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'96 Subaru 2.5 AT: rebuilt engine: perfect idle, no power on acceleration

 

'91 Vanagon, '96 EJ25 AT
?
I damaged the crankshaft of my 35,000 mile engine, so I found another '96 EJ25 and rebuilt using the small block of a 'known running' second engine with 121,000 miles. I used the heads from the 35,000 mile first engine. New timing components. New pumps. Both engines have heads w/buckets and no shims- so same engine, right?
?
The engine was reinstalled a year ago- idles perfect, but it has little/no power on acceleration and before long throws misfire codes for multiple if not all cylinders. Otherwise, there haven't been any codes.
?
I feel like I've gone over everything:
- replaced plugs, wires, coil
- replaced throttle position sensor
- replaced crankshaft position sensor
- replaced front O2 sensor
- new PCV valve
- cleaned MAF, replaced with spare MAF
- cleaned EGR, replaced with spare EGR
- IAC adjusts when swiveling the top/idle adjustment
- new fuel pump; pump functions
- new fuel filter
- new air filter
- new neutral position switch
- new ignition switch
- injectors are firing, have not replaced injectors
- compression test okay all cylinders
- oil pressure better than okay
- timing checked
- vacuum hoses replaced
- replaced VSS: ECU has speed reading
- tank mostly full with Shell '91 octane, also has a bottle of fuel system/injector cleaner in the tank
- transmission has no more than 3k miles on it after rebuild
- installed adjustable fuel pressure regulator in series after the Subaru FPR. Holds fuel pressure at 36psi
- spare ECU has the same result
- using Torque app, all readings appear within spec.
?
Every time I try something, I feel like I am just one step away from this thing working- but I've felt that way for a year now!
?
What am I missing???
 

开云体育

Morning Mr. Hersh.
You’ve certainly done your due diligence!
Here are a few suggestions.

Check/clean ground connections, especially those serving the intake manifold, engine to frame, and ECU to frame.
You replaced the plugs/wires/coil but there is a chance that you got a new-bad part in that mix. ?Is there a chance you could take the old parts and swap them in for a test?
You state that your timing is spot on. ?I’m going to hold you to that as an improperly installed timing belt could result in the symptoms you mentioned.
Question: ?You mentioned it has little to no power on acceleration. ?Is the symptom the same in neutral when just revving the engine?
Is your catalytic converter clogged?

Hope we can get you through this.
Best,
Brent

On Aug 8, 2024, at 8:37?AM, walking upstream via groups.io <walkingupstream@...> wrote:

'91 Vanagon, '96 EJ25 AT
?
I damaged the crankshaft of my 35,000 mile engine, so I found another '96 EJ25 and rebuilt using the small block of a 'known running' second engine with 121,000 miles. I used the heads from the 35,000 mile first engine. New timing components. New pumps. Both engines have heads w/buckets and no shims- so same engine, right?
?
The engine was reinstalled a year ago- idles perfect, but it has little/no power on acceleration and before long throws misfire codes for multiple if not all cylinders. Otherwise, there haven't been any codes.
?
I feel like I've gone over everything:
- replaced plugs, wires, coil
- replaced throttle position sensor
- replaced crankshaft position sensor
- replaced front O2 sensor
- new PCV valve
- cleaned MAF, replaced with spare MAF
- cleaned EGR, replaced with spare EGR
- IAC adjusts when swiveling the top/idle adjustment
- new fuel pump; pump functions
- new fuel filter
- new air filter
- new neutral position switch
- new ignition switch
- injectors are firing, have not replaced injectors
- compression test okay all cylinders
- oil pressure better than okay
- timing checked
- vacuum hoses replaced
- replaced VSS: ECU has speed reading
- tank mostly full with Shell '91 octane, also has a bottle of fuel system/injector cleaner in the tank
- transmission has no more than 3k miles on it after rebuild
- installed adjustable fuel pressure regulator in series after the Subaru FPR. Holds fuel pressure at 36psi
- spare ECU has the same result
- using Torque app, all readings appear within spec.
?
Every time I try something, I feel like I am just one step away from this thing working- but I've felt that way for a year now!
?
What am I missing???
 

Have You confirmed that AT is in 1st @ start out,,,
Is it possible that Cat or Muffler are clogged,,,
Have You tested with O2Snsrs disconnected,,,
 

Thank you-?
?
Among my laundry list, I forgot to mention a replaced Cat with no change in symptom. It's possible to have gotten a new-bad part- but I really hope not.
?
I can't confirm that the muffler is not clogged; how might I do that?
?
If in park and I rev the engine, it is no problem, sounds and feels good- there is only a problem when in gear and driving. It feels good going through 1st gear, but gets all sputtery in 2nd.
?
I tested previously with O2 sensors disconnected with no difference in performance
 

Is your fuel pump noisy..cavitation...fuel pressure changes under load...I had a similar issue...install a fuel pressure gauge and setup my IPhone to video the gauge while driving...and saw the pressure was way low under load...air lock from fuel tank to fuel pump would not allow enough fuel to keep up the pressure needed...purged the air and all is great
Rod

On Thu, Aug 8, 2024 at 6:11?PM walking upstream via <walkingupstream=[email protected]> wrote:
Thank you-?
?
Among my laundry list, I forgot to mention a replaced Cat with no change in symptom. It's possible to have gotten a new-bad part- but I really hope not.
?
I can't confirm that the muffler is not clogged; how might I do that?
?
If in park and I rev the engine, it is no problem, sounds and feels good- there is only a problem when in gear and driving. It feels good going through 1st gear, but gets all sputtery in 2nd.
?
I tested previously with O2 sensors disconnected with no difference in performance
 

Is it the engine or the transmission? How did you install the torque converter - 3 clicks to set? Then connect the engine to bellhousing and TC to flexplate? Was TC distance within spec (3/8 inch or whatever it is from end of bellhousing?
 

This is a good question. I did not install the transmission.? Both engine and transmission were out of the van at a guy's shop. He bolted both transmission and engine back into the van and then sent me on my way (long story) to tow it home and finish the installation. I had to do all final hookup: wiring and hoses.

What should I look for or do to ensure it is correct?

On Sat, Aug 10, 2024, 8:12?AM Wayne Sitarz via <wesitarz=[email protected]> wrote:
Is it the engine or the transmission? How did you install the torque converter - 3 clicks to set? Then connect the engine to bellhousing and TC to flexplate? Was TC distance within spec (3/8 inch or whatever it is from end of bellhousing?

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