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.
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
On 2 Jul 2006 16:35:21 -0700, firstname.lastname@example.org 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.
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
On 2 Jul 2006 19:20:44 -0700, " email@example.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.
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.
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.
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
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.
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