96 850 NA AT Serious Lack ofPower.

Post by **Ozark Lee** » 19 Oct 2011, 17:14

waynej wrote:The more I push the pedal the less power I get. With a very light throttle 0 to 40 MPH is 12 seconds. With full throttle 0 to 40 is 37 seconds. In first gear it will not go above 3400 RPM in second gear it's 3000 RPM. On the highway it won't go past 65 and sometimes only 60 and it takes 2+ miles to get up to 60. Will not go up steep hills. No codes. Performance is the same with MAF disconnected. Have replaced air hose between filter housing and throttle body. Fuel pressure is to specs under all conditions. Replaced TPS.

Can you elaborate on how the car feels and sounds? Is it obviously missing and if so is it rhythmic or does it stumble worse at full throttle? Any black smoke out of the tailpipe?

...Lee

Post by **erikv11** » 19 Oct 2011, 17:30

OP has been fighting this for a while. In his other post he reported that the more open the throttle, the worse the stumbling. Note he has already replaced the TPS.

waynej · Post by **waynej** » 19 Oct 2011, 18:15

Thanks Lee, I was hoping one of the experts would see my post. Feels very smooth but weak. Seems louder than normal but that is probably because I'm having to operate at a higher RPM just to get around. No smoke of any kind. Had the wife rev it to 2, 3 and 4k in park while I felt the exhaust to check for a plugged CAT. The exhaust seems very hot. I will try the same on my sons 850 for comparison when he gets home. We tried the same test again after the car had been running for 1 or 2 minutes and it would only go to 3500 RPM and still no smoke. I think this problem probably began a few months ago. In June we had to drive over the mountains and it seemed very weak. I blamed it on the altitude but looking back on it I think this problem had started then. It got really bad about three weeks ago and at that time when it got to around 3500 RPM it would be going up and down about 200.RPM as if a governor was cycling in and out. Now it is a smooth and steady 3400 RPM limit. There is never any stumbling, it is a very smooth weakness. It feels fairly normal at light throttle and only looses power when I push the pedal more than about 25 or 30%. I guess you could call that a stumble? Normally with a stumble some power comes back again after a second, this never does. It stays smooth steady and very weak.
Thanks in advance for any help you can give.

waynej · Post by **waynej** » 20 Oct 2011, 20:43

Lee, Here's more info. It seems to be temperature dependent. Was worse in the hot weather but ok for the first minute or two after starting. I mentioned that it would rev to 4000 right after starting but only 3500 a minute or two later, that day was about 70. Today was a cool day, driving home after work it was only 50. Before pulling in the garage I put it in park and revved it, went very quickly and smoothly to 4000.

turbozutek · Post by **turbozutek** » 21 Oct 2011, 06:14

A few things occour to me:

1. Blocked air filter or ducting

2. Blocked CAT (How does the exhaust feel flowing out it at the rear pipe?) [As a blocked cat heats up and expands, it sometimes flows even less, which might explain the temperature / RPM difference]

3. Timing - could the belt have jumped a tooth?

These are all simple, quick checks and might turn up something, though honestly I'd have thought all of the above would throw a code or two.

Chris...

waynej · Post by **waynej** » 21 Oct 2011, 08:24

Thanks Chris, Is there an easy way to check the timing without pulling the covers and looking at the belts?

Post by **erikv11** » 21 Oct 2011, 09:28

waynej wrote:Thanks Chris, Is there an easy way to check the timing without pulling the covers and looking at the belts?

Nope

But you only have to pull one cover, by removing one bolt. Very easy.

gilhuly · Post by **gilhuly** » 21 Oct 2011, 18:47

Does your car have EGR? If so there's a good chance that it is the EGR temp sensor which acts as an intake air temp sensor, i believe. If I had the car on a scanner I'd look for air/fuel ratios, Intake air temp and coolant temp at the ecu. If you threw an EGR temp sensor and a coolant temp sensor at it it would surely cure your issue. How does your temp needle behave? I believe you are definitely onto the right path with temperature at the ECU: perception or reality? I think you may be running lean in closed loop, but kind of OK in open loop at startup. Interesting problem.

waynej · Post by **waynej** » 21 Oct 2011, 19:35

My cheap scan tool just gives codes for Volvo. I do have EGR and if I disable it by blocking the vacuum line to the EGR valve the problem gets worse. Temp needle right in the middle as always. I fully agree it acts like way too lean as soon as it gets into closed loop as far as the lack of power goes. I don't see how going lean could limit the RPM even with no load. Where are these temp sensors located and if I unplug the EGR temp sensor will it run in limp mode? Thanks for the help.

waynej · Post by **waynej** » 22 Oct 2011, 18:10

Can anyone tell me where the EGR temp sensor is located? I see a coolant temp sensor on the thermostat housing, is this for the ECU or the instruments or both? If it's not for the ECU, where is that one. Does anyone know what resistance values I should have on these sensors with a cool and warm engine?

96 850 NA AT Serious Lack ofPower.

Re: 96 850 NA AT Serious Lack ofPower.