996.2 Strange set of faults, help please! (Resolved)

Hi Guys Having rebuilt the engine on my brothers 996.2 Tiptronic (see enter the 996.2 thread) it is now running like a sewing machine. Except for the following faults and running issues. It was showing ABS and PSM failures, but after a new MAF those are gone. The speedo has only worked once, after fitting the new MAF. But now it has stopped again. The Duramertric is currently showing no faults. The engine idles and revs great in park. A soon as you put it in Drive, or manual mode, it will still idle, but refuses to rev. Disconnecting the MAF makes no difference. (PSM and ABS warnings reappear) Even if you feather the throttle it just will not catch and rev, just starts farting and missing. The gearbox dashboard lights operate as you would expect. The car is up in the air on ramps with the rear wheels off the ground. Even though the gearbox is almost certainly low on fluid (have not been able to fill it correctly because cannot run thru the gears) it has operated correctly before now, it just will not at the moment. The car has not run on the road in our possession, and was bought missing it's ECU, so it has a few unknowns. Does the above ring any obvious bells? Many thanks! Berni

First off .. please explain sewing machine as to me that means its rattling and running rough .. so you mean its good or bad ? Ok so this is not going to be a normal issue .. What we have is a car that runs and revs fine but as soon as its put in gear it wont rev up. speedo doesnt work but as the car is not moving it wont ? do the rear wheels spin when in drive ? off hand i can't remember which wheel the speedo gets its signal from or if its a combination of all but either way if the wheels are not spinning it wont work .. if you mean Tacho then that's a different story ... CPS . So .. logically if its running ok with no load on the engine ( that signal comes from the maf and is calculated by the dme ) then there must be a massive load on the engine / gearbox . Looking at a tester in dme or tiptronic and you need to find the value for load .. it will be a percentage from memory . I don't know the usual readings without checking a car but lets say not in gear you have 25% load .. put it in gear and try to rev the car .. what do you get then ? If it shoots up .. let's say 75% then something is dragging on the engine so that no matter how much air ( open throttle ) or injector duration ( fuel amount ) it cant rev up .. anyone can push a car down hill .. no one can push one up hill !! high load example . So thats the first check to be done .. Off hand .. Incorrect or faulty programming in the DME .. Engine ancillary .. scavenge pump seized .. alternator .. water pump .. anything engine driven . Fuel pressure to low .. Tiptronic box is faulty .. Torque converter .. Wiring issues and can bus but i would have thought there will be a fault code if a can bus fault .. actually there will be one but it's still something to think about .. an overloaded can bus .. thats too many signals from a faulty control unit will cause issues .. rare as hens teeth but possible . Some thoughts anyways .

Hello DeMort Thank you for some interesting thoughts. The car is in the air and when in "D" the rear wheels spin as expected. Backwards when reverse is engaged. Will not rev in reverse either. It's the speedo that is not working. When I said runs like a sewing machine, I meant purrs like a kitten. When in Park it will rev happily, although since it is a fresh rebuild we have not gone above 3k. We did had it running through the gears last week and well before 5th gear we knew the rear whee(s) need balancing badly. Very strangely on that occasion the car also would not rev in "D", but as soon as we disconnected the MAF it would, and that was when we ran through the gears. This led to us changing the MAF for a new one. Some further strangeness. On swapping the MAF the speedo came to life, and the PSM/ABS fault went away. Then we had a look and cleared some faults with the Durametric. On restarting the car it went into an indicated 3rd gear and the box would not respond. We did put some more fluid in and on the next start the gearbox behaved as expected, apart from the car refusing to rev when in "D". But the speedo had stopped working again. A spot more detail, if you start the car it idles perfectly even from cold, then when put into "D" the revs rise to about 1100 rpm, then as soon as you touch the throttle even a tiny fraction it stumbles and does not really recover until back in "P". At one point last week we were getting wheel speed sensor codes pretty much for every wheel, but the replacement MAF seems to have fixed that also. When this was going on (pre MAF change) I did look at the Durametric and it was reporting a speed of 22 kmh on every wheel I think. It does not sound like the engine is in any way dragging or labouring. It has new scavenge pumps and every ancillary turns fine. We have only very recently put the engine back together from a total strip. I will have a look at the load parameter if the Durametric will let me. I must get hold of some more fluid for the box also. Many thanks again Berni

I would check for broken reluctor rings or failed wheels speed sensors. MC

As MC says I think the reluctors stop the speedo working, I had that issue when I had put my engine back in, it took some head scratching to work it out? Both my rear reluctor rings had swollen with corrosion and also damaged the ABS sensors. http://911uk.com/viewtopic.php?t=145230

Does it rev in N or only in P? Where did you get the replacement DME? Could it be incorrect? What about the gearbox ecu? Could that be faulty? Sounds electrical to me, especially with the MAF weirdness.

And as it turned up without an ECU, are you 100% sure you've now got the correct one on the car?

Revs in both N and P That's a slow build up in revs very smooth, but blip the throttle and it hesitates for a bit. When in gear holding revs say 2000 it starts hunting.

ECU is same engin type M96.03 same transmission A9610 3.6 2002 Only difference is Country C10 we in UK.

Hi Further strangeness update, we put my damaged Boxster (3 Chain facelift 2.7 Tip) ECU and Alarm in and with the car ran like a pig. Would not idle or respond to the throttle. There is a possibility that the 996 ECU we bought was from a 4wd Tip. I do not know if that would make a difference. The ECU in my 2.7 Boxster is from a manual car and it runs perfectly. However, with the MAF unplugged it was much better, and in "D" the throttle responds and the car will run through the gears 1st - 5th and back down again. So I guess we can assume that the gearbox is OK. I will take the MAF off my Boxster and try the new 996 one in that (same part) in order to rule it out..... Further ideas appreciated! Many thanks Berni

My first 996.1 had an issue with rough idle, the previous owner had put a cheap MAF sensor on, I ended up with a Bosch one and it ran perfectly, just a note All the best in sorting it out

It was replaced with a bosch.

C10 is Switzerland I think. Do or did they have different emissions standards to the UK 20 years ago? There are several reasons ECU's would carry a country code, one of which surely is to do with required emissions, climate and available fuel quality in that country. Are MAF's country specific too? O2 sensors? Just wondering if this ECU is not fuelling correctly on a UK car, with UK sensors and fuel parts.

Putting a DME from a totally different model and engine size in is not to be recommended .. potential damage to components and as you have found out .. it don't run very well . Durametric and look for the load signal .. if that cant do it then get a tester or garage that can .. all we are doing is guessing and throwing components at it .. Diagnose please ... i can help there .. im happy to chat on the phone and do my utmost .. but throwing components at it and i'll leave you to it . Have you checked fuel pressure ? have you drained out the oil from the tip to see if its now black and has bits of metal in it .. car originally ran as i understand it in gears but now doesn't . reluctor rings and speedo not working .. that's Not going to stop an engine from reving up ... worry about it later or it may be connected in which case it will work when the engine does . The load signal will tell us if the engine OR the gearbox has an issue .. fuel pressure check will tell us if thats ok as it can have enough fuel to idle but not rev up . Actual values .. injector duration .. fuel adaption in Rkat or idle .. hell id even look at cam deviation and specified / actual values .. Rule out items one at a time . Sorry .. im frustrated .. please test things and take as many pictures of what ever values you can see and post them here .. need something to work with basically . Every part on every car has a part number if this is different from what you are fitting then its either a superseded number or its wrong .. you always check this ... wrong part number often means it's wrong for your car including DME,s . A dme can be reprogrammed with the latest software .. any garage can do this .. Indy/opc but it must be the correct one for the car .. part numbers .

Hi There Agreed on the ECU, but actually it is the exact same part number. The flash may well be different though. I swapped the Boxster ECU in because it allowed me to run the engine up though all the gears which I did do. That way I could discount a gearbox issue. I did look at the load value on the Durametric and remember it was in the low 20's although i have not tracked it carefully. I will revisit that. I think the figure went down a bit when I revved the engine. The engine turns over by hand as easily as it ever has. I will note down the actual injector duration and fuel adaptation numbers. Fuel pressure we definitely do need to check, thank you for the suggestion (and others). I think if all of the above checks out, then it's time to flash the ECU. Many thanks again Berni