[gmagic]

1997 Tahoe, automatic transmission, 5.8L V8 engine, 140K miles, engine light on. When problem occurs, will be driving at highway speeds, engine continues to run, but vehicle loses speed and must move to side of road (engine still running). The engine is turned off and re-started, chugging/clanking sound is heard/felt from rear, also lurching/surging is felt and gradually smooth/normal speed can be resumed. For background information, I have never waited with the engine running to see if normal operation is regained. I have always turned the engine off and re-started. Any suggestions what to look for?

[Knotbored]

A million possibilities
but
I had similar situation on old ford eeconoline and found the converter (between engine and auto-trans) was leaking down-losing fluid back into the trans where it overflowed. Its supposed to fill then stay full of trans fluid.
The van would run fine-lose power to the wheels-coast to a stop-restart after 2 minutes and run a few blocks then same condition.
Most trans shops will check out for free.

[Farmgirl22]

Originally Posted by gmagic

1997 Tahoe, automatic transmission, 5.8L V8 engine, 140K miles, engine light on. When problem occurs, will be driving at highway speeds, engine continues to run, but vehicle loses speed and must move to side of road (engine still running). The engine is turned off and re-started, chugging/clanking sound is heard/felt from rear, also lurching/surging is felt and gradually smooth/normal speed can be resumed. For background information, I have never waited with the engine running to see if normal operation is regained. I have always turned the engine off and re-started. Any suggestions what to look for?

Is it 4x4??

[Jedi_Master]

Howdy folks...

Sounds to me like it may be flooding out...

When is the last time you changed the air filter, or did a tune up?

chugging/clanking sound is heard/felt from rear

Sounds like you have a broken muffler/tail pipe mounting bracket as well...

[gmagic]

No, it's not a 4 x 4.

[Farmgirl22]

Originally Posted by Jedi_Master

Sounds like you have a broken muffler/tail pipe mounting bracket as well...

You sure?? I'm thinking tranny's stripped out. If those gears are shot, it could make a grinding noise until it hits teeth and grabs for a while, plus it would make it easy for it to slip gears and essentially go into neutral.

If it had been 4x4, I would have guessed transfer case (early to mid 80's had a problem with the 208 case, could've easily happened again)...but since it isn't, I'm gonna have to guess tranny. The idiot light would come on if the oil needed changed, so that might not necessarily be relevant to the real problem.

It's hard to tell what is going on from the description though....Knotbored hit the nail on the head when he said millions of possibilities....without seeing/hearing/driving it for myself, that is.

[Farmgirl22]

I guess the question I forgot to ask was this: Does the engine pull down? Or does it maintain RPM's?? If the engine is pulling down, I'd agree with Jedi-Master. If not....I'd be thinking about going to a shop.

[Jedi_Master]

Originally Posted by Farmgirl22

You sure?? I'm thinking tranny's stripped out. If those gears are shot, it could make a grinding noise until it hits teeth and grabs for a while, plus it would make it easy for it to slip gears and essentially go into neutral.

About 99.9% it's not the tranny or rear end ect...

If it were, I kinda doubt that the OP would be getting it up to highway speeds, without noticing the tranny or ect. is grinding...

[JohnWill]

The obvious thing would be to see if an error code is stored in the on-board computer. FWIW, transmission issues can cause a "check engine light" on many cars/trucks.

[Farmgirl22]

Originally Posted by Jedi_Master

About 99.9% it's not the tranny or rear end ect...

If it were, I kinda doubt that the OP would be getting it up to highway speeds, without noticing the tranny or ect. is grinding...

It would not surprise me...some people can ignore anything, especially with a radio blaring. I know someone that drove all the way to Wichita (about 45 miles) without realizing their tire had blown out and they were driving on the rim. And I've heard of people driving far distances with their driveline dragging the ground.

However, you are probably right...as I said earlier, it's going to be hard to tell without actually seeing/hearing/driving it for myself....

[crjdriver]

All cars built since 1996 use standard codes. These are easily read with a code reader that you can buy at any auto parts store. BTW the connection for the reader should be right under the steering column. This is the same connection used for smog checks.

From the post I would be looking at a fuel problem ie clogged filter, weak pump in the tank, etc. Have you ever changed the fuel filter?

[gmagic]

The fuel pump was changed out some time ago, don't know if filter has been checked/changed. There were 4 codes returned from the computer: P0101 (mass air flow sensor - this code appeared twice), P1133 (O2 sensor bank 1 sensor 1), P1153 (O2 sensor bank 2 sensor 1).

[JohnWill]

Mass air flow sensor = expensive! I think most of the time the O2 sensors are a lot cheaper.

[Jedi_Master]

Ya know...have you checked the air filter just to be sure?

[crjdriver]

It is not that bad. The mass airflow sensor most likely just needs cleaning. Remove it and clean with electrical contact cleaner. Be careful not to break the filament. Reinstall the MAF.

Change the O2 sensors. Note you may have 2, 3, or 4 sensors. Change all of them. This will be pretty expensive.

Now clear fault codes from the computer and test drive.

BTW if you do not know when the fuel filter was changed, I would just replace it.