'96 850R Very low mpg, very low power.

bmessina · Post by **bmessina** » 27 Dec 2012, 15:14

erikv11 wrote:I didn't read through the whole thread again, don't know what all the symptoms were but when an engine "gets better" without doing anything, it usually indicates a small vacuum leak or an intermittent sensor problem (e.g. MAF or TPS). Which means it will come back, so keep an eye out for it.

Not sure if you are serious about swapping in an ECU, but for the record any turbo ECU will be just fine.

A 96 or 97 ECU would be best to avoid CEL from potential emissions differences (EGR or SAS) between the swapped vehicles, but otherwise the only difference in the R ECU is that is has an extra 18 hp in the top of the RPM range. Without a stopwatch it us very difficult to notice the 18 hp difference between an R ECU and a regular T5 ECU.

Of those 2 things it would have to an intermittent sensor (or other electrical issue), as adding another car to the electrical system is what "brought it back" so to speak. Even if it was for a short time.

Post by **northernlights** » 27 Dec 2012, 20:09

bmessina wrote:Haven't gotten back to the timing, but something weird happened. I had a flat tire and the battery about died today. Wife came out to jump me, and when I got the 850 started it's... not 100% but 2-3x better than it was. Revs more freely, and actually feels good throughout the rev range. I have changed NOTHING else. Just jump started it.

So... yeah.

Out of curiosity, when you jump started it, did you connect the negative terminal to the battery or to the body? Assuming the MAF isn't possessed, I'm starting to wonder if you have bad ground(s) somewhere. On the later model S70/V70's and similar I believe there is a shared ground point for the ECU/TCU near the passengers side front bumper, but I am not sure if it is the same on the 850's. All of the low voltage signals can get incredibly messed up by poor grounding.

A number of years ago my son drove an 87 Jetta. One day he told me that it wasn't running right. His threshold for not running right was about 10x higher than mine

, so it was pretty bad. The cause was actually very amusing, and I was actually pointed in the right direction by a friend of mine. There were either two or three wires (it's been a while, but I believe for things like the Kjet mixture control unit) which were supposed to be grounded to the intake via eyelet connections, and all were broken off. I suspect they individually failed, but were ignored until it became unbearable to him. I fixed the grounds, and it magically worked again.

bmessina · Post by **bmessina** » 27 Dec 2012, 20:25

As is the standard, I grounded the dead car somewhere other than the battery. The bracket for the throttle spool, specifically. Yeah, I'll be checking my grounds

Post by **rspi** » 28 Dec 2012, 02:54

Try not to get to distractedly, check to make sure your timing is correct and go from there.

bmessina · Post by **bmessina** » 31 Dec 2012, 11:01

rspi wrote:Try not to get to distractedly, check to make sure your timing is correct and go from there.

Thanks - I had to reign myself in this weekend and focus on the timing again.

I found the notch on the sprocket, I think it looks good. All images taken based on this crankshaft position:

Notch is barely visible here:

Exhaust cam:

Intake cam (looks a little off, but not enough to cause me a huge problem):

Cleaned up the 2 engine grounds I could see (the 2 on the top rear of the engine), but they were in pretty good shape. Also finally picked up a replacement MAF, TPS, and FPR at the junkyard this weekend as well. Once the tire goes back on (had to buy new, stupid nail RIGHT on the edge of the tread), I'll be doing some testing.

Post by **erikv11** » 31 Dec 2012, 12:49

That's very useful info to have, the cam timing appears spot on. The marks are all lined up (intake is not perfect, but not off by a tooth either), the triangles are in the right orientation. At least you know cam timing is not the problem.

As an aside: I wonder if the belt is a bit old and stretched, explaining the slight misalignment of the cam notches. Don't get me wrong, there is no problem with the timing. But if you can't find any records of when the timing belt was done, you may want to do it soon. You said it is at 50k which is nearing time anyway, then you will be certain. How many years ago was the 50k?

bmessina · Post by **bmessina** » 31 Dec 2012, 19:37

erikv11 wrote:How many years ago was the 50k?

I would say at least 4-5 years. Timing belt is definitely on the list of things to do in the next month while I'm on leave.

bmessina · Post by **bmessina** » 03 Jan 2013, 11:18

Put the junkyard MAF in a few days ago, no change. Trying the TPS next.

Likely won't be able to touch it for a while after that, havin' a baby this weekend!

Post by **precopster** » 03 Jan 2013, 15:24

After all this have you taken compression figures yet?

This may or may not be relevant. Last week I replaced a transmission on a 960 and we assembled the gear selector piston incorrectly on the valve body. The gearbox was able to stop the engine from revving past 2500rpm when in Park. Yours doesn't rev past 4500rpm. I'm wondering if your transmission is loading the engine down. Food for thought.

At this point compression test would be in order.

Hope all goes well with the new arrival.

bmessina · Post by **bmessina** » 03 Jan 2013, 15:32

Yes - It's here on page 1. 170-175psi across all cylinders. So, ruled out as an issue.

It's still very striking to me that the car was magically better after being jump-started, then got back to "normal" over the course of a few minutes.

'96 850R Very low mpg, very low power.

Re: '96 850R Very low mpg, very low power.