2003 Volvo C70 with 42,000 mi has acceleration problems with jerking. I tried high performance gas, octane booster, replaced gas filter. No engine light coming on for codes....

sounds ,more like spark knock. could be poor timing ,bad plugs, wires if it has them, possible weak coil packs

If you are using 91 octane and there are problems with performance and economy and pinging in the engine under acceleration then shift up to 98 octane . I would steer clear of any e- fuels as they are not doing the job generally. Any Honda hand book will have the recommended octane rating for your engine.

Throttle position sensor, or just dirty. Try running higher octane gas, (premium) and/or a gas treatment supplement like STP every other tankfull. High performance engines won't run right on regular gas. My mom uses premium, she gets great performance and better gas mileage in her 99 oldsmobile.

The knock sensor is making your engine light blink, and motors "knock" when the gas in them does not have enough octane (poor quality fuel may have water in it) I would first try a bottle of octane booster in the tank. It simple makes gas burn better. If this does not help after 50-60 miles, replace your fuel filter, as you probably got some dirty gas which has partially plugged the filter not letting your car get enough fuel and could cause damage.

The air/fuel mixture screws are usually capped off and the adjustment might not be possible, but if the air/fuel mixture screws are exposed then turning them in will lean out the fuel mixture, and turning the air/fuel mixture screws out will en-rich the fuel mixture.

With the engine fully warmed up and at normal idle speed adjust the air/fuel mixture screws one at a time, and turn each air/fuel mixture screw in until the engine just begins to mis-fire, then back out the air/fuel mixture screw one and a half turns to two turns to achieve a smooth idle.

Be certain that the air and fuel filter(s) are not plugged up (there might be a fuel filter inside of the fuel pump as well as the fuel filter/stone at the fuel inlet to the carburetor) and keep in mind that the minimum octane requirement for that engine is 91 octane, and 92 octane is the average octane rating for the premium higher grade fuel, so a bottle of octane booster added to a full tank of fuel will greatly improve the way the engine idles and performs.

That engine should have an electronic HEI (High Energy Ignition) distributor with the large distributor cap and with the ignition coil inside of the top of the distributor cap, and keep the tune-up parts in good condition and replace them when they wear out. The tune parts would consist of the distributor cap, ignition rotor, spark plugs, spark plug wires, and the spark plugs should be gapped at .045 in.

For better performance from your El Dorado a 1 inch spacer under the carburetor will really help a lot if the hood clearance will allow it, and you will need to set the ignition timing to 10 degrees before top dead center, and adjust the accelerator pump on the carburetor for maximun pump efficiency so that as soon as the throttle is opened there is two healthy squirts of fuel from the accelerator pump, and they should squirt as soon as the throttle is opened, and if the throttle can be opened and the accelerator pump does not squirt fuel at the same time as the throttle is opened, then there will be a lag or stumble from the engine on take-off and a severe loss of engine performance. (The accelerator pump must pump fuel into the carburetor at the exact same time as the throttle is opened)

For better performance check the adjustment of the secondary throttle linkage, and let me know if you require assistance with any of the proceedures.

Be sure that the vacuum lines to the EGR valve are correctly routed and that the EGR valve is not operating at idle.

Also, that engine has a plastic timing gear that was used for the camshft timing gear, and I would seriously suggest that it is changed before trying to get any performance from that engine.

Other than those modifications, the engine would need a better camshaft and the catalytic converter removed to increase the performance of that engine.

Here are some images to help assist you.


Fuel Pump Filter:










Rochester Carburetor Secondary Adjustment:

When it revs high, is it down shifting? if so you may be running out of gas. low fuel pressure or lack of fuel getting to the injectors. (fuel filter)

It's easy to do, except the plugs. As far as a tune-up, the only thing i would recommend is new plugs, air filter, fuel filter, clean the throttle body, and run a octane booster through a tank of gas. I prefer not to use a basic injector cleaner so I use a 104 octane booster.

I would have to hear it. may be the engine mounts.

Even a small amount of bad gas can cause your problem.
So the first thing you need to do is remove your fuel tank so you can drain all of the old fuel out,then remove the fuel sending unit and fuel pump assembly thats in your fuel tank and clean the filter screen, after that you can reinstall the fuel tank,replace your fuel filter and I would have a fuel injector sevice done.
Unless you are very skilled in automotive repair, leave this one to a pro.

for the fist little while you can drive 2 footed and the first thing you shuold do for the time being is get some fuel injector cleaner and some high octane gas or some octane booster good luckwith the car