Leak down Test Results Question

[suprunner]

Hi all,

EJ251 shortblock, EJ25 D heads, STI gaskets

I'm getting an unbalanced shake/hesitation from 1800-2500 rpm. I can't effectively accelerate until rpms are above 2500. Taking off from a stop, the car feels bogged down.

Plugs, Wires are less than a year old. Fuel pump/filter/strainer within 6 months. Coil and ignition module are within spec according to an FSM that I read. There was a vacuum leak with the purge solenoid under the intake manifold. It was not operating. Before I found that, my STFT, and LTFT indicated (at idle) 3-10%, and 18-25% respectively. After plugging the vacuum line I have the numbers seen in the photo below. 

 I just did a leak-down test. According to the gauges, I'm within 10% for each cylinder. ALTHOUGH, I do hear/feel air escaping through the intake, and the oil filler tube. I followed this for instructions: 

I have also done multiple compression tests. For cylinder #3 is 225 psi, the remaining cylinders are between 210 and 215 psi. Can one cylinder being higher than the rest cause an unbalancing/misfire/poor low-end acceleration? Even if the numbers are good, the fact that I have air coming through the oil filler tube and intake, does this suggest the motor is shot? 

Check my timing again? Is there any change in timing instructions when mating an EJ251 with 25D heads? The heads are closer together, and the bolt holes for the intake manifold needed to be filed down a bit in order to properly bolt it onto the long-block. I've done a smoke test in/around the intake/intake manifold/hoses etc, and don't come up with anything. 

 

Thanks for the help,

 

Greg

 

 

Edited December 2, 2020 by suprunner

[suprunner]

[1 Lucky Texan]

I feel it's worth checking for a slight timing belt slip - bring the marks on the pulleys around to belt install position, and do a tooth count. You can find tooth counts on line for different Subaru engines.

[wtdash]

1st: Post your Ride - year/model  - A$$uming this is a '90-'98/'99 if you're running those heads.

2nd: Did it EVER run right after the engine install?

3rd: Hopefully the smart guys will reply as I'm not an engine expurt....but those #'s comp/LD all seem 'good nuf'. 

4th: Those are the good gaskets (depending on STi-based year), but I didn't know they were that skinny. Did you double-check your clearance between pistons/valves etc? The '99 OB/GT/SUS use a similar engine (Phase 1 heads on Phase 2 block) but pretty sure the pistons are Phase 1.

5th: My guess (!) is that you  have a vacuum leak - maybe the IM isn't sealed since you had to mod-2-fit? 

6th: And if your CEL is on what are the CURRENT codes - after they're cleared/ECU reset?

Edit:...I'm thinking 1LT is on track. If you had to mod the IM, the timing is likely suspect, but not sure how it affects the comp/LD tests if it IS off?

Td

Edited December 3, 2020 by wtdash

[nvu]

For the slightly shorter block and needing to open up the holes on the intake, I've ran into this before with using an ej257 block on an ej22 intake.  The slight shortening causes more slack on the passenger side cam.  This was sohc and the timing was maybe just under 1/2 tooth off, everything worked ok.  Maybe for dohc the differences matter more with 4 cams in the mix.

There are adjustable eccentric idlers that can correct for this, but I don't know who makes them anymore.  Last set I used was maybe 2015 from lic motorsports to correct an ej257 with overmachined ej255 heads.  They're no longer around.

[idosubaru]

Those compression numbers are good. that small difference is not even close to an indicator of issues.

No check engine light?

Have you checked timing marks?  Were the heads milled or shaved or tested to be within spec?

[suprunner]

6 hours ago, wtdash said:

1st: Post your Ride - year/model  - A$$uming this is a '90-'98/'99 if you're running those heads.

2nd: Did it EVER run right after the engine install?

3rd: Hopefully the smart guys will reply as I'm not an engine expurt....but those #'s comp/LD all seem 'good nuf'. 

4th: Those are the good gaskets (depending on STi-based year), but I didn't know they were that skinny. Did you double-check your clearance between pistons/valves etc? The '99 OB/GT/SUS use a similar engine (Phase 1 heads on Phase 2 block) but pretty sure the pistons are Phase 1.

5th: My guess (!) is that you  have a vacuum leak - maybe the IM isn't sealed since you had to mod-2-fit? 

6th: And if your CEL is on what are the CURRENT codes - after they're cleared/ECU reset?

Edit:...I'm thinking 1LT is on track. If you had to mod the IM, the timing is likely suspect, but not sure how it affects the comp/LD tests if it IS off?

Td

The body is a '98 OBW. The motor was originally put together and placed in a '96 Lego.

From the beginning it has always had a shake/unbalanced feeling between the RPM ranges of 1800-2500. It gets worse when it is not at operating temp, and/or the ambient temperatures cool down. Now, if I want to lightly cruise in any gear at 2400 rpm, it is starting to almost buck me around. It doesn't feel like I'm lugging the motor, it's a different symptom. I've driven ej22 Lego wagons with 15" steel rims and BFG TA/KOs at the same RPMs and gears (obviously lugging, but I was young, and hyperbole makes a point) and not felt this.  We've been in the 40's in the mornings/evenings here in 'Vegas. It now also momentarily stalls anytime I touch the accelerator upon startup for the first 45-50 seconds, or 6-10 depressions of the accelerator...whichever comes first. Above 2500 rpm, the motor runs very nicely. Smooth and powerful all the way to redline. Temp sensor is brand new too. 

How else can I check for a vacuum leak if I've already done a smoke test, AND i've also used a propane torch... I think my fuel trims are within spec? I replaced the intake manifold gaskets last summer. They were only about 3 years old. No change. I used a small amount of Toyota FIPG above and below the gasket to help ensure a good seal. 

No CEL. I was getting misfire codes, but they went away after I blocked off the purge valve solenoid. It was allowing a full-time vent from the fuel tank, and the fuel trims were way out of spec according to @GeneralDisorder. 

Edited December 4, 2020 by suprunner

[suprunner]

30 minutes ago, idosubaru said:

Those compression numbers are good. that small difference is not even close to an indicator of issues.

No check engine light?

Have you checked timing marks?  Were the heads milled or shaved or tested to be within spec?

No CEL anymore. I had misfire codes before I found the purge valve solenoid was defective. Now nothing pops up. I will check timing marks soon. In your opinion where should I be aligning the Intake marks with? I've used the marks on the timing cover, but I've read conflicting remarks... That I should use the seam(s) of the valve covers or head-to-block interface as the vertical orientation. 

[suprunner]

6 hours ago, nvu said:

For the slightly shorter block and needing to open up the holes on the intake, I've ran into this before with using an ej257 block on an ej22 intake.  The slight shortening causes more slack on the passenger side cam.  This was sohc and the timing was maybe just under 1/2 tooth off, everything worked ok.  Maybe for dohc the differences matter more with 4 cams in the mix.

There are adjustable eccentric idlers that can correct for this, but I don't know who makes them anymore.  Last set I used was maybe 2015 from lic motorsports to correct an ej257 with overmachined ej255 heads.  They're no longer around.

Yes, I originally was running JUST the DOHC timing components, but I later put in a tensioner-idler bracket from a 251 or 253, that had an extra idler bearing on it. That didn't make a difference. Sounds like I need to check timing again. I've looked at timing quite a bit on this motor. I've put together toyota motors, and quite a few ej25Ds with their timing components, and never had an issue. 

Can you have too high of compression? I run a blend of 91 and 100 octane. I've run straight 100, but there's no difference. Same symptoms. 

[wtdash]

May have missed it but did you count teeth on the Tbelt? That's the 'safest' way to ensure timing (or so I've read).

 

[1 Lucky Texan]

since there seems to be a difference idle vs cruise rpms and cold vs warm, kinda thinking live data would help a lot. check sengine temp readings and fuel trims at idle vs higher rpms, etc.

 

NGK plugs with proper gap?

plug wires in good shape? try spraying them and the coil with water from a spray bottle.

no oil on plug boots?

[idosubaru]

13 hours ago, suprunner said:

In your opinion where should I be aligning the Intake marks with? I've used the marks on the timing cover, but I've read conflicting remarks... That I should use the seam(s) of the valve covers or head-to-block interface as the vertical orientation. 

I'd be more worried about the crank than cams.  Use the flywheel/flexplate for crank alignment in case the crank sprocket/keyway is hogged up from prior issues. 

As for cams - if it's off enough to cause very poor drivability I think either way is fine.  To start this is more like "are there two elephants or one", rather than "break out the micrometer".   

Have a glance at both the cover marks and block seams, you can't see one without looking at the other so just look and see - if the covers are loose or seem off (missing bolts, cracked, prior work) it should be clear they're not lining up and you can see when you're in there staring at both of them. 

Edited December 4, 2020 by idosubaru

[suprunner]

On 12/4/2020 at 6:07 AM, idosubaru said:

I'd be more worried about the crank than cams.  Use the flywheel/flexplate for crank alignment in case the crank sprocket/keyway is hogged up from prior issues. 

As for cams - if it's off enough to cause very poor drivability I think either way is fine.  To start this is more like "are there two elephants or one", rather than "break out the micrometer".   

Have a glance at both the cover marks and block seams, you can't see one without looking at the other so just look and see - if the covers are loose or seem off (missing bolts, cracked, prior work) it should be clear they're not lining up and you can see when you're in there staring at both of them. 

I'll do that, thank you. The covers are brand new along with the cam gears. 

[suprunner]

On 12/3/2020 at 11:30 PM, 1 Lucky Texan said:

since there seems to be a difference idle vs cruise rpms and cold vs warm, kinda thinking live data would help a lot. check sengine temp readings and fuel trims at idle vs higher rpms, etc.

 

NGK plugs with proper gap?

plug wires in good shape? try spraying them and the coil with water from a spray bottle.

no oil on plug boots?

No Oil on plug boots, Plugs are maybe 5 months old from the factory with less than 8000 miles on them. I will try the water-bottle spraying. What should I be looking for? Recreation of stumbling? Arcing? 

 

Greg

[suprunner]

On 12/3/2020 at 6:29 PM, wtdash said:

May have missed it but did you count teeth on the Tbelt? That's the 'safest' way to ensure timing (or so I've read).

 

Thank you for pointing this out. I didn't mention it. When I do the timing, I count timing marks when doing alignment. 

Z1: 54.5 tooth length Z2: 51 tooth length Z3: 28 tooth length

[idosubaru]

58 minutes ago, suprunner said:

I'll do that, thank you. The covers are brand new along with the cam gears. 

Yeah then it doesn’t matter what you look at.  The belt and sprockets can only be exactly right or off  by some multiple of teeth - it can’t be off by a little bit.  So as long as you’re looking at an engine that’s not beat up in some way, has new covers bolted on right, you’re looking straight on and share, and not hacking it from a weird angle - you can only be exactly right or obviously off. 

Edited December 9, 2020 by idosubaru

[1 Lucky Texan]

yeah, see if a mist of water on the wires or the coil cause stumbling/missing. Some folks do it at night and can see arcing.

[suprunner]

On 12/10/2020 at 10:26 AM, 1 Lucky Texan said:

yeah, see if a mist of water on the wires or the coil cause stumbling/missing. Some folks do it at night and can see arcing.

Nothing to report on this.