My 91' Accord has a misfire that is pretty noticeable. At idle it shakes so badly that I can feel the whole car shake and see and feel the steering wheel shake. But if I give it just a little bit of gas it goes away. When I turn on the rear defroster it just amplifies the miss, and also drops the idle a little bit. Any ideas?

What i've done:

Full Tune-Up

Fuel Filter

Injector cleaner

Fuel Pressure Regulator ( Because It would backfire through intake )

o2 Sensor

and just the other day the alternator because it was weak

When I got the car it sat for 3 years and I ran the old gas through it, when I got it the fuel filter was gunked up bad, should I change it again?

 

Can you specify what you did? What parts did you replace? How do the plugs look? Have you been able to tell which plug is misfiring? Can you do a compression or leak down test on the engine? It could be a sticking valve not fully closing.

I would dump a can of Sea Foam into the tank at your next fill up, run it through and then replace the filter.

 

I replaced Cap Rotor wires and plugs. I also replaced valve cover gasket because oil was in the spark plug tubes. The plugs look good a light brown. I have no idea what cylinder is is missing. I removed the plug wires one by one and everytime the miss got worse.

I just did a valve adjustment, but it did it before as well.

If I used seafoam wouldn't i have to do a oil change as well?

 

Put the seafoam in the gas tank.

What is the rpm at idle-with no load?

 

It is usually around 850 but sometimes it will idle down to 750.

When I add load it idles down about 50 rpms and gets rough

 

I know you have been through a lot with this car, can't even remember what all you have done and tested.

Seafaom in the tank, see what happens.

IAC and boost valve (I think you have a 4th gen). Make sure the passage from the tb to the IAC is clean...heck, clean the snot out of the tb while there.

I'm pretty sure you've already been thru all of the ing stuff.

Does this only happen once warm, somewhere I think I saw you might have EGR port issues.

 

I have cleaned the IAC but I haven't removed the 4 bolts on the intake and clean behind the tongue. If I did remove it to clean behind and clean all the passages. My only question is could I use former gasket if I removed it?

The car runs good. The issues I have don't affect the fuel efficiently or cause any performance issues. They are just annoying. I mean I took a 300 mile trip a couple days ago with no problems at all.

The engine burns no oil and is always reliable. So I am going to keep running the car and fixing all the minor issues till it won't go anymore.

Thanks for you help

 

Me, before going that far. I'd open the butterfly and use an old tooth brush and get both sides of the butterfly and the edges. Then be sure to get the tb where it would "seat" off. When the butterfly is open you should see two "pinky" size holes/ports, these lead to the IAC and FITV....

Then with a full tank of gas, put the whole can of seafoam in the tank.

 

If I had to guess it could be related to your egr ports being plugged.

 

How do your engine & transmission mounts look?
Is it an automatic or manual trans?

The automatic trans Accord has an electronically controlled rear trans mount. it is operated via a vacuum diaphragm. Could be something wrong with it or one of the other engine mounts.

 

It is a manual and the mounts look good. I have cleaned the throttle body before by doing that.

My only question about sea foam is do I have to do an oil change even if I put it in the gas?

 

No, you do not. If you only add it to the gas tank.

 

Ok next fill up i'll try that. You say to use the whole bottle?

I have tried the tune-up in a bottle stuff and it didn't help.

 

I think the can says something like 1oz per gallon, so (estimating as I'm too lazy to look it up right now) that the gas tank on your car holds ~14 gallons. So the 16 oz in the can.......dump it all when the tank is full.....I'll be honest and say I don't think this alone is going to help/solve the issue but it can't hurt.

Does this only happen once the car is warm-normal oper temp? ...wait, I asked that once already.

 

Yeah my tank is 17 gallons, I am starting to think it might be bad grounds because it does it when the headlights are on or the rear defroster. Another thing is when I put on the turn signals once in a while the lights flash out.