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Suburban Expert's, Need Your Expertise.

Discussion in 'Off Topic Threads' started by Duck, Jul 9, 2009.

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  1. Duck

    Duck Member

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    Suburban Expert

    Afternoon,

    I have a 99' 4X4 GMC burb. Has been a great truck until Monday going up grade to gun club 40 mph it started to shake/vibrate etc. I honestly thought I had a loose tire by the vibration though the steering wheel. letting off the throttle helped somewhat as did kicking it down in passing gear better but not gone. I can't make it do it on normal grade!, start's great, idle's great, just got 17.4 mpg on a 380 mi.trip. Fuel pump replaced last fall not sure what it could be?.
    Transmission shift's fine on the level also, converter maybe under load?,
    egr valve?, oxy sensor?. Anyone else encounter this on their truck, burb, etc.

    Don;
     
  2. ExFedex

    ExFedex Active Member

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    It was an earlier model Suburban that I had and it did it a few times. I think it was happening after I had used the 4WD function and one of the front hubs had failed to unlock. It was recommended that you back the vehicle up to unlock the front hubs then. This was with the automatic hubs. I also had the driveline checked but that would not have been an intermittant fault. Still a great vehicle though.
     
  3. Rebsmith

    Rebsmith Member

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    Don.....If the fuel system is a throttle body, one of the "pods" is probably plugged up. It will put out enough for light loading but not enough for a loaded vehicle. I had it happen on one of my Jeep Wagoneers with the 360 V8. It sounds like it's starving for fuel under load.

    Jere
     
  4. Quack Shot

    Quack Shot Active Member

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    Possibly a fuel filter, fuel pressure, or delivery issue. Also the possibility of an ignition problem. You could be losing a few cylinders under load. Real hard to give you a good idea without having the vehicle in front of me. "Vulcan Mind Melds" don't work well over long distances. Is there a "check engine" light on? Are there any codes in memory?
     
  5. Duck

    Duck Member

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    Thank's All,

    I'll check all that was mentioned. Quack Shot the check engine light did come on, went out overnight. Checked with the local auto zone about reading the code
    and they said their tester would only read code with light on did'nt have the type that would read the stored codes?. Called the closest dealer and he said bring it next monday and asked how many time's I would cycle the key before then, not sure if he did say how many start's before the code's clear. But that's what I got out of it. I'll try and set up the situation again and see if it will repeat?.
     
  6. Texas Ton

    Texas Ton TS Member

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    Try an O'Reillys or wherever, someone will have a scanner to read the code. And, I've never seen an OBD II scanner that would only read while the light was on.

    If during the meantime, it does this again, tap the brake pedal------just a light tap, enough to make the brake light come on. Does this stop it?
     
  7. AveragEd

    AveragEd Well-Known Member

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    I think Texas Ton is on the right track. It sounds like the torque converter clutch (TCC) is chattering or engaging and releasing right away. It could be due to a failing sensor, a clogged oil passageway or the converter itself.

    Be sure to keep the throttle applied while you ride and release the brake pedal - the TCC releases when the throttle closes or when current flows to the stop lamps, so tapping the brakes with the throttle closed won't show you anything. If the converter is the area of concern, the condition will clear when the stop lamps are on because the TCC will stay disengaged.

    I'm trying to forget everything I knew about the auto repair industry, but if I recall correctly, the TCC isn't active until the coolant temperature reaches 140 degrees or so. If that's correct and the TCC is the problem, the condition should not be evident with a cold engine.

    Ed
     
  8. RickN

    RickN Well-Known Member

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    My Buick 3800 car did something similar to that. Turned out my intake manifold was going bad.
     
  9. AveragEd

    AveragEd Well-Known Member

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    Rick, Chevrolet V8s have a different style intake plenum, so they can't experience that same failure. But that is common on Series II 3800s and usually crops up at or a little past 80,000 miles - the composite plastic intake manifold plenum burns through around the EGR valve. But if every domestic engine only had that problem (and that's about the only one the 3800 has) and delivered the kind of performance and fuel economy a 3800 does, the industry wouldn't be in the shape it is.

    Ed
     
  10. RickN

    RickN Well-Known Member

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    Ed, I'm on my 4th Buick with the 3800. I believe the one I have now is a Series 3, but the prior ones were the Series II. Those 3 all had the intake problem between 80-100,000 miles. Fixed that and ran them up to +200,000 miles.
    Probably the best engine ever made.
     
  11. Mismost

    Mismost TS Member

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    How are the tires? I had one do this and went tiring to figure it out and never did. Replaced the tires and the problem went away. You might try swapping the tires around and see if the problem moves with the tires.
     
  12. Duck

    Duck Member

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    Jan 29, 1998
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    Thank's Again All!,

    Before I sat down to read your post's, I was out thrashing the truck on
    hill, could not make it repeat exactly like the other night. It was there but not as bad. I will check again tomorrow and bump the brake under power and see if it cease's. Also the tire's were rotated awhile back. Tonight I kind of lugged the truck in and out of OD around 40mph on the hill. Finally I just stepped it down into passing gear and held it there, I lifted slightly not enough to make it upshift so it ran over 4500 RPM up the hill almost seemed like it should have upshifted on it's own if that make's sense?. However when I got to the top of the hill and slowed for my turnaround it was stumbling badly. I goosed it a couple of time's and that cleared up the idle?. No engine light either?. Any idea's?.

    Don;
     
  13. Ed Y

    Ed Y TS Supporters TS Supporters

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    I had a problem like that with my '99 and it turned out to be the fuel filter in the line that passes along the frame, just about even with the passenger seat. It was about 35.oo and it fixed it fine. I thought there was something wrong with the transmission.

    Ed Yasnchok
     
  14. Duck

    Duck Member

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    Ed Y,

    Thank's I'll check my receipt's can't remember if I changed the filter with the fuel pump in 08' or not?.
     
  15. Quack Shot

    Quack Shot Active Member

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    Duck,

    I'd still try to get the codes from the processor and see if they can give you the Freeze Frame Data that was captured when the code was set. There are many code readers out there, but I haven't seen any OBD 2 compliant tester that couldn't pull codes from memory, light or no light. The freeze frame data will be erased if they clear the codes, so write it all down before someone does that. I have several scan tools at my disposal and would offer to pull the codes for you and get you on track. If you live in the Northern VA, Eastern Maryland, or Delmarva peninsula, I'd meet you somewhere and help you out. You mentioned something about hills in your first post, so you probably don't live around here. :) A good fuel pressure guage is also a great idea to hook up for a road test, along with a scan tool that can display real time data with capture capabilities.

    You can buy your own code reader for less than $100, or one with few more features that can actually display data foe a little more. Even Harbor freight has one for around $50-$60 that can read codes and there's one on Amazon for $40. Just be sure to get one that is compatible with the CAN networks (newer). Just remember that the codes tell you what the processor saw as a problem. It won't tell you what to replace or what the problem is. For example, an oxygen sensor code could end up being a bad fuel pump or injector, a contaminated MAF sensor, or even a vacuum leak. You'd be surprised at how many oxygen sensors get replaced because that's where the code pointed, when it was something else that caused it to read out of range.

    Here's a cheap one on Amazon:

    http://www.amazon.com/gp/product/B001LHVOVK/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=304485901&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000EVYGQY&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=12W1SHDXMNGW9599N8D4

    Here's a better one on Amazon:

    http://www.amazon.com/Actron-CP9145-AutoScanner-Diagnostic-Capability/dp/B00020BM2S/ref=sr_1_3?ie=UTF8&s=automotive&qid=1247284263&sr=1-3

    Here's a whole bunch more:

    http://www.amazon.com/s/ref=nb_ss_gw?url=search-alias%3Dautomotive&field-keywords=obd2+scanner

    In no way am I telling you to buy one of these from Amazon. If you want to buy one for yourself, some of the AutoZone and other parts stores carry them too, along with places like Harbor Freight. Amazon just has a lot to compare, as does eBay and other sites.

    Codes stay in memory for as long as the OBD2 Diagnostic Executive Program is programmed to store them. It is usually around 40 cycles or a drive cycle or two, depending on the type of code. Might be more or less. If it is a hard fault, then it won't go away until the problem is fixed.

    With all of the capabilities to read codes and display data, it sometimes becomes a difficult diagnosis since not everything is monitored or would set a code. Since you said the light came on, there might be something to go by. Was it on steady, or did it blink during the event?
     
  16. Duck

    Duck Member

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    Quack Shot,

    Thank's for the most generous offer, I wish I was close. I'm in MN.
    I'm going to check with some of the local body shop's may find something I can borrow. I'm not against purchasing one tho. The check engine light came on steady for the evening and was gone the next morning.
     
  17. Texas Ton

    Texas Ton TS Member

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    The single most important thing you can do on an injected engine is maintain it's required fuel pressure. Yours is a CSFI injection system, with the key on, engine off and the pump cycled, it should have from 60-66 pounds. At idle, no less than 57, at least mine won't run well at less than that.

    If you've got a gauge setup, it takes 30 seconds max to test fuel pressure, I test mine every oil change and change filters every 25K miles. Wix or AC are best, but using clean fuel and changing regularly, even a brand X would be OK and O'Reillys has them for $6, Wix/AC for $16.

    I hate to tell you to buy some china crap but that may be all you can find unless you go Snap-on. Harbor Freight has a test kit for ~$10, and you can just about test anything with it. I made my own, and made it 25 years ago along with the fittings, and I have more in it than that.

    If you can come up with a tester, you've got two stainless lines coming up along the drivers side of the intake manifold, to the injection head. One is 3/8", one smaller, follow the 3/8 line back to almost the back of the intake and you'll find a plastic cap over a Shrader Valve. Remove that cap and test there. You're going to lose some gas there most likely, so be aware.
     
  18. Duck

    Duck Member

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    Can't seem to find anything to borrow should have thought about asking to borrow on the weekend. Duh!. So I'm off to Amazon + Harbor Fgt.shopping.
     
  19. Big Az Al

    Big Az Al Well-Known Member

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    I to think the Texas Toom is onto something, because tapping that break peddle will unlock the OverDrive function that locks the tranny right to the engine bypassing the torq converter.

    Over drive at to low a speed on a hill................

    That would feel like some slipped a saddle bronc at full buck under the hood!

    Al
     
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