Sudden change in behavior: hard start, low-lumpy idle, change in powerband
 

Hey all,

so.. My 81 targa has decided to stop running like a top. It's been a few weeks since I drove it, but there have been longer lapses with no problems.

So, I tried to start it today, and it started, but the idle was extremely lumpy and at about 200-400rpm. It stalled. Started it again, same deal, but it kept idling as long as I didn't touch the throttle. It was also backfiring intermittently. (I have the airbox mod done). Finally, with gentle throttle I was able to get it to idle halfway decently. This is, now that I think about it, the first truly cold weather start it's had in a long time.

But, once I got going, it would always have a very lumpy idle around 600-750 rpm. Idle is usually pretty steady at 900rpm.

I then noticed, once it warmed up that the power was WAY off. If I floored it, no matter what gear, I'd get very soggy throttle response, low power until about 4000rpm where I'd feel a definite step up in power, but not like i'm used to. Then there would be another big surge at about 5200-5500 that would finally feel like the power I usually get at that 4k range, and it would pull like that till redline.

I don't understand it at all. I did the quick check for vacuum leaks via removal of the oil cap while "idling", an even in this sorry state, I could feel the proper change in idle quality.

A couple other things. Normally when I'm decellerating, there's no burbling out of the exhaust. But it was there anytime I decelerated in gear today.

This car has been a SOLID car for the duration of ownership, which is coming up on ten years. It has all the standard upgrades like the carrera tensioners, the head studs were replaced about 50k ago, and they put new rings on the pistons at the time, along with various other things.

I'm just really at a loss as to what could have happened since I last parked it, running just fine, and now, where in 5th gear I need full throttle to maintain 60mph up a SLIGHT grade.

Any and all help will be much appreciated.

Thanks everyone in advance.

Michael

probably lost the lambda function. dome light fuse powers the system, via a relay under the right seat, in front by the tunnel. remove the fuse or unplug the relay to check. when you do this, the engine idle should drop off and run rough. it's usually a bad relay. the system goes way lean and it feels like you're dragging an anchor.

Thanks for the reply. I'll go check it out. If the fuse is intact, how can I verify whether it's the lambda unit or the relay(which I have read is one of the common failure points on this otherwise reliable car)

when I check this out, barring an obviously blown fuse, how will I be able to tell? I'm guessing that if I pull the relay while the car is running and there is no change, then that confirms lack of lambda control, but if the car runs even worse, then it's time to move on to the next suggestion?

Sorry if I seem amateurish. It's been a long time since I've really worked on cars. And even though i have a little bit of familiarity from when my urquattro still had CIS, it's tough applying that to this p-car.

I'm just happy that the first thought isn't that it's something really bad and expensive.

Keep those suggestions coming! (please).

Michael

i don't replace many lambda computers, unless they've been in water. cracked solder joints on the computer board are something to look for too. mostly it's the relay. try wacking it a few times. sometimes there's a wire off the relay plug.

Well, you did ask for suggestions, so here would be my first thought. You stated "it's been a few weeks since I drove it"....I think I'd take a look at the condition of the gas in the tank and/or the fuel filter. You didn't say what period of time "a few weeks" IS, but gasolilne has a way of producing crud/sediment when left sitting for extended periods of time. If the car was operating properly before it went into "hibernation", then I would consider this as a possible cause of the current problems. Just my two cents worth!!

Ok, so I just went out to the car and checked the fuse for the oxs system, it isn't blown, but I pulled it, cleaned off the contacts and then put it back in. So, the fuse doesn't appear to be the issue. (damn)

so, I started the car up (it's running almost worse now. Barely idling, backfiring as soon as I touch the throttle)

anyway, I found the little silver relay that you were talking about, and I pulled it. The car's behavior stayed exactly the same. It's like it didn't even notice that I had just pulled it's access to a major component.

I did give the relay a couple/few knocks on the floor of the car, hoping that maybe it's just sticky, but no luck. Plugged it back in, and removed it again a few times. Same result. With or without that relay, the car rubs the same.

So, I'm HOPING that means that it is almost definitely the relay is bad and that is what is causing the car to spontaneously take a hiatus from reality.

So, is my next step to get a relay, or is there anything else I should be checking for?

Thanks again in advance. I'm still freaked out, but I'm feeling better thanks to your help.

Michael

Oh, so if it really looks like it's this relay, does anyone have one that I can buy?

And, if not, I'll order a new one I suppose, I just hope that it solves the problem.

Michael

The relay's something like 12 bucks new from our host.

If you're looking to diagnose more than fix, I'm sure there's a Pelican in your area with a known working one to try. So a bump back to the top...

bosch # 0 332 019 150. standard 5 terminal relay.

Loose points or loose distributor?

Thanks for the suggestions everyone.

As far as how long it's been since I last drove it. I'd say three weeks is the last time. And it's generally my primary car, unless my stomach I acting up, in which case I will borrow my room mates BMW for the gentler ride. Also, the gas that is in the tank was put in the car the las time I drove it, so I'm thinking it is peobably ok. Thanks for the suggestion, though. I actually had thought about the same thing, but when I remembered that the gas is less than a month old, I figured it's ok.

Mr. Workshop - so, are you saying that if I go to my local generic auto parts store, like a kragen or something, i can just grab a standard 5pin relay and it should be ok?

And DAE - sorry for the ignorance, I'm assuming I would check for a loose distributor by verifying that the nut/bolt that holds it in place preventing it from rotating would be whatim looking for? As far as points - I don't have any experience with seperate points. My experience has been with a standard cap and rotor kind of setup.

Hopefully I'm not sounding like an idiot. I'm just trying to learn this car as fast as I can.

Michael

You do not sound like an idiot - you are just gathering info in a reasonable way on a great forum IMHO.

As for the loose distributor, I was just wondering if the timing could have changed and yes, you could check to see if the entire distributor is tight. You could also check the timing with a strobe/timing light.

As for points, I had a set come loose in my 72 that caused it to run just as you described. However, I am quite the amateur here!

Btw, I'm in daly city, just south of san Francisco, if there happens to be anyone in the vacinity. I just wanna try another relay in there. I don't wanna take it in to the shop because if it's just the relay, thatt would be such a waste of money.

I'm gonna order a couple of 'em from our host now. It appears that a spare isn't a bad idea.

And I'm also extra pissed because I was sure I'd be able to pull a 5pt relay from my urquattro, but no luck. They are all 4pt relays.

Dammit.

Michael

Don't think an '81 year model has ignition points, so that can be eliminated as a possibility. Please keep the community advised of the final outcome of this situation, as this will assist others in the future.

Happens to most men after age 40 ;<)

The relay from Pelican I just purchased for my 81 did not have the little hanger on it. You will see what I mean when you compare the parts. Not a functionality issue - you can still plug it in - but you may have to get a little crafty to put it back on exactly the way it was.

Unmetered air test......
 

Quattro,

What was the idle speed (RPM) when you removed the oil cap? How much did it change? The engine must be fully warmed up to make the test valid. At this point, I would check the fuel pressures (control and system for cold & warm), FV's operation, and lastly a vacuum test for air leak/s. Don't tinker the air mixture screw!!!! This is used for calibration and tuning purposes in conjunction with a suitable gas analyzer. Start with the basic troubleshooting. For all you know, you have a significant air leak in the system. Your guess is as good as others so you need to do the basic tests.

If you don't have tools like pressure gauges, timing light (strobe), etc., troubleshooting would take a lot of guess work. Plus fuel injection systems do not need help like depressing the pedal accelerator like in carbs. Keep us posted.

Tony

I'm with the oxygen sensor relay crowd. Order 2 so that you always have a spare.

So, I'm at a loss here.

When I checked for a vacuum leak w/ the oil cap as I mentioned above, the car was fully warmed up. It was running oil through the trombone cooler.

Anyway, after she got home I grabbed my room mate's car and went over to kragen to see if they have a relay to match the original one.

After much searching, the guy there was able to find a 5pt relay that matched up perfectly as far as pins and circuit diagram.

I installed the replacement relay, started the car, and it did start a little more easily. (and I do know that cis cars don't need throttle at startup). But it stalled the first time. When I restarted it, it fell in to the low lumpy idle that it had before. I grabbed hold of the new relay to feel what it wa doing while the car backfired or failed to respond correctly to throttle.

Every time it backfired, I could feel the relay click.

Ultimately, the car seemed to sort itself out, and it started idling just fine, though about 150-200rpm low.

So, I decided to take it for a drive. It ran great, with full power for the ten minute drive, except for the slightly low idle.

I actually drove to kragen again because I forgot to get the oil that I meant to get the first time.

So, I started it up, and again, it was acting as it was earlier, not behaving properly. I opened the oil filler cap, and it was just about stalling, but barely maintaining it's idle.

On the drive home, any time I started from a stop, it would backfire twice, and would not have any power at all.

Oh, I just realized something else. During the drive where I thought things were ok, at first it wouldn't make any burbling wounds upon deceleration, but the longer I drove, it started doing that a little more and more. Soi knew it wasn't back to normal.

Made it home, and here I am.

Somewhere in the garage I think I have my CIS testing equipment. But I am not sure where it is exactly. It's possible it's in storage with all of my tools.

Unless someone can think of something, I'm thinking that taking it to a shop is gonna be the way to go.

What's the best Porsche shop in san Francisco or south of san Francisco on the peninsula.

Thanks
Michael

be sure all the terminals in the plug are tight and corrosion free. maybe the cheap kragen relay is still the problem.

Yah, it's possible. It wasn't one of the 1.50 relays. It was foe some other usage, but cost 15.00.

It would just be strange that all this happens essentially overnight and out of nowhere.

It almost seems like the new relay was working alright for that first drive, but then it failed again.

What would have been causing it to click repeatedly in sync w/ the backfires. My guess is that there was a temporary short in the circuit. Maybe the o2 sensor itself causing problems. Or it could be the controller couldn't it?

Michael

Also, what are the chances that i have a faulty oxs control unit.

When my car leaked a while ago, it did get a fair amount of standing water on the passenger floor. It's not that there was an inch of water or anything, but because it was covered at the time (supposedly by a waterproof cover - I've learned differently now), once the weather got better, I pulled the cover off, ready to go on a nice ride through my favorite mountain roads, only to discover that my car became a greenhouse for mold.

I got that taken care of really well, and I haven't let more than a drop or two get inside the car since.

But maybe that ended up starting a process that ended up destroying the "ecu".

I hope I'm wrong. Cause I know they are really expensive. Does anyone have one I could buy from them?

What are the symptoms of a failed o2 sensor? But again, why the sudden failure.

Oh, I just thought of something that might be of some potential significance. The weather here in san Francisco has been lousy. It's been very foggy, cold temps, and very misty all the time. So maybe since it's been a few weeks since I drove the car, it isn't that something came out of nowhere, it's that sitting outside over the past three weeks in this kind of weather helped along some corrosion.

I dunno. At this point I'm grasping for straws.

Barring some awesome idea, I think i might just take it to a shop because it really does need some tuning, even before this happened.

In cold weather especially, cold starts have presented performance issues. Similar to the basic issues I've had now, but much more mild.

It would start fine, but anything more than 1/3 throttle would have no additional response as far as power, especially once the car hits about 3500-4000rpms. Once it warmed up after about 3-5 minutes, it ran fine. But Ive been getting HORRIBLE gas mileage ever since I got it back on the road last July after it had been stored for about 4 years after my dad died. I had it resurrected properly, with all new fluids and very carefully cranking the engine over by hand, etc etc. I had that done by the shop that my dad used. They always seemed to do a decent job, but after looking back at the work, there was something that never felt right. They always stood by their work. But I dunno, I wanna give another shop a try.

I dunno if any of this is helpful. But i figure that more information is better.

Michael

Oh, the gas mileage that I've been getting is something like 12mpg city and MAYBE 17mpg highway. Even when I made sure to use a tank by driving conservatively, and I still got 18mpg.

It's sofrustrating to hear about other people getting 20+ mpg regularly in mixed driving.

The tranny was totally rebuilt 55k ago, and the engine was redone 10k after that. That's when they replaced the head studs and piston rings as well as installed the oil fed chain tensioners and the new style alternator.

Thanks again for all the help. Past present and future.

Michael

So, I think I'm going to have it towed to Valhalla Porsche repair in Lafayette, which got a few recommendations when I pinged y'all about shops in the sf bay area.

I have a brand new WUR that I'm going to bring along just in case it needs replacement, and a line on an ecu for an 81 sc.

One question: in the bentley, it says that the ecu for 80 is different, and the one for 81-83 are identical, with more pins and an acceleration enrichment module.

But I don't completely trust the bentley, so does anyone know for sure?

Michael

+1 on relay connections. Was hunting for vacuum leaks in my 81 last week and pulled the O2 relay and re-installed. On re-start the next day ran like crap. The 200 rpm syndrome. Fine start then an anemic death shortly thereafter. Maybe after 6 starts it would stay running at 200. Forget throttle response.

I said to myself (I swear to God) , "JW said to check the connections at the relay". I fart around for two more days with other household projects - pick up another relay at AutoZone thinking of a world shattering post of how my new-ish PP relay (three months old) just died. Installed the AutoZone one and no change.

So tonight I get my lazy rear end under the passenger seat with my multi-meter at ready and really look at the connections. I had pushed the ground wire connection out of the female harness when I did the unplug / re-install last week. Runs fine now.

Suspect the addition of the acceleration enrichment caused the boxes to change.

I think your problem is a very simple fix. Don't work it too hard and focus on the O2 system. Once fixed you will be very happy.

Keep us posted.

Ok, so.... Resolution time!

Firstly, to whomever named Valhalla Auto Repair in the sf bay area - THANK YOU SO MUCH!

Anyway, they started working on it today, turns out that the main issue was..... That fracking relay! I guess that the one I got, even though it was spec'd to work in my car was crap and made it seem like the computer went.

BUT that's not all.

I'm glad that I had bought a brand new WUR on the board here for I think 1/3 of retail, because mine wasn't doing it's job properly. So, new WUR is now in the car.

Additionally, the timing was EIGHT degrees off - toward the retarded side.

AND - the mixture was extremely off as well.

he's taking it for the final test drive now, but he thinks it's gonna be ready to go.

Cost: 1.5 hrs labor + a new oxs relay.

So, I guess all of this would explain why my car has been getting, at best, 16-17 mpg.

I imagine that the 8 degrees of retard, along with the hosed mixture has impeeded the power output of the car for the whole time it's been driven by me.

I'm both incredibly excited by this as well as incredibly pissed off at the shop that I had been taking it to up until now. Since my dad got it in2001, upon the recommendation of a coworker of his who had a really nice 912, the car has been taken to the same shop the whole time. And they aren't cheap. That shop is responsible for the horrible state that the car is in. And they would have charged me a TON of money for today, I'm sure.

Anyway, hopefully he won't find anything else on the test drive. Or, if he does, at least I have a feeling I'll be able to afford it.

I just can't wait to drive it now.

Michael

Congrats! Let us know how it runs when you get it back.

I experienced similar frustrations during my first 2 years of 911 ownership. Spent nearly $5000 and had nothing to show for it except pressure fed chain tensioners.

Long story short ... I learned how to work on my car. I'm comfortable doing most stuff now. Even did a rebuild 2 years ago with the help of some guys from this forum.

I also finally found a shop that I can trust. They kick ass. I still take my car to them when needed.

So, I have the car back now, and it runs better than I can ever remember the car running in the 10 years that it's been in my family.

What I'm most impressed with is the improvement in throttle response during tip-in and the first, I dunno, 30% of throttle pedal movement.

Before, I'd really have to give it a bunch more throttle in the lower rpms before I was satisfied.

Additionally, the car is significantly quicker than it has been. It pulls so strongly right up to redline.

And, it's hard to tell so far, but my gas mileage seems to have improved noticably as well.

Yesterday I finally bit the bullet and had a set of the Direzza star spec tires installed. I had kumho ecsta spt's on the rear and old bridgestones re730s on the front. The tires are obviously still a bit slick from having only ten miles on them, but I can tell already that there is a HUGE improvement in high speed stability as well as steering feel.

The high speed stability had been an issue for me. I'm very sensitive when it comes to feeling sidewall flex on tires, and though I had never gotten a chance to physically give the spt's a squeeze with my hand to test the sidewalls, I have strongly suspected that they must be very soft. I wasn't wrong. On the new tires, I could barely cause any deflection when I squeezed them to check the sidewalls, but when I did the same to the kumhos, I was able to easily compress them completely. I was blown away at how soft they are. How can a manufacturer claim to have a high performance tire if it has sidewalls that have the ridgidity of jell-o.

Anyway, I'm looking forward to breaking in the new tires, and it is a comfort to know that I finally was able to get those old tires off the front, and get rid of the tires that I really suspected I just did not like on the rear. Plus I know how important it is on a 911 to have matching tires front and rear.

Yup, I love this car.

Michael