[JonNelson]

Hi folks. I've been reading up on some other problems that people have had with rough running, hard starts, and the like. My problem with my '92 which has been steadily getting worse is this:



Runs poorly while accelerating (hard or mild) - as in coughs and sputters without making full power. Idles just fine. Appears to be more noticeable in first and second gears as opposed to accelerating in the same RPM range in other gears, though it may just not be as noticeable to this driver given New Mexico roads. <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" /> Occasionally demonstrates hard to start problems. That is, it takes more cranking than it did when I first got the car. When that happens (~50% of the time), it doesn't matter whether I engage throttle or not while trying to start, and appears to be independent of being cold or warm, though perhaps more common on cold starts (engine cold, that is).



I've already replaced the O2 sensor, mostly because it was old and needed it anyway. No positive effect at all - in fact, it's still slowly getting worse. I hesitate to go replacing all sorts of parts, and I plan to take someone's advice in the "hot start problem" thread and inspect the cables, plugs, and any/all vacuum hoses I can this weekend.



I drive at very high altitude (5000' to ~8800' - mostly lower than 7000') and over long freeway miles (~90 miles a day at average with a mean speed of ~60mph - I'll keep median speed classified <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" /> ), and neither altitude nor temperature seems to have any affect while cruising along, which leads me to believe that it's most likely fuel related. I kinda doubt it's spark plugs since cruising/set throttle or RPM works fine. Cruise control even works fine, for what it's worth - no problems with hiccuping while the computer is controlling, but then the cruise control isn't really doing any hard accelerating on the freeway.



I am hoping that this might be a Hall sender or DME relay issue (though I only know what those are from diagrams) and not a MAF sensor (which I do understand, but note that it's very expensive to replace!). Anyone else have this problem? I'm not familiar with the DME relay or Hall sender, but since it seems that everyone has had problems with this and it seems simple enough to clean the DME relay ... I'll probably try that too. Dunno 'bout the Hall sender.



Any other experience with this problem (which seems somewhat different than others, but very similar) ... ?



Thanks in advance!



- Jon

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[Stephenwz968]

My bet would be on the fuel pressure regulator-either the vacuum line to it isn't connected or working, or the regulator itself isn't working right.



Have you run any fuel injector cleaner through the car to clean those up?



There is a MAF cleaner you can use to clean that, and then the FI cleaner, I would check the plug wires to make sure they're not arcing, and then I would go to fuel related things such as the check valve on the tank. Check/replace the fuel filter and go from there; good luck getting it sorted out!



Steve

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[kwikt]

I would first check spark plugs to see if one is fouled. Could even be valve cover around the spark plugs are leaking then filling the plug holes with oil and fouling spark plugs. This happened to my 968. Doesn't cost any thing to check this!



Kevin

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[JonNelson]

Thanks guys, will definitely check plugs tomorrow. Good idea re: fuel cleaner and MAF cleaner ... after hose inspection, might try that as well. Will post back on Sun/Mon with results.



Cheers!



- Jon

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[gryphon]

It could also be a dirty fuel filter, since it seems to be related to higher flow rates.



Tom

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[bob blackwell]

Hey Jon, give me a call and lets see if we can get together, I am right down the hill in Albuquerque (West Mesa). 839-0775 I have a spare DME Relay and if that doesn't help, I have a spray can of MAF Sensor cleaner. We can probably work it out. Bob Blackwell.

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[Cloud9...68]

Before you do anything else, do a blink test, since it's free, and might save you a lot of troubleshooting down the road. Do a search on it if you're not familiar with the procedure. Good luck, as I know first hand how frustrating chasng down a problem like this can be. I had a severe stumbling problem durng wide open throttle acceleartion, and after checking about twenty things, it turned out to be bad plug wires. Testing your wires is also very easy and free - just drive the car at night long enough to get it warmed up, pull into a very dark spot (your garage, if there are no street lights nearby), and stare at the plug wires (and the coil too while you're at it) and see if you can spot any arcing. Again, good luck!

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[JonNelson]

Thanks again guys. Just talked to Bob (it'd been a while, but we know each other - good guy, Bob is). Planning some diagnostics tomorrow with all the sage advice. I'm sure glad this forum is back up and running without all the spam spam spam spa...



Sorry.



- Jon

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[968gene]

rotor? cap?

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[PorscheDude]

As cloud stated, start with the blink test. This will tell you if you have a bad hall sender or any other problems. Then go thru the basics.

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[94SilverCab]

Hi Jon,



It sounds like you have a combination of "deferred maintenance" issues...Bob Blackwell is an excellent resource to help you sort these things out. I would not consider replacing these parts as "throwing parts at the problem...."



Just to review.



Plug Wires

Spark Plugs

Cap and Rotor

Air Filter

Fuel Filter

Clean MAF

Fuel Injector cleaning

Heater Control Valve (brittle plastic that tends to break down under heat)



Check Condition of Caster Blocks



Fix leaking passenger side Power Steering Hose



It could be DME Relay (You should have a spare anyway)

Hall Sensor(s)



Have you changed Brake fluid recently?

While your replacing Brake fluid may I suggest Stainless Steel Brake lines and S/S Clutch Hose.



Pull Clutch inspection Port plug (if yours isn't missing like everyone else's) and Lubricate the fork and bearing.



Flush coolant



Change differential fluid.



If you are in anyway unsure of the time or mileage since the belts were changed, do them...$5k for head work and valves is a terrible thing to waste (ask me how I know).



After all that, if you have the strength, wash and wax your car and post some pics. We like to hear about/see others 968s.



Happy driving,



Jay

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[Cloud9...68]

While I agree with all the items Jay (94SilverCab) mentions, and I've done or checked most of them myself, your problem sounds to me more like one or at most a couple of very specific things. Therefore, I would be concerned that replacing a long list of "general" items, as impoirtant as they may be for the overall health of the car, may actually make troubleshooting your problem more difficult. What I mean by that is, for example, if your go ahead and replace, say, the cap, rotor, plug wires, plugs, and either do the Run-Rite treatment (do a search on this when you get a chance) or send your injectors in for cleaning/balancing, the car will probably run somewhat better, but may not get at the root cause of your problem. So, you might find yourself with a less "crisp" case of the poor running problem you describe, making it harder to tell if subsequent things you replace are helping much.



I would carefully check things like the plugs, wires, cap, rotor, and air filter (see how dirty it is), but not actually replace them unless you clearly see something wrong. And if you do feel, based on the appearance of these components, that they need replacing, I would replace one at a time (though I would do the cap and rotor as a pair), and see how much of an improvement each item makes, if any.



Best of luck - we all feel your pain.

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[JonNelson]

Thanks again for all the suggestions, and the laundry list of maintenance items ... <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />



Actually, I am pretty comfortable with DIY stuff and somewhat experienced working on cars (the 968 included), though I'd never lay claim to mechanic status. I've had the car for 18 months now and have been doing things while owning her - some hoses, belts, and a replacement heater core (and thanks to another thread here I found it much simpler than taking the whole dash out!).



Of course, such things as air filter were first to be upgraded/changed along with the oil some time ago. New Mexico is a dusty place! K&N now with air box mod - was easy to do.



As for my present problem, I have a new DME relay going in Tuesday. If it isn't that, I still find the idea of having an extra very comforting since it basically can make the car unstart-able if it fails. I really do not think it's the DME relay, but ... well, it's easy and relatively cheap. For starters (hah! great pun!) on the other "typical maintenance" stuff, I'm going with new fuel filter and possibly cap & rotor. Plugs were very clean when I pulled them. I'll still clean MAF and fuel injectors though. Here's hoping it isn't the actual fuel pump ... though I'm considering it could be.



I'll try that "blink test" <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" /> to see if its the reference sensor (Hall sender) as well as look for arcing in the wires and coil. Still frustrated with how poorly she's running, but my only car and daily driver ... I'm a getting mildly concerned. Sort of backhanded luck, but we've had snow around here and so I'm obviously driving very mellow right now - glad I got snow tires on in time! - and it's not that noticable on lower power applications. Still ... it's not good.



In the spirit of helping others with this, I'll keep updating as I get parts/time to fix things and investigate further.



- Jon



PS: Good call on the leaking power steering line! Obviously another common failure. Mine's very mild, but it is there.

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[JonNelson]

Update: so far putting in some really good injector cleaning fluid has helped greatly. It's still a little rough (most noticeable in lower RPM range), though much more driveable now. Going to put in another dose of the stuff since its working. Also have rotor/cap/fuel filter on the way to replace. DME relay replaced, and as I suspected it did nothing to help ... still, it's good to have an extra one on hand. I'll check back in later - it's looking less like a MAF or fuel filter now ... but one never knows. Also those maintenance items needed replacing anyway, so ...



By the way, the blink test resulted in one code coming up only ... a "poor connection" on the oil temp sensor. Might be adding to the list of things to replace. I was mildly surprised that no other error codes came up, but then it is an older computer setup.



Going to have to fix that power steering fluid leak at some point soon ... <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" /> Other than that, I'm still loving this car even in the mild ice/snow we get!



- Jon

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[flash]

based on the improvements you ahve found so far, it sounds like injector issues



i would find a local Run-Rite center - that is the best fuel system and intake cleaner out there, but you can't buy the full treatment yourself - you have to have it done - MAJOR improvements on every car we have tested



it still might need real injector cleaning for perfect performance, but you may well be satisfied with the results

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[JonNelson]

OK, well here's the final update. First off, she's back to running great! Now I can't wait for the dirty, salty roads to clear up a little bit for me to put the summer tires/wheels back on ... although I love snow ... it's a dichotomy I know.



The issue was apparently this: 15 year old fuel filter, rotor, and cap. <img src="/forum/images/smilies/968/ohmy.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" />



Yes, as in, the original parts from Porsche. Even had "Porsche" on the filter. I'll pay more attention when I purchase a used car in the future ... the owner had stated that it had had "some tune up work" but all he mentioned was the spark plugs and wires. I'm glad about the wires, but the plugs looked to be about 60,000 miles old or so, so I'm guessing that the wires are near that age. They aren't arcing, at least.



So ... the final word is a lesson I've learned time and again ... and just had to re-learn one more time. Frequently, just over $150 on some general maintenance items can go a long way towards making such a nice engine (even one over 130,000 mi) run like a purring tiger again. Recommended if one does not know the condition of the parts and is experiencing hesitation, hiccups, and/or poor running. I am really still shocked that the car ran at all with those parts (rotor/cap/filter) being original 1992 parts. Not pleased, but ... well, at least she's back to herself again. <img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" />



- Jon

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[94SilverCab]

Jon,



So glad that your car is running great now...these babies purr when they are up to snuff.



PLEASE PLEASE PLEASE, replace your Timing and Balance Shaft Belts unless you have absolute certified evidence of the last change date (I will never again go more than 5years/15,000 miles whichever comes first, Amen). If all that stuff was old, it is almost a sure bet that the belts were ignored.



and now...Pictures Please! Have you joined PCA? Did you send your info to the register, etc.



Regards,



Jay

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[968gene]

[quote name='968gene' post='44432' date='Dec 7 2007, 08:54 PM']rotor? cap?[/quote]

<img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />

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[doster]

Did bob end up helping! He's a great guy and would love to meet in person <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> Maybe Parade this year

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[Cloud9...68]

Wow, I'm amazed this ended up being the source of your problem. Maybe it's just been my personal experience, but I've never had any luck curing poor running problems by just changing things like plugs, rotor, cap, filters, chemical treatments, etc. It's always been something specific that was broken in my case. Maybe the previous owners of my cars have done a decent job of taking care of the basics. Glad yours is now running well!

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