Flat Spot

[eros8201]

Hey guys I am having an issue with my 94 Galant. It is an auto with a 4G63T and I am getting a flat spot when cruising at highway speed, it only happens when the car is in overdrive. When I get to around 60ish MPH the car seems to fall flat on its face and almost sounds like it loses a cyl. If I step on the gas and get the car to downshift it runs like a champ :-D. It seems to happen when I am on low boost less then 5 psi to about 10lbs into vacuum. It also may be a fuel issue, it sounds like it is bogging and smells like it is running rich, so does anyone know the fuel pressue of a stock 4G63T? I am going to throw some fuel system cleaner in the engine to see if it helps the issue any. Thanks for the help

[eros8201]

Well no answers so I have got some more questions. I took out my gauge cluster yesterday because the lights in it are like 4 differernt color, I guess the previous owner was slow changing them over? The light for the check engine was missing as well as the plastic clip that holds the light in, I was wondering where I can pick up these plastic clips and the best place to get bulbs, not sure if autozone or pepboys would carry them. I am also having an idleing problem where when I put my car into park it revs up a little and then back down, and continues to do this. I would assume it is associated with the TB needing to be cleaned, but I dont really know which sensor would need to be cleaned. Any chance that the flat spot is because of a bad o2 sensor causing the car to run in safe mode causing it to run really rich. Sorry if I am totally off basis with my presumptions I dont know anything about this car so I can only compare it to other cars I have owned.

[4-G-rim]

The best place to get the clips and bulbs are either from Mitsu or go to a salvage yard and pull the parts off you need off another 7g gauge cluster.

You idling issue happens only when the car is in park or just when its not moving in general? The IAC motor tends to go bad especially with the age of 7g's in general so that may be your problem. Cleaning the throttle body and intake can sometimes fix the issue also for whatever reason causing it.

Do you have anyway to log the car? You could be running rich which may be causing the "flat" spot but its hard to tell. Have you checked the condition of your spark plugs if any of them a fouled?

[eros8201]

I will be sure to pull the plugs this week and clean the TB and intake and see what happens. I have no way of logging anything. I want to eventually get DSM link.

[eros8201]

Well spark plugs didnt look like they were running overly rich however they were corrorded to hell on the tops. I replaced them and it seems like it is running smoother but I am still having the highway problems. I have an auto so the car only revs up and down when I am in park. The engine is a 4G63T so I am not sure if they had the IAC problem as well but I am going to clean the TB hopefully today, after re charging the GF's AC, and see if that dosent help out at all. The manual says that I should drain my coolant but does anyone know if I can just stick a bolt in the hose going to the TB so I dont have to drain it? I will see if I cant find the clips for the lights online so I at least know if I have a check engine light. In the meantime I may switch one of the lights from something else over.

[RedGalant2k1]

Yes, make sure you drain the coolant, once you open the system you let air in. Once air is in you could have heating issues, so make sure its drained and refilled. There is a large coolant funnel you can buy to help when you are 'bubbling down' the coolant system. Essentially it just lets you put a fair amount of coolant in the funnel while you work out all the air bubbles that are trapped in the system. If this process isn't done you could overheat the engine or have other issues.

[eros8201]

Yeah I was going to do this yesterday but I had some other things come up. I had the coolant drained and I refilled it with new coolant yesterday as the coolant that came out was nastly looking. Hpefully with the 3 day weekend I have coming up I can get the TB taken care of and then if that dosent take care of the issue I will work from there.

[RedGalant2k1]

When you service your throttle body make sure to check your vacuum lines for damage or deterioration, because its possible you have a vacuum leak also.

[eros8201]

Yeah I would like to get new vacuum lines all together. One I am not feeling the blue vacuum lines I am not sure If I want to go with colored lines or just go with black, taking all opinions. They also plugged a bunch of vacuum ports on the TB with some kind of red sealant, I want to clear that out and find some kind of plugs to cover the ports, also taking suggestions. I would think vacuum leak but the car only does it when in over drive and it seems like sometimes it is fine and then it will just start. There is a meet in late July that hopefully if I havent figured it out by then I can get some opinions from them. Thanks for the help

[eros8201]

Does the 4G63T have a TPS? The problem does seem to be happening in every gear just normally crusing in OD. When I get the problem if I let off the gas and let it fall back in RPM with the throttle completly realeased and then step on the gas again the problem goes away...for a while. I am going to be pulling the TB apart this upcoming week and cleaning the TB and as far back into the intake manifold that I can get. Any advise on the best way to clean? I was just going to pull the TB pull the sensors and clean with brake cleaner and a tooth brush. For the sensors themselves I am going to use a Q-tip. I will keep you guys updated on how things go.