User 41221

Okay, so I finally take delivery of the '87 951 that I bought from Matt Ledbetter (and a big "thanks" again to Matt for selling it!). I bought the car knowing that its not fully sorted out, but thats okay, as I don't mind a challenge and figure I might learn a thing or two in the process.

The car is set up with the following:

Stock K26/6 turbo
Stock injectors
Guru Stage II MAP
Guru Chips
Lindsey CBV
Lindsey Adj Fuel Regulator
Lindsey Dual Port Wastegate
Lindsey Fuel Pump
Lindsey Intercooler Hard Pipes
Lindsey Blue Vacuum line kit
Lindsey Fuel Pressure Gauge
Bursch Cat Bypass pipe

The car, when I got it, was running fine, altho it had the dreaded off idle stumble/hesitation that have been reported when running a MAP set up. So what to do first? How about making it so the car doesn't start anymore!

Here's what I did. I started by observing that the vacuum lines were very long and all run all over the place, so I figured that I would shorten them and reroute them so that they were a bit prettier. To the best of my knowledge, I did not misroute anything, they all run to the same place they did before, they are just shorter. While I was at it, I removed the line that was run from the CV and was left open at the other end (this was the line that used to run to the banjo bolt on the intercooler pipe). Finished rerouting the vacuum lines, and decided to remove the alarm/keyless entry and miscellaneous "monster" stereo cables (I'm not a big fan of aftermarket wiring). The wiring was pretty significant, but was relatively straightforward. It involved unplugging the Link AFM unit, so while I was at it, I verified the wiring for the unit and rerouted the ribbon cable for the Link handheld tuning module. All done, I decide to fire the car up and make sure that I hadn't run afoul of the factory alarm unit.

The car cranked over fine, but wouldn't fire. $#%^@%$. Checked under the hood, and saw that the fuel pressure gauge was registering 45lbs, so I was pretty sure fuel wasn't the problem, which given what I had been working on wasn't a total surprise. Upon further investigation, I found that in the process of removing the CV boost line, I managed to bump one of the reference sensors hard enough to break it. $%^&#%. I don't feel TOO bad, as I looked at the other one and it had been glued together at some point, so I was going to have to fix these soon anyway, but still...

Anyway, I plugged it back together as best I could, and it seemed to be holding okay, so I went to start the car. Fired up quickly, but only idled for a second or two, and then died. Restarted it immediately, and again, it died pretty quickly. Restarted again and tried to give it some gas, and it died quickly again. Thats pretty much where the car sits at the moment. I checked the tuning module and noticed that as the car starts to die, the MAP reading goes from 65-70kPA to around 85-90kPA, at which point it dies. The car idles pretty good at 65-70kPA, but it doesn't stay there... which makes me think the problem is vacuum related, and not the reference sensors.

Talk about reinforcing my belief in the practice of only working on one thing at a time, so that you can identify when you have done something wrong... if you have read this far and can give me some advice, it would be greatly appreciated.

Regards,

User 41221

By the way, I know *nothing* about the Link box or tuning it, so cut me some slack if I sound like an idiot when talking about issues concerning it. I just downloaded the manual and am planning on digging in and learning. Any tips on it would also be appreciated.

Regards,

Jake951

If you have the stock AFM, reinstall it and reconnect the plug that was orginally connected to it. Unplug the wire harness from the LinkAFM box so it no longer connects into the DME and DLR. Now try to start the car. If the MAP computer or sensor were faulty, the car should now start because the GURU chips will work with the stock AFM. If the car doesn't start, then it's something in the MAP computer, sensor, or wiring to it.

mochman

UGGHHHHH! sounds like a fishing trip you just don't know. Re-trace your steps to start with, get a proper vac. diagram and make sure your lines are routed properly, Above all re-place both your ref. sensors and make sure the gaps are correct, I'm almost positive you are getting an interrmittent signal from them which wreaks havoc with the cpu. Make sure all your i/c connections are secure as well as all others. If any questions ask.

Jake951

OK, I missed this part first time I read through your post. What sensor is this?

Also, check all those small hard plastic vacuum lines that run off the manifold tap and make sure you didn't pull off one of those by accident. Check the vacuum/pressure line to the LinkAFM box and make sure it's connected properly.

User 41221

Yep, fishing trip for sure... lol I deserve it, but oh well, I don't think it can't be too bad (famous last words, eh?).

I am already planning on doing the reference sensor, so thats a given. I grabbed OZ951's vacuum diagram and will go through it thoroughly. Does anybody have an updated one that bypasses the CV. I am also thinking about pulling the intake manifold so that I can redo the vacuum lines, put in the later idle stabilizer valve that simplifies the undermanifold lines and make it easier to replace the ref sensors, but i honestly think that will be a mistake, and I should wait to do that until after I get the car running again.

I don't have the old AFM, and the car came to me with the Guru Stage II MAP on it already. I am tempted to install a Lindsey Stage II MAF that I have sitting in my workshop, but again, that would just compound things, in my opinion, and I think I will hold off for the time being.

Regards,

m42racer

sh944, don't mess around, call Link and ask them. They WILL help you.

User 41221

Thanks, M42, I am putting that off until I rule out the ref sensors and the vacuum hose routing, but that will probably be my nnext step. I just hate to pester them, as I wasn't the original purchaser. On the other hand, they may be interested in trying to keep me from swapping the thing for a MAF... lol

Regards,

nine-44

Try capping the open port from the CV. The rising airflow then dieing would explain a boost/vaccume leak. It's quick and easy, why not try it? Do you have an A/F guage? does it show lean as it is dieing? I'd guess that it isn't registering or at least not accurately that soon anyway. It is also possible that it is part of an alarm kill too. I'm not sure about the aftermarkets but I know alot of newer Porsche/Audi alarm will allow the car to start breifly before dieing out. Just my thoughts, good luck.

nine-44

Oh I was thinking it was a MAf, oops. Hmm. I was also thinking if you had the battery cable off possibly loosing the programming? Also maybe a bad fuse from pulling the alarm and other stuff? It's been known to happen to the best of us.

Sami951

Do you have the tools you need to adjust the MAP (link tuning module, or the datalogger)? You're too rich at idle. This was the case in both my and Tommy's car, needed to lean out something like 10-15% from the appropriate zones (200, 205, 300, 305, maybe even 400-405).

65-70kPa doesn't sound good for idle vacuum! I get just below 40kPa on mine, and it shows as 15" on my autometer boost/vac gauge.... aren't the 951's supposed to get like 18" of vacuum at idle?

'86 944 turbo

Like Sami said you need a link tuning module.

User 41221

I have the Link tuning module, I just need to spend some time learning how to properly use it!

I am thinking that its a vacuum problem at this point, so I will concentrate on that first.

Thanks for the help, guys, keep it coming!

Regards,

Sami951

If the link box was connected to the stock O2 sensor wire (like it should), you can see the approximate a/f ratio on the tuning module (says "oxygen" on the screen IIRC). The voltage you're aiming for is somewhere around .80, more on WOT and less on cruise loads... so when the car stumbles, see if it's overly rich (O2 voltage 0.9 or more) or too lean (0.5 or under I'd guess).

Now that I think of it, I'm not entirely sure how much vacuum leaks should matter with a MAP system... of course they do kill some of the performance, but it should still get the air flow calculated right...

User 41221

The O2 sensor wire (green w/yellow stripe) and the boost control wire (purple) were NOT connected on my car. I was thinking about installing the O2 wire, but elected to go with the Rennbay AF Gauge that mounts in the clock location instead. It would be easy enough to hook it up too, tho.

Interesting comment about vacuum and MAP, which make sense. It sure feels like a vacuum problem. Does anyone know if the Link box will reset itself back to default values if it experiences a power disruption (like someone disconnecting the batter, for example?). I wouldn't think so... I can't imagine having to retune every time you service the car.

Hey Sami, you sound like you are pretty well versed on these things, want to fly over and give me a hand? lol Seriously, thanks for your continued help.

Regards,