Random Studdering Problem - Need Help

[Eclipsegst2gen]

I have a 95 GST and my car would be running fine and all of a sudden it would studder and would lose power, like I'm running on only 2 cylinders. It would backfire when I push in the clutch or decelerate and I would smell unburned gas. I can just imagine what the cars behind me are smelling. When this happens my EGT gauge would shut off. The engine light does'nt go on though. I would drive like this for sometime and then the car would run normal again. Sometimes when I first start the car it would be in this studdering/missing mode and after a few minutes it would run normal again. I've taken it to the shop 4 times but everytime I've taken it, they can't get the car to studder. As far as they're concerned, the car runs fine. I've changed the plugs and plug wires but still have the problem. Any help that you guys can give me would be greatly appreciated 'cause I'm about to dump this car in frustration.

 

[Syndicate13]

Well my handy dandy Haynes manual tells me that if your car stutters under acceleration then one or more of the following may be the culprit.

Fouled plugs
Faulty fuel injection component
Fuel filter clogged
Ignition system malfunction
Vacuum leaks


The problems associated with backfiring are the same also. Since you already changed the plugs and wires I would start looking to the fuel system. When's the last time you changed your fuel filter? If you never have or can't remember then change it again. It's the cheapest thing you can do anyhow. Then search for vacuum leaks, inspect all the lines on the throttle body for damage and replace as necessary. Just for fun, what kind of spark plugs did you use and what did you gap them at?

 

[Eclipsegst2gen]

I don't remember ever changing the fuel filter so I'll do that. As far as the spark plugs, I used NGK 1 degree colder and gap it at .28. Maybe a silly question but if it's the fuel filter, would the studdering/missing be continuous and not eratic and random?

 

[Syndicate13]

Well if you're still all stock I would suggest still using BPR6ES plugs. You don't need to go to the colder plugs until you're flowing more air and making higher boost. At stock levels they could cause the car to stutter. Can you post the number from the NGK's that you used?

 

[Eclipsegst2gen]

I'm using BPR7ES plugs. I did'nt think to mention what I have on my car in my initial post but if it helps, here it is. I have a ported big 16g w/ 10degree clip, 1st gen head, 1st gen intake manifold, 1st gen throttle body, 720cc injectors, Denso 190lph fuel pump, Web cams, 3" exhaust system, MSD DIS2, Apexi AFC (1g), Greddy boost controller, Greddy boost and EGT gauges, FMIC and other goodies. Now, this studdering/missing problem just started happening recently. I've had these mods for over 3 years now with no problems till now. Any other suggestions? Thanks.

 

[midnght]

Sounds funny and all, but a local DSM guy here was having the same off-on symptoms.


All he had to do was tighten down the battery terminals again. Both - and + had worked themselves loose.

 

[Eclipsegst2gen]

Well, I did change the battery terminal on the positive side because it had a build up so instead of just cleaning it, I put in a new terminal. The negative side looks fine so I left it alone.