Author Topic: 87 V10 TBI - No check engine light & inconsistent idle  (Read 3792 times)

Offline VileZambonie

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #15 on: October 16, 2022, 06:07:10 PM »
Sounds like a vacuum leak.
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Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #16 on: October 17, 2022, 10:41:45 AM »
I honestly wouldn’t doubt it. Been correcting issues from the previous owner for a while. Would hvac vacuums effect it as well or are they separate

Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #17 on: October 18, 2022, 02:01:01 PM »
Lord check out all these codes


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Offline bd

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #18 on: October 18, 2022, 03:57:54 PM »
Many of those codes may be fictitious due to unplugging or activating sensors with the ignition ON during testing and swapping parts.  You need to clear the trouble codes out of the ECM's memory and then determine which codes are active by seeing which reset during vehicle operation.  Disconnect the battery ground cable for ~30 seconds then reconnect it and perform a vehicle road test - do not disconnect any sensors or wiring in the interim.  Recheck for codes afterward.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
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Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #19 on: October 18, 2022, 04:04:29 PM »
How long should I drive it and letting it run in the garage isn’t the same right


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Offline bd

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #20 on: October 18, 2022, 05:16:06 PM »
Assuming it's road worthy, take it out and use it.  Take a buzz down the highway and drive it normally.  Run some needed errands around town.  See if any codes return as a result.  Just remember to write down any codes that occur along with the date that you retrieve them so that you have an organized record and history, before disconnecting the battery or pulling the ECM B fuse, which will erase the memory.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #21 on: October 18, 2022, 07:42:54 PM »
Ok will do. I did unhook the battery and checked them right after. Still there. Will do what you said my next day off


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Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #22 on: October 21, 2022, 04:21:08 PM »
So I drove it around. Codes would never reset. I checked grounds again, pulled ecm and reseated prom. Resinstalled. Same 10 codes there. Should I try grounding the ecm somewhere other than the intake or what other suggestions do you have


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Offline VileZambonie

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #23 on: October 22, 2022, 07:34:23 PM »
Have you verified your grounds at the intake and the back of the cylinder head? If you have then the next step is to do some pinpoint testing.
,                           ___ 
                         /  _ _ _\_
              ⌠¯¯¯¯¯'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #24 on: October 25, 2022, 05:00:25 AM »
ive verified the grounds that i know of and can see. with those 10 codes i imagine its 1 component causing this. i noticed my alternator gauge was a bit low. unhooked the positive and the truck shut off. old school shade tree mechanics have told me that means i need to change the alternator. so thats what ill be doing tomorrow. other than that im leaning towards my computer

Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #25 on: October 26, 2022, 05:13:23 PM »
I replaced the alternator and checked codes a few times. Still the same 10 codes…I’m stumped. Anyone feel free to message me

Offline MIKE S

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #26 on: October 26, 2022, 05:54:59 PM »
Code 51 indicates a prom problem. Diagnostics says to reseat prom and see if code returns. Make sure you clear codes after reseat of prom or any component disconnect. If code 51 comes back it says replace prom. If it still comes back replace ECM. This is from Mitchel Pro Demand.

Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #27 on: October 26, 2022, 06:37:55 PM »
I’ve reseated it. Just found two terrible grounds beside the distributor. One of them had four wires connected into 1. Im not sure why but I cleaned it all up and it’s running a little better. Haven’t checked codes yet. Will soon


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Offline buzzman351

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #28 on: October 26, 2022, 06:44:06 PM »
When it’s running every now and then I’ll hear a little huff out of the exhaust too


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Offline JohnnyPopper

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Re: 87 V10 TBI - No check engine light & inconsistent idle
« Reply #29 on: October 27, 2022, 02:02:55 PM »
Is the gas old? If yes, they make treatments that suspend crud like water condensation.
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