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Recent 87.5 XT partial rebuild with a few hiccups


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#1 mdcc2010

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Posted 26 February 2013 - 10:26 PM

So I fairly recently reassembled my XT's EA82T. I replaced the very blown head gaskets and every other gasket on the engine except the rear main seal, removed as much corrosion as possible and painted any rusty bits (mostly pipes), had the heads pressure-tested and resurfaced, all new rubber hoses (coolant, oil, fuel, and vacuum), new fuel and air filters, new timing tensioners and springs (the belts are used but good, reused in case there were leaks and because I'm running without any covers until I get new ones), new plugs and wires, and as thorough a cleaning as possible with the short block in situ.
It usually runs well enough and has good power when it starts and is up to temperature, but has some issues:

*There's a bit of a light clink-y noise from the LH side of the engine most noticeable at low engine speed when warm. It's not TOD, but pulling the spark plugs doesn't change its nature, so it's likely to be somewhere in the valvetrain. The lifters and HLAs looked and felt good when I put it all back together, but it's possible something is out of spec.

*The computer sometimes flashes the CEL and shows a TPS code while driving (probably a dead spot in the range), but that's it; no other problems show up. I'll try cleaning/adjusting the sensor before replacing it since it isn't cheap.

*It has new Delta torque cams. It also has a really lopey idle. I'm thinking the two are related since I've noticed other cam'd engines do the same thing, but if not, that would give me a new problem to try to solve.

*The fuel pump often makes loud variable buzzing noises, especially at idle, after the car has been running for a while. It did this when I bought the car back in September and still does it now. I replaced the fuel pump (which was a cheap-looking generic affair) with a brand-new OE pump, and it still will occasionally make noise. The louder the buzzing, the rougher the engine. A fuel pressure test shows a drop in pressure corresponding with the loudest buzzing. So, I'm thinking a potential restriction in the tank (probably rust blocking the strainer). Does anybody know if that filter can be removed for a thorough tank cleaning and reseal, or if it's unserviceable? I guess it could also be the FPR sticking open or something: unplugging its vacuum line really doesn't change the measured delivery pressure any.

*No fast idle when cold. Air is pulled into the AAV hose on the intake side, but idle doesn't seem to change when I block it off (warm or cold). When the hose is removed at the manifold side, the engine gets rough and wants to stall (I assumed this was because it was pulling in unmetered air and upsetting the AFR). It's possible the valve may be stuck open and I have the base idle set way too low, or that the valve is stuck partially closed. It's also possible that the ECT sensor is faulty and reporting a warm engine at all times but not out of range to the point of setting a code. Because this car has the spider manifold, I really do not want to have to replace any of these things...

*Starting the car cold requires partial throttle. After sitting a while following a drive, starting up warm results in a surge in engine speed and then a stall. Normally partial throttle application while cranking will get it running, but the throttle needs to be feathered once it catches and it's a bit rough for a few minutes. Recently, the car has not wanted to start a few hours after driving it. Liberal amounts of starting fluid get it to fire up and it usually stays running after it smooths out. I'm suspecting this has something to do with the fuel pump or maybe sticky/leaky injectors. I've read that the hot wire MAF can cause issues like this so I'll clean mine to see if it improves matters any.

*Warm idle is erratic: usually it sits at 650 (or 550 if the lights are on), and other times it'll drop to 650 and slowly creep close to 900 before staying there. If I reset the idle speed to the proper 750, the creep stops around 1100. The FICD seems ok, since idle increases appropriately when the A/C compressor is on, always a bit above whatever the current idle is (so if it's 650, idle increases to 800 or so; if it's 900, idle goes to 1100 or so).

Also, I'm a little curious: has there actually been a comparison of the performance of the old-style turbo intake manifold with the spider manifold? According to their respective FSMs ('88 L-series, '87 XT), the old-style and spider manifold-equipped turbo engines produce the same amount of torque and HP (in the US, anyway). Just kind of interested, because the spider manifold seems to be more difficult to service than the old flat type.

 

Any input is welcome. Thanks in advance.



#2 naru

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Posted 26 February 2013 - 11:19 PM

What is the fuel pressure?

It should change significantly w/removing FPR vacuum.Low engine vacuum from the cams may be a factor.

 

I would check fuel pump volume at 35 psi.

Recently my car had somewhat similar issues.Fuel pressure at idle was OK,but,volume was terrible.Tricky to diagnose until I removed the return line.

An Airtex 8312 fixed that problem.

 

I would check pump voltage and grounding.

Fuel pressure should not be changing on its own



#3 grossgary

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Posted 27 February 2013 - 02:13 AM

i think i'd attack that fuel issue as well - "the louder the buzzing, the rougher the engine" sounds telling.   seems like it must be restricted in some way or bad power/ground/relay.

 

the only strainer i'm aware of between the tank and pump is the screen/sock connected to the tank side of the OEM pumps.  pull the line and see if it's clogged already?

 

i don't think they were the recommended grind for a daily driver but my XT6 (ER27 - EA82 + 2 cylinders) was lumpy with cams (delta).

 

ticking sound - could it be an injector?

 

a guy over at subaruxt.com carefully pulled his TPS apart and cleaned the contacts inside with excellent results, may be able to with the EA82 as well.  they don't fail that often, not often enough to warrant getting a used on to me. can get a used one and swap it out if you still have issues.  someone on here surely has one, pretty sure i do.



#4 mdcc2010

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Posted 27 February 2013 - 07:01 PM

Thanks for the cam note. I'm perfectly accepting of a lopey idle and a little noise (this isn't a BMW 7-series, after all), but I don't plan on daily drivering this car, really; I'm not even sure I'll keep if for long once it's back in a relatively decent state mostly because I don't have the time, training, or facilities to properly fix the body imperfections and repaint it. It's structurally sound and doesn't have enormous rust holes (except under the battery), but it's still going to be a lot of work to make this thing pretty again and I just can't do it myself right now. Even having someone else do it around here was quoted at about $20k and a year or more to complete it (this includes completely stripping the car, media blasting, rust correction, body work, multi-layer paint, and reassembly). I figure I may let someone else have a go at it if I move again; I'd rather keep my much more versatile RX if anything.

 

Anywho, according to the FSM's fuel system diagram, there's a strainer in the tank in addition to the little screen on the pump inlet. It's not mentioned anywhere other than in that diagram. It's possible that it's an error, but I'm inclined to believe it since it would make more sense having a strainer with a large surface area as an initial filter rather than the tiny inlet screen on the fuel pump be the only thing there.

 

I couldn't get the car to start at all today and removing a the fuel return hose on the engine showed zero flow even in Test Mode with the fuel pump cycling. There's still fuel in the tank (4 bars on the digi-gauge), but removing the supply hose from the tank results in nothing flowing out. Looks like it's totally clogged, so it'll have to come out. Since I can't remove the strainer to keep it from being damaged or sealed up, and because it's a perfectly huge pain removing the tank in the first place (diff + muffler must come out first), I think I'll buy a new one as opposed to attempting to de-rust and reseal the existing tank.

 

edit: yes there is fuel in the tank: about 1" of it visible through the fuel level sender aperture; somehow the fuel just isn't getting to the pump.


Edited by mdcc2010, 27 February 2013 - 09:03 PM.





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