Low vacuum, poor idle

[vroomzoomboom]

that rules out valves

 

[fastpakr]

Pointing away from the cam as a root cause, correct? If that's the case, I need to focus more on a smoke test. Any quick thoughts on the vacuum line video?

Thanks again.

 

[974X4BLACKSPORT]

You cranking compression looks real good. I understand the 5.0 ha D.I.S., however, if you have not put a timing light on it to watch the ignition timing at idle (may need to install timing tape on harmonic balancer), then you don't know what it is doing, and you cant rule out spark timing.

 

[donalds]

I'll bet that the word " timing " is used more than any other word on this forum lolol

 

[fastpakr]

With computer controlled running, what would I be looking for? On the TFI system there was a SPOUT plug to disconnect to verify base timing. Not sure whether there's an equivalent with EDIS.

 

[974X4BLACKSPORT]

The computer controls the spark timing, but if the computer does not have the exact location of both the crank and camshaft, the spark timing will be way off, even a little bit, say...10 degrees ATD will make it run baaad.

 

[boominXplorer]

Compression seems a tad low. When you installed the timing chain did you use a standard chain and sprocket or an adjustable cam gear? Installed it at 0* I assume if so?

 

[fastpakr]

I'm not positive about the accuracy of the gauge. It has been sitting in my garage for years, no idea when I last used it.

Timing set is a non adjustable sealed power kit that I intended to set to zero degrees.

 

[fastpakr]

The computer controls the spark timing, but if the computer does not have the exact location of both the crank and camshaft, the spark timing will be way off, even a little bit, say...10 degrees ATD will make it run baaad.

On cold start I got 10* BTDC, progressing to almost 30 as it warmed up. Ignition timing seems good.

 

[fastpakr]

I went all over the engine yesterday afternoon trying to find a possible vacuum leak. Wasn't able to throw a smoke tester together, but I stuck a meter on while I disconnected and plugged every vacuum source I could with no significant change to vacuum levels.

At this point, is it reasonable to focus on a screwed up timing chain installation? Compression seems to point away from a cam grind issue, ignition timing looks good, and an external vacuum leak seems unlikely.

 

[boominXplorer]

The timing chain is pretty easy to install but you can be off a link if your not careful. I am not sure if the truck is smart enough to throw a cam/crank correlation code like newer vehicles letting you know it's off.

Are you getting any codes? Still running stock injectors?

 

[fastpakr]

No codes at all, and still running stock injectors. I checked with a stethoscope to ensure they're all mechanically functional.

 

[CDW6212R]

Did the intake ever come off, is there any chance the intake gaskets might be leaking?

 

[boominXplorer]

I am not leaning towards intake / vacuum leak as after a few drive cycles a p0171/174 would have come up by now. You have left the battery connected through a few drive cycles I assume?

 

[fastpakr]

Did the intake ever come off, is there any chance the intake gaskets might be leaking?

The upper intake has been off several times (fix an EGR leak and on the way to swap the pushrods) and the lower has been off once during the pushrod replacement. The vacuum issue has been consistent throughout all of this.

I am not leaning towards intake / vacuum leak as after a few drive cycles a p0171/174 would have come up by now. You have left the battery connected through a few drive cycles I assume?

Yes, the battery has been connected virtually the entire time and no codes have appeared at all.

 

[Turdle]

Ok, before going in the timing cover, and since you would have to remove this anyway, remove the fan. This will eliminate fan wash wind .

Now with engine running, use an un lit, ( no flame) propane torch, let the propane flow around the vacuum fittings. Pay special attention to the metal elbows under the upper plennum. These are pressed in and often work loose. Removing the fan will help to pinpoint the propane application.

It'll take more of a vacuum leak than this to trigger p0171-174 on the v8 pcm. You should be pulling at least 17 in of vacuum with that cam.

If the timing was off you'd be getting a cam sensor code for sure. My bet is some propane and no fan wash will find t vacuum leak.

 

[boominXplorer]

To add it is possible to put the cam gear off a tooth but correctly time the cam sync to the crank when installing it and not have a code. It is kinda obvious to be off a tooth when installing the timing set but stuff happens.

Have you put 25 miles on it and drove it 5 different warm up cycles? For sure a lean code would show up by then.

 

[fastpakr]

Ok, before going in the timing cover, and since you would have to remove this anyway, remove the fan. This will eliminate fan wash wind .

Now with engine running, use an un lit, ( no flame) propane torch, let the propane flow around the vacuum fittings. Pay special attention to the metal elbows under the upper plennum. These are pressed in and often work loose. Removing the fan will help to pinpoint the propane application.

It'll take more of a vacuum leak than this to trigger p0171-174 on the v8 pcm. You should be pulling at least 17 in of vacuum with that cam.

If the timing was off you'd be getting a cam sensor code for sure. My bet is some propane and no fan wash will find t vacuum leak.

I've done that and got no indication of an external leak with a propane torch or carb cleaner. Also no clear noise like you'd associate with a vacuum leak.

To add it is possible to put the cam gear off a tooth but correctly time the cam sync to the crank when installing it and not have a code. It is kinda obvious to be off a tooth when installing the timing set but stuff happens.

Have you put 25 miles on it and drove it 5 different warm up cycles? For sure a lean code would show up by then.

I think so, but wouldn't swear to it given that the battery was disconnected while pulling the lower intake for the pushrod swap. It may not have accumulated 25 miles before or after. All that said, it behaves like it's running extremely rich rather than lean. O2's indicate a rich condition, and on a warm restart I have to go to WOT to clear out the cylinders before it will fire.

 

[Turdle]

Would an exhaust restriction cause low vacuum?

sorry if I missed this, but what does the vacuum gauge do with slow throttle input? does it drop off and rise back up or just drop off?

 

[fastpakr]

I'll have to check on the vacuum gauge question. Sometime this evening. I do know that the donor engine ran okay, so unless something took up residence in the y-pipe or converters, there shouldn't be an issue there.