Idles fine, but at half throttle, freaks out.

[TheBassist]

Okay, I searched and searched and read all of the suggested similar threads. But it seems no one has my problem. Hopefully I don't make an idiot out of myself; I'm new here.

Okay. First off: 1999 Eclipse GS. All I've done performance wise is a CAI.
I'm getting a CEL for an Inefficient catalyst. But I've had that since I bought the car 7 months ago. But it's been running fine till last week.

I also changed plugs and wires a couple of weeks ago because it wasn't accelerating smoothly. Those fixed that problem.

MY PROBLEM: It idles smoothly, but at half throttle (just normal driving throttle, nothing outrageous), it starts to lag and lurch. As in, I was in first gear earlier going slow (~1500 rpm) and floored it. It accelerated for a split second, then just stopped accelerating (car is still moving, engine still running). Then starts again and shoots up to 3500 then starts lagging, like I'm pumping the gas pedal like a kick drum. It does this in all of the gears (MT) but is most noticeable in the first three.

I checked the plugs today, they seemed fine (visually). I checked the wire connections: all okay, though one of them after i plugged it into the coil and i heard the *click, it seemed to slide out some, but I'm pretty sure it's still connected in there. I was low on oil but I topped it off, and still had the problem.

Sorry for the copious amounts of info, I just want to be thorough. I'm going to check the resistance on the Ignition Coil tomorrow to make sure it's not shot. I've heard bad o2 sensors can cause this? I would love any help! Thanks in advance.

Ethan.

 

[pgarland]

Whats the exact code for the CEL (is it P0420)? Couple of things can cause that, a bad cat, exhaust leaks upstream of the cat, or contaminated fuel. Here is the step by step out of the Mitchell manual:

1. CATALYTIC CONVERTER EFFICIENCY FAILURE DTC sets if PCM senses that output voltage of downstream O2S copies that of Upstream O2S (with a pre-determined time lag) after 2 sequential trips. Possible causes are: failed catalytic converter, exhaust leaks upstream of catalytic converter, contaminated fuel, or mechanical engine problem. Go to next step.

2. Start engine. Check exhaust system for leaks between engine and downstream O2S. Repair exhaust leaks as required. If no exhaust leaks exist, go to next step.

3. Check exhaust for excessive smoke caused by oil or coolant consumption. If a high oil or coolant consumption condition exists, repair engine as required and replace catalytic converter. If no high oil or coolant consumption condition exists, go to next step.

4. If downstream O2S has not been replaced within 5000 miles, replace catalytic converter. If downstream O2S has been replaced within 5000 miles, go to next step.

5. If upstream O2S has been replaced within 5000 miles, replace catalytic converter. If upstream O2S has not been replaced within 5000 miles, replace upstream O2S.

I'd recommend going the extra mile and clean or replace the air filter, clean the throttle body, and clean the MAF sensor too. Hope this helps.

 

[TheBassist]

I'm not sure the exact code, I just had it checked at a 76 Station and he didn't tell me the exact code and I didn't bother to ask. Is it worth knowing the specific code?

Oh, and I tested the Ignition Coil today against a new one, and it seems to be working just fine. So it's not that.

Tomorrow, I'll try cleaning the TB and MAF...where is the MAF? Wait, does the 2g N/T have the MAF? I'm also going to run some Fuel Injector cleaner through tomorrow. I'll also check that stuff you quoted from the Mitchell Manual.

Thanks for the help, I'll let you know if any of it helps!

 

[ceristeare]

i had a chunk missing from one of my fuel injector seals and my car had the same symptoms as yours...

 

[bullettdsm]

Quick check for a blocked cat; unbolt the exhaust before the cat; Tie up the exhaust with a coat hanger or something so that it doesn't fall down; take it for a quick ride and see if the problem clears up (and sound really cool while doing it )

This has a possibility of being a blocked cat with a piece that comes up and blocks of the air flow, then falls back down.

Of course it could also be a fuel delivery situation, but you might start there (as well as pull the full code).

MB

 

[TheBassist]

Quick check for a blocked cat; unbolt the exhaust before the cat; Tie up the exhaust with a coat hanger or something so that it doesn't fall down; take it for a quick ride and see if the problem clears up (and sound really cool while doing it )

This has a possibility of being a blocked cat with a piece that comes up and blocks of the air flow, then falls back down.

Of course it could also be a fuel delivery situation, but you might start there (as well as pull the full code).

MB

Ooh, that sounds fun! I definitely want to know if I'll need a new cat or not, so that'll be good!

i had a chunk missing from one of my fuel injector seals and my car had the same symptoms as yours...

That sounds expensive. Was it when you got it fixed? And I assume it helped?

Again, thanks everyone for the input! Can't wait to try everything out!

 

[ceristeare]

no they are cheap and easy to replace

1990-2008 Mitsubishi Eclipse - OES Genuine Lower Fuel Injector Seal

my car is a turbo and the hole in the seal was causing a huge air leak when the car tried to accelerate.
when idling i did hear a hisssssssssssssssss coming from the injector area. i looped off all my emissions vacuum tubes to eliminate any potential for air leaks. vacuum leaks are a bigger problem with turbo cars but i would check extensively for air leaks or install new tubing.

btw yes it made a huge difference i went from 0 to 200 hp for $1.95

 

[pgarland]

btw yes it made a huge difference i went from 0 to 200 hp for $1.95

Thats like 9 and 1/2 cents a horse...I wish they were all that cheap!

 

[TheBassist]

Okay, so a quick update: I filled up with gas and ran some fuel injector cleaner down and it helped with the major problem (the 1st/2nd gear lurching) but I think have lagging problems starting at 3k-ish.

To be honest I haven't done any of your suggestions yet, I'm hoping to do the fuel filter today or tomorrow.

And a quick question: I have the back seat out right now so I can hear the fuel pump...is it supposed to make a high pitched sound? It's not abnormally loud, just high pitched.

Thanks.

 

[e96eclipse]

I would say check all your vac lines...my old 95 was doing kinda the same,ended up being a vac line had come off and the motor was getting to much air! but could be in the fuel also!! but finding out the who;e CEL code would help alot

 

[TheBassist]

Okay, so another quick update: I changed the fuel filter yesterday and when I disconnected the fuel lines gas and a bunch of black crap came out (there is still a black stain on the road). I replaced it, and today gave it a bit of hell on the road (only a little) and I seem to be running smooth.

I thank you all for the help and support and suggestions. If I encounter this problem again, this is where I'll turn.

 

[TheBassist]

Hey guys. So an update, I know this is old, but I figure it will be good for future readers.

About a week after this, my car freaked out even more. It got to the point (overnight I might add) that I had to be super super light on the throttle or it would lurch like a bucking bronco. Couldn't even drive to work or anything. I drove it gingerly to a mechanic and they looked at it and reported that the fuel pump was out. Idle was somewhere around 120 psi if I recall correctly, but under load dropped to under 20 psi. So, after a $450 ish fix, I'm running fine, and have been ever since. I thank you again for all of the help! I love this place.