Stumbles in overdrive

[Jamest0809]

95 k1500 224k miles 5.7 tbi and rebuilt 4l60e, truck stumbles to accelerate in overdrive, mostly at lower rpm

 

[Schurkey]

95 k1500 224k miles 5.7 tbi and rebuilt 4l60e, truck stumbles to accelerate in overdrive, mostly at lower rpm

The "usual three":

1. How old are the typical "tune-up" parts--cap, rotor, plug wires, plugs, PCV valve, air filter? When was the ignition base timing and EGR last inspected? Throttle body cleaned and engine checked for vacuum leaks?

2. What is the fuel pressure? How old is the fuel filter?

3. Connect a scan tool, look for "codes" but more important, verify ALL the sensors, and computer outputs. Check fuel trims. See if the torque converter clutch is being commanded when the "stumbles" occur.

 

[Jamest0809]

New cap,rotor,wires,plugs,throttle body, fuel filter, pcv, it has 11psi. Got the truck with around 210k so I don’t know when the timing or egr have been last checked, no vacuum leaks, only code 32, and how do I check the torque converter clutch?

 

[DerekTheGreat]

In addition to what Schurkey said, has it always done this? I originally acquired my '89 with 224k miles on it. Ran fine for about three hundred miles, developed a stumble similar to yours. Cylinder #1 had burnt up it's exhaust valve at some point and so it was fouling out the spark plug. Felt like a fish bite when trying to accelerate in OD as it first started to act up.

 

[Jamest0809]

It ran poor when I got it entirely so I’ve been just replacing things here and there, and it does have a broke manifold bolt, so that could possibly contribute to it, it runs and shifts mostly fine now other then the stumble after it gets into overdrive. if I’m going slow it will go into overdrive around 40-45 mph is that normal?

 

[Schurkey]

I don’t know when the timing or egr have been last checked, no vacuum leaks, only code 32, and how do I check the torque converter clutch?

Time to verify the ignition advance, and the EGR. Code 32 is an EGR code.

Connect a scan tool, find out when the converter clutch is commanded "on".

it does have a broke manifold bolt, so that could possibly contribute to it,

Intake or exhaust manifold? If exhaust manifold, is it on the same side as the O2 sensor? If intake manifold, is it near a runner for the left-side bank?

if I’m going slow it will go into overdrive around 40-45 mph is that normal?

Depends on your gearing and tire diameter.

I'd expect it going into 4th gear sooner than that, with the torque converter clutch engaging about 40--45.

 

[Jamest0809]

Exhaust manifold, and it’s not on the o2 side, and it has 31x10.5. And the egr was replaced with the throttle body. How can I verify my ignition advance? And what scanner would I need to check the torque converter?

 

[Schurkey]

Exhaust manifold, and it’s not on the o2 side,

That's the better situation, at least until you can fix it properly.

And the egr was replaced with the throttle body.

Did you verify that the exhaust passages weren't plugged, and the EGR vacuum system including the solenoid is working properly? The computer controls the solenoid, is the computer working, and is the wiring harness in good condition? Is the EGR valve made right--other folks have reported that some EGR valves don't have the tiny orifice engineered into the original nipple on the valve they replaced, causing sudden opening and driveability problems. The fix would be to cut the tiny orifice out of the original EGR valve nipple, and cram it into the vacuum hose ahead of the new EGR valve.

How can I verify my ignition advance?

Put a timing light on it with the timing connector disconnected and the engine running at idle. Should be 0 degrees advance. Shut engine off, reconnect the timing connector, disconnect the battery for fifteen seconds to clear the code. Reconnect the battery, start the engine, timing should be ~12--15 degrees advanced. Add some RPM. Timing advance should increase.

And what scanner would I need to check the torque converter?

The only scan tool system I have experience with is Snap-On. Any Snap-On scan tool would check this.

Lotsa folks buy "software + cable + Laptop" systems, or consumer-grade scan tools, or "Dongle + smartphone" solutions, and I can't help with that.

Let's say that ANY decent scan tool should tell you whether the TCC is commanded "on"; and if it doesn't, it's a crappy "Tool-Shaped Object" that should be pitched in the trash or sent back for a refund.

 

[udidwht]

Could be a bad TPS.