My '86 245 has been a loyal friend for two years now even though I probably have saved it from a junk yard with it's body problems that previously owner's couldn't deal with....(leaking exhaust into car...) New Brakes I paid for and engine's been relatively great until my recent replacing AMM (which I couldn't afford a mechanic to solve..and this Board figured it out for me... Thanks again to "Lucid" and Volvodad!

Now this time: My engine's needing some timely help and this DIYer is starting down the usual road of perdition that many of the "hobbyists" here seem to be on...like keeping the Old Volvo long past any "normal" person should keep a car.

So Be It. My Questions are why is my engine surging??: sounding well at idle for about 3 seconds, then less well for the next 3 seconds, and over and over again...getting better after warming up but still surging at idle/ .

Also, My new rebuilt AMM obviously works as the old one stalled my car completely BUT my idle speed is slower after new AMM. Is that other people's experience?... I did turn my idle speed knob under throttle body counter clock-wise quite a bit....after noticing that it'd been turned almost as low as it could go before... by previous mechanic in response to my complaints that idle used to be too high.... well, My old AMM coulda been going bad for sometime... but shouldn't AMMs not effect idle speed? Used to be about 1000 rpm and now it's about 750.... I like it about 850-900 according to my dash tach which I know many of you don't trust...but I don't want to buy a handheld yet....


first choice ideas as to surging? Ignition timing? new timing belt?..(mine's over 5 years old even if mileage is only about 40 to 50 K)

anyone else experience either surging or differences in idle speed when replacing AMM?

My '86 245 has been a loyal friend for two years now even though I probably have saved it from a junk yard with it's body problems that previously owner's couldn't deal with....(leaking exhaust into car...) New Brakes I paid for and engine's been relatively great until my recent replacing AMM (which I couldn't afford a mechanic to solve..and this Board figured it out for me... Thanks again to "Lucid" and Volvodad!

Now this time: My engine's needing some timely help and this DIYer is starting down the usual road of perdition that many of the "hobbyists" here seem to be on...like keeping the Old Volvo long past any "normal" person should keep a car.

So Be It. My Questions are why is my engine surging??: sounding well at idle for about 3 seconds, then less well for the next 3 seconds, and over and over again...getting better after warming up but still surging at idle/ .

Also, My new rebuilt AMM obviously works as the old one stalled my car completely BUT my idle speed is slower after new AMM. Is that other people's experience?... I did turn my idle speed knob under throttle body counter clock-wise quite a bit....after noticing that it'd been turned almost as low as it could go before... by previous mechanic in response to my complaints that idle used to be too high.... well, My old AMM coulda been going bad for sometime... but shouldn't AMMs not effect idle speed? Used to be about 1000 rpm and now it's about 750.... I like it about 850-900 according to my dash tach which I know many of you don't trust...but I don't want to buy a handheld yet....


first choice ideas as to surging? Ignition timing? new timing belt?..(mine's over 5 years old even if mileage is only about 40 to 50 K)

anyone else experience either surging or differences in idle speed when replacing AMM?

Someone else earlier mentioned that a bad Air and fuel intake manifold gasket could do something like my bad idle (esp. if it gets better after warming up). I used a 13 mm wrench to "lightly" tighten those nuts as Foster suggested and there seemed to be an improvement in power and less 'missing'. But it could be only that it's warmed up more?

The surgeing? I was off a little on 'times'. Not every 3 seconds more like every one and half second (or less)? . I checked my distributer cap and saw some corrosion and Attempted to take off distributor rotor.... it didn't come off. Am I doing something wrong? I didn't want to muscle it and break it. It should just come out upwards shouldn't it? I lightly sanded the corrosion of the contacts inside cap...but nothing major in improvement.

I found one cracked and open vapor line from fuel throttle body to emissions canister and disconnected it and it didn't affect anything....perhaps a lot of leaks in that system... would that effect the idle and general performance if either opening to emissions control from top of throttle body? I completely disconnected it and left the gaping hole while engine ran and heard no performance difference. Also the surging (maybe more like 'missing') is really throughout the whole rpm spectrum but more noticible in idling...but I just don't notice when in drive mode in higher rpm... I think this has been bad since I got the car ...but not enough even to bother the two or three mechanics I have had on it....as they were more interested in racking up the bill on the brakes and tie rod repairs. I asked them about it and they didn't think it was bad enough to notice.

So far seems like keeping the oil level at the top of the line of dipstick and tightening these bolts afore mentioned and adjusting idle/throttle body adjuster upwards (loosening it) have made the most improvements....

I tried to find my PCV flametrap thingy and so far I am having trouble finding it. (I am sure it needs to be cleaned....)

So far with idle adjustment, warmed up engine and tightening some bolts seems to have been an improvement. Don't stall while idleing and turning at the corner I am hoping like before.

I still suspect that maybe valve/cam contacts, timing belt might be a big part of my engine not cleanly turning around without cycling on and 'off' vibrations ("missing") or surging in lower rpms. First I need to find that 'flame trap', what a hidden "treasure" that thing seems to be with all the other various 'sensors' and vacume and fuel lines all over the place. Volvo's have a lot of room ...but still some quirks it seems. (man, changing that fuel filter was awful compared to just some little plastic filter on my ol' toyota truck.

I mentioned keeping the oil at the highest on the dipstick gauge as I do notice improvement in 'clackity-clack' sounds from cam and valve areas....(another maintanince detail I've seen in the Hayne's book but my last mechanic didn't seem to think it was worthwhile pursueing ...(I suspect he didn't see the 'longivity' that I do in this car..)

I know I should clean the throttle body..... but maybe on the weekend?

if you have an intake leak, it can cause symptoms like you describe. take a can of carb cleaner and while the car is on, spray it around the intake manifold gasket area. if the idle suddenly goes up, you have a leak.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Thanks, maybe on to something.

I am going to clean the idle control thingy and throttle body this weekend. While I am at it. I'll check and see if I can get new gaskets all around the area.

Also, think I found the 'flame trap' PCV thing... but it's a ways underneigh the throttle body area... and I disconnected the hose from their and noticed some lessening of engine performance... so It must a least be doing something ....?

The engine's already sounding better with this little bit of tinkering.

(when I get to that timing belt change I'll be really needing this board's help....)

it never hurts to clean out your flametrap, although i don't think the flametrap should affect performance. it'll cause oil leaks though if it's clogged so you might as well do it anyway.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Yes, like Kenric says, focus on cleaning the throttle body first if not already done. Make sure the TPS (Throttle Position Switch) clicks when the throttle is allowed to close-- sometimes a tech will adjust the throttle stop screw (not the bypass knob you're adjusting) to make up for another problem affecting idle. If TB is clean and TPS working, the sticky goo in the IAC Kenric mentioned is often the culprit for surging. It works like an electric motor limited to 3/4 turn, so it acquires the usual motor problems with brush and commutator wear. Sorry if previous posts covered this...
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Art Benstein near Baltimore

start with the simple stuff like cleaning out the idle air control motor as well as the throttle body.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'