Jitter/surging/bucking While Climbing Incline

[JRLowey]

I purchased a 98 Silverado 4x4 last week which has 177,000 km on it. It has the 5.7 and 4L60E tran.

 

Truck rides very nice and seems to have been taken well care of. I am the 3rd. owner.

 

Today, I drove 70km. into Calgary to get new tires installed. It ran fine the whole way into town. I had the cruise set at 120km/hr most of the way.

 

Coming back home I had the cruise set at 125km. and all was fine until I came to two short, but steep inclines. The truck started to buck/jitter while climbing these small hills. On the second one I attempted to accelerate, which only made the bucking worse. Once on level ground again, all was fine.

 

No CEL came on, so I have not bothered to check for codes as of yet.

 

As a side note, this past weekend the CEL did come on and when I pulled the codes they were P0141 and P0161, both 02 sensors behind the cat. I cleared those codes and all had been fine until today's trouble. But again, no codes were set today.

 

Anyone with some insight/ advise on what I can check?

 

Appreciate it!

[tanked_darren]

A long time ago I owned a 1990 oldsmobile that would do that, it would stumble at lights sometimes also. I had an O2 sensor code on it that would come and go. I eventually replaced the O2 before I had to do aircare and the problem went away.

 

 

Not saying thats your problem because Im not there to diagnostic it myself but thats my 2 cents

[remington351]

I'd start with the simple things then look deeper. Three things needed to keep an engine running smoothly when climbing a steep hill; fuel, air, and a properly timed spark. With 170km first thing I'd check is the distributor cap (5.7 right?) then I'd check for bad plug wire that might be shorting out under load, then pull the spark plugs and see how they look. Next move to the coil and see what ohms that thing pulling.

 

If none of that clears it up I'd be looking for a vacuum leak that's affecting your manifold pressure. Some of the other guys may chime in with more details, but don't the 5.7's have a documented intake manifold gasket failure issue that might be causing this problem? Good luck!

[JRLowey]

Thanks remington, I will look into those suggestions

[KMGZ400]

i had that same exact bucking/stumbling happen on my old truck that had a 5.7 and to fix the problem i replaced the 02 sensors and the fuel filter

[ColoradoSkiCountry]

At that millage the O2 sensors tend to start wearing out. Hopefully your Cats are in good shape though and didn't cause the failure of the O2 sensors. It sounds more to me like issues with the fuel system. Could be a tired pump and or clogged filter.

[rodram]

.. just to repeat some of the advice given already..

 

- check the fuel pressure... should be 61 to 66 psi

- check the condition of plugs, plug wires, and distributor cap

- also... run some good injector cleaner through the fuel system

 

someone mentioned intake manifold gasket... check all these other things first because you are going to want to find that it is something cheaper to fix that this gasket.....

[Samsfire]

Father-in-law just had similar issues with his 01 S10 crew cab. Dealer around here said its a 10yr old truck should just need a 'tune up'. He changed plugs wires/plugs, and it helped a little, changed the cap, helped a little more. But in the end he changed fuel filter, and needed 2 new injectors. Swapped them out, and truck runs like new again. He was thinking about trading it in, but the truck barely has 60k miles on it, so now he said he is just going to keep it as a winter/shop truck and buy a new Camaro whenever they release the convertibles.

[jus]

Hi,

 

I have exactly the same problem with my engine (99 Tahoe, 5.7 Vortec).

I found out, that ignition timing dropped when the engine is asked to produce more power (accelerating).

Driving with 80 miles constantly: 30 degrees, accelerating : going down to 13 degrees and engine is bucking.

 

I changed knock sensor and put on new distributor-rotor and -cap, new spark plugs and new cables, but the problem is still there.

And I get no error codes.....

 

Next will be checkin' distributor and -shaft for wear.....

 

 

Any more ideas?

 

 

 

Jens

[JRLowey]

Well, the problem is fixed. Turned out to be the intake gaskets.

 

The surging progressively got worse and then I noticed the truck was losing coolant and oil. Turned out the intake gaskets were shot. Replaced them and all is fine now.

 

Thanks for all the replies!