New GS 300 owner here.

145k miles on it, so I decided to run seafoam. Not through the vac lines (a little too aggressive, IMO, on such an old car). Just through the gas tank.

Must be a lot of crap in the system, because that has created some problems. I'll try to describe them and hope to get a good diagnosis from you folks who have had these cars longer.

Once starting it, if I rev the engine under no load (in P or N) up to 2k+, it will stay running. If I let off the gas, or if I shift to D to try to drive, it will choke out within five seconds. Which is unfortunate, because I feel like if I could get it out to blow everything out of it, it might be ok. If I try to immediately restart it at that point, it won't go. It has to set for an hour or two. I do get some white smoke from the Seafoam. Seems like the Seafoam in the gas tank is actually acting pretty aggressively, and/or the engine is gunked up like crazy.

I've changed the fuel filter. Twice, actually, thinking maybe the Seafoam let loose sediment from the gas tank that was clogging it. But when I was able to keep it running at 2K RPM after the second change, I realized that is likely not the problem.

Now I'm thinking it could be a sensor problem. Perhaps one that got gunked up by the released carbon and is now making the engine run far too rich at idle? It could be flooding it, which is why it has to set between starts. Or the intake manifold could be really gunked up.

That's really all I have at this point. Any ideas?

 

How much did you pour in the tank? How much gas was in it at the time?

 

Full tank of gas, went with 1 oz per gallon, so about a can and a third.

Thinking about this more, good chance it's the EGR valve all gummed up. Now I just have to find it and see if it's something I can easily remove and clean on this vehicle.

If anyone knows, let me know. In the meantime, it's more forum searching for me!

 

Sounds like the EGR on these things is a huge PITA to get to.

I'll start by cleaning the MAF and cleaning/adjusting the TPS first.

What cleaner is gentle enough for the MAF?

 

I never liked Sea Foam i get so many cars in that half to be repaired because of that stuff, that stuff eats thru gaskets and seals like crazy. I always ask the customer why did they add it, and they say because it looked good on the commercial. Try to stay away from all those additives it just hides the real problems the car is having. It sounds like you have a vacuum line disconnected check or listen for any hissing sound comming from the engine bay usually its the pcv hose that tends to crack or come undone, or check the Brake booster line. Good luck!

 

^^ wow jpgs300 i just have to say i LOVE your car.

 

I've had great luck with it in the past on other vehicles. It's the only additive I use. Well, except on my 1980 Ford F-100...but that's another thread altogether.

The MAF on these things is weird. I wasn't even sure it was actually a MAF until I came on here to verify. I'm still not sure I really cleaned the sensors. I wonder if mine is broken? If anyone has a pic of the portion of the MAF that extends into the intake, please put it up. Are there supposed to be wires between the plastic columns? Mine didn't have any. Not really sure how that thing works--looks different from other MAF's I have seen.

I'll peek around to make sure everything is hooked up. Where is the brake booster line?

Thanks for all the help.

 

That is a Karmen Vortex meter and you do NOT spray clean them. The last person I heard of doing that ruined it.

 

I've cleaned several parts: sensors, PCV, etc and now here's the update: Last time I started it up, it came to idle properly and was humming along ok. I let it idle for a few seconds and then tried the gas pedal. As soon as I touched the gas, the car died. That was a few hours ago, and it still won't start back up, just chugs along a little and then dies.

It will start again after a few hours, or else by morning. Then I plan to let it idle without messing with anything until it comes up to temp and seeing if it dies then.

Any ideas in the interim? Would really like to get this up and running in the next few days.

 

Wow, I was actually thinking about using seafoam also, Besides the GAS tank, what is the best possible place to add seafoam if any? PCV Valve, Brake Boost Vacuum line(Where is this located?!?), Throttle Body?

Sebastion: Ive been reading up on some things on seafoam, and some guys on a few forums said that its not recommeded on engines over 150k, Because it can actually damage some old seals, but theres alota people who did it and it worked out fine, Also Im not sure if this is related, but how much gas do you have in the car now?

 

i did it on my car when it had 220,000 miles. i put 1/3 in brake booster, 1/3 in oil, 1/3 in gas tank. afterwards i changed oil, oil filter and spark plugs. and the results were great, car used to idle high, after it dropped to normal low idle.

 

Yeah, I probably wouldn't run it through a vac line on a car that old if you don't know where it's been. The fuel treatment isn't nearly as aggressive.

The gas is 3/4+ full.

 

After cleaning several sensors, the PCV, all that stuff and adding a gallon or so of gas to the tank to help shake it up some and make sure I wasn't running too strong on the Seafoam, I started 'er back up a few minutes ago.

It popped off pretty quick and started idling nice and smoothly. I didn't touch anything, just to see how long it would go. After about 30 seconds or a minute, it promptly died.

Not sure if that info gets us anywhere on solving this mystery...

 

Forget about seafoaming and cleaning out engine gunk; you have a TPS related issue. Either out of calibration, malfunction, or the wiring is damaged from heat.

 

I cleaned the two sensors located on the TB yesterday. Looks like I'll have to grab a multimeter and find those threads I searched for a few days back about calibrating it. Never done that sort of thing before, so that should be fun. Not really sure how to even adjust it.

You sound like you're fairly certain about the TPS being the issue. I hope you're right! Thanks.