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

[UrQuattro]

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

[john walker's workshop]

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.

[UrQuattro]

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

[john walker's workshop]

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.

[curiousone940]

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!!

[UrQuattro]

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

[UrQuattro]

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

[NOLAsc]

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...

[john walker's workshop]

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

[daepp]

Loose points or loose distributor?

[UrQuattro]

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

[daepp]

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!

[UrQuattro]

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

[curiousone940]

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.

[tazzieman]

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

Happens to most men after age 40 ;<)

[Bob Kontak]

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.

[boyt911sc]

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

[mca]

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

[UrQuattro]

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

[john walker's workshop]

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