Interesting Rough Idle

Hello All,

I have just joined the page and own a 1995 Volvo 940 non-turbo wagon. It idles very rough, and when under a load, put in either reverse or drive, it usually dies. Also, when I press on the throttle, the rpms stay up for a few seconds after I let go of the throttle. I thought this was the crankshaft position sensor at first, but it has a code for a MAF sensor fault. I tried the usual trick of unplugging the MAF sensor, but when doing this the engine would not start. I have not tried plugging/unplugging the sensor while the engine is running out of fear of frying the computer. I then cleaned the MAF sensor with no progress in the idle.

Thanks all.

Welcome.

Check for torn air ducts.

or a wacky i.a.c. motor possibly a bad coolant temp sender

ZVOLV said:

Welcome.

Check for torn air ducts.

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This.

ZVOLV said:

Welcome.

Check for torn air ducts.

Click to expand...

No torn air ducts.

Ok so... I'm going to implore you to check again and also check various vac hoses on the intake manifold. The reason is... they're truly challenging to track down some times. I have a super long thread in performance about surging idle and injectors. THAT ended up being a bad AMM, but I also found a torn IACV hose that didn't easily show up in my vac or boost leak tests because of where it was situated on the hose.

Not to imply that you didn't, but I would take that corrugated air hose OFF the car and get a good solid look at it. They tear all the time in the valleys and people miss them.

I don't trust statement of "no air leaks" unless you have smoke tested it. They can be very tough to find and on these old cars with all their rubber hoses running around they are VERY prone to air leaks. (versus a modern car)

ZVOLV said:

I don't trust statement of "no air leaks" unless you have smoke tested it. They can be very tough to find and on these old cars with all their rubber hoses running around they are VERY prone to air leaks. (versus a modern car)

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Yes you are right. Sorry I did not quite understand your statement because I am pretty new at this. I will come back with more updates later. Thank you for the help.