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yamarider

yamarider

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Looking for ideas here, about why a 98 GMC truck i'm looking to buy isn't idling until it warms up. It's got the 5.0 vortec in it.

I was thinking that it could be either the throttle position sensor or idle air control valve, but i'm not much of a mechanic. The guy that's selling it (and I don't think he knows much about modern vehicles) thinks that it just needs plugs and wires to get it running right. I will probably replace those anyways, they look like the originals and they've got mud and gunk all over the bottom halves.

The truck has good smooth power when you get on the gas, it's just that for the first couple minutes it doesn't want to idle, so i'm sure it's just some dumb little sensor or something and not actually a major problem, i'm just trying to figure out what to look for before I spend any money on it.

Normally I wouldn't think about buying a vehicle with problems, especially a construction truck that's all beat up like this one, but I can get the truck for $1,400 and it's a 98 with 112,000 miles so it seems like a hell of a deal.

If anybody has any other ideas of what could be causing it, or agrees with my thoughts, let me know, thanks.
 
Does the check engine light turn on? If it does borrow/rent/steal an OBDII scanner and see what's up.
 
The light doesn't come on when the engine is running, only when you turn the key for the lamp test. I have an obdII scanner and tried it anyways, it came up clear. The battery had been replaced on the truck recently though, so I don't know how much the truck has ran since that was cleared out.
 
I brought it home yesterday evening, and between last night and tonight we got it running perfect. It turned out that it was mainly the throttle position sensor and idle air control motor, but the spark plugs were also so worn away that I can't believe it was running on all cylinders and didn't have a misfire at all.

All in all, looks like i'll be getting a good solid truck for around $2,000 when it's all said and done. I just have a few little things left to do before inspection. I need to replace an oxygen sensor that was broken off, replace the front brake rotors and pads, possibly the rear brake shoes, and I have good tires that need to be mounted on the back of it.

I drove it around for almost an hour tonight, and it runs very smooth, shifts nice, and can lay down a nice 75 foot patch of rubber from a standing stop.
 
YamaRider said:
I brought it home yesterday evening, and between last night and tonight we got it running perfect. It turned out that it was mainly the throttle position sensor and idle air control motor, but the spark plugs were also so worn away that I can't believe it was running on all cylinders and didn't have a misfire at all.

All in all, looks like i'll be getting a good solid truck for around $2,000 when it's all said and done. I just have a few little things left to do before inspection. I need to replace an oxygen sensor that was broken off, replace the front brake rotors and pads, possibly the rear brake shoes, and I have good tires that need to be mounted on the back of it.

I drove it around for almost an hour tonight, and it runs very smooth, shifts nice, and can lay down a nice 75 foot patch of rubber from a standing stop.
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After owning a 98 silverado with a 305 I will tell you that ACDelco plugs and o2 sensors are worth the extra $$. DO NOT GET BOSCH. Gm does not like bosh plugs or 02s.
 
also watch the tranny in it if its 700r4 if it ever seems not right go have checked out asap before it explodes lol and costs more to fix
 
first thing that comes to mind is the IAC. may need to be cleaned and may not throw a code.
 
Ya, got that fixed a long time ago. It's still going strong. Even got the front steering tighter than most 2 year old Ford trucks and when I got it I could have gone about a quarter turn each way without changing my direction of travel. Just new tie rod ends, ball joints, and adjusted some of the slack out of the steering box.

I didn't have a problem with the Bosch 02 sensor, this truck is extremely tolerant to shitty parts, it took about a year before it started to misfire on one cylinder with the shitty Autolite plugs I put in it. Put NGK V-Power plugs in it and it's been perfect ever since. Made many 80+ mph runs down the turnpike to Breezewood Proving Grounds with a quad in the back and 2 on the trailer and it tows better than my buddy's 98 Ram 2500 with the 5.9 that's supposedly rated for a lot more horsepower... found out it has an absolutely bulletproof transmission in it too, I guess the construction company that bought it knew what they were doing because it has the 4L80E trans in it. 120,000 miles of hard service and it still shifts smoother than I can believe.

Sure does suck in the snow and ice though, it's all about momentum once I get off the dry pavement. That's any 2wd truck though.
 
warriorgirl09 said:
NGK is the only way man! all else sucks!
Click to expand...
+1 NGK plugs are great
NGK or AcDelco (same thing) NGK makes Ac Delco. The plugs I pulled out of my 03 had both names stamped on them


Dude, sounds like you lucked out getting the 4L80E instead of the 4L60E. The 4L80E with the addition of the Transgo HD2 shift kit has been known to hold up to around 800hp for quite a while.

I'm glad you got lucky with the bosch o2 sensor, my trucks haven't been so lucky, I put some bosch platinum 4 plugs in my truck and it gave random misfire codes...switched to delcos and it went away.

And a few tips about the truck, If you start smelling burning coolant, it's likely your intake manifold gaskets are going bad. There is an upgraded felpro part, it is rubber laminated over stainless steel, they're about $65, they're worth it, If you dont pay, you'll end up having to do it again.

Also, if you ever get a misfire at light throttle apps check your distributor gear for wear. Mine wore out at 150K and it caused a cylinder 3 misfire and random cylinder misfire. GM uses a soft distributor gear to avoid wearing the cam.


And yeah, lol I need to start reading the dates on these threads, lol. I guess the fourms here aren't quite as active as TT or Ktmtalk.
 
My little Chevy Z71 walks some pretty nasty mud holes. 3" body lift and 34" swampers, it has gone through mud that was half way up the door.

I've only ever bought GM products when it comes to daily driver or drag racing.
 
zraffz said:
My little Chevy Z71 walks some pretty nasty mud holes. 3" body lift and 34" swampers, it has gone through mud that was half way up the door.
Click to expand...

Haha like it has been said before no pics? then it didn't happen lol
 
i believe it check out my toys thread seeing is believing. those are 35's and well under the mud completely
 
This really might sound like bullshit, I think it has to do something with the small wheel base and light weight but that little Z71 does better then the bigger trucks in mud. We are all running a comparable swamper, within 2" of eachother.
 
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