bucking when cold

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LaGrasta
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bucking when cold

Post by LaGrasta » Tue Apr 01, 2014 4:10 pm

Hello guys, it's been so long since I've visited; that's a good sign the 'ol Astro is running great. I'm now at 191k.

My problem as of late is the stuttering, bucking, etc when it's cold. I leave the neighborhood early in the morning and it's fine, but once on the freeway, until it warms, it starts to buck. I'll put the cruise control on and leave it. After a bit of bucking, it works it's way out of the system and it continues to run fine the entire rest of the day.

My guess is a sensor …ideas?
1998 Astro, 224,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
iPOD, CD, DVD, Dutch door mounted 12s, 400w
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

Astrofarian
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Re: bucking when cold

Post by Astrofarian » Sat May 03, 2014 9:17 pm

Check & be sure that the heated air intake duct (That crinkly cardboard vacuum cleaner looking hose thingy) from the exhaust manifold to the air intake isn't crushed, missing, disintegrated etc. Air filter would be next followed by fuel filter. Poke around a bit...surprising what you can see that WON'T throw a code. THEN run the codes, if any. Gotta start somewhere. right?

WHOOPS...just saw you have a K&N; are you running a cold air intake?

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LaGrasta
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Re: bucking when cold

Post by LaGrasta » Mon May 05, 2014 3:08 pm

thanks for your response. K&N, but not a cold air intake, all stock ducting.
1998 Astro, 224,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
iPOD, CD, DVD, Dutch door mounted 12s, 400w
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

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v8famvan
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Re: bucking when cold

Post by v8famvan » Tue May 06, 2014 5:18 am

Cleaned your mass air flow sensor lately?
James from B.C.
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LaGrasta
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Re: bucking when cold

Post by LaGrasta » Tue May 06, 2014 3:04 pm

I changed the intake manifold gasket and replaced the spider injectors. At that time, I also cleaned the Mass Air Flow. That was about 30k ago. Due for another?
1998 Astro, 224,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
iPOD, CD, DVD, Dutch door mounted 12s, 400w
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

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v8famvan
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How many wheels are on an Astro van? (4): 4
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Re: bucking when cold

Post by v8famvan » Thu May 08, 2014 5:05 am

No harm doing a mass air flow sensor cleaning & it is simple to do & costs nothing. Since you are asking for ideas, another suggestion is a slightly restricted fuel filter or fuel pressure dropping to the threshold of meeting the minimum required amount. A cold (not warm) engine requires more fuel to operate. If the fuel pressure or flow amount is low, this could result in your issue.
James from B.C.
1992 Safari - R.I.P.
GM Grand Master Techncian

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LaGrasta
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How many wheels are on an Astro van? (4): 4
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Re: bucking when cold

Post by LaGrasta » Thu May 08, 2014 2:56 pm

a few ideas i hadn't considered. fuel pumps never last on Astro's so you may be on to something.
1998 Astro, 224,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
iPOD, CD, DVD, Dutch door mounted 12s, 400w
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

User avatar
LaGrasta
I sleep in my van
Posts: 715
Joined: Fri Jan 19, 2007 10:07 pm
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How many wheels are on an Astro van? (4): 4
Location: Mission Viejo, CA

Re: bucking when cold

Post by LaGrasta » Thu Jul 13, 2017 10:42 pm

UPDATE: It turns out it was low on trans fluid
1998 Astro, 224,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
iPOD, CD, DVD, Dutch door mounted 12s, 400w
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

User avatar
LaGrasta
I sleep in my van
Posts: 715
Joined: Fri Jan 19, 2007 10:07 pm
antispam: No
How many wheels are on an Astro van? (4): 4
Location: Mission Viejo, CA

Re: bucking when cold

Post by LaGrasta » Mon Apr 09, 2018 3:01 pm

So many miles later, the problem returned and became worse. It bucks when idling along, such as when on cruise control on freeway. Basically, it's noticeable when no or little fuel is being supplied. With this determination, I finally figured it out and 100% fixed it. The distributor was worn and needed replaced. $100 and an hour of labor and it is back to perfect. This was a long term troubleshoot experience. We're now at 221,000.
1998 Astro, 224,000 miles

K&N air filter
TruCool trans cooler
2" Overland lift & 15" BFG Terrain, 3.73 gears
JET Performance SCU-2000 (Speed Control Unit)
Gabriel Ultra shocks, rear AirLift bags & sway bar
iPOD, CD, DVD, Dutch door mounted 12s, 400w
Draw-Tite Dual Port Hitch System, hitch-mounted bike rack (4), hitch-mounted cargo tray, Thule roof-mounted cargo box

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Re: bucking when cold

Post by Herbie » Mon Apr 09, 2018 3:14 pm

Great work!
"My minivan is cooler than your bro-truck"
2003 Astro AWD Astrolander/ZMB - GTRV Top Transplant, 4" OLV Lift, NP233 T-case, evolving interior
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Re: bucking when cold

Post by Mmusicman » Tue Apr 10, 2018 12:49 am

Bucking at "part throttle" while cruising, (especially when you have over 150K miles) is typically a worn distributor. It happened to me. Sorry I didn't see this post in 2014, to post my reply! Glad you found the problem!
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