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OutofTime's avatar
OutofTime
Explorer III
Mar 01, 2023
Solved

Difficulty timing a 1995 Chevy 454ci

I'm helping my brother clean up a 1995 Gulfstream Sunsport that is built on top of a 1994 Chevy P30 Chassis. It comes with a Chevy 454 big block v8. For the life of me I can't get the thing to fire ...
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  • OutofTime's avatar
    OutofTime
    Feb 10, 2024

    Hello all.  It's been awhile but I can finally put to rest why this 454 ran so poorly.  My brother and I are currently doing an engine swap for his RV and we finally had the chance to pull the intake manifold... broken and bent pushrods everywhere.  A lifter was out of it's hole as well.  I'm not sure if a pushrod escaped due to bad lash, or a cam lobe wiped, or a valve got stuck but I think one rod got loose then started banging around damaging others.  I'm pretty impressed it was even starting on command.

    The 454 we are putting in has no such issues so I think as long as I put everything back together correctly the engine issue should  finally be put to rest.  I am filming the process of engine removal and installation if anyone would be interested in that.

udidwht's avatar
udidwht
Explorer
Mar 14, 2023
OutofTime wrote:
I have updates. Today I worked with my brother and we got the base timing set to 4 degrees BTDC using a timing light. Once computer advance turned on it advance to around 16 BTDC at idle. It seems to be idling much better and will idle around 850rpm or so when warmed up and on closed loop running.

However, it's still running a bit rich and still stumbling and falling on its face when revved. I pulled the IAC, cleaned it and the bore it sits in and checked for operation. I did see the pentile tip move in the throttle body when I turned the key to the run position.

I checked the voltage on the TPS and at full stop it read .568V, which is within spec I believe.

At this point I'm thinking my next move to fix this rich running is to replace the FPR.


The advance at 16 after connecting the distributor wire is correct.

Idle at normal operating temp should be 800rpm. There is an idle set screw covered by the factory on the front side facing forward. Is it covered? If it is don't mess with it. If it isn't covered then it's likely some PO did mess with it.

The coolant temp sensor in the front side of the intake manifold will need to be checked. If it's running rich after warm up it is likely bad.

Get a ohm meter and ohm it out.

Coolant sensor approximate resistance specifications:

177 ohms @ 212 deg. F. or 100 deg. C.
241 ohms @ 194 deg. F. or 90 deg. C.
332 ohms @ 176 deg. F. or 80 deg. C.
467 ohms @ 158 deg. F. or 70 deg. C.
667 ohms @ 140 deg. F. or 60 deg. C.
973 ohms @ 122 deg. F. or 50 deg. C.
1188 ohms @ 113 deg. F. or45 deg. C.
1459 ohms @ 104 deg. F. or 40 deg. C.
1802 ohms @ 95 deg. F. or 35 deg. C.
2238 ohms @ 86 deg. F. or 30 deg. C.
2796 ohms @ 77 deg. F. or 25 deg. C.
3520 ohms @ 68 deg. F. or 20 deg. C.
4450 ohms @ 59 deg. F. or 15 deg. C.
5670 ohms @ 50 deg. F. or 10 deg. C.
7280 ohms @ 41 deg. F. or 5 deg. C.
9420 ohms @ 32 deg. F. or 0 deg. C.
12300 ohms @ 23 deg. F. or -5 deg. C.
16180 ohms @ 14 deg. F. or -10 deg. C.
21450 ohms @ 5 deg. F. or -15 deg. C.
28680 ohms @ -4 deg. F. or -20 deg. C.
52700 ohms @ -22 deg. F. or -30 deg. C.
100700 ohms @ -40 deg. F. or - 40 deg. C.


For TPS info:

https://www.gmcmi.com/wp-content/uploads/2013/02/TBI-Initial-calibration.pdf

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