Syncro running rough and lacks power

[kuchiman]

My 87 Syncro (stock 2.1, daily driver) started running poorly after recently replacing oxygen sensor - started lurching/jerking w/ erratic RPMs. Replaced the ECU with a good spare - solved the jerking/RPM issue but still runs rough in 3rd and 4th gear w/ pedal to metal: heavy vibrations and severely lacks power up grades. I mean way more than usual – I can’t even climb a moderate grade in 3rd gear. Anybody have any ideas/suggestions what to try next?!? Thanks in advance for your contributions...

[0to60in6min]

how old are the followings:

- fuel filter

- temp2 sensor

- fuel pressure regulator

- dist rotor and cap

- spark plugs

[insyncro]

Check all grounds.
Carefully inspect the green wire connected to the oxygen sensor and do a search for how the make sure it isn't grounding out....it is a shielded wire, hint hint.

Tencent has a writeup somewhere.

Good luck.

[kuchiman]

Thanks for the replies guys. Regarding the grounding of the green OS wire: I did do that first - rookner move - but found the tencent post and fixed that.

Regarding

[morymob]

U can get new/bad parts, i would stick old sensor back in to test,won't take long and it ran ok before swap.

[Ahwahnee]

You might take a look at what your new O2 sensor is putting out (disconnected, will be in the 0-1.0 VDC range) when the engine is operating under various conditions.

Possibly easier to interpret with an analog multimeter but a digital will give you some idea too.

[0to60in6min]

if you don't have it yet, I'd suggest switch your spark plugs to NGK BP6ET (3 prongs style)

[kuchiman]

Well, after replacing ECU (which resolved the jerking/bucking issue) found out its just a simple lack of engine compression. All 4 cylinders are running @ 125 of less. So looks like its time for a new engine.

Debating the options now. Leaning toward a Bostig conversion but also toying with Suby2.5. Anybody had any experience with the Rocky Mountain Westy conversion kit? Just wondering if this is as complete of a step-by-step as the Bostig sounds to be. I consider myself of moderate mechanical ability and knowledge at best, and so don't want to get in over my head. If youve had experiences, please PM me if feedbacks not appropriate for broadcast.

[morymob]

From your 1st post it was running ok before oxy sensor replaced, now wiith an ecu change(???) the q is = All cyls dropping compression??, this the 'now' problem?. I would go back to sq-1, oxy sensor, new /wrong one bad?, my 2-cts worth.

[Ahwahnee]

[IdahoDoug]

Agree with A. In the absence of a major engine event like a loss of coolant and overheat, a compression test is a poor indicator for why an engine ran well last week and is not this week. A major overheat or no-oil between last week and this week along with that test - yes. But simply "ran well last week, doesnt this week" then a first ever compression test is not a good decision point to spend $6000.

DougM
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[Tram]

Why did you replace the oxygen sensor in the first place? Put the old one back! You replaced the sensor and now the van runs like garbage. Isn't it as plain as the nose on your face?

And yes, you want to use the compression test to check for big discrepancies between cylinders.
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[kuchiman]

Well, here's the deal. I replaced the OS cuz I was getting crappy gas mileage, down 3-4 MPG from usual. The OS light came on, so I figured that's what must be causing the reduced fuel economy. I botched the install by grounding the shielded wire which triggered a bunch of black sputum out the exhaust. Test driving, I noticed couldn't even go up a hill faster than 40 at high RPMs and shortly after the bucking/jerking problem began escalating.

So first step, I fixed the grounding issue which surprisingly didn't resolve anything. I replaced the OS with known good one and this didn't do anything either. Took to the mechanic who swapped out the ECU; this fixed the jerking issue but not the power. They measured compression at 125 each for cylinders #1 & 3 and 120 for #2 & 4. The Bentley Manual calls for compression between 145-189 psi, minimum of 116. So it appears to be on the lower end of the scale.

I had not mentioned previously but I bought the van in southern cal 2 years ago. Bringing to colder northern Nevada climate, a small coolant leak from the right side of the cylinder head was revealed at first only on cold nights. However, a ring is now evident on the ground pretty much every morning.
So these are the reasons are why I and the shop came to the conclusion that a new engine is needed. But I agree though that the timing of the OS replacement with these problems seems too much to be just a coincidence.

I know with a leaking head, a new engine will be needed at some point, but I was hoping it would be further down the road than this. If there was an evident solution, I'd prefer to do it and postpone the new engine purchase. But I feel like I've tried many of the obvious potential things it could be and am getting real tired of throwing good money after bad. That said, maybe I should replace the fuel pressure regulator and check the fuel injector delivery rate prior to assuming a new engine is in order.

[boof1306]

Have you checked for a blocked cat converter? Greg

[Wildthings]

A rebuild long block isn't going to fix a problem with the ignition system or FI. Your problem could easily be transferred to the rebuild. Your compression sounds fine, especially if you are at a higher elevation. My ratty 83 1/2 barely registered compression at all and ran fine with good power and gas mileage, the only thing it wouldn't do is start easily at temperatures below 10°F while at higher elevations.

Buy some Subaru coolant conditioner and add it to your coolant. This may buy you a few years on having the heads redone. In general so long as you have good oil pressure at idle, you don't have to mess with the bottom end.

Have you just done a normal tune up? If you had a questionable spark plug you may have gotten away with running it in conjunction with a non functioning O2 sensor, but once you replaced the sensor the miss from a bad plug could cause the sensor to throw the mixture off.

[insyncro]

X2 on chemical sealants.
They will stop weeping.....leaking, not so much.

[kuchiman]

Just wanted to report out that I finally solved the issue. After Replacing rotor, t2 sensor, fuel pressure regulator, I finally got around to checking the injectors ( mainly because this is a 2 person job - finally thought to put a paper bag down to observe if there was spray). No spray on one injector. Like a rookie I ordered a new one without swapping the connectors. Installed the new one and it didn't work! Doh!

Switched the wires and it worked. Pulled up the boot on the injector and sure as $hit it was broken right at the connector. Soldered it and the Kuchvan is working just like she used to! Couldve saved $30 on the injector but the good news was that my old ECU worked and so didn't have to spend the money on one. George at Valley Wagon was nice enough to let me use an extra one for quite a while until I got this all figured out. I figure what was causing the jerking was that the wire wasn't completely severed.

Another amusing rookie move that you may get a kick out of. Forgot to move the plug wire out of the way and it ended up getting chewed up by the alternator pulley. No sooner had I thought I solved the problem when the van started jerking! Had to buy a new wire set but $100 on everything - a drop in the bucket compared to the false diagnosis of a new engine. This is a great resource and network to be a part of; thanks to all who contributed!

[insyncro]