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Please help me - SC400 runs very poorly

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Old 09-17-11, 09:13 PM
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ballhooter
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Unhappy Please help me - SC400 runs very poorly

I've been a long reader of this forum and have enjoyed all of the great help and advice that has been shared - truly a great community.

I've owned a 1994 SC400 for 13 years and have thoroughly enjoyed it, but lately it has run into a serious problem. I was hoping you guys could help point me in the right direction.

When the engine light goes off, the car runs perfectly - idle is correct, shifting is correct (drive downshifts through all the gears) and I have plenty of power.

When the engine light is on [which it is almost all of the time ] -
* The car takes a long time to start/stay started (needs to get warmed up)
* The idle is high
* Smells like the engine is running rich
* 'Drive' starts out in 3rd gear (won't downshift)
* I have to manually shift gears (start in L, shift to 2, then D) to drive
* I have no power. If I give it a little bit of gas (accelerator quarter way pushed down), the engine sounds like it is bogged down, but it doesn't accelerate any faster.

I have tried the paperclip trick to get the codes and I have not seen any blinking. I took it to a local shop that had an OBDI tester and he couldn't get the code either (although the engine light was on).

One guy thought it may be a sensor.
Another guy thought it may be a bad catalytic converter.

I'm very handy and have a multimeter, but I'm not sure what to check.
Thoughts? Thank you in advance.
Chris
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Old 09-17-11, 09:18 PM
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You can start off by checking the alternator and the ground wires, let me know what you get after checking those
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Old 09-17-11, 09:34 PM
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Sorry don't mean to get your hopes up, I'm not here to give advice, not a mechanic. Just moral support. Breath deep, take your time. I hope she makes it.
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Old 09-17-11, 09:36 PM
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ballhooter
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Thank you for the quick reply!

* I replaced the alternator a few months ago. (battery not charging)
* I replaced the drivers side ignition coil 6 months ago. (only four cylinders were firing)
* I replaced the spark plugs and wires 8 months ago. (troubleshooting a badly running engine)

Any other thoughts?

Gate: Thanks for the support! My ride looks much like yours. What a fun car when it works.
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Old 09-19-11, 01:58 AM
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No prob! Yes, my sixth car and by far the best, love it (my last was an 04 Rio). Some of these things might not be related, but I'll suggest them because they're all extremely cheap to do. Even if these aspects couldn't possibly be the direct source of the problem, covering all the easiest bases might still reveal something and can give you a better overall perspective. Best of all, you wont feel as bad if they truly give no help because as I said, they're extremely cheap, you wont really be digging a hole. So, no one give me lip about how doing these things wont cure the car.

Replace your vacuum hoses or just get some clamps for the old ones. Whichever you think is better. Once again, just suggestions. You might find it more wise to leave them alone if you're sure they're fine. Clean the throttle body. replace oil and/or trans fluid. Stuff like that.

You might also feel better just waiting for more professional advice from experienced guys on here who aren't kids like me, or maybe you just want to ensure enough thought goes into any of your next actions - if that's the case, strain to provide us with any other symptoms that might be occurring and try to give detailed expansions of the symptoms already provided. Any additional information can potentially increase everyone's ability to direct you.

btw the sensor and cat were pretty good guesses from those guys. maybe someone here can help you check those and more before you shell out for something unnecessary to a local know it all who will quickly promise you salvation. I had bad tranny fluid once. changed the fluid and gained power in a snap, all better, done and done. 3 jack holes in my town ranted about how badly I needed a whole new transmission. They probably knew the fluid was bad, were planning on just changing the fluid, charge me for a new trans plus labor, and go party. This site helped me deny them those selfish dreams.

Last edited by Gate; 09-19-11 at 02:06 AM.
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Old 09-19-11, 05:30 AM
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Thanks Gate: I'll check out the vacuum hoses.

Anyone else have some ideas of where to start troubleshooting?

Thank you in advance.
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Old 09-22-11, 11:45 AM
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Anyone else with some ideas of where to start troubleshooting?

Thank you in advance.
Chris
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Old 09-22-11, 01:43 PM
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could be a dirty throttle body/maf sensor

its really annoying diagnosing these issues

did you open up your ecu to check if its all good?
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Old 10-10-11, 12:21 PM
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Sounds like u need shift solenoid #1.....especially if it takes off in 3rd.
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Old 10-10-11, 12:27 PM
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Look up a diagram of the valvebody, both #1 and#2 are same part #. drop the trans pan and change the solenoid. If u can't find the correct one from diagram, it's one of the 2 short solenoids seen with pan off, add battery voltage to unhooked solenoids and one will be stuck or not click, that's ur problem
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