foxj0001

Hello,

This is also posted on the 993 forum so apologies for those who might be seeing it twice.

I've recently acquired a 1996 993tt, 28K original miles, very lightly used by the second owner (4K miles over 5yr), which is beautiful to look at and great fun to drive. All is well except for the following mysterious engine symptoms:

Event consists of the throttle pedal "going soft", accompanied by momentary loss of power and CEL transiently illuminates. All these simultaneous, the event is over in less than a second, CEL goes off, throttle response and power come right back. Happens when fully warmed up (or at least has not yet happened when cold). Happens up to 3 or 4 times within a 5min period. Happens whether driving hard, accelerating, decelerating, or driving "family style". Even happened twice this morning at idle, as I was letting the engine cool down after driving to work. No backfire and seems like it is not misfiring, certainly not running rough. No smoke. Oil recently changed, has always had Mobil1. Using 93 octane pump gas, and I do not let the tank run too low before filling up.

Prior owner had ECU reprogrammed through Fabspeed, who also installed custom, "stock-like" mufflers (very quiet) which I had them take off and replace w muffler bypasses (not quiet!).

I had it to the dealer where I bought her to look into this and they told me that because she was chipped she was not storing any CEL-related codes, and they could not reproduce the symptoms. Battery cables checked, they are fine, looks to be a fairly new battery.

So here I am, mystery unsolved. MAF sensor dirty? Distributor problem? ECU hiccup? Grunge in the fuel tank/pump/filter? Any ideas?

Thanks for thinking about it.

Jonathan





____________________
2012 C2GTS Meteor Grey Coupe - daily driver
1996 993tt Guards Red Coupe - recent acquisition
2001 Audi S4 Silver Sedan - foul weather car
2011 Mini Cooper S Clubman British Racing Green - wife's ride
2008 C2S Midnight Blue Coupe - sold

Quadcammer

ecu hiccup if you ask me. Not sure how they modified the ecu, but if its a "chip", I believe they get soldered into the 96s. Could be a bad connection

ScottMellor

Has the wiring harness recall been done on the car?
If you took it to the dealer they probably verified that it had been done.
Borrow a stock ecu and see if the problem disappears.

budge96

Sounds like a very nice car,do you know or are there any records of the flywheel being changed?

Sounds a bit like a reference sending or receiving issue,but a long shot...Bert

foxj0001

Thanks for replies.
Dealer checked 993 wiring harness recall, mine is a later build and not subject to the recall.
Really put my foot in it on the way home today to see if stress on the system had any effect, only result was pushing me back into the seat with a silly grin on my face.
That was ok, actually!
Had one "blip" event, was while cruising at 65mph in freeway traffic with little throttle pressure. About as lamb-like conditions as one might expect to encounter.
I will keep driving and see what happens.

Basal Skull

+1

Felix

Was the CEL flashing while the problem has heppening? That indicates a misfire. I would think about changing plugs and wires.

An ECU being chipped should not affect its ability to store fault codes - did they actually try to read the codes or just say it couldn't be done once they heard it had been chipped?

No HTwo O

Congrats on the new Turbo. We need pics, please!

Will the car rapidly make 0.8 bar boost when you get on it?

foxj0001

No evidence of flywheel change, have some but not all service records.
CEL not flashing - have seen that on other cars I've driven - simply illuminates momentarily during event.
Will find out if they actually tried to retrieve codes or simply backed off because of the history of being chipped. From what they told me so far it sounds more like they went looking, and did not find any codes. Could be because a) the revised chip prevents the diagnostic tool from talking to the ECU, b) the immobilizer was not disabled, or c) there simply weren't no steenking codes. Will f/u.
Car promptly builds 0.8 bar w/o complaint. Can't say the same for my human or canine passengers ;-)
Good news to report: have now driven her close to 100mi w/o any blips. Could be gas tank grunge now gone, could be the new BMC air filter (oiled) that one correspondent questioned - possibility of oil droplets making their way into the MAF sensor, could be gremlins or the Geico Gekko for all I know!

foxj0001

Meant to keep typing but text window froze.
Anyway, so far so good and thanks everyone for good ideas that I will incorporate into my data gathering.
Will post pix when back at my desktop computer. I already posted some on the RTR-PCA Forum for those who simply cannot wait...911 Air-cooled forum.
Jonathan

UserA

It seem like a diverter valve, but I would think that it would only happen under harder acceleration. Where in PA are you located?

sfbanchs

sorry for the OT but did I read correctly you take your dog with you in your pristine 28k mile TT??????

IamSMC

Alright, someone has to say it...

No more questions until you post pictures of your turbo

However, welcome aboard

foxj0001

Hi again
Had tech check diverter valves, they are ok.
I am just outside Philadelphia location-wise - Narberth.
Yes, I took one of my two 9.5# Manchester terriers for a ride to the gas station, he sat quietly in my lap and took it all in. Would not have done so if it had been one of my 90# labs from an earlier phase of my life...
Pix hopefully uploaded, try #2 in progress.
Jonathan

No HTwo O

Jonathan, very nice! Guards Red with Cashmere Sport Seats. Sweet combo.