1999 Silverado Stumbles

I have a 1999 Chevy Silverado 4x4 with 64k miles, 5.3 L engine and automatic tranny. The truck "stumbles" at different times. The problem generally occurs when I first start the engine and put in gear.
Once I begin to give it more throttle, the problem starts to dissipate. During acceleration at low rpm and slight throttle it also stumbles/bucks. The truck seems low on power in overdrive but when it kicks down, it seems to be ok. I have changes plugs and fuel filter. No trouble codes or check engine light. The dealer was unable to find anything wrong...it was working well when I took it in. Any Ideas? I can recreate the problem by holding the brake and throttle, loading the engine. Mostly this is noticed under 1500 rpm.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Try some fuel injector cleaner, I've used the Chevron Techton (sp) stuff and Lucas Fuel system cleaner. Both seem to work in my 99, but leaning toward the Chevron cleaner. I'd double the dose per tank full , but thats up to you. BG
snipped-for-privacy@win-4-u.net wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I've tried different cleaners over a period of time. No change in problem.
snipped-for-privacy@hotmail.com wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2 Jul 2006 16:35:21 -0700, snipped-for-privacy@win-4-u.net wrote:

These problems can be hard to find when it does not code. If you can get access to a real time OBD2 scanner and read live data, you will likely be able to nail it down. Their is a chance that you have a cam position sensor that is getting flakey and providing bad timing info at time but not bad enough to code. ----------------- The SnoMan www.thesnoman.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SnoMan wrote:

I'll amen that (good scanner). I'm having ongoing problems with my Battery Warning light (intermittly) on for no good reason. I had it to a GM dealer service center on the road and nothing was found using the scanner they used, However later (like weeks) I had someone with the official GM ($3500 +) scan tool and he found the problem right away, even without a Service Engine light being set. Turns out the "L" wire circuit from the alternator has a problem, and today thanks to a monitor wire I ran to inside the cab and reading with my Fluke DVM, it is a bad "L" wire circuit inside the new (Auto Zone) alternator causing the problem. BG
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2 Jul 2006 19:20:44 -0700, " snipped-for-privacy@hotmail.com"

A while ago I had a erratic idle problem on my 2000 K3500 with a 5.7. From time to time it would deleop a eratic idle in that it would vary a few hundred RPM quickly for and then slowy clear after 15 to 20 seconds when engine was hot and you first came to a stop.. It would not code and dealer said it was fine (it was under exstended warranty at the time). It turned out that it was a flay crank position sensor because by using a real time OBD2 data reader I discovered that the engine timing was swinging wildly at times causing the problem..The scanner I used cost me a little over 100 bucks on Ebay. ----------------- The SnoMan www.thesnoman.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I would also try changing out the plug wires as well. They can cause some pretty stupid idling/running problems at certain rpm ranges. My Grand am was doing a similar thing at about 1900 - 2200 rpm. and the plug wires were the problem. I can't say for sure that changing them will cure the problem, but considering the age of the vehicle and the cost, it might be well worth it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My '00 Silverado was doing the same thing. The scanner showed odd fuel adjustments to "Bank 2" compared to relatively stable adjustments on "Bank 1"... turned out to be a bad spark plug wire. It literally fell apart in my hand when I was removing it. David

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
David how many miles on the "00" Silverado when this happened? I'm thinking about replacing my plug wires now on my "99". BG
David Courtney wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I replaced the wires at about 180,000 miles... but I think the "stumble" was present for a long, long time before it got bad enough for me to starting really looking for the cause. I put new plugs in it about 20,000 miles before that and the "stumble" went away for a little while and then came back. The plug wires seemed "normal" at the time and I sprayed them down with silicone then, too. My guess would be 140,000 to 150,000 miles when I first noticed it acting goofy? David

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'll second on the plug wires... My truck (same year and motor) was doing the same thing, new plugs and wires fixed it.
Adair
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Plug wires seem t have done the trick. Truck runs better than it has for quite some time. One of those things that creeps up on a person.
Adair Winter wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I have Autotap to read the information but my problem is knowing what the numbers should really be. Experience is the best but for me, I need a bit of guidance.
snipped-for-privacy@win-4-u.net wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Can't help you nail down the problem but as far as scanners go you can find a real time scanner el cheapo. Do a google or yahoo or whatever search for ALDL/ serial cables. You can also buy them pre made for about 30 bucks on eBay and other sites. The software is free on the net. Or if you want to get real fancy you can buy emulators for about 250 bucks. Set in the seat and changer parameters and watch it run on your laptop.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.