Unable to rev past 5000 rpm.. Whats wrong..?
09-24-06, 08:43 PM
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Unable to rev past 5000 rpm.. Whats wrong..?
I am a new entrant to the LS400 club. I have a 1993 with 122k miles on it.
Because of various misfire issues,recently, I got new plug, wires, rotors and caps. I also got a MAF installed (a preowned unit unfortunately).
However even after all this I think there is something seriously wrong with the engine, it runs ok at low rpm but it seems to be lacking power, it pulls slowly and doesnt seem to rev freely, the revs climb kinda slowly..and whats really frustrating is that at about 5000 rpm, it feels like the engine runs out of breath and starts sputtering. I tried revving the engine by standing on the throttle from a standing start. It revved till 5000 rpm (not as smoothly as my Audi S8 used to) but then it feels like the engine runs out of power and it starts sputtering. I hope its not a bad MAF again (I have to get a new one again??). or is it a fueling issue? When the mechanic was diagnosing the misfiring, he didnt think there was a problem with the injectors (but then again he is the dude who miswired my spark plugs ). The alternator seems to be fine, it is recharging my battery. Could it be a fuel pump issue? Another thought that occured to me is if the catalytic converters are clogged and hence it is unable to rev..? Also I dont know if the timing belt change has been done, is it possible the belt has slipped a notch or two and my cam timing is whacked?
Anyone have any possible thoughts?
Because of various misfire issues,recently, I got new plug, wires, rotors and caps. I also got a MAF installed (a preowned unit unfortunately).
However even after all this I think there is something seriously wrong with the engine, it runs ok at low rpm but it seems to be lacking power, it pulls slowly and doesnt seem to rev freely, the revs climb kinda slowly..and whats really frustrating is that at about 5000 rpm, it feels like the engine runs out of breath and starts sputtering. I tried revving the engine by standing on the throttle from a standing start. It revved till 5000 rpm (not as smoothly as my Audi S8 used to) but then it feels like the engine runs out of power and it starts sputtering. I hope its not a bad MAF again (I have to get a new one again??). or is it a fueling issue? When the mechanic was diagnosing the misfiring, he didnt think there was a problem with the injectors (but then again he is the dude who miswired my spark plugs ). The alternator seems to be fine, it is recharging my battery. Could it be a fuel pump issue? Another thought that occured to me is if the catalytic converters are clogged and hence it is unable to rev..? Also I dont know if the timing belt change has been done, is it possible the belt has slipped a notch or two and my cam timing is whacked?
Anyone have any possible thoughts?
09-26-06, 01:30 PM
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Alright Solution found. I found an independent mechanic who said he would take some time to diagnose it. Here is what he found
1. Bad ground in the car. Because of which, the ignition wasnt doing a great job. He found the bad ground in the trunk of the car? (The trunk mat was open when I got the car back from the Toyota dealership, wonder if they messed with it).
2. Intake air restriction near the air box (something was on the filter)..
I suspect its the first issue that was causing most of the problems.. Oh well, just tells me that my armchair diagnostics was way off
.. But I got the problem fixed for an hour of labor.. This mechanic is going to get all my business..
Alsalih, your diagnosis was very close to what was going on
1. Bad ground in the car. Because of which, the ignition wasnt doing a great job. He found the bad ground in the trunk of the car? (The trunk mat was open when I got the car back from the Toyota dealership, wonder if they messed with it).
2. Intake air restriction near the air box (something was on the filter)..
I suspect its the first issue that was causing most of the problems.. Oh well, just tells me that my armchair diagnostics was way off
.. But I got the problem fixed for an hour of labor.. This mechanic is going to get all my business..Alsalih, your diagnosis was very close to what was going on
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