Low vacuum, poor idle

[fastpakr]

I'm at my wit's end with the final stage of the '99 Explorer 5.0 transplant into my '99 Ranger. Everything is installed, the truck is inspected, etc. If it ran right, I'd be done...

But it doesn't.

I'm getting about 13" of steady vacuum at the intake manifold. The engine is a fresh rebuild, and it's all stock except for a high lift/low duration cam (Comp Cams 35-510-8 / XE258HR, specs here) with matching valve springs and corrected length pushrods, plus a phenolic intake spacer.

Because of the low vacuum, I've got a crappy idle and awful off idle power. Brakes don't work well at all.

No codes at all. I've checked for vacuum leaks. While chasing down possible other issues I've verified fuel pressure and that the injectors are all firing. Fuel pump and filter are new, pressure is around 65psi. O2 sensors are new. Plugs are Autolite iridium (XP104), wires are new stock Motorcraft. Using the Torque app, IAT and ECT numbers look correct. EGR tube, valve, and DPFE hoses are new. The engine ran okay when I pulled it from the donor, so I have no reason to suspect any of the sensors or wiring that came with it.

What on earth am I missing? Idle quality is awful. It stalls sometimes when shifting into gear, and struggles with a warm restart (a WOT flood clear gets it to start). Power is decent above 3000rpm, but pretty terrible otherwise.

I took it to a local shop that I trust today, and they want to blame the cam. I'd accept that, but it's a pretty mild grind and others here have used the same one without reporting any of these issues.

 

[974X4BLACKSPORT]

Are you sure you have the cam timing is correct? That I mean that the dots on the crank gear and the cam gear where line up exactly when the timing chain was installed?
Next thing, are you sure that you dont have a large vacuum leak somewhere?
That cam should get you at least a solid 17-20" hg at idle.
Another thing that can have a large effect on engine vacuum is ignition timing (initial timing), are you sure that is dialed in properly?

 

[fastpakr]

Ignition timing isn't really adjustable, so unless I totally wrecked installing the cam synchronizer it should be good there. No codes at all, and I used the tool to set it in place.

As far as vacuum leaks - I'm not 'absolutely' sure, but I've looked all over the place and sprayed a lot of carb cleaner around trying to find something. Shop didn't see/hear anything either.

I suppose it's possible that I screwed up the cam and crank lineup, but it's not a particularly complicated procedure. Is there a way to verify that without pulling the front cover?

Thanks, by the way. It may seem like I'm arguing, but I'm just frustrated at this point.

 

[fastpakr]

For what it's worth, I had to use longer pushrods with my cam install and nobody else seems to have needed to do that. What are the odds that I got the wrong camshaft in the box? The box itself was labeled correctly.

 

[fastpakr]

Next step I think will be doing a compression test to rule out an external vacuum leak. If compression is low across the board, I suspect we're dealing with a cam issue for sure.

Anybody have other suggestions? Tagging a few off the top of my head just in case they haven't seen the thread (apologies in advance).
@VR4 @CDW6212R @vroomzoomboom @Dono @boominXplorer and any other obvious gearheads who've been around forever and/or tossed in a camshaft here and there.

 

[vroomzoomboom]

my vac/boost gauge can be off one or two sometimes, but at idle mine varies. it will be 10 one day, and 15 the next day as goofy as it sounds. i know you have said you have sprayed the motor with carb cleaner, but the best way is it "smoke" it. thats when you pull off a vacuum line (i have done it from the line going to the brake booster) and force smoke into the motor, then start looking for leaks from there. you can make a engine smoker for really cheap.



a friend made one, but instead of burning stuff inside the can, he used a element from a space heater, baby oil, a wick from a lantern and hooked it to a batter so the element will heat up.

i can also say it might be your cam, however do you have a tune for your truck as well? it might not be happy without one.
also are your rockers adjusted correctly? if they are too lose or tight, that will also cause a low vacuum, and make everything run poorly

 

[fastpakr]

If I pick up the truck tonight from the shop I'll try to do a compression and smoke test over the weekend. Had forgotten about that possibility. Thanks for the idea .

I don't have a tune at this point. Eventually I plan to get one, but I wanted to wait until the mechanical side was definitely working correctly. I know vr4 has this exact cam with no tune and none of these issues.

For what its worth, I drove it for a few minutes this morning and went full throttle all the way through second gear. Very little power until 3500 RPM, then it's still pulling hard from 4000 until it shifts just under 5000.

I'm running the stock non adjustable pedestal rockers. Pushrods should be correct length now though so I don't think that's an issue.

 

[CDW6212R]

Given the long list of new parts and vacuum checks etc, no codes, I'd suspect something else. Go back and stab the cam synchronizer again, going very methodically. I'm hoping it's off one tooth(22 degrees), or the cam gear is off and messing up the valve events(and vacuum).

Forcing smoke through the engine is a great idea to find a leak, or rule it out.

 

[fastpakr]

Can the cam synchronizer cause a change in vacuum levels? I thought it could just affect ignition timing (I'm still glad to check, just making sure I understand).

 

[boominXplorer]

I did have to run longer pushrods for my cam install, .300 longer I think with .010 shims under the rockers (don't quote me).

I'm still running my stock booster and master from the ranger even though I have an explorer rear disc axle out back.

Cam sync would give you a code. I'm going to unfortunately say your issue probably is from the cam install but where? Are you sure the pushrods arnt too long? Any valve train noise?

 

[fastpakr]

I initially failed to check the pushrod length and had tons of valve train noise. A friend helped me diagnose that issue and order new ones in the right length. Stock length is 6.248, the new ones are 6.35. I've got .040 shims to get the preload right.

I haven't touched the braking system or the axles at all yet so no concerns about mismatches there.

I installed a cam synchro incorrectly on the old 3.0 and got a code very quickly. Nothing here yet.

 

[boominXplorer]

Now that I think about it mine are actually 6.300. Can you spin the pushrods with no load on them with the rocker arm tight?

 

[fastpakr]

I'm not sure. They're set up with almost .04 preload on the lifters, so there would be at least some friction to resist that.

 

[CDW6212R]

The lifter preload should be in the .035 range, 3/4 of a turn of the rocker stud thread, isn't that still the goal.

I'd be checking the small things you can before pulling the timing cover to get at the cam/gears. be sure there's no vacuum leak, and the valve springs are installed right, and the cam synch since those are easier than the timing cover.

Do you know the set up if the valve springs, the installed height, and the coil bind height? There's a best coil bind height that determines the installed height(cam lift is part of that equation).

 

[fastpakr]

As I recall the range on the cam instructions was .02-.04, and the shim kit options forced me closer to the .04 side.

No idea on installed height, coil bind height, etc. The springs were selected by Alex's Parts based on the cam spec sheet and installed by the local performance machine shop when they did the head and block work.

 

[CDW6212R]

As I recall the range on the cam instructions was .02-.04, and the shim kit options forced me closer to the .04 side.

No idea on installed height, coil bind height, etc. The springs were selected by Alex's Parts based on the cam spec sheet and installed by the local performance machine shop when they did the head and block work.

There's usually a recommended installed height with a spring kit made or selected for a cam. That's not always obvious to find in specs. I doubt if there's anything wrong with the spring install, but best power and spring longevity comes from getting close to the coil bind height. That's one of many engine building tricks, like the piston quench height is ideally in the .040 range. I don't know the current industry goals for those, I just read of them every once in a while, when a well known engine builder talks seriously about how they make good power.

Those are just details you as a builder or owner want to check into if can.

 

[boominXplorer]

I also used the alexs parts valve springs in my build. They setup perfect for me. I've got probably 12k miles on my cam swap now without an issue. I've got just over 20k miles on the swap itself.

I also built my truck on the stock platform to work out any bugs and avoid chasing issues like questioning engine build or the install. My install went smoothly and same with the cam.

Double check everything like vacuum line routing and all ports on the bottom of the intake manifold or going to evap valve.

 

[fastpakr]

I'm going to pick the truck back up on the morning and try to go over it all again carefully. You guys may be inundated with pictures of vacuum lines as I confirm things.

Thanks again for all the help. I truly appreciate it.

 

[fastpakr]

I did my best with an impromptu walk through of how everything is connected.

 

[fastpakr]

Cylinder compression 1 through 8 respectively: 145, 150, 150, 145, 145, 159, 145, 159