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Hi Speed Lack of Power

tdm571

tdm571

New member
1997 SE 3.8 NA 109k
I'm having an issue with alack of power at highway speeds. When it first started happening, I would notice it at about 55mph. So, I wondered if it was as lull point in the tranny. But as it's getting worse and starting to feel different, I doubt that's the case. Now it sputters and feels like it is not getting enough gas. I get no response from the throttle unless I give it enough to downshift. If I'm going up a hill, I'll actually slow down. I changed the oil, air & fuel filters, plugs (iridium) & wires At 105k with no effect. I'm wondering if I have a bad injector(s) or fuel pump. Also, my fuel gauge doesn't work with less than a 1/4 tank. Another note, the car starts fine, but if I turn off the car after it's been running a minute, it won't start unless I give it some gas. Sorry for the novel, but I wanted to be thorough.

Any thoughts?
 


Try cleaning your MAF and clean the IAC valve. Beyond that it might be the beginnings of a clogged cat.

Is your CEL on? Have it scanned for codes and see what comes up (if anything).
 
CEL is not on, so I haven't scanned it for codes. I'll break out the scanner when I get home and try to clean the MAV and IAC valves. Didn't think about the cat. Hate those jobs I can't do myself.
 
you can change a cat yourself. you can A, buy a catted down pipe. or B take your down pipe off, bring it to a muffler shop have them cut and weld in a new cat. buy new cat on line.
 
If you do decide to change the cat at home- expect the bolts to break where it bolts to the resonator. At the very least, be prepared to apply heat with a torch before attempting to remove them. I have done two 99 model Grand Prixs and was able to save the threads on three out of four bolts, but penetrating oil like PB blaster just didn't help. Heat was required in both cases and the cars are not rusty. The oxygen sensor was not a problem, and the nuts at the manifold came off OK. With yours being a couple years older, I would definitely prepare for this. I found the downpipe with u-bend delete, hi-flow cat, and stainless flex joint to be a great mod for an L36. Whether or not this is causing the performance issue, I do not know. I replaced mine because I was beginning to smell the cat at about 120K miles and the flex joint had been rattling too.
 
I'm not far from 120k. What did it smell like? I've been smelling something funny lately. Might be time to dive under and get a closer smell.
 


Kinda like rotten eggs. Not like healthy exhaust. Smell by itself really isn't an indicator, I had a rattly downpipe too so I went for it.
 
UPDATE: I got down and did some smelling around. I didn't smell rotten eggs anywhere. At 110k, I'm probably still going to change the cat. On the way home today, my ses light came on. When I got home, I checked the code being thrown, P0306. The plugs(iridium), wires, and coils all have < 10k miles on them. So, I'd hate to think it's one of them. Using this logic, I'm left with fuel injector. Opinions on my logic?
 
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