1996 850 T5 Wagon - anti-surge (hesitation)

[jackdaniel]

Good morning ladies and gentlemen,

As a noobie here, please forgive any FUBARS. I have searched the forum (which probably means this issue has been discussed at least a dozen times before and the answer is already here right infront of my face), but any help with a little issue I have would be appreciated.

• 1996 850 T5 wagon
• Silver (yuck - but I can live with it), black leather.
• 260,000km, and other than glove box and tailgate rattle, and a bit of cracked leater on the front seats (the joys of Australian sun),not much wrong with it.
• Perth, Australia.

I am a long time euro car nut, but this is my first Sweedish mistress. I only picked her up last week and she is in pretty good condition for being 15 years old. But I do have one challenge.

There is an anti-surge (hesitation), that is most noticeable on small throttle openings.

There are no fault codes, there doesnt seem to bee any fuel pressure issues (pressure gauge is steady in the driveday), and I cant feel or hear any other issues.

The hesitation is there both 'on' and 'off' boost, but is much more prominent 'off' boost.

Air filter is clean, fuel filter and all fluids done ablut 6 weeks ago (previous owner supplied reciepts).

It doesnt 'feel' like a cam angle sensor (had that before on an Alfa), and I am suspecting a vacuum leak (havent found one yet) or more likely, a dodgy sensor somewhere - maybe an O2 sensor, MAF/MAP (dont know what it is yet), or throttle position sensor.

Is it possible that its the wastegate or the boost blow off thingy?

Any thoughts or experiences would be greatly appeciated - before I start pulling things apart.

[jblackburn]

Welcome to the site!

I'm going to go with the mass airflow sensor, since they're known for causing little hesitation issues. You can pick up a can of electrical contact cleaner (or even better, MAF cleaner spray) at an auto parts store and just spray the inside of it to clean it and let it dry.

Better yet, unplug the thing entirely and see if it will still drive and/or hesitate without it. This makes the car run on a best-guess estimate.

But, it probably wouldn't hurt to change plugs (gap to .028") and wires/cap/rotor first if they look old or pitted.

[Marcobrick]

Had similar behaviour that went away after replacing the coolant temp sensor at my last thermostat change.

[jackdaniel]

Thanks guys,

I'll give the MAF a clan, as that seems to be the cause of many issues.

You sugested unplugging the MAF - will it actually run without?

As a follow on, the hesitation is of on on/off cyclical nature - of about 1 - 1.5 second frequency, and its not there all the time, the severity also seems to vary - but the frequency is always about the same.

[Gentleman Mac]

Yes, it will run with the MAF disconnected.
1995 854 167k
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