Yukon/Tahoe Performance

[honkon]

I'm reading that, when new, Vortec 4 door Yukon/tahoes did 0-60 in 8.5-9 seconds, depending on who you ask. My 97 Yukon with only around 5k on a rebuilt engine and transmission does it in 11.

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It's also had a new fuel filter, spark plugs, spark plug wires, and fan clutch since the rebuild.
I suspect my cats are clogged from the tired old oil-burning engine. It has a bit of a rough idle and will stumble and stall when getting on the gas right off of idle if you aren't gentle enough with it. I'm also not sure if the ignition timing is dialed in correctly. I've had a cam position sensor code since the rebuild. I also suspect a bad o2 sensor or 4. Listing all of this out makes me ashamed for leaving my **** janky as **** for so long.
What's y'alls 0-60 times? Most interested in Yukon/Tahoes but would also appreciate Silverado and Sierra owners weighing in.
9 seconds seems awfully damn fast for a big ol suv. I didn't know until just now that they were that quick new. Maybe that'll give me the motivation to finally get this thing running right. Didn't have any sort of stumbling or stalling issues at all before the rebuild, but it was even more down on power then. I'm thinking that it might have not had enough compression for the clogged cats to be very noticeable.

 

[L31MaxExpress]

I'm reading that, when new, Vortec 4 door Yukon/tahoes did 0-60 in 8.5-9 seconds, depending on who you ask. My 97 Yukon with only around 5k on a rebuilt engine and transmission does it in 11.

xc_hide_links_from_guests_guests_error_hide_media

It's also had a new fuel filter, spark plugs, spark plug wires, and fan clutch since the rebuild.
I suspect my cats are clogged from the tired old oil-burning engine. It has a bit of a rough idle and will stumble and stall when getting on the gas right off of idle if you aren't gentle enough with it. I'm also not sure if the ignition timing is dialed in correctly. I've had a cam position sensor code since the rebuild. I also suspect a bad o2 sensor or 4. Listing all of this out makes me ashamed for leaving my **** janky as **** for so long.
What's y'alls 0-60 times? Most interested in Yukon/Tahoes but would also appreciate Silverado and Sierra owners weighing in.
9 seconds seems awfully damn fast for a big ol suv. I didn't know until just now that they were that quick new. Maybe that'll give me the motivation to finally get this thing running right. Didn't have any sort of stumbling or stalling issues at all before the rebuild, but it was even more down on power then. I'm thinking that it might have not had enough compression for the clogged cats to be very noticeable.

My 6,200 lbs Express conversion van did 0-60 in 9 seconds with a 5.7 Vortec/4L65E and 3.42 gears. PCM was tuned and I had a tiny 206/210 @ .050 Comp Xtreme 4x4 cam at the time. Yea the engine had a little work done to it but it was also pulling around nearly 1,000 lbs more.

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I would get your crank sensor code resolved (could be timing) and distributor timing set correctly before proceeding with any other diagnostic work.

Will also say the transmission was slipping on the 1-2 shift in that video. Had a very noticeable shift flare. It died about 4,000 miles later. When it died I swapped out the 65E for an 85E. I also added electric fans and a homebrew cold air intake. My 0-60 stayed the same 9 second despite the heavier trans with taller 1st and 2nd gear ratios but my 0-80 times dropped considerably.

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[east302]

Here’s a thread on setting the CMP offset with a Bluetooth adapter and an app on your phone.

Are you running the original injectors? Any other codes? Did a shop rebuild it...they should have set the offset when the distributor was replaced.

https://www.gmt400.com/threads/car-gauge-pro-can-read-cmp.35275/





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[CCLB3500]

Acceleration is affected by lots of variables. Looks like your truck runs well enough given the CEL, resolve those issues and you should be plenty happy.

my 99 tahoe 2wd with 5.7 and 3.42 is right about 9.

 

[MatSLO]

It's also had a new fuel filter, spark plugs, spark plug wires, and fan clutch since the rebuild.
I suspect my cats are clogged from the tired old oil-burning engine. It has a bit of a rough idle and will stumble and stall when getting on the gas right off of idle if you aren't gentle enough with it.

Seems to me that your engine needs some more work to get in proper order. Later you mentioned you're getting some codes - might want to look into that and fix the issues.

Speaking from my experience, I did the following stuff to get rid of rough idling, and generally make the engine run very smooth and also somewhat improve performance (subjectively, I didn't take any measurements):
- new sparks, spark plug wires, distributor cap&rotor, ignition coil, fuel filter
- new fuel pump (don't know if you need it, but mine died completely and when replacing it, I also had the above mentioned stuff replaced)
- new air filter
- manually cleaned the throttle body (you wouldn't believe how much sooty gunk there was in there)
- I put Liqui Moly Valve cleaner in my gas tank (in one tank, no need to add it all the time, do it once or twice a year)

 

[honkon]

Here’s a thread on setting the CMP offset with a Bluetooth adapter and an app on your phone.

Are you running the original injectors? Any other codes? Did a shop rebuild it...they should have set the offset when the distributor was replaced.

https://www.gmt400.com/threads/car-gauge-pro-can-read-cmp.35275/





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I rebuilt it. It's the first engine I've ever built and it's been trial and error. Original injectors as far as I know.
I've been delaying messing with the ignition timing because the intake has to come back off and I'd rather knock out two birds with one stone. I need to reseal it because it's leaking oil like a sieve, and it's got some top end noise that sounds like a lifter or two. I also want to verify the rocker adjustment while I'm in there.
I wasn't just flying blind, I did a lot of research and I rebuilt my 4l60e before this without fault. Seems like I screwed up at every step of the way on the engine build though.
It's had an o2 code since I got it. I think upper circuit low voltage.
I've just got some tuning up to do. Come winter break when I'm off school I'll get rid of the cats, put new o2 sensors in, and sort the ignition timing out.

 

[east302]

I've been delaying messing with the ignition timing because the intake has to come back off and I'd rather knock out two birds with one stone.

For the distributor CMP Retard code, the intake doesn’t need to come off. You’ll loosen the hold down clamp on the distributor and twist the distributor until the offset number is within spec (zero degrees +/- 2 at around 1100-rpm). Tighten the clamp and it’s done.





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[honkon]

For the distributor CMP Retard code, the intake doesn’t need to come off. You’ll loosen the hold down clamp on the distributor and twist the distributor until the offset number is within spec (zero degrees +/- 2 at around 1100-rpm). Tighten the clamp and it’s done.





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I'm saying I need to take the intake back off for other reasons (oil leak, top end noise) and I don't want to set the timing twice. It probably wouldn't take but a few minutes though. When I was putting everything back together I was twisting the distributor every which way and it wasn't making any difference at all in the idle. Wasn't looking at obdii data though.

 

[honkon]

Got the CMP offset dialed in to 0.1 at 1100 rpm. It runs way better now. Idles smoother, no more bogging off idle, even fixed a harsh tc lockup issue I was having. Really appreciate y'alls help with that.
It's still slow though. Timed a 0-60 at 11s.
No more cmp codes, but I'm getting a knock sensor code. The wire for that got pinched when I replaced the transmission about a year and a half ago. I repaired the wire when I had the engine out so I dunno why it'd be causing issues. I guess I'll have to poke around some.
No o2 codes either, which is weird because I know I used to have one. Still convinced the cats are clogged. CEL is off for now.

 

[Stepside_fever95]

My 1999 K1500 Suburban does it in 7.8 seconds. 3.42 gears, 33" tires, electric fan swap, 0411 pcm tuned by Blackbear performance for 93 octane, high flow cats, and a Jones max flow muffler are the only mods. That's on a 280k mile 350 with the original head gaskets and a year and a half old GM reman 4l60e.

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