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87 GMC 5.7 ltr TBI running rich (new motor setup)


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jacob844
New User

Mar 13, 2019, 9:09 AM

Post #1 of 5 (277 views)
87 GMC 5.7 ltr TBI running rich (new motor setup) Sign In

I have an 1987 GMC V2500 5.7 Ltr TBI. Motor developed surging issue and had various form of advice and repairs made but never fixed the issue. Motor went and shop replaced it with a JEGs 5.7 setup, from new edelbrock intake, injectors, distributer, wire, plugs, coil etc, replaced throttle body, rebuilt TBI. When shop fire it up, surging was worse. They checked from fuel tanks forward, vacuum, charcoal canister etc. They could not fix it. A local shop promised they could fix it. After a month and new map sensor, smoking motor and other "technical stuff" they said it was running better as previous shop had timing off and some other items. He disconnected air pump as well. Came down for a checkout drive, till I got back to shop it was running poorly. He popped the hood and disconnected the new $117 dollar map sensor (cost $34) which made it run better but runs really rich. Drive it for awhile he said... when I took it back, "oh it's been too long and I don't remember your truck". I don't think he is will to honor his promise to fix my truck. That all being said, I did replaced a number of items with no difference. Temp sending unit, vacuum booster, vacuum lines, etc. Even put on two new fuel tanks, straps, fuel sending unit in tank and dash guage as well.

The exhaust burns your eyes and the dual exhaust puts out black carbon. My concern as I only have 2000- miles on the new motor that it will seriously mess up the motor at some point, let alone my catalytic converter. Plus my gas mileage is sooooo poor.

Any thoughts.....


Hammer Time
Ultimate Carjunky / Moderator
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Mar 13, 2019, 11:35 AM

Post #2 of 5 (271 views)
Re: 87 GMC 5.7 ltr TBI running rich (new motor setup) Sign In

Have you scanned the computer for codes?
Have you tested the fuel pressure?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 13, 2019, 3:09 PM

Post #3 of 5 (264 views)
Re: 87 GMC 5.7 ltr TBI running rich (new motor setup) Sign In

Question quoting top post, "> new edelbrock intake<"
Why this brand? I don't want to search the web blind but unless that is exact OE spec even for 1987 I smell trouble. Where's the original intake manifold and or what happened to it?


T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 13, 2019, 3:28 PM

Post #4 of 5 (262 views)
Re: 87 GMC 5.7 ltr TBI running rich (new motor setup) Sign In

Edelbrock is a performance brand replacement that has been the "go to" for performance intakes forever.

I wonder what was done about the EGR when that was installed because I doubt it was equipped to accept one.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 13, 2019, 5:20 PM

Post #5 of 5 (252 views)
Re: 87 GMC 5.7 ltr TBI running rich (new motor setup) Sign In

HT - Familiar with about all the names of stuff for performance improvements a lot more possible to get somewhere if pre-smog engines. Not my thing. Lived it watched more cracked open engines, rear ends and folks come back for more of that. NOT MY GAME nothing seemed to work if one came along even ancient now putting it back made it drivable again. Still see the chrome stuff just looks same items. K&N has to be having trouble where I am zero tolerance for street use I think 1983 up. Trucks no longer exempted for quite some time HERE - is MA. Pictures to registry and live film showing the vehicle even underside with light! It's cruel if a thing is wrong, missing or altered.


EGRs are going to vary like nuts when they are needed up to a must have for smooth operation the intake would matter a lot for even trucks - vans or call them what you wish, for`87.
I'll never find specs or info exactly but think the EGR was made to leak vacuum right at the thing for this would NOT be a leaking diaphragm so there was a reason for it doing that was TRUCK stuff not the cars.
Back to re-think a reman engine I never approved of no real choice now for this.


OP (original poster) just try this: Pull dipstick while running at idle. Check the tube for vacuum or see (careful how you test this) if smoke will suck DOWN dipstick tube. If not this is already not right either the manifold fit or wild excessive blow-by at cylinder already a reman block that might not have been good enough to redo the prime reason I'd do anything not to go that route,


Tom







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