A couple years ago I bought an '85 Vanden Plas that was pretty good cosmetically but ran lousy. I worked on it a lot and finally found the culprit was clogged fuel injectors. After having them ultrasonically cleaned she ran great and passed Colorado Smog.

Two years and 12,000 miles later we are in California and next month I have to pass California smog. And she is not running quite up to snuff. Over the last couple months mpg has dropped from 16.1 to 14.8. And occasionally, when not warmed up, she backfires. [Backfiring (all the time) was her problem two years ago before I got the fuel injectors cleaned.] I've already tried a few simple "fixes" like new spark plugs, air filter and fuel filter. Now I'm suspecting maybe a fuel injector is clogged again.

Here's my question: Should I try one of those fuel injector cleaning services they advertise at chain places? My understanding is that it's more involved than putting seafoam in the tank, but is still just a chemical flush. They tap into the fuel system ahead of the gas tank and run this concentrated cleaner through it.

The alternative is to remove the fuel injectors and send them out for cleaning again. That's a lot more work and money and the car will be laid up for a week at least.

In CA if you fail smog you are no longer allowed to fix it yourself, so I really want to pass on the first try.

Thanks in advance for the good advice I know I'll get.

-mB

 

Right, and that type of service is often effective. Worth a try, IMO, as opposed to off-the-car cleaning

However...

*If* your injectors are dirty again so soon after last cleaning I'd be wondering why.

Cheers
DD

 

As Doug suggests, why the need to clean so often? If the dirty injectors are confirmed, it's time to look for the root cause.

 

You could first try running it on pure seafoam yourself.
Have done that on several vehicles before and it always did the trick.
After that, add a can of Seafoam to both tanks and drive.
Never drain your tanks completely though, as all the crud that had built up in the bottom will get pulled into your fuel lines....

 

There's nothing in Seafoam that will effectively clean a bad injector. This product is nothing more than 25% naphtha, 25% rubbing alcohol and 50% light mineral oil. It worked great for it's original purpose, which was dissolving varnish in post-WWII vintage 2 stoke outboard motors, but that was almost 70 years ago.

Modern fuels have far more effective additives than Seafoam ever had, and in greater quantities.

 

The name Seafoam is widely known and used for any carburettor cleaning fluid.
In the Netherlands we don't have Seafoam, but we do have Wynn's, Forté, Fortron and a lot of Naphta based cleaning fluids.

The motorcycle community stills swears on the real Seafoam though....

 

Small carbs on bikes are one thing, fuel injectors on car engines are another.

Many bikers have strange beliefs about octane levels and other similar fuel topics too. Not that some people here don't.

 

Thanks again guys. I mainly wanted to know if it would hurt anything. Since the consensus seems to be somewhere between "It might work" and "it'll do nothing" I figure I'll give it a try.

As far as the root cause I'm thinking dirty gas tanks. The car sat for a very long time before I bought it two years ago. And in fact I never even tried using the right hand tank until after the injectors were cleaned the last time. I've added fuel pump prefilters and have replaced the main fuel filter (two years ago and again yesterday) but I can imagine crud getting by.

That's IF it's actually a fuel injector problem. I had really thoroughly gone through everything , again two years ago, but things have been known to break on Jaguars during the span of two years. The thing is though it's a very gradual decline in MPG, from over 16 to, now, 14.7 (just lost another 0.1). Which sounds to me like something degrading with time rather than suddenly not working, like something electronic.

So I'll try the fuel injector service and see what happens.

Thanks again,

-MGB