Engine timing puzzler - Fixed

[Tripwire]

I had my 4.2 rebuilt by a reputable shop and ever since i cant seem to get the timing correct ( the timing mark on the ballancer is WAY off)

I seem to remember RE- checking the gear/chain setup at some point because i thought that might be the issue ( my factory manual has fingerprints and notes in that section)

The engine always idles real high 1000 RPMS sometime a bit more. the rpms stay high when shifting and dont drop like a normal rig

the timing hash mark is at the 12:00 position when looking with a strobe light and i cant get it anywhere near the timing marks on the cover.

the isle set screw is backed all the way out and i dont have any vac leaks ( i have 22-24 HG at 1000 RPMS

I have bypassed the IAC motor ( set it to zero) and disconnected and that helps some

I think the chain has slipped or the cam gear is not the correct one - is that possible?

I set the dizzy in corrctly ( at least 20 times) #1 cylinder on compression stroke , feel it move to the top, set the timing mark on the balancer to 0 TDC
and dropped in the dizzy... I have to rotate it around to find the spot it wants to start and run worth a darn....cant use timing marks just by ear till it wont ping...it drives great and has power - just an annoying high RPM at idle

Right now i have the manifold vac advance line plugged as hooking it up causes the engine to idle even faster

i really just do not understand.. help me Obi-Wan

[babywag]

Have you ever done an IAC reset/min. idle adjustment?

What's the TPS voltage @ closed throttle?

100% sure you don't have a vacuum leak somewhere?

[Tripwire]

I shorted the A-B connector pins and adjusted the stop screw, thats how its done right? i suppose i could have a vac leak...i will look deeper....but why is the !@#$ timing so far off?

[babywag]

If the throttle stop screw is all the way backed out, and the IAC is closed, the engine should stall.
It's getting air from somewhere or it wouldn't run.

The set screw is NOT to control/adjust the idle speed, the ECM does that.

Either something is holding the throttle plates open, or you have a vacuum leak.

[Tripwire]

I'm on it like white on rice....may take a few days i will post up, thanks !

one shorts a-b with the key on then starts the engine right? that sets the IAC to zero/closed position?

i will check the TPS voltage with my laptop...good tip i did not think of that

[babywag]

No...
jumper wires, key on, IAC closes, unplug IAC, key off, remove jumper
THEN start engine and adjust min. idle speed and tps.

Verify IAC goes to zero in WinALDL or whatever you're using.
Check after starting to see if IAC is actually closed and not sucking air.

Howell and high idle problems are pretty common as well...

[Tripwire]

if i unplug the IAC how do i check the VDC with the laptop....there would be zero right? - or would that be a clue to a wiring issue?

ill bet you are right about the vac leak - fun

[babywag]

WinALDL will show IAC counts...when jumpered and key on they should drop to zero.

[Tripwire]

Do i need to disconnect the battery for a few minutes to clear the ECM programming? i would assume it would retain the Old IAC stepper calibration?

[babywag]

Do i need to disconnect the battery for a few minutes to clear the ECM programming? i would assume it would retain the Old IAC stepper calibration?

No...just the steps above.

[Tripwire]

I am going to tackle sunday the Vac leak issue, i was planning on using my propane soldering tool for copper pipes with a piece of tubing to direct the gas around the engine seals...

any better ideas?

[babywag]

I've always just used carb spray or brake cleaner, but I'm sure propane would work just as well.
If rpm changes you found the leak.

[Tripwire]

You were right - it was a Vac leak at the gasket for the throttle body - one of the screw threads had decided it no longer wished to keep the TBI attached to the adaptor plate, a new gasket and a longer bolt solved the issue.

After adjusting everything my timing is at 8 degrees , it still ran a little bit high in RPM so i switched the vac advance from manifold to ported vac and she idles at 800 RPM

[babywag]

Now you can reset the TB as described above, and verify TPS is adjusted correctly.

Highly recommend adding timing control, and get a tune on that thing so it runs properly.

[Tripwire]

i did not know the TPS was adjustable i will have a look at that and check its voltage at idle. I really dont want to spend the money right now on timing control, i dont drive the rig that much