Low power/low vacuum

[fastpakr]

I'm 99% done with the 5.0 conversion on my '99, up to the point of driving it around the neighborhood for a few short test trips. That's created some questions that I've failed to find the answers for, so I'm reaching out for ideas...

Quick info: Full rebuild with a mild cam and an intake spacer. 4R70W trans, 4406 case. Ultrasonic clean of the injectors with new wiring connectors (each of them broke during removal).

Pre-drive symptoms included a rough/chugging idle.

On the initial drive, I noticed that the brakes were wonky. Brief power assist when hitting the pedal, then it would disappear and the engine would stall. I thought it was the booster, but a vacuum gauge on the intake manifold only shows 13 inches. I disconnected and plugged the booster line, then drove it again. No more stalling and the brakes felt normal (aside from getting a leg press workout trying to stop), but the engine's still running rough and on a short near full throttle burst I didn't get nearly the power I was expecting. Enough to get moving, but more like a lethargic tired V6 than a freshly rebuilt 8.

No check engine light (pending or otherwise) according to Torque.
Fuel pressure is showing 70psi on my gauge at idle (spec is 65+/-5 IIRC).
Each plug wire is making the timing light flash (and all plugs and wires are new).
Unplugging the IAC causes an immediate stall. Capping each vacuum line from the intake manifold seems to have no effect on the vacuum gauge. An unlit propane torch also has no effect when moving it near all vacuum lines.
Short term fuel trim is 1-3% on both sides, long term around 15%.
IAT shows 107.6* which seems reasonable.
MAF reading at idle is about 7.3g/s
O2's are fluctuating wildly like I'd expect, except the bank 2 downstream sensor which seems stuck at .065 volts (all O2's are new).
Timing advance comes up at 15*, TPS at 18.82% (both at idle).
Idle speed is averaging around 750RPM.

In 'test results' on Torque, the only fail I get shows up as 'TID: $41 CID:$12' with an allowed max of 896 vs actual of 65,371. I -think- this PID has something to do with the DPFE system, but not sure. For what it's worth, there's also a new EGR valve, tube, and DPFE hoses.

What am I missing? Acts like a misfire, but I can't confirm it. Is there an easy way to test the injectors?

The original donor engine drove fairly well on the trip to the house and I'm using the same exhaust collector/upstream cats, so I don't think there's any issue with the converters. Right now there's no exhaust after the converters at all.

Rough idle:

https://www.youtube.com/watch?v=aZreKiwup2s

Vacuum gauge at idle:

https://www.youtube.com/watch?v=0B7fDR9MLfc

 

[RonD]

Yes, partially blocked exhaust will lower vacuum and reduce power, but it would stall out engine as RPMs increased and the back pressure went up

The 13" vacuum doesn't read right with "mild cam".

There are no vacuum leaks if unplugging IAC Valve drops RPMs down on warmed up engine.

Most Big cams will come with "warning" label that 14" is max vacuum for vehicle systems, so vacuum pump would be added

Standard cam vacuum should show 18-20", mild cam maybe 16-18"
Can't see losing 5" with mild cam UNLESS........
Timing mark on cam gear is off, which would also mean low power

I would do compression test to take that off the table

 

[fastpakr]

Yeah, I know the 13 inches is way too low for the cam I've got. Will do a compression test and follow up. Thanks for that suggestion.

I really, really hope the cam isn't timed wrong...

Camshaft specs are here (Comp Cams XE258-HR aka 35-510-8):
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1055&sb=2

 

[fastpakr]

Ron - wouldn't a misfire also cause a low vacuum reading? Thought I'd read that, but not sure.

Assuming the compression test shows an issue - how do you actually check cam timing? I know you can get a kit to degree one, but that's usually done with the heads off and the engine out of the vehicle.

 

[scotts90ranger]

stupid question, but it's something I would probably do on accident since I work on GM engines every day at work... did you connect the plug wires on the coil pack right? Ford's are numbered 1234 down one side and 5678 down the other instead of 1357 and 2468 like a GM...

Other than that I'm not sure at the moment.

 

[fastpakr]

Worth checking. I was cautious about it, but at this point I'll give it another look.

 

[RonD]

Misfire would show as a vibrating vacuum gauge needle, steady up and down of the needle.

You could pull a spark plug wire to mimic misfire reading on the vacuum gauge.

Also REV engine and watch vacuum level as RPMs drop with throttle plate closed, should go above 20+"

And when you quickly open throttle to REV engine you should see needle drop to 0" quickly, that means exhaust is not blocked, and then a quick jump to 20+" when throttle plate closes.


Yes, +1 on firing order, I get that wrong all the time, and would SWEAR it was right,

The Ford 302(5.0l) also used TWO different firing orders/Cams, crank and pistons were same Matched Pairs, but the Cams were different
1-5-4-2-6-3-7-8 was common 302 order
1-3-7-2-6-5-4-8 was alternate and usually only used with 351, 302HO used this as well

5 and 3, 4 and 7 are reversed in the firing order
If you put in a 351(or 302HO) cam then you just need to change the firing order, thats the only difference

But...............with Ford's Waste Spark system it shouldn't matter because 3 and 5 BOTH get spark at every TDC, same for 4 and 7, so no change would be needed

 

[fastpakr]

It's using the HO firing order from the factory. Verified that it's set correct. Had a far more experienced friend give me a hand looking at it and he instantly questioned the valve train noise when he heard it running. We pulled the valve covers and lower intake, then verified that the lifters are fully pumped up but with slack in the pushrods when the valves are closed. Ergo, I'm an idiot and failed to check pushrod length.

Easy fix.

 

[Craig0320]

Thought I heard a lifter noise on the very first video. ?

 

[RonD]

Yes, that would cause the low vacuum and low power

 

[fastpakr]

Son of a...

Fixed the pushrods. Valve noise is gone now.
Idle issue and low power remain. Vacuum gauge still shows about 13".

What on earth am I missing here?

 

[Craig0320]

Whats your spark plug gap?

 

[fastpakr]

I don't remember off the top of my head. They're Autolite iridium plugs that theoretically shouldn't need to be gapped. Can a plug misfire cause a vacuum issue of that magnitude?

I let a local shop that I trust look at it this morning. They're convinced it's the cam causing the problem, but I wasn't expecting a lift increase to do this. Especially when others have used the same cam with no issues.

 

[85_Ranger4x4]

What cam is it?

 

[fastpakr]

Comp Cams XE258HR / 35-510-8