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SPFI idle quality issues


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25 replies to this topic

#1 GeneralDisorder

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Posted 05 August 2006 - 02:33 PM

I've got the SPFI on my EA81 working quite well.... except the idle. The idle quality is not good enough for me. There is a slight miss at idle that I can't get rid of - it idles about 800, and the tach moves around slightly - about 50 RPM one way or the other when the missing is occuring. This miss was not present with the Weber - nothing else on the engine has changed. Here's a list of stuff I've done:

- Fuel pressure is 20 psi. Tried another regulator as well - no change. All dampeners are in place, and I've tried two different fuel pumps. Fuel filter is new.

- New coil, plugs, and wires. Tried changing the ignitor, noise condensor, and alternator (EA82) - no change.

- IAC clean and shiny - I have two, and both operate perfectly (I took them off to watch their operation). I soaked both in carb cleaner for 24 hours - they might as well be new now.

- Removed and cleaned entire throttle body - tried a different TPS, and a different injector. Took the injector filter off and cleaned that. Reset all TPS adjustments to factory, and verified operation of the idle switch. With the MAF disconnected I can see the spray pattern of the injector is good.

- Cleaned entire PCV system, checked for vac leaks on entire engine with carb cleaner, and I've permanently disconnected the EGR, and EVAP systems - no possiblity of a leak there.

- New cone air filter, and I've tried about 4 or 5 MAF's. Each MAF acts a little different, and I usually have to adjust the idle speed for each one, but the miss is still there, and it's there even with the MAF completely unplugged.

- Tested, and tried at least 4 different CTS's - all seem to do their job of idleing down properly. Again miss is there without the CTS plugged in too.

- Unplugged the 02 - didn't make a bit of difference - miss is still there.

- I've rewired everything under the sun - the whole ECU is now supplied directly with a 10 guage from the battery - fused and relayed off the ignition switch.

- Vacuum test shows ~21 in/hg at idle - it does fluctuate rapidly (needle is blurry it's so fast) about 1 - 1.5 in/hg, but it did that before with the Weber as well - I think it's probably a valve seat or something.

I'm nearing my breaking point here. I've been working on this problem for a week, and haven't got anywhere. The idle quality isn't much better than it was when I first started the engine after the SPFI swap. I've done a ton of work and troubleshooting with almost no gain.

When I went up to work on Jerry's hatch, once the problem was figured out (fuel pump wireing) the engine started right up and idled back to a perfect 700 RPM smooth idle. What am I doing wrong?

I haven't replaced the PCV valve yet..... I feel vacuum when I pull the hose - maybe I should get an OEM one? I kinda doubt that's it, but I'm running out of things to replace here....

The MAF does change things a bit.... I've been replacing just the sensor not the whole casing and all - could I have a problem there? I cleaned the thing out really well with brake cleaner, and from what I can see inside of it looks clean....

GD

#2 NorthWet

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Posted 05 August 2006 - 02:50 PM

Distributor? I suspect that you have already checked this, but since you didn't mention it...

#3 bgd73

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Posted 05 August 2006 - 02:52 PM

keep it very very tight. An undetectable vacuum leak can even set it off. My own spfi had porous rubber lines, no leak detected. The screw on the top left of spfi is a good one to keep barely open as well, once you're confident it is all sealed.. I can't even emphasize how tight that has to get-- the rubber intake boot seems to be number one prob ,engine shakes it into a micro leaker over time. Other than that-- I wouldn't have any idea besides tune up stuff, clean fuel with stabilizer etc.My fix inadvertantly was replacing rubber lines with aluminum where I could, it wasn't even my goal to stop vac prob, but it sure did-- the idle smoothed.Scrapping egr also helped me too :)

#4 NorthWet

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Posted 05 August 2006 - 02:59 PM

keep it very very tight. An undetectable vacuum leak can even set it off...

Maybe I am just lucky, but my family's 89 SPFI DD is probably anything but tight, no real maintenance by PO or much by me yet, but it idles nice and smooth. It is in desperate need of attention (stalls when cold, down on power; needs plugs and wires at the least) but a lovely idle. Go figure.

#5 GeneralDisorder

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Posted 05 August 2006 - 03:00 PM

I haven't checked the distributor.... I mean the shaft play is fine. What else can go wrong with the crank angle style? Do they fail like this. I can get another, it's just a pain to swap the gear out.... it does have 250k on it, so I suppose anything is possible.

As far as vacuum leaks, I'm pretty sure it's tight. I've sprayed the thing down with brake cleaner to no effect.... and I think my vacuum test would show a lower value than 21 (which is pretty high I'm told).

GD

#6 GeneralDisorder

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Posted 05 August 2006 - 03:08 PM

Oh yeah - compression is between 175, and 190 on all cylinders. In case someone is wondering.

GD

#7 NorthWet

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Posted 05 August 2006 - 03:28 PM

I am no expert (duh!), but I have read of a lot of "miss" issues with the CAS disties that were related to disty shaft wobble or CAS problems.

#8 GeneralDisorder

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Posted 05 August 2006 - 03:40 PM

Interesting - well I tore it apart and it's all clean inside - zero shaft play. I'm thinking about just going to the junk yard and grabbing a whole throttle body, MAF, and disty just to see. This is getting rediculously expensive.

GD

#9 Prospeeder

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Posted 05 August 2006 - 03:47 PM

I would say get a new Fuel injector, Idle issues can be caused by shorted or sticky injectors. ALso leaky injectors.

#10 GeneralDisorder

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Posted 05 August 2006 - 03:58 PM

Tried changing it out - the one I used came from a junk yard car with 122k on it. I'm going to go get a whole throttle body if I can't figure this out by tommorow.

GD

#11 keltik

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Posted 05 August 2006 - 04:42 PM

Just out of curiosity here, how often does the miss occur at idle? I know john's brat does it, but its by no means an issue. Just one of those old car quirks.

#12 NorthWet

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Posted 05 August 2006 - 05:48 PM

Does the miss happen often enough that you could use a timing light and see if the timing wanders or (spark is absent) when miss occurs?

#13 GeneralDisorder

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Posted 05 August 2006 - 06:45 PM

The timeing does wander as it's running rough - even with the test connectors connected it's not a hard and fast 20 degrees - it's like 19 to 21 degrees. I figured that was just an artifact of the "missing"..... does it point to a specific problem?

Grabbed another disty, throttle body, and complete MAF (sensor and body) from a 90 Loyale (same year my stuff came from) with only 150k on it. Verified that the butterfly adjustment screw has never been touched (still has the white paint on it), and all parts look good if a little dirty. So I'm ready to build a second disty, and try that out.... and maybe trade out the TB and MAF as well.

The miss occurs enough to make the idle wander, and the car shake - any miss at all is too much for me. I don't beleive in "old car quirks".... "quirky" just means broken to me.

GD

#14 NorthWet

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Posted 05 August 2006 - 08:13 PM

The timeing does wander as it's running rough - even with the test connectors connected it's not a hard and fast 20 degrees - it's like 19 to 21 degrees. I figured that was just an artifact of the "missing"..... does it point to a specific problem?

My understanding is that with the green connectors connected that the timing should be pretty rock steady. I think that the (slight...) timing jitter is indicative of bushing/CAS unit issues; possibly ECU/connection issues, but still on the disty side of the equation rather than fuel delivery. Can you tell if the timinglight ever "skips" a cycle around the time of the miss?

#15 daeron

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Posted 06 August 2006 - 04:20 AM

i swear to god, this is NOT a thread-jack..

but i had a post (click) where i described where a specific vacuum line that had been disconnected and was causing a constant miss at idle.. and i have no idea what it was that the vacuum line was connected to.. but simply plugging it did not help. it went up to a small white canister-like object located at the extreme rear of the engine bay on the far passenger's side, and through that into another line that went across the firewall and into the cabin. I have no idea what it was, but it seemed to want manifold vacuum pressure for the car to run right. can anyone identify this object for me, and what it does, AND is it possible that this is something that you (GeneralDisorder) have overlooked, or is it something that you have bypassed?

like i said, im not trying to steal the thread, but i never did get an answer and i AM trying to help you with your issue, too.. ;)

#16 GeneralDisorder

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Posted 06 August 2006 - 06:58 AM

The canister that you speak of is the vacuum accumulator for the heater controls. It operates your buttons on the dash that change the vent configs for heat/defrost/AC ect.

Unfortunately my problems aren't that simple. EA81's have no vacuum operated controls, and thus no white canister to give me grief. In fact, the whole engine bay has exactly one vacuum line now as I am not running EGR, or EVAP either. And I know I don't have a vac leak - I wouldn't be getting 21 in/hg of vac at idle if I did......

GD

#17 GeneralDisorder

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Posted 06 August 2006 - 08:03 AM

My understanding is that with the green connectors connected that the timing should be pretty rock steady. I think that the (slight...) timing jitter is indicative of bushing/CAS unit issues; possibly ECU/connection issues, but still on the disty side of the equation rather than fuel delivery. Can you tell if the timinglight ever "skips" a cycle around the time of the miss?


I installed the new disty last night, and it actually seemed to help a bit. It's hard to tell, but I think I noticed a reduction in the missing. I've thought I had the problem solved before however..... thanks for the tip though - I wouldn't have thought the disty could cause this with seemingly perfect bushings. I wonder what goes wrong with the CAS - it seems pretty simple in design.

Checked the timing, and it's pretty solid now. It's right on 20, and only moves maybe 1/4 of a degree. That could just be that I haven't ovaled out the hole for the disty mount yet, and the disty is moving just a tad. Timing light doesn't skip any cycles that I noticed.

I then went and replaced the throttle body as well. After that, my idle won't drop below about 1500 with the IAC screw all the way in - bottomed out. IAC is working - if I unplug it, the idle drops to 1100 or so. I'm thinking maybe I need to adjust the TPS.

This is getting to be absurd. I hope when I get it right it won't need adjustment for a long time....

GD

#18 bgd73

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Posted 06 August 2006 - 08:21 AM

-(General Disorder) Vacuum test shows ~21 in/hg at idle - it does fluctuate rapidly (needle is blurry it's so fast) about 1 - 1.5 in/hg, but it did that before with the Weber as well - I think it's probably a valve seat or something.

I went through this to no avail really, except fuel additives that clean injection, and thoroughly cleaned top of spfi unit,and all the lines that were hardened.
The fluctuating is a culprit-- if it is engine internals due to high mileage, make up for it elsewhere (egr for example). The intake is so small, 21 solid as a freakin rock would be normal with the carb/spfi whistling at an idle like a tea pot ready to throttle respond quickly (I had it once on this spfi -- and it faded away- there is quite a demand on the vacuum system as a whole).
On the other side of air sucking is fuel to go with it -- a pin hole in fuel system can trick into a vacuum oddity (idle).
A stubborn fuel damper (with no leaks) at low speeds can do it.
That sensor at thermostat housing keeps idle way up unhooked/bad.
Nothing EGR bothers it unhooked (it was my biggest helper).
Hardened rubber vac lines (petrified) does not mean sealed forever- that was my old engines other hidden problem. It is quite a nuisance if it decides to shake around on a perfect miss -- and it isn't even firing/cylinder sometimes :)

#19 bratsrus1

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Posted 06 August 2006 - 10:50 AM

Hi GD This is Jerry, have you figured out what size of ohm resistor i need for the EGR solenoid valve? Let me know i would like to get rid of the cluter. Thanks Jerry

#20 GeneralDisorder

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Posted 06 August 2006 - 01:22 PM

Hi GD This is Jerry, have you figured out what size of ohm resistor i need for the EGR solenoid valve? Let me know i would like to get rid of the cluter. Thanks Jerry


The recomendation seems to be a Ceramic, 68 Ohm, 5 watt resistor or right around those values. Anything between 50-100 Ohms will fool the ECU acording to the FSM. Any electronics supply should have something along those lines.

GD

#21 GeneralDisorder

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Posted 06 August 2006 - 05:58 PM

Alright - I'm not getting anywhere. Changing the disty really didn't help. I mucked around with the idle speed and it seemed to help a bit, but in the end it's just as bad as it was.

Lets take this in a new direction. The engine has really never been all that smooth. With the Weber I had the idle set at right around 1,000 as much less than that would result in a similar rough idle situation.

I strongly suspect it has pretty worn main bearings - the compression is top-notch at 175 - 190 on every cylinder. Hydro lifters, and no ticking is evident. It has nothing that sounds even remotely like a rod knock, but it has a dull "thud" like knocking that you can feel in the gear shift, and you can actually hear it as well. I'm fairly certian that it's NOT a rod bearing. For one it does not sound like one, and for another it's been there for 40,000 miles since the day I aquired it. Clutch has been worked on and replaced as well as the rear main seal to no effect - no strange noises there. I worked hard to get the oil pressure up where I like to see it. I put on a new OEM oil pump and sender shortly after I got it, and it's got 20 psi or better at idle, and over 50 psi at cruise when hot. The perfect oil pressure seems to point away from any internal problems, but everything else seems to sugest heavily worn mains.....

The idle is satisfactory at 1,000 now - only a little bit rough, but now that I think on it, it's about where the Weber was at 1,000. I have fought with this problem for two years on this engine, and I'm beginning to realize that it's probably internal.

I'm going to try a valve adjustment just for good measure as I never did like the way it looked when I adjusted them after milling the heads. I'm hoping that at least it will even out some of the roughness.

I have a complete Fel-Pro G-set, rings (EA71, and pistons), undersized rod/main bearings (also Fed-Mog), and a turned crank. All I need is a Delta Cam to go with....

What say you?

GD

#22 GeneralDisorder

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Posted 06 August 2006 - 11:05 PM

Adjusted the valves, and no real difference to be seen there either. I don't know if the "thudding" is related to the roughness, but I suspect I have a cam journal that's bad. I'm going to shoot a little video with sound - it's actually quite noticeable from the oil fill tube. Pulling each spark plug makes no difference in the noise, so it's not piston or rod related it seems. FSM points to badly worn lifters or cam journals near as I can tell from the troubleshooting chart.

GD

#23 pressingonward

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Posted 20 November 2012 - 06:30 PM

GD - what ever happened with this car?

You mentioned that you swapped throttle bodies and it had a high idle with the IAC disconnected. Did you figure out why it idled high with that throttle body but not the other throttle body?

I am having the high idle issue with my SPFI swapped BRAT. Idles around 1100 rpm when warm. If I disconnect the IAC it idles at ~900 rpm with the air adjustment screw all the way in. No vacuum leaks that I can find.

I know this is an old thread but I was curious if you came to any conclusions with this car

#24 Crazyeights

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Posted 20 November 2012 - 08:48 PM

Since this thread is 6 years old I imagine GD has moved on to EJ swaps by now. I fought this same battle a coupe years ago and I finally gave up right after it ate the intake lobe on the re-ground cam at about 5000 miles. Are you dealing with a stock or performance grind cam?

#25 pressingonward

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Posted 20 November 2012 - 08:53 PM

Stock cam, motor has never been rebuilt. Timing properly set at 20 degrees




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