I have a 1988 240 that hasn't run in a few years. I bought it not running. Now it's running and I just repaired the overdrive. I got it out on the open road for the first time, and it will not go over 45 MPH. It sounds like it needs a valve adjustment, but other than that I don't know what to do next.
Plugs, wires, distributor cap, rotor have all been replaced. Fuel pumps both working fine, Idles pretty smooth, good fire on all cylinders.
What's next?
Just below the throttle body there is some type of adjustment screw. It's a big black plastic thumbscrew. What does that adjust?

Thanks for whatever help you can provide.

 

I think the adjustment screw on the AMM is for emissions. I would do a compression test you can get a kit at harbor freight for ~50. See if you have good compression, then I would pull the timing belt cover and see if everything still lines up, slipping a cog on a timing belt can hurt power... just my two cents...

 

Thats a manual idle adjustment. I would check for obstructed exhaust.

 

its probably not an electrical issue, since it idles fine. Obstructed catalytic converter can do that in a snap. Happened on my police car which I drove daily. Went on a call over a bumpy road, got back to the interstate later, and got to maybe 50 mph. That said, maybe a fuel injector flush, but in my advice, I've put good money after bad chasing down these and other gremlins in my 87 240. Take it to a good shop. I dont see why the valves would need adjusting

 

Thanks for your ideas guys. When the plugs and wires were replaced, my son had two plug wires reversed. When we first attempted to crank it, it backfired and chugged a lot. So, I'm thinking it may have possibly jumped timing.
Can anyone supply me with some pictures of the timing belt and marks. Basically, what should I expect to see when I get the cover off?
Thanks,

 

pictures are in this thread ...

https://volvoforums.com/forum/volvo-240-740-940-12/no-spark-89-240dl-wagon-41389/

 

Make sure you have the firing order correct. From left to right should be 1 3 4 2. A clogged Catalytic converter can cause at high speeds or up hills only so it may be that. Also I've seen bad MAF sensors cause loss of power and bad ECU's. The timing marks are on the pullies and the timing belt cover. They make timing belts today that have stripes on them so you can't mess up position. Also on an 88 you can do distributor timing(power timing) unlike an 89 and on. Get a 14mm long socket an extension and a ratchet. Loosen the nut on the diributor. Distributor should the turn freely it it doesn't don't force it it's frozen. Then move the distributor left or right (retard or advance timing) you can do this by ear if you have someone in the car with foot on brake car in gear and stepping on gas. If you hear the car pinging then it is off time adjust until it sounds correct...kind of hard if you don't know what you're listening for. I would check firing order first and foremost. Then I would unhook the connector to the MAF sensor while the car is running, then plug it back in. If there is NO change then your MAF sensor is bad and that is most likely your problem. If there is a change in how the car idles then test all your wires with a multimeter. If they read less than 2 ohms or more than 10 they are bad. Also pull your plugs to see if they are black, not firing, or wet...since they are all pulled do a quick compression test on all cylinders...If all these things are OK then get to a mechanic and have him check your CAT. If CAT is ok proceed to replacing ECU. If none of that works....open up your wallet and leave the car with a Volvo specialist to figure it out... Hope this helps and Good Luck!!

 

I may be wrong, as I always am when i'm not right, but just crossing the wires cannot cause a mechanical reaction like a belt jumping time, not to say there isnt a problem with the belt or tensioner, or the crankshaft position sensor( but thats usually a no start siotuation) volvoguy has some outstanding, insightful advice. I need to keep him on my blackberry instant messenger list haha

 

I took out the plugs and went on the internet to find that the gap should be .028. I noticed that the plugs came gapped to about .050, so I regapped the plugs and it runs much worse. I checked the timing marks and they are all lined up and at TDC, the rotor is pointing at the #2 plugwire.
I've got the day off to work on the thing, but have no idea what to do. If your recommendation is to unplug something or look at a sensor, can you please send a pic of where that sensor is or describe what it looks like?
Thanks in advance for your help.

 

Sorry, at TDC the rotor is pointing to the #1 position on the cap. So, timing is correct, or close to it, I do not have a timing light, but I'll try adjusting it by ear. I haven't done that in about 35 years when I used to work at a gas station. You know, a "SERVICE STATION" where we pumped your gas for you checked under your hood, washed your windshield and even checked the air in your tires on request.
Oh, the good 'ol days.

 

unplug the mass airflow sensor which is located under the hood drivers side between the throttle body and the air filter box. It is in the middle of a black corrugated hose(bellows) it has an electrical connection on top. While the car is running unplug it then plug it. If no change then it is bad. I also just rembered that if your flame trap and flame trap hoses are not connected this will definitely cause loss of power and car will run like crap. Check to see if maybe it got disconnected while working on the car...also check for any vaccuum leaks including on the bellows (black corrugated hose) a lot of time it rubs against other parts on the car and gets holes on the bottom of it that cannot be seen. You must either take it off the car and inspect or run your bare hand down underneath it and feel for rough spots(holes). A ripped bellows will also cause loss of power...I jave seen people sell there cars cause of this very simple fix but tough to diagnose if you don't know what your looking for...hope this helps

 

forgot to mention the big black scre that is on the throttle body will adjust idle higher or lower. You should set your idle at 800RPM. The black screw opens and closes throttle. Also to check for vacuum leaks get yourself a can of starting fluid when the car is running spray it along the intake manifold, bellows, injectors, anywhere there could be a potential vacuum leak or seal leaking. If the car idles up when you spray...you have a vacuum leak. Pinpoint the leak by spraying again until you find where it's coming from. Also, make sure your throttle is opening up all the way and is clean. To do this you need to detach the bellows(black corrugated hose) which takes about 20 seconds with a flat blade screwdriver. You will need a mirror(dentist style preferably) and a flash light. You will probably see black which is built up carbon etc. Clean this with a small wire brush and some throttle body cleaner. Also make sure you hear a click from the throttle switch(black switch on side of throttle body) when you open the throttle. To do this lean down close to the switch with your right ear slowly open the throttle you should hear a click if you don't either the switch is bad or you throttle body is filthy...won't really cause loss of power but should be done if you are truly tuning your car or giving it a "major" service or 30K service. If you are only giving it a "minor" service 15k service it is not necessary unless it has never been done. Also remember to change your timing belt every 50k. If you go over no big deal cause if it breaks you're ok...non interference motor gotta love it!! Feel free to ask for any additional help. OH yeah balve adjustments are only needed every 30k. You should here a 240 motor...if you don't(sounds like a Toyota) your valves are too tight

 

I'm thinking it should be pointing toward the #1 plugwire....

 

I have never seen a 240 jump timing. I have seen the cam shaft freeze up and belt break but I have never seen one jump timing and I have owned hundreds of them...I guess it could happen but if it idles perfect then it's probally right on timing. If it only happens when you are accelerating at high speeds 40mph+ it's most likely your Catalytic converter, your fuel delivery system(fuel pressure regulator,plugged fuel filter, MAF sensor,Vacuum leaks) or weak spark(bad rotor,bad cap,bad wires). Just to rule it out I would go to your cheapo exhaust chain shop (Midas or Meineke) or whatever you have close to you and let them check to see if your CAT is clogged. They all do free inspections. If it is clogged you have 2 choices 1. Buy a new CAT(expensive fix) or 2. take the guts out of it(inexpensive fix-free if you can do it yourself.