Hesitation Gone

TheStock · 06-30-2006, 09:43 AM

Just last Saturday I purchased an 87 944 Turbo from a gent out of Portland, OR and noticed that I really had to rev the engine to get moving from a dead stop. In the range of 2.5 to 3 thousand RPM just so it wouldn't stall. This is way to much and something didn't seem right, but I was told by the previous owner that this was normal. I found that it was even worse with any incline, even of the smallest kind. After reading through several already posted threads about hesitation, I thought the problem might have been something with tuning the GURU MAP setup that had been installed or a "vacuum leak", which I saw a lot also.
But, after a few days it dawned on me that I've had a similar problem before on a different vehicle. Last summer I had the head on my protege rebuilt and in the process of re-installing it I put in a new universal O2 sensor. I didn't notice much of a difference, but then again I hadn't been driving it much before I did all this. But I did notice that it seemed sluggish and would studder a lot when I was going up my driveway. Sometime in Feb. of this year I started noticing my check engine light coming on when I'd go above 55 mph and stay on until about 15 mins after going below that speed. The code read that it had something to do with the emissions/ oxygen sensor. I did the generic test on the O2 sensor that the haynes has outlined and it seemed fine. After I couldn't think of anything else I took it to a mech. to diagnose the problem and for a $100 was told that I need to put a OE O2 sensor in. To never go with universal because of this reason or that, they just don't work properly. After the swap, it ran much better and no more check engine light.
When I was checking the 944 for the first time I remember the seller mentioning that there was a universal O2 sensor installed, but I didn't think anything of it since he didn't seem to have any problems. But the hesitation and studdering on inclines was so similar to my protege that I figured it had to be the damn universal sensor. I found an OE online for $105 OE O2 sensor Porsche 944 Turbo part# 13012 and had it shipped 2-day delivery (only $9 s&h). Install was a PITA because somewhere along the line, someone snipped the male end coming from the car; I was forced to snip and solder which I hate doing since there was hardly any space to work with and plugging the female into the male would've taken all of a min.
Anyways, took it out last night and what do you know! No more hesitation. I can get it fully engaged right off of idle without it dieing or studdering, it accelerates better, it doesn't jerk when I give it gas at low RPM, and the studdering and dieing is gone when on inclines. Maybe this has been mentioned before, but anybody that has bad hesitation might want to consider installing an OE sensor instead of universal or at least checking to see if you already have an OE in.
Sorry this is so long.

Eldorado · 06-30-2006, 11:21 AM

never solder in your O2 connector..
other than that, glad it's working again!

TheStock · 06-30-2006, 11:52 AM

Quote:

Originally posted by Eldorado
never solder in your O2 connector..
other than that, glad it's working again!

Did I have a choice?

Ford-o-phobic · 06-30-2006, 12:01 PM

Hey i live in portland. Did you buy that blue one? Ive seen it driving around a few times.

TheStock · 06-30-2006, 12:33 PM

Quote:

Originally posted by Ford-o-phobic
Hey i live in portland. Did you buy that blue one? Ive seen it driving around a few times.

I bought this one that was advertised by Jason, it's silver.

1987 951 for sale in the NW

Eldorado · 06-30-2006, 01:07 PM

Quote:

Originally posted by TheStock
Did I have a choice?

yea..
if you're talking about the signal wire for the o2 connector, you're supposed to just twist the wires together and tape it... the sensor works off of resistance, and soldering the connection changes the resistance of the wire causing the DME to receive faulty signals.

TheStock · 06-30-2006, 02:05 PM

Quote:

Originally posted by Eldorado
yea..
if you're talking about the signal wire for the o2 connector, you're supposed to just twist the wires together and tape it... the sensor works off of resistance, and soldering the connection changes the resistance of the wire causing the DME to receive faulty signals.

Ah, I see what you're saying. I guess you'd just hope it never comes apart for some reason then. I'll keep that in mind when it comes time to change, which I hope won't be for a while.

onZedge · 06-30-2006, 08:22 PM

Actually, for this application only, you would be MUCH better off using butt style crimp connectors. Easier than soldering in a tight space and mechanically more sound than twisting and taping.

gtroth · 07-01-2006, 01:56 PM

Soldering doesn't change the resistance significantly. But resistance is not the reason not to solder in any case. Believe it or not, you don't solder because if you do, oxygen molecules can't diffuse down the wire to properly reference the sensor. Crimp instead.

944 Ecology · 07-01-2006, 02:07 PM

Quote:

Originally posted by gtroth
Believe it or not, you don't solder because if you do, oxygen molecules can't diffuse down the wire to properly reference the sensor. Crimp instead.

Oxygen molecules diffusing down the wire???

Ah, it's a joke!!!

gtroth · 07-03-2006, 06:13 AM

Well, diffusing down the air gaps between the strands in the cable. It does sound like I joke, but it's not.

944 Ecology · 07-03-2006, 06:15 AM

Quote:

Originally posted by gtroth
Well, diffusing down the air gaps between the strands in the cable. It does sound like I joke, but it's not.

OK, if you say so!

Eldorado · 07-03-2006, 07:22 AM

Quote:

Originally posted by gtroth
Well, diffusing down the air gaps between the strands in the cable. It does sound like I joke, but it's not.

LOL
either you're a very funny guy.. or a very stupid guy.. I mean that in the nicest possible way, of course....

gtroth · 07-03-2006, 08:18 AM

all about O2 sensors

Post number 9 is where the Bosch Engineer chimes in. Maybe he was joking too.

Eldorado · 07-03-2006, 08:21 AM

you misunderstood his point entirely.

"Also, it is important to use the unversal connector system. Do not use butt connectors when hooking these things up. The sensor must replenish the reference air inside in-order to create the oxygen gradients necessary for voltage generation."

this doesn't say anything about carrying o2 particles down the wire...

Eldorado · 07-03-2006, 08:24 AM

read this:

http://auto.howstuffworks.com/question257.htm

it explains it fully. a soldered connection screws with the resistance of the wire, which in turns relay's a faulty voltage signal to the DME... just like i said.

944 Ecology · 07-03-2006, 08:30 AM

Actually, the wire is hollow, and there are O2 molecules being pumped into the dme. If you solder the wire, the hole in the wire is plugged and the O2 molecules don't get there. You have to use a hollow butt connector to make sure that the O2 molecules get through to your butt!

Of course, I could be wrong... I read it on the internet somewhere!

SoCal Driver · SoCal Driver's Garage

The hollow wires are derived from the discarded fir of the Lock Ness Monster or the Yeti for the higher performance cars. These are streatched using the residual warp field left over at Roswell, New Mexico.

LOL!!!!

I bought a gerneric Bosch single wire O2 sensor for a replacement. In the box with the sensor and it's two feet of stranded insulated wire was a piece of shrink tubing and a butt to butt wire crimp connector. Now what do the Bosch engineers know that some of you don't?

http://auto.howstuffworks.com/question257.htm

The sensor itself has to be in both free air and the exhaust stream. This is why the exterior end of the sensor has a cage like structure. There are no hollow wires and no reason to have any o2 transport down the wire. Just the cage end of the sensor body has to be clear of any obstructions like mud or a used diaper. Don't laugh the mexicans leave them all over the streets here.

gtroth · 07-03-2006, 10:09 AM

So what are we saying here, that the "reference air through the harness" idea is a wives tale? Could be I suppose. That Bosch Engineer keeps comming back to it, though (post 27, 30). And there are many more threads around that say similar things, IIRC.

I'll admit, if the reference side could be vented reliably, that would seem to be a much more straightforward approach. Probst even shows the vent in his book:

Now, if you've ever dealt with gas permeation issues in a production design (like I have), relying on the harness as a vent path might not seem like a terrible design choice to you either (it doesn't take much).

There's more to it here than that gtroth is stupid, gentlemen.

SoCal Driver · SoCal Driver's Garage

"Leaks" are one thing. Intentional venting is another.