98 suburban k1500 sputters when shifting and torque converter problems

[james28909]

most of the time 1-2 is ok, if i apply any pedal while it is shifting, it shifts hard and there is hardly any sputter.
the 2-3 shift is when you can really hear the sputter, it almost sounds like the engine falls on its face for just a split second. then after it changes gears it feels like it just misses or the timing is off. i thought that maybe somehow when the gears change and the rpm changes in the motor, somehow this was making the distributor shaft rise up a little or something? has anyone ever heard of something liek thi?

things i have very recently done is all new gaskets for heads/intake and upper intake manifold etc.
this problem was there before i redone the upper side of the engine, and it is running much better after done all of that work, but this problem persists. i cleaned the maf sensor and that brought the truck back to life so to speak. and then i changed the throttle position sensor with no change.

but if anyone has any ideas, please dont hesitate

oh also forgot to add that when i am driving in overdrive. if i let my foot off the pedal and try to press it again, the torque converter unlocks for a few seconds and relocks. anyone know what might cause this issue?

 

[evilunclegrimace]

Got any codes? Have you hooked it to a scanner a watched the data stream? Throwing a wild ass guess out there TPS?

 

[james28909]

codes are p0452 and the 2 rear o2 sensors are disconnected because i thought they were causing a severe bogging issue. so the rear o2 sensors and cats are sawed out and disconnected. i also changed the tps with a known good tps from a junk yard. my original tps, the return spring inside it had failed and it was just loose. the new tps has great range when checking with multimeter and has a good working return spring.

i also cleaned the MAF and that made a tremendous difference, but problem still persists.

one other symptom i have is sometimes while in 1st and its about to change, i can hear it sound as if it jumps time for a split second and then goes back. the engine sounds real weak when it does this. almost as if the distributor is raising up and causing it to misfire or something.

ive put a new timing chain and gears, another cam from a donor truck, new lifters, had valve job done, put new seals throughout motor. set timing to -0.2 (couldnt get it set perfectly and it stay). new head gaskets, all done by me and to spec and i have went back through and checked and made sure everything was still set to spec and it is. engine breathes good, gets good fire (ac delco plugs and new wires) and has a new fuel pump as well. oh the fuel pressure regulator has been changed for a new one too. edit: also has upgraded distributor with new blue cap and rotor with brass contacts

at this point i am unsure what else to do to the motor. block and heads are not cracked. valve job and new gaskets throughout and all set to spec. new fuel pump, FPR, new tps. i am just not sure what else to check at this point. ive always considered myself a pretty good mechanic, but this 98 vortec 5.7 is about to get the shotgun treatment

 

[Schurkey]

the 2-3 shift is when you can really hear the sputter, it almost sounds like the engine falls on its face for just a split second. then after it changes gears it feels like it just misses or the timing is off.

My '88 had a lack of engine power instantly after the trans upshifted. I jacked-up the fuel pressure, and that went away (mostly) Let's say it's 85% better. Maybe I need still more fuel pressure. It's always worse as the weather gets colder.

Verify your fuel pressure/volume. "New" parts doesn't mean they're working like they should. The Chinese can screw-up ANYTHING, and it's not like companies that source from the Communists have a great track record of QA when the product hits these shores.

Newer vehicles with electronically-controlled transmissions have "Torque Management" built-into the computer. The computer retards timing during each shift, so the clutches/bands engage with less stress on them. Maybe your Torque Management isn't working right. In addition to "Torque Management", they've also got "adaptive shift quality"; the computer measures the time each shift takes, compares it to "optimum" timing, and then plays games with the shift solenoids and maybe line pressure to make the trans shift "properly" until it's so worn-out that it can't adapt any farther.

A proper scan tool should let you look at the adaptive strategy part of the computer programming. I've never needed to look at torque management; I'm not sure if my scan tools will display any of that info.

oh also forgot to add that when i am driving in overdrive. if i let my foot off the pedal and try to press it again, the torque converter unlocks for a few seconds and relocks. anyone know what might cause this issue?

Totally normal. The converter unlocks when you pull your foot off the gas pedal, and it takes a moment to re-engage after you stick your foot back on the pedal. That's a function of the torque converter clutch control mechanism, not which gear you're in. It'll do the same thing in 3rd.

codes are p0452 and the 2 rear o2 sensors are disconnected because i thought they were causing a severe bogging issue. so the rear o2 sensors and cats are sawed out and disconnected.

That ought to be fixed.

one other symptom i have is sometimes while in 1st and its about to change, i can hear it sound as if it jumps time for a split second and then goes back. the engine sounds real weak when it does this.

Torque management???

ive put a new timing chain and gears,

Did you "degree" the cam?

also has upgraded distributor with new blue cap and rotor with brass contacts

Define "upgraded". Chinese junk replacement parts aren't really an upgrade, and that's what most aftermarket distributors are.

The color of the plastic and "brass contacts" means nothing when it comes to quality and service life of the distributor cap. Thin, cheap, low-grade plastic can be made in any color you want. Thick, sturdy, high-quality plastic can be made in any color you want (except "clear", apparently.)

 

[james28909]

yes cam was installed correct. and the heads were done by me as well. everything is in time and truck fires right up and runs good for the most part. the distributor gear looks great and it turns freely. the cap and rotor are brand new and the distributor looks to be an aluminum housing, and the cap is this one i am pretty sure. i will also check fuel pressure, but i am positive that it is good because when the truck is cold started and while in open loop, it runs good af.

i have a elm32 bluetooth and car gauge pros full version with extended pids. i notice a lot of the pids do not work though, but maf and map and o2 and gear indicator. what do you think would be the best thing to check with it? also, is there a way to graph more than 1 thing at a time with car gauge pros? seems i can only ever get it to graph one thing at a time.

if the elm device that i have isnt enough to scan the right things, what kind of scan tool would i need? that is affordable?

one other thing is that when i put it in reverse, i have to pat the gas just right, and this will make the engine flutter/misfire (but only does this in reverse), and then it usually slams into gear, but the engine smooths out and i could backup for 10 miles if i needed to.

 

[Schurkey]

yes cam was installed correct.

"Correct" because it was checked with a degree wheel and dial indicator; or "correct" because you aligned the dots on the sprockets carefully?

the distributor looks to be an aluminum housing,

Yep. Almost certainly a machined casting (NOT a "billet") and almost certainly made in China.

and the cap is this one i am pretty sure.

So it has the vent on top? Far as I know, only that brand has the vent...but lots of brands use blue plastic.

For the record, I bought one of those vented caps. Haven't installed it yet.

i have a elm32 bluetooth and car gauge pros full version with extended pids.

I can't help with that. ZERO experience with either one.

I had a Snap-On MT--MTG 2500 for about twenty years until I finally damaged it. Trying to get used to the Snap-On Solus Pro for the last couple months. Both are obsolete, no longer supported by Snap-On; and haven't been supported for years. But they work for me, I'm not a professional. All my scan tools have been Snap-On, and all of them have been bought used on eBay.

one other thing is that when i put it in reverse, i have to pat the gas just right, and this will make the engine flutter/misfire (but only does this in reverse), and then it usually slams into gear, but the engine smooths out and i could backup for 10 miles if i needed to.

So it doesn't really matter what gear you're going into, the engine runs bad as or just after the trans engages the gear?

 

[james28909]

motor runs good but when it changes gears is when it has the missing/hesitation. its mostly felt right when changing from 1-2 and 2-3 and 3-4, the motor will stumble/misfire/hesitate for just a split second almost as if the timing changes. i did not check any timing degree or use any dials or anything when installing the cam. there are timing marks on the crank and the camshaft gear. i used these two and lined them up and torqued everything back down to spec. the truck runs but has this problem once it is in closed loop. on cold start the thing runs good. if i could only force it to stay in that mode lol

 

[Schurkey]

motor runs good but when it changes gears is when it has the missing/hesitation. its mostly felt right when changing from 1-2 and 2-3 and 3-4, the motor will stumble/misfire/hesitate for just a split second almost as if the timing changes.

The timing DOES change during the gear changes. That's part of Torque Management. The computer is supposed to do that. But if it's done properly, it's not noticeable.

On my truck, it was mostly a fuel-delivery problem. In the end, there's probably a half-dozen things this could be.

i did not check any timing degree or use any dials or anything when installing the cam. there are timing marks on the crank and the camshaft gear. i used these two and lined them up and torqued everything back down to spec.

"Dot-to-Dot" is no guarantee that the cam is synchronized to the crank properly. Any one or a combination of about six machining operations can cause errors.

the truck runs but has this problem once it is in closed loop. on cold start the thing runs good. if i could only force it to stay in that mode lol

Disconnect the O2 sensors. You'll have poor fuel economy, and the catalyst will be in danger...but it'll stay in open loop.

 

[james28909]

there are no cats installed and the rear o2 sensors are disconnected as well. i will try to disconnect the front o2 sensors and see what happens. if it runs good then do you think that most likely the o2 sensors are the problem?

 

[Schurkey]

Probably not. If the O2 sensors were bad, you'd have problems all the time, not just during upshifts or going into reverse. I'm wondering about the ECM, the ignition module, and the wire harness that connects them. I'd connect a scan tool, have it record the data stream, so you can drive the vehicle then look at the sensor data when the thing shifts gears and acts-up.

Losing the O2 sensors will keep the computer from going into closed loop. You'll set codes, there may be other problems...this is NOT A LONG TERM FIX.

But short-term...maybe it helps you diagnose what's really wrong.

I wasn't actually expecting you to disconnect the O2 sensors. I figured you'd be dissuaded by the reduced fuel economy.