Is the 944 reliable?

I see many people asking is the 944 reliable and the answer is yes and no. Mine had a few issues when I got it but got them sorted and daily drove the car for 6 years, mostly incident free, then had some more serious issues(hard to diagnose) but now its super reliable. The engines on these cars are incredibly reliable, so most issues come down to a few other causes, mostly electrical, but in this article I’ll address those issues, and what can be done to get rid of many potential reliability issues for many years. It is just a general guide based on my experience and not a technical guide for diagnosis of problems.

DME, the sensors, and relay

Speed and Reference Sensors

944’s have an engine management system made by Bosch called a DME(Digital Motronic Electronics). It is a fuel injected system the uses 2 sensors{on most models later that changed to one sensor) known as the speed and reference sensors. These tell the engine management system(DME) what the pistons are doing and when to fire the fuel in and when to to trigger the spark plugs, etc. Unfortunately when people get a “no start” situation, often the first thing people suggest, is replace these 2 sensors. That’s not bad advice, as it is a possible cause, but replacing parts that aren’t faulty, not only gets expensive but won’t fix the issue, unless you are lucky and that it was actually the cause. As the wiring harness is very old now, often its not the sensors but the wiring back to DME, from the connectors at back of engine, that then goes to the DME box itself. You can buy replacement harnesses from Lindsey Racing and I highly recommend this. Personally I have replaced all the engine harnesses, as it gets rid of all potential electrical gremlins related to old wiring adding massive reliability

Click here to buy sensor harness

Click here for instructions on how to fit harness

The testing procedure for sensors is at a site all 944 owners should have bookmarked, called Clarks garage click here to sensor test page. This site has so much information and apart from some advice written over 25 years ago, that’s now a little out of date, the site is invaluable. One of the things it suggests is glueing an 0.8mm washer to an old sensor, to set depth of sensor. Do not do this because if that washer comes off, you are in a world of pain, as it falls into a place that is expensive to open up and also we now have a cheap tool to do the job Click here to buy tool. The reason you need to set depth is, its critical the sensors are the right distance to flywheel, to get an accurate trigger signal for DME. If you can get sensors out without removing bracket, then you don’t need to set depth again. Unfortunately more times than not, the bracket needs to be removed to get old sensors out.

There is another alternative to fitting all new harnesses from Lindsey racing, which is what I did, and requires fitting them into factory connector at DME, which can be a bit daunting(but isn’t that hard, as long as you are patient and methodical), is to buy a complete harness. Recently a company called Kroon wiring decided to support the 944 community and is making complete replacement engine harness. This isn’t a cheap option but the harness is probably better built than when car left the factory, so will ensure reliability for many many years to come and just plugs in to DME and avoids the fiddly work needed with the Lindsey racing replacements to be fitted in factory DME connector, although obviously both still need to be hooked up to everything in engine bay. Its also possible for them to wire in custom integration for other non-original sensors, like to monitor intake temps or something, directly into the harness.

Click here to buy Kroon Harness

DME relay

The DME relay is used by the DME and ignition, to turn on fuel pump. For many years people often carried 2 or 3 in glovebox, as they are an old analogue relay, that’s prone to failure at the most random and inconvenient times. Quality of replacement vary and I had a lot of problems with ones I had, so genuine Porsche are the best but we now have an option that should mean the end of being stranded by these. It a solid state relay made by Focus9 technology and I was a beta tester for them and been using one since 2016 and highly recommend them. They have 2 versions, standard which I use and pump prime that activates the fuel pump for 3 seconds before starting, to make starting easier. If buying today I’d get pump prime but have no issues starting with standard unit. Some people re-solder broken relays and get them working again but as they are only putting off the inevitable, I think the solid state are way to go for reliability.

Click here to buy Solid state relay

DME(engine control unit)

With my car the DME box(ECU) had a random problem when I first got it 10 years ago, and the guys I sent it too couldn’t work it out exactly what it was, even though it tested faulty, so sold me a rebuilt unit. Now we have more options and I wouldn’t suggest getting the DME rebuilt as its very old now, and there are several better options. Even if fixed, the age means it may cause further problems later, due to age and construction, and technology available at the time car was built.

Which option is best depends on a couple of factors. If you own a normally aspirated(NA) car(a non turbo), or a turbo, whether you don’t plan to modify it or not. One option is the Focus 9 technology solid state DME(ECU) replacement. This is made with latest technology and will outlast most of us. These guys reverse engineered the DME and then made a new version that is built with 40 years newer technology. It does require a core exchange. They also have a version for “spec” racing version that is a control class of racing, so cannot be modified

Click here to buy F9tech DME

The more advanced options, for those who either want to do modifications at some point or want to improve basic performance, like throttle response, is to go a tune-able set up. These allow the fuelling, timing, and other settings to be changed and are essential on turbo models, if you want to improve performance by upgrading turbos, injectors, etc, but they will still benefit an NA(whether the expense is justified on NA’s is another matter). They also allow changes to be made at any time and can be retuned to accommodate the new changes


VEMS(versatile engine management system) is the stand alone system I personally use. My factory Air Flow Meter(AFM) had begun to play up and couldn’t be fixed. I could have bought a refurbished AFM, but as they are no longer made, so how long it would last is unknown, and they are very expensive refurbished. Buying a used one, then it may not even work at all, a gamble I wasn’t willing to take. I decided on VEMS because although, like all stand alone systems, a dyno-tuner can tune the car, it also has an autotune function, that basically self calibrates the system enough for it to be very drivable without the expense of dyno tuning time. It allows removal of the factory AFM, which not only improves air flow into engine but adds reliability, as it uses an Air temp sensor and wideband oxygen sensor for precise tuning. Far more precise than the original DME. It’s also a plug and play system that plugs directly into factory harness. It does require IAT(internal air temp) sensor and a wideband O2 sensor to be fitted, but that’s not complicated or expensive, and any decent mechanic can get that done easily or can be done yourself if you can weld the bungs required for sensors in. I added wasted spark ignition too, as it takes distributor out of equation, that needs parts that need to be maintained.

Click here to buy VEMS

MAXXECU, MEGASQUIRT, Motorsport Engineering and other options

These ECU’s are known as stand alone units, as they are a complete management systems. Some like Motorsport engineering are packaged into a plug n play like VEMS is, and others require a bit more work to install. Some come with a raw harness that needs to be installed, which is a lot of work, some with base tunes to get you going, and some that will not only require a wiring loom to be built from scratch but require dyno tuning before car will run and drive. They do offer virtually unlimited performance upgrades, with monitoring at the highest level of anything possible and you can add features like boost by gear, traction control, anti-lag and more, easily.

The thing about stand alones is, without the community support, you are on your own and either need to know how to tune, wire and set up yourself, or are at the mercy of your tuner and mechanic. That’s ok too, but if relying on someone else to install and set up, it is very expensive. Megasquirt has a huge amount of community support on rennlist forum, Maxxecu(new option for turbos and in early days) on the facebook group “Premier 944 turbo and 968 turbo group” and Augtronic and Motorsport Engineering by tuners in UK and Europe, as does VEMS, so making a decision between them, can be important just based on where you live, or based on your tuning skills and fabrication and wiring skills.

Click here to buy ME ECU for NA and Turbo Plug n Play

Click here to buy Megasquirt Plug n Play for NA 944

Click here to buy Maxxecu Race(basic)

Click here to buy Maxxecu Pro(advanced)

Click here to buy Augtronic

Vacuum Leaks

These cars have vacuum lines running all over the place in the engine bay and even in the car for the heater control. The original lines often have leaks that can cause all sorts of problems. These should all be replaced and you can get kits or just buy silicone hose yourself. Although you would think that replacing them would solve any vacuum issues, there is one other place a leak can cause an issue, and that’s the throttle body. The throttle body is meant to be sealed and a leak can mean the DME is getting the wrong reading of air going into engine, so car will have incorrect air to fuel ratio, and can run poorly

Click here to buy throttle body reseal kit

Click here to buy vacuum lines

Fuel Lines

More than just a reliability item, these are a safety item too, as having the car burn down does effect the drive-ability a bit. The original fuel lines can split and fuel is under tremendous pressure so if they go, its right over a hot exhaust. You can buy braided lines but I prefer aeroquip fuel lines, as it means they are easy to visually examine as they age. The lines at rear are less of an issue regarding an instant fire, as not over hot exhaust but also a good idea to inspect regularly and replace if needed.

Click here to buy Fuel lines


The importance of good grounds can’t be over stated. Luckily it costs nothing to clean and reattach them. On some cars ground straps from battery may need to be replaced. For the engine, the ground point is just near the speed and reference sensors at the back of engine between bell housing and firewall. Cleaning is just a matter of removing them and cleaning area of grime and cleaning the terminals with light sanding. There are I think 7 ground points and its a great idea to clean them all. It varies from models being LHD and RHD but there are diagrams online that show you locations. As everything from DME, sensors, and gauges, require a good ground signal, it’s definitely worth doing and free

Is my car reliable?

I bought my 86 turbo in 2010 (today, so its our anniversery 🙂 As mentioned above I had a problem with DME when I first got it but had that sorted a few weeks later. It went great and I was driving it everyday but occasionally I’d have the dreaded random no start. it was very rare but also very frustrating. I could always roll start it, so always parked with that in mind and often had work colleagues who would get roped into helping. I actually put up with this for about 6 months while searching online for possible solutions. I read that you could sometimes jiggle wires at back of engine where speed and reference sensors connect to factory loom and car may start. Sure enough it worked and I realised it was the factory wiring back to DME that was the problem. I ordered the Lindsey racing replacement harness and as I am down under and shipping here is so expensive, I thought I may as well get some other things at same time. Luckily one of those was the fuel injector harness. Now when the stuff arrived, I kept driving for a bit using jiggle method if the car wouldn’t start, but when I finally got around to fitting the harness, I thought it made sense to look at fuel injector harness too. Although I hadn’t had an issue with it, when I touched the connector at the injector, the factory harness broke off in my hand. I then fitted the new fuel injector harness. I realised I’d dodged a bullet, as it was just a matter of time till that harness would have broken and left me stranded and scratching my head to the cause. This is why, if you want a reliable car, I think the harnesses are so important.

When I started to have the issues, that the worn out Air Flow Meter(AFM) caused, I tried replacing many parts to fix it, not know what the cause was. Often I knew it was unlikely to be the solution but figured at least the parts would be good for many years and I might get lucky and also some things I was planning on doing anyway. I was also between mechanics and so sort of stuck on my own trying to work it out. I replaced the fuel pump to a HV unit from Lindsey Racing, fuel filter, distributor, cap, leads, fuel rail(CEP), rebuilt injectors, Tial F38 dual port waste gate and Turbosmart electronic boost controller, AFR gauge(Zeitronix ZT2) with EGT, and probably a few other things I’m forgetting. I also had to fit most of these things myself, so learned a lot doing it and am far more confident tackling mechanical tasks these days

Once it was figured out it was AFM, I weighed up options and decided on stand alone. Initially I bought an M tune set up but couldn’t get car to run. This wasted a lot of time and money but I eventually gave up and bought VEMS. A few weeks later it arrived and once fitted to the car, she started first time and I’ve never looked back

So yes my car is very reliable and starts first time, every time, and I wouldn’t hesitate to take it on a long trip. Yes its had some issues as you would expect for a car of its age, but the majority of the time(90+%) I have owned it, its been driven daily and reliable. I have done the things to it, I think are needed, to make it reliable and will make any 944 very reliable. If you also want a reliable 944, then it takes a little work but if you address the primary causes of problems, outlined above, then these cars are very reliable and very few other cars have the engineering behind them mechanically, to do the sort of mileage these cars do consistently, combined with handling, style, and looks that are hard to beat.

Published by kewlhunter

I love gadgets and technology and will post about what I have and why I like it or dislike it

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