2002 Mitsubishi Eclipse GT, stumble/bog on throttle input

[jlee]

My roommate's Eclipse has been dead in front of the house for months. We swapped the battery today (within free replacement period) and I started it up. It took a few tries to start, and I had to keep on the starter for about 5 seconds after it caught in order to keep it running (otherwise it'd stall). Once it caught idle, it was fine. However, it then started acting like a cold carb'd motor...give it a little throttle and it'd bog down and almost stall.

After it ran for a little while, I was able to (slowly) rev it up - from 3-4k, I could give it gas and it'd rev up normally, then drop back to idle. However, an abrupt throttle input from idle caused it to bog down again.

Apparently there's a vacuum line that runs from the fuel regulator to the intake manifold, which wears out over time - I'm going to look at that tomorrow. I don't know anything about Mitsubishi V6's..other than the typical check on vacuum lines & MAF, any ideas?

Total list of what's wrong, other than the stumble:
Peeling tint ($125ish)
Maybe motor mount(s), I haven't checked (front $16.96, rear $40.99, left $60.99, right $62.79)
Sunroof doesn't work (may or may not fix that, depending on what it costs - assuming switch, relay, or motor)
CD player is broken (swap MR2 head unit into Eclipse, buy new one for MR2)
Driver's side headlight bracket is broken ($35.99 for headlight assembly)
Heater core is leaking and has been bypassed ($46.99)
He said the brakes may need work because they're rusty - I haven't looked at them yet...guessing they are probably ok (set of pads $28.88, set of rotors $79.58)
Hatch hydraulic supports are toast ($17.62/ea)

If I can fix the stuttering/bogging issue for free/cheap, I should be able take care of the hatch supports, sunroof, and stereo for not too much money, then get it re-tinted and throw a cheap paint job on it and flip it. He said he'd be happy to get $1k out of the car, so I'm quite confident there's some money to be made for the both of us.

 

[Bartman39]

Check the fuel pressure... That vac hose from the manifold to the reg is to reduce rail pressure when off the throttle... But if its stuck open it may not be building pressure in the rail (or enough for more than idle)...

 

[jlee]

Check the fuel pressure... That vac hose from the manifold to the reg is to reduce rail pressure when off the throttle... But if its stuck open it may not be building pressure in the rail (or enough for more than idle)...

If I slowly give it gas, it'll build up to 3-4k - punching it then causes it to rev up normally.

 

[Bartman39]

Might just be working at a certain point but not when demand is high from an idle...?

 

[jlee]

Hmm, perhaps. I'll check it out in the morning and see.

 

[IcePickFreak]

It's not throwing any codes though?

Since it's been sitting, maybe check/clean the TB. Make sure the bypass ports in it are clear of any debris.

 

[jlee]

It's not throwing any codes though?

Since it's been sitting, maybe check/clean the TB. Make sure the bypass ports in it are clear of any debris.

The reason it was sitting is because it wasn't running properly - he got tired of fixing stuff and just bought another car. I think it was more of an excuse to get a new car than anything else, TBH. I may do that anyway, though- has over 100k on it and wouldn't hurt to clean it anyway!

I'm not sure on codes. The "service engine soon" or "maintenance required" (forget which it is) light is on, but no CEL. I ordered a bluetooth OBDII gadget so I can check stuff out, though.

 

[SyndromeOCZ]

Smell the fuel, if it smells bad then it probably is. Bad gasoline can cause you worlds of trouble if you don't suspect it. And it doesn't take long for it to spoil.

The 'Service Engine Soon' light is the CEL.

 

[jlee]

Smell the fuel, if it smells bad then it probably is. Bad gasoline can cause you worlds of trouble if you don't suspect it. And it doesn't take long for it to spoil.

The 'Service Engine Soon' light is the CEL.

If the car ran fine when parked, I'd agree with the fuel possibility- however, my roommate said it's acting now like it was before.

I'm wondering if spark plugs could cause an issue like this...not sure they've ever been changed, so plugs/wires/cap/rotor may not be a bad idea either.

 

[Bartman39]

If the car ran fine when parked, I'd agree with the fuel possibility- however, my roommate said it's acting now like it was before.

I'm wondering if spark plugs could cause an issue like this...not sure they've ever been changed, so plugs/wires/cap/rotor may not be a bad idea either.

If it were the plugs or other ignition related issues the problem would be a lot worse under load... It would be hell to drive...

 

[exdeath]

Check the fuel pressure... That vac hose from the manifold to the reg is to reduce rail pressure when off the throttle... But if its stuck open it may not be building pressure in the rail (or enough for more than idle)...

Other way around. No vacuum on the regulator = too much fuel pressure.

 

[kornphlake]

Could be the TPS. I'd start by pulling the diagnostic codes, otherwise we're just guessing. Autozone should do a scan for free if you can drive it down there, or you can buy a cheap code reader at Harbor Freight.

 

[IcePickFreak]

Could be the TPS. I'd start by pulling the diagnostic codes, otherwise we're just guessing. Autozone should do a scan for free if you can drive it down there, or you can buy a cheap code reader at Harbor Freight.

He said he already has an OBDII bluetooth reader on order. Much better than the cheap code readers because with one of them and an app like Torque you can read live data as well.

 

[waffleironhead]

exhaust blockage?

 

[manimal]

Sadly problems like this OP require you go keep at it and start crossing possibles off the list.

TPS, clogged cats, fuel filter blockage, injectors, etc.


If you have a steamer in the house use that to get off the blue tint.

 

[bobdole369]

Blown turbo (those cars have a turbo?) dry rotted intake snorkel or air inlet? I agree with the bad fuel comments. I would drain it, or at least put a few more gallons of fresh gas in it.

 

[jlee]

Blown turbo (those cars have a turbo?) dry rotted intake snorkel or air inlet? I agree with the bad fuel comments. I would drain it, or at least put a few more gallons of fresh gas in it.

n/a V6. It kinda feels like it'd be some sort of vacuum leak causing the ECU to get all confused - I'll put some pics up now that it's light outside.

 

[bobdole369]

If thats the case - force a test condition - usually a motor will ignore inputs from certain sensors in the event of malfunction, using set values in their place. Dunno how the eclipse works though. Maybe you can disconnect something like the TPS or a pressure sensor somewhere.

 

[manimal]

n/a V6. It kinda feels like it'd be some sort of vacuum leak causing the ECU to get all confused - I'll put some pics up now that it's light outside.

My VG30DTT did all kinds of crazyness before I figured out the 5 or so leaks and the bad maf. The clogged and non functioning egr didnt help either.

 

[jlee]

If thats the case - force a test condition - usually a motor will ignore inputs from certain sensors in the event of malfunction, using set values in their place. Dunno how the eclipse works though. Maybe you can disconnect something like the TPS or a pressure sensor somewhere.

Good call, see below.

My VG30DTT did all kinds of crazyness before I figured out the 5 or so leaks and the bad maf. The clogged and non functioning egr didnt help either.

I unplugged the MAF and nothing changed. I guess I have a starting point, haha.

 

[Bartman39]

Other way around. No vacuum on the regulator = too much fuel pressure.

Exdeath I think you did not understand how I meant it...?

That vac hose from the manifold to the reg is to reduce rail pressure when off the throttle...

Meaning yes with high vac at idle it opens the valve which bypasses the fuel back to tank so the rail pressure is not to high and flooding the injectors... If the valve is staying open dumping the fuel back to the tank instead of closing it will not build pressure to give the system enough for full throttle operation...

 

[jlee]

Apparently DSMs use Karman-Vortex MAFs and they aren't able to be cleaned with regular MAF cleaner. I may try electronics cleaner, or pull one from another car to test. I think the IAC may need cleaning as well, but since nothing changes when I unplug the MAF, that kinda points in one direction..

 

[Raduque]

My mom's 02 Eclipse GT has the same problem whenever the battery is disconnected. Takes 3 days to a week to get it running right.

Of course, her car needs plugs and is throwing a #5 misfire code too.