jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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 03-06-12 07:31 AM - Post#2199114
I have an'88 K1500, with a 5.7, T700R4. I can't get rid of a stumbling problem. It happens at around 35-45 MPH, the truck runs great at highway speeds and idles well, but when I slow down it stutters under load(34-45MPH). I have changed the EGR valve, EGR Vacuum solenoid, IAC valve, MAP Sensor, rebuilt the throttle body and still can't find the problem. I don't think it's a fuel problem as it runs so well at highway speed and rapid acceleration. If anyone has any ideas they would be GREATLY appreciated. Thank You
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Allan In NE
Contributor
Posts: 922
Reg: 12-27-11
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03-06-12 08:00 AM - Post#2199128
In response to jimbolyo
That "stutter" is almost always a secondary ignition issue.
The only other remote possibility is wobbled out valve guides. Is this a real high mileage unit?
Allan
| Lifelong GM automatic transmission specialist |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-06-12 08:06 AM - Post#2199132
In response to Allan In NE
Thanks for your quick reply. As to your question, the engine and trans have about 5k on each. I am wondering if a plugged cat could cause this problem?
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Allan In NE
Contributor
Posts: 922
Reg: 12-27-11
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03-06-12 08:19 AM - Post#2199135
In response to jimbolyo
No,
They usually show up as 'no power'. If it were a fuel delivery problem, just don't think it would run on out at hiway speeds, idle and starting.
Has it been this way since the overhaul?
Allan
| Lifelong GM automatic transmission specialist |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-06-12 08:26 AM - Post#2199136
In response to Allan In NE
It started a couple of months after the installation. What exactly were you meaning by secondary ignition problems,and wouldn't they be happening at all conditions?
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jham0077
"2nd Year" Silver Supporting Member
Posts: 329
Loc: Greenville, Il.
Reg: 11-04-11
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03-06-12 08:59 AM - Post#2199143
In response to jimbolyo
I assume it's always around the same RPMs because of the automatic transmission. You could ohm your TPS just to eliminate that part. Is there any "bucking" when it stutters? Maybe a lock-up problem in the transmission? Didn't put a cheap EGR valve on it did you? I guess with the quality of parts nowadays what's the difference.
Keep throwing money at it, it'll get better...
95 Tahoe 5.7 w/5 spd
Gone but not forgotten,
87 LWB 4x4 5.0 w/3 spd granny,
84 SWB 4x4 5.7 w/3 spd granny,
93 Full Size Blazer 5.7 w/5 spd,
97 Step-side Vortec w/5 spd.
I like shifting gears. |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-06-12 09:06 AM - Post#2199148
In response to jham0077
Thanks for your response. I did forget to mention that I installed a new TPS. The EGR valve that I got was from Advance Auto. I don't think the part would be that poorly made(I verifired OEM part#), also the problem didn't really change that much when I replaced the the original EGR.
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jham0077
"2nd Year" Silver Supporting Member
Posts: 329
Loc: Greenville, Il.
Reg: 11-04-11
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03-06-12 10:16 AM - Post#2199179
In response to jimbolyo
The way my luck has been with parts the past two months just makes me gun shy. As long as it wasn't a "universal" that came with a bag of numbered orfice washers. I'm with Allen, clogged cat would be sluggish and it doesn't act like fuel. But if you can get your hands on a gauge check it anyway. Maybe leave it hooked up and lay it on your wiper and drive it till it does it and see it if varies any.
Keep throwing money at it, it'll get better...
95 Tahoe 5.7 w/5 spd
Gone but not forgotten,
87 LWB 4x4 5.0 w/3 spd granny,
84 SWB 4x4 5.7 w/3 spd granny,
93 Full Size Blazer 5.7 w/5 spd,
97 Step-side Vortec w/5 spd.
I like shifting gears. |
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Allan In NE
Contributor
Posts: 922
Reg: 12-27-11
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03-06-12 11:26 AM - Post#2199207
In response to jham0077
- jham0077]Maybe a lock-up problem in the transmission? quote Said:
Hmmmmm,
Naw, that's an old wives tale. There's absolutely nothing in that transmission that will cause a stutter, miss or vibration.
Allan
| Lifelong GM automatic transmission specialist |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-06-12 12:11 PM - Post#2199219
In response to Allan In NE
I would think as with a fuel problem it would be consistant at all rpm, or show up at higher engine speeds?
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wymjym
Frequent Contributor
Posts: 1322
Loc: near Austin,Tx
Reg: 04-12-02
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03-06-12 12:33 PM - Post#2199227
In response to Allan In NE
- jham0077]Maybe a lock-up problem in the transmission? quote Said:
Hmmmmm,
Naw, that's an old wives tale. There's absolutely nothing in that transmission that will cause a stutter, miss or vibration.
Allan
not a miss but the feeling can be similar
I had a 'shutter or stutter' around the speed where the transmission would typically shift into a higher gear. Changed out the fluid and it was a bit better but still there. Replaced a solenoid in the tranny and it was 'fixed'.
wj
Edited by wymjym on 03-06-12 12:33 PM. Reason for edit: No reason given.
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-06-12 01:09 PM - Post#2199240
In response to wymjym
Would you happen to know which solenoid you changed, and also is there a way to test?
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wymjym
Frequent Contributor
Posts: 1322
Loc: near Austin,Tx
Reg: 04-12-02
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03-06-12 02:15 PM - Post#2199269
In response to jimbolyo
sorry but it was years ago and I don't recall the specific name of it.
I'm thinking it might have been a modulator valve solenoid but I might be confusing that with a ford tranny I fixed.
One thing that made it apparent to me was that when I encountered the situation I could repeat the same feeling on level ground at the same throttle opening, road speed. If I would give it more throttle or try it on a slight grade it would not be as apparent or even occur.
wj
Edited by wymjym on 03-06-12 02:15 PM. Reason for edit: No reason given.
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Allan In NE
Contributor
Posts: 922
Reg: 12-27-11
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03-06-12 02:49 PM - Post#2199286
In response to wymjym
Ford, yes. I'll go with that.
Seen that one time on a Crown Vic; 'bout a '91 or so. 'Course, back then, they used that "soup" for tranny oil. They even had a TSB out on that situation.
Never, ever on a GM tho and I've been in a million of those darned things. 
Allan
| Lifelong GM automatic transmission specialist |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-06-12 03:02 PM - Post#2199290
In response to Allan In NE
I have noticed, that when I changed the EGR valve the stuttering is not as pronounced. I've been trying to think of anything in the tranny that could cause that. If the shifts change due to hydraulic pressure, I would think the stuttering would be felt throughout the RPM range? I'm just trying to avoid the tranny unless absolutely necessary.
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jham0077
"2nd Year" Silver Supporting Member
Posts: 329
Loc: Greenville, Il.
Reg: 11-04-11
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03-07-12 09:22 AM - Post#2199549
In response to jimbolyo
If I remeber correctly, and I may not due to too many parties, the lock-up solenoid can stick and give a shutter/miss feeling when coming to a stop or down shifting. That's why I mentioned rpms instead of mphs. My stick shift can run 35 in four different gears where an automatic, unless being abused or sticking, won't. I'm just throwing ideas out there to get the wheels turning.
Keep throwing money at it, it'll get better...
95 Tahoe 5.7 w/5 spd
Gone but not forgotten,
87 LWB 4x4 5.0 w/3 spd granny,
84 SWB 4x4 5.7 w/3 spd granny,
93 Full Size Blazer 5.7 w/5 spd,
97 Step-side Vortec w/5 spd.
I like shifting gears. |
Edited by jham0077 on 03-07-12 09:25 AM. Reason for edit: can't spell
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-07-12 09:46 AM - Post#2199556
In response to jham0077
Thanks for the ideas, It's starting to look like i've worn out just about all other possibilities. I don't suppose you know of an easy way to check that solenoid? The problem seems to be noticeable under light acceleration though.
Edited by jimbolyo on 03-07-12 09:48 AM. Reason for edit: No reason given.
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jham0077
"2nd Year" Silver Supporting Member
Posts: 329
Loc: Greenville, Il.
Reg: 11-04-11
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03-07-12 10:23 AM - Post#2199562
In response to jimbolyo
Sure don't. But the occurence under light acceleration probably rules out the transmission. When you say rebuilt the throttle body, did it get injectors and a regulator or just gaskets?
Keep throwing money at it, it'll get better...
95 Tahoe 5.7 w/5 spd
Gone but not forgotten,
87 LWB 4x4 5.0 w/3 spd granny,
84 SWB 4x4 5.7 w/3 spd granny,
93 Full Size Blazer 5.7 w/5 spd,
97 Step-side Vortec w/5 spd.
I like shifting gears. |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-07-12 10:33 AM - Post#2199567
In response to jham0077
I put in brand new injectors, and IAC. I don't mind telling you, I'm about ready to start pulling my hair out!lol
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 stumppuller
"3rd Year" Gold Supporting Member
Posts: 449
Loc: Canada
Reg: 11-01-04
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03-07-12 12:10 PM - Post#2199593
In response to jimbolyo
A stutter on decel and on light acceleration sounds a lot like an EGR valve. I know you changed it, but I'd make a blockoff plate and remove it completely for a test run. It'll set a code and be prone to some detonation, but you'll have long enough to tell if it's an issue, and it only costs you time and $1 of metal.
Is there any difference between a cold and hot motor?
To check the TCC solenoid, hit the highway in OD and hold the throttle at a steady speed. With the other foot, tap the brake pedal moderatly and you should see the RPM's rise ~200 RPM and then fall back when the TCC engages. This doesn't guarantee that's its working at 100%, but will confirm it's functioning.
Another little known test you can do is what's called "field service mode". Start the truck, then ground the ALDL test (do not ground it before starting, this can damage the ECM). The check engine light will flash accordingly while driving around,
-Twice per second = Open Loop
-Once per second = Closed Loop
-Stays on = Rich (Accelerating)
-Stays off = Lean (Decelerating)
-91 Sierra C2500, now K2500
-81 Chev K20 |
Edited by stumppuller on 03-07-12 12:14 PM. Reason for edit: No reason given.
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-07-12 12:21 PM - Post#2199596
In response to stumppuller
Thanks for your response. There isn't any stuttering during deceleration only during light acceleration after highway speed. Under hard acceleration and steady throttle the truck runs great! It however does stutter when the truck is at operating temp.
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D.Mac
Senior Member
Posts: 971
Loc: Ontario Canada
Reg: 03-22-03
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03-12-12 07:08 AM - Post#2201511
In response to jimbolyo
Unplug the TCC to disable it for a diagnostic test. See if your stumble changes.
Keep in mind that a locked torque converter can enhance an engine studder/vibration that may not be felt with the converter un-locked.
Dave MacDonald
Ontario, Canada
'66 Impala LT1/C950-,EFI,700R4,(sold 07/2011)
'12 Sonic LTZ, Turbo, M6
'07 Pontiac Solstice GXP
'06 Caddy CTS-V |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-12-12 08:58 AM - Post#2201544
In response to D.Mac
Thank you for the advice, I've ruled out the transmission. I guess the only thing left is an ignition problem.
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 CowboyTrukr
"2nd Year" Silver Supporting Member
Posts: 730
Loc: Salt Lake City
Reg: 06-20-09
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03-12-12 09:04 PM - Post#2201806
In response to jimbolyo
Jim, do you know what your fuel pressure is? Only reason we ask is so you know it's good. Also, throw a timing light beam into the TBI throat to watch the fuel spray pattern while you open it up. I know you replaced the injectors, but it's good to at least watch them so you know what the pattern should be. You should see a continuous smooth cone spraying onto the butterfly. Any deviation would indicate problems with the injectors or possibly the pressure.
Greg
'94 Silverado K2500 4X4 5.7 5spd Xcab LB
RV cam, Pace Setter Headers, TBI spacer, Flow Tech air cleaner adapter, Hypertech street chip
"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-13-12 03:44 AM - Post#2201862
In response to CowboyTrukr
I haven't checked fuel pressure yet, but I don't think that is the issue as it runs so good at full throttle. The fuel pattern has a solid conical shape. I'm thinking maybe the coil might be breaking down or some other ignition problem.
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jham0077
"2nd Year" Silver Supporting Member
Posts: 329
Loc: Greenville, Il.
Reg: 11-04-11
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03-13-12 10:53 AM - Post#2202013
In response to jimbolyo
But you did say it stutters at operating temp. Like an idle stutter? I agree with CowboyTrukr on the fuel pressure. It does funny things.
Keep throwing money at it, it'll get better...
95 Tahoe 5.7 w/5 spd
Gone but not forgotten,
87 LWB 4x4 5.0 w/3 spd granny,
84 SWB 4x4 5.7 w/3 spd granny,
93 Full Size Blazer 5.7 w/5 spd,
97 Step-side Vortec w/5 spd.
I like shifting gears. |
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 4dr 57
"6th Year" Silver Supporting Member
Posts: 2762
Loc: The Texas Hill Country
Reg: 11-10-04
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03-14-12 03:58 AM - Post#2202337
In response to jimbolyo
I have an'88 K1500, with a 5.7, T700R4. I can't get rid of a stumbling problem. It happens at around 35-45 MPH, the truck runs great at highway speeds and idles well, but when I slow down it stutters under load(34-45MPH). I have changed the EGR valve, EGR Vacuum solenoid, IAC valve, MAP Sensor, rebuilt the throttle body and still can't find the problem. I don't think it's a fuel problem as it runs so well at highway speed and rapid acceleration. If anyone has any ideas they would be GREATLY appreciated. Thank You
What happens if you just leave the truck in Park and rev the engine s l o w l y to the rpm the engine is at between 35-45 mph?
Stanley
| Wife: "Don't race the Police car, Stan!" |
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355Cheyenne
Senior Member
Posts: 3746
Loc: Northern MN
Reg: 10-27-04
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03-14-12 09:40 AM - Post#2202449
In response to 4dr 57
Have you tried changing the CTS? Have you tried plugging the EGR lines to disable it? It could still be a bad egr solenoid.
| 98 Silverado k1500 4x4 350 |
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350whip
Contributor
Posts: 116
Reg: 02-24-12
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03-14-12 12:08 PM - Post#2202506
In response to jimbolyo
CTS pull it and get a new one 20 bucks. another quick fix:) a hot ICM can do it 2. just pull it off and see if you still have paste under it. my last ICM was burnt inside but the truck would still run but with a stumble new CTS 20 bucks new used ICM(wrecker) 20 bucks and it was fixed after i did that it might throw codes at you, just unplug your timing bypass set it to TDC #1 plug back in your bypass turn her on. total repair and time at the junkyard and in my garage 40min total repair cost 40 bucks time spent on internet 9 hours lol.
RickT.
- 1989 chevy k1500
- regular cab, shortbox
- chevy SB350tbi (little piggie!)
- L60E Automatic 4speed
- corvette servo
- 30"BFG AT's
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350whip
Contributor
Posts: 116
Reg: 02-24-12
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03-14-12 12:16 PM - Post#2202512
In response to 350whip
i will get hell here for my farmboy fixes but if you don't want to turn your motor to TDC some people are afraid to turn it just crank on your starter till you get it to line up just little taps on the key before it starts. it takes me about 10 or 15 tries 30 or so the first time i did it. my starter is stock its still strong and i have been doing it since i lost my cheater bar 2 years ago lol. the best thing is you can't turn it the wrong way:)
RickT.
- 1989 chevy k1500
- regular cab, shortbox
- chevy SB350tbi (little piggie!)
- L60E Automatic 4speed
- corvette servo
- 30"BFG AT's
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