them even had the little nipple on the end stay inside the wire when I popped it off. They screw on and it had apparently backed completely off! That was something is never seen before.

So I put on the new plugs and wires and the truck is running better than it did when I got it!! I couldn't be happier!! I've been putting up with this issue for a long time now. So glad it's over! Thanks again guys for the help

Dogluvr · June 21, 2019

3 minutes ago, sefiroxx said:

Back to fuel trims, o2 and injectors.

O2 signal should fluctuate around .5. Fuel trims should fluctuate around 0 ( or 128 if using old system).

You stated fuel trims were normal at 0-9. This would indicate the computer is adding fuel to make up for about lean condition. Lean due to vacuum leak, clogged/failed injector, failing o2 sensor, MAF (replaced already), dirty throttle body.

Just a mechanics stethoscope to verify each injector is opening, and an not lite to verify the computer signal is reaching reach injector

I'm thinking low fuel pressure too. I had been operating around 45-47 before this new FPR but then even with that it was still idling at 49. So I still have it unplugged from vacuum. It idles at 55 without it. It ran great today I just got home from a good bit of driving and it didn't miss a beat. Noticeable power difference, I even was able to set cruise and leave it while on an incline!! I haven't been able to do that in a long time.