98 silverado - buck/jitter/surge

[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 or what may be causing this?

Appreciate it!

 

[99z28monster]

So it only does it when under a load like pulling up a hill or heavy throttle? I wonder if the cat is not clogged up choking the engine when it starts putting out a lot more exhaust.

 

[JRLowey]

Thanks 99z,

That gives me somewhere to start... Off to research how to troubleshoot a clogged cat.

 

[99z28monster]

Thanks 99z,

That gives me somewhere to start... Off to research how to troubleshoot a clogged cat.

smack it with a rubber mallet see if anything is rattling around in it. Some times they will corrode from the inside and the broken pieces are to big to blow out but big enough to restrict the exhaust flow.

 

[bizzo15]

Also sounds like it could be your trans not shifting into a lower gear to help gain power to climb the incline.

 

[dcZ71]

what wires do you run?

 

[Hodges87]

Have you checked your fuel pressure? Changed fuel filter? Checked cap and rotor?

 

[JRLowey]

Thanks for the replies all.

I checked the trans fluild before purchasing the vehicle and it looked and smelled fine, but I really did not have a close look at the fluid level at that time. A couple of days ago I checked the when it was hot and it was down a tad below the add line. I topped it up with Lucas tranny additive and I have taken the truck out and tried to duplicate the issue I had on the incline, but so far I have been unable to do so. Possibly this could have caused it?

 

[daddy_dandy]

I'm betting your distributor gear is knife edged. It is a VERY VERY VERY common problem with this platform. Grab a billet distributor from ignitiondk on Ebay.

 

[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!