Rally Guy

I have a 1990 S2. Most of the time - it runs well, but feels a bit sluggish.

Every once in a while - it makes huge power and is tons of fun to drive. Then the power will go away for a month or so (I drive the car only occasionally).

This morning I drove to work (15 kms) - "regular" power. On the drive home? Massive power! I drove it a couple more times tonight (errands), and it still made great power. I almost want to go out and drive it all night - as if this is some rare gift I get that will suddenly be taken away.

But the strange thing is - IT WILL RETURN SOMEDAY, unannounced. This has happened several times over the last year or so. It can be so long between "power visits" that I'll begin to doubt my memory - was the car really that fast? Then - bam - the power returns! But only for a drive or two. Then it goes back to being "regular".

Clearly, the car (depsite high milage) is capable of a proper 200hp, so all the things you'd think were bad must, at these rare times, all work - just not all the time.

What could cause this??

RK

special tool

Timing - what fuel are you using?
Have you done a tuneup?
What about the cat?
Air filter?

KuHL 951

Sounds like your timing is advancing to normal or above and it's retarding all the time when power is down. Knock sensor? DME glitch?

Rally Guy

Fuel is 91 octane at least (we can get 92 and 94 up here)
No recent tune up. BUT, the car will run amazingly well suddenly and for awhile - then return to "blah, but okay", then occasionally run aweseomly again later! Air filters/cats don't unclog - AFAIK.

It's this on again - off again - on again pattern that's so confusing.

SOMETHING is fixing itself/making contact/engaging/working intermittently - allowing the car to make full power once in a while. What can that be?

Thanks for any advice...

RK

xsboost90

common problem w/ s2's is they have the wrong plugs, too cold. Check that out first. Alot of them will flood out alittle and especially when they sit for awhile they will get loaded up and then when you try to start it sometimes maybe it wont start or starts hard. Then it runs like *** until you get it moving and burn the crap out of it and it starts running correctly. Check your plugs, and gap.

Clint's 944

Any pattern match to the weather? Time of day? Is it cool out when it makes more power?

SoCal Driver

Check your knock and hall sensors and their wiring. Anytime the DME does NOT see these sensors it reduces the timing by over 6 degress. Has a noticeable effect on performance.

bader$

I have an S and sometimes when the temp and humidity are just right it runs noticeably better.

Rally Guy

Thanks for all the suggestions - I'll try to comment on each in turn... (and thanks a ton for each and every suggestion!)

Plugs are newish and the proper heat range. The performance can be strong right from start up, and the car always starts easily.

There appears to be no direct relation to temp/hum. Yes, the overall performance will improve in the cooler weather - but yesterday it was warmer and more humid on the drive home and the car was rockin'. I've watched for this with past episodes of power and I can't discern a pattern.

Knock/Hall sensors retarding timing: This one's interesting and I'll dig deeper. If one or both of these can fail/fix intermittently - then would the 6 degrees of timing retardation dramtically impact performance? I'd suspect so - and this might be the right path.

Anything else along those lines to check?

Thanks, this is encouraging.

RK

joes

I'm going to butt in here. The hall sensor is located on the distributor and the reference is is still on the flywheel. Is it not true that you can lose the reference sensor but not the hall? ( or visa-versa)

eohrnberger

I noticed a significant and consistent improvement when I put new plug wires in. Do you think that this may be related? An intermittend short or ground drain in the ignition?

Rally Guy

I think that's possible - I'm gonna do the "dark garage" test tonight - see if I see anything curious.

But wouldn't a bad plug wire or ignition compoment lead to really bad performance?

RK

Trucho-951

Don't know about S2's, but on the pelican parts website, I found a thread where a 951 was experiencing similar simptoms as yours, turned out the valve timing was off, and then on, and then off again. The final diagnosis revealed a faulty woodruff key on the cam timing gear, and since this had gone on for a while, it ultimately also required a new camshaft and key to fix it.

If your problem is anywhere similar, then when the cam timing slides to a retarded position, you lose some low rpm torque and the car seems sluggish or lazy, but when the cam timing changes back to a more advanced position, then the low rpm torque returns and your car will feel peppy and zippy (yes, those are technical terms). Just a swinging wild axx guess... good luck.

Rally Guy

I wonder aloud if the 16v enginces can suffer from this?

This raises another thought. Is there some kind of timing alingment that can be off most of the time and then once in a while "line up" - making power? Such as the sensors menetioned earlier?

There can't be anythign fundementally wrong with the engine, belts, etc - since it CAN make big power. A slipping cam shaft does seem possible but...

I have had instances where the car would run in "lazy" mode from start up and then suddenly "come alive" under me (literally, without moving my foot on the gas pedal while driving at a steady speed on the highyway for example, the car would instantly "feel" stronger) and run strongly for the rest of the drive. Next time out? No power. This further suggests to me a short or something intermittent with a sensor or other input that retards timing.

In addtion to the Hall and Knock sensors - what other (potentially intermittently failing) systems retard timing and/or reduce power?

Lastly - how do I test to see if I'm at correct timing or "retarded" timing?

Thanks,

RK

eohrnberger

One would think so. But here's what happened to me.

I put on a strut brace, and the thing ran on just 3 cylinders. Took it off, and was running on 4 again. Weird.

Replaced the plug wires, put the strut brace back on, and then ran on 4 again. Not only that, it ran stronger than before. Much more torque.

I don't know what it was, I suspect that the plug wires were borderline, but am sure glad that it's all better now!