2G 98 Eclipse GST jerking back and forth when driving

[kyler021]

Hello everybody,

I've just recently purchased a 1998 Eclipse GST as a project car, it was running perfectly fine during the test drive, but on the way home after purchasing it, it would randomly jerk back and forth while I was driving. The car was violently jerking back and forth so much that people behind me could see it. (I would compare this to the first time learning manual, although way worse cause I wasn't expecting it) At a stoplight I shut the car off, turned it back on, it would run fine for about 2 minutes, and then go back to jerking back and forth. Although nothing seemed wrong when I pushed the clutch in and was coasting. At one point I was full throttle and nothing... I watched a video of my car, and as it's bucking, I saw a cloud of black smoke come out of the tailpipe. I also believe it was sitting for a while before I got a chance to look at it. I don't know if this is of any relevance but it was raining when I drove home, and the hood was misaligned to where the hood was more opened on the side where the MAF is. I'm not sure if enough water got into the filter for it to cause this though.

I'm gonna take a thorough look at the car during thanksgiving break, so far I've replaced the fuel pump, and I'll soon be replacing the fuel filter, cleaning injectors, and replacing some gaskets, checking timing etc... I have some ideas as to what it could be but I would like to know what you guys think. I appreciate any help I can get. Don't flame too hard this is my first post here .

Thanks for your time!

Edit: I should’ve definitely mentioned that I smell fuel in the oil as well as the compression test results I did were much below optimal: Cylinder 1: 120psi, Cylinder 2: 115psi, Cylinder 3: 105-110psi and Cylinder 4: 105psi. I smell a rebuild coming soon Also, the bucking problem would happen around 2000-2500 rpm.

 

[pauleyman]

I'm confused....Jerking back and forth like steering input? Or front and rear like on and off throttle?

 

[kyler021]

I'm confused....Jerking back and forth like steering input? Or front and rear like on and off throttle?

I'd be on the throttle, and out of nowhere I'd be jerking back in forth in terms of losing power, comparable to on and off throttle, but more violent

 

[pauleyman]

Please make a vehicle profile. We need to know what's done to the car. Next what maintenance or checking have you done?

 

[kyler021]

Please make a vehicle profile. We need to know what's done to the car. Next what maintenance or checking have you done?

I added the compression test results and some other information to the original post, I’m going to try to do a leak down test and boost leak test in the near future. As for maintenance I only replaced the fuel pump but I’m going to change the oil and probably get a sample to send to a lab. I’m also going to check the fuel tank again and probably end up draining the current fuel out of there since I suspect it was sitting before I bought it. I filled out the first part of the vehicle profile, can’t do the rest just yet haha.

 

[pauleyman]

So you don't know what boost its running? Plugs? Wires? Etc?

 

[luv2rallye]

Do a BLT and check input air hoses, throttle body shaft seals and gaskets, and intake mani for loose connections/leaks. Also can spray all these connections while idling with water or wd40 to see rpm effect (will drop if leak).

 

[chrysler kid]

sounds like you may have a bad vacuum leak, can you post a picture of the engine bay??

 

[kyler021]

So you don't know what boost its running? Plugs? Wires? Etc?

Magnecor plug wires, NGK plugs. Other than that I have no clue but I’ll check everything over when I get home during break.

Do a BLT and check input air hoses, throttle body shaft and gaskets, and intake mani for loose connections/leaks. Also can spray all these connections while idling with water or wd40 to see rpm effect (will drop if leak).

Will do! Thank you for the suggestions

sounds like you may have a bad vacuum leak, can you post a picture of the engine bay??

I attached a picture, that’s probably the best picture I got

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[idkiliketurbos]

Definitely check over all of the intercooler pipes/hoses to make sure one of them isn't off. What you're describing definitely is similar to when a coupler pops off the intercooler pipe and you can hardly get on the throttle without the car bucking all over due to the maf reading being skewed because of the large boost leak.

 

[kyler021]

Definitely check over all of the intercooler pipes/hoses to make sure one of them isn't off. What you're describing definitely is similar to when a coupler pops off the intercooler pipe and you can hardly get on the throttle without the car bucking all over due to the maf reading being skewed because of the large boost leak.

Sounds good thank you for the suggestion, i’ll post an update when I get a chance to look it over

 

[kyler021]

Sounds good thank you for the suggestion, i’ll post an update when I get a chance to look it over

Okay, it's been a while but the solution to my problem was installing a new gas tank. After that she runs good while driving so far. My guess is that the sump was picking up rust and debris from my old tank and clogging it, and when i turned the car off the debris would fall back down, which is why it would run fine for a little bit before occurring. Thanks for the replies everyone!

Kyle