surging going uphill Topic is solved

Post by **Clemens** » 31 May 2017, 17:37

I noticed a few months back that my 96 R has a symptom that I never noticed on my 95 NA.
I don't even know if it is a real symptom.

Mainly with a cold engine i realize that going up that hill by my house at a slow and steady 20mph with soemwhere around 2000 rpm and steady light throttle that something feels like the fuel is being cut intermittently, pulsing interval is about a 2 seconds. I can also feel that very slighty on flat surace, but less than uphill. I think i can even feel it with a warm engine if the slope and speed are in a certain range.

I have never felt that on my NA. I have to mention though that the NA needs more trottle application to get up that hill.

I have no CEL, all new OEM ignition parts except the coil, volvo spark plugs, did the pcv twice, replaced a few vacum lines, cleand the injectors, put new orings on, cleaned the MAF and the crank position sensor, the IAC and the throttle body. The car runs really nice overall for 20 years and 200.000 miles. Am I hunting ghosts or is there something to find?

Post by **abscate** » 01 Jun 2017, 05:38

You might be floating right at the point where the boost is coming on. In my 1999 T5 ( kind of an R lite car) at 2500 rpm the boost is ramping up.

Post by **Clemens** » 01 Jun 2017, 12:43

Thanks, that is the answer I was hoping for.

Post by **scot850** » 01 Jun 2017, 12:50

And particularly when the engine is cold it is running richer which may add to the 'hunting' you are feeling. Is it as bad once warm? Have you checked the system for air or vacuum leaks, including thinks like the diaphragm in the turbo compressor valve? You could try pulling a small vacuum on it and see if it holds. The rubber goes brittle with age and can start to develop small pin holes.

Chances are that you may be over sensitive to a non-issue. If you need to find problems you are welcome to come to Calgary and look for issues on my cars (and preferably fix them!!!).

Neil.

Post by **Clemens** » 01 Jun 2017, 14:12

might as well be, I´ve been worrying about tiny issues on cars I´ve owned for almost 20 years. My mechanic hates me, I believe.

That´s why I started wrenching again.

Neil, I doubt I would be of significant use to a pro wrencher like you except for the Entertainment factor. Surprisingly, I enjoy drinking responsibly. Other than that I probably wouldn´t contribute to your Problems too much - especially if you drop the P80s...

Post by **mrbrian200** » 01 Jun 2017, 16:42

It could be harmless 'hunting' right at the point where boost ramps up.
But you should also consider surging at part throttle can also be a symptom of a 02 sensor that needs replacing (very slow response lean-rich cycling). ECU software back then wasn't as complex and you might expect odd drivability symptoms over a period of time before the CEL ticks on. You didn't show the O2S that on your list of things replaced. The older non-AFR/non-wideband sensors generally had a service life around or under 100k miles, which I'm pretty sure what you have on a '96 for only $90 (Bosch OEM part price).

Post by **Clemens** » 01 Jun 2017, 23:35

Yeah, that O2 sensor is on the list of things to fix this year. Just hadn't had time yet. I am sure the o2 semsor is old, at least 10 years. So i'll go and order one rightaway.

I will also change the turbo diaphrag. Someday soon because it is old (although i get full boost).

Thanks for all the ideas.

Post by **mrbrian200** » 02 Jun 2017, 16:25

Do those items one at a time and test drive in between so if one of them solves it, you'll know which.

Post by **Clemens** » 02 Jun 2017, 16:52

Great idea, i will do the O2 sensor first and report back.

Post by **Clemens** » 21 Aug 2017, 02:50

Just to close that topic: I replaced the front O2 sensor with the OEM Bosch unit and it seems to have cured the problem. Well, the old one lasted 200.000 miles. Not too bad. Let´s see if the fuel mileage improves now. I doubt it though, boost is just too much fun