deanshark

My '93 LS400 loses it's "umph" when it warms up. Take off from a COLD start it has all the power I can use. From a stop it will go like hell or if I go around a corner and give it gas, it will fly like it's supposed to. After the car reaches normal operating tempature it just doesn't have the power anymore. I mean, it will still go but no "umph". If I'm just cruising, say about 40mph, if I floor it it takes a while to downshift and doesn't want to take off. It gradually (real slow) will pick up a little speed and after about 4 - 5 seconds with it floored it will pick up more speed as the RPMs go up. I don't understand why the RPMs don't go up instantly when it down shifts. I just did the T-belt, plugs and wires, and caps and rotors. I also have a problem with my heat, that's why I'm thinking head gaskets.
Anybody have this problem before? TIA for any ideas.

curiosul

Dirty oil, dirty coolant, overheating when idling are usually the "main" symptoms for bad headgasket(s). What you're talking about sound like a bad sensor (maybe O2).

Unless you have a known "problem car" (like Acura Legend or Toyota Supra Turbo), usually you "need" to overheat the engine once or twice in order to screw up the gasket(s) ...

JimsGX

Maybe the temperature sensor? A lot of people have reported good results with increased acceleration after replacing it.

Banshee365

Did this problem occur RIGHT after you did the tune-up? Heater issues associated with head gasket failures usually just mean that the coolant is low and the heater core doesn't have enough coolant to put out sufficient heat. If you have coolant in your degass bottle you have another issues, check your mixing valve. Are you losing coolant from your degas bottle? Are you blowing white smoke/steam out of your exhaust. Smelling any coolant in the cabin? Check for milky look to engine oil or oil deposits floating in coolant. Any black smoke out of the car when you're getting on it hard after it warms up? Warm up the car, unplug the ECT sensor under the plug wire bridge and drive it like that and see how it does to diagnose the ECT sensor. You still get P0115 or something associated to that but you can clear it again after you hook it back up. Also try unhooking your batteries and starting the relearn process over again. If you did that before doing the tune-up don't bother. Also think about your MAF, maybe it's reading incorrectly. Hard to pinpoint your issue without checking each piece and excluding it from the diagnoses. ECM's can cause all sorts of weird issues (my '96 went bad) but I havn't heard of many '93 with ECM issues. Seems to be 94's and 96's with higher mileage.

willhickey

iTrader: (1)

bleed the coolant system and add coolant for the heat . and how many miles on it? a delay in the transmission thats what my sc4 did before it shat on me had a bad delay which got progressively worse

avalon42

iTrader: (1)

I think your Idle Air Control Valve is stuck or going out. I had the same problem when I cleaned mine. The heat thing wasn't there though.

Amskeptic

Losing power when warm and good power when cold gets rid of a lot of possible problems, and head gaskets is one of them. If you have access to an exhaust analyzer, see what your fuel ratio is with a cool to cold engine and a hot engine. If you have ratios above 15:1-18:1 as the engine warms up, you have a lean condition that the O2 sensor is unable to overcome, vacuum leak or sensor issue. Air intake clamps snug at the AFM?
Colin

deanshark

Thanks alot for ALL these diagnosis answers. I bought the car 5 months so IDK how it was taken care of b/f that. I did the t-belt and tune up after only driving for 300 miles, I got about 2k after it. Figured I'd do it b/f anything went wrong. The car has only 113k on it.
This morning when I took it out I figured I would push it a little to see if I can tell anything. It sounded like it was sort of pinging a little going up hill with gas. When I shut it off I smelt a burnt smell, not coolant. I'm starting to think it might be tranny related. It's way too cold now to be working on it.

python

iTrader: (4)

head gaskets? no way! vaccum leak wont cause that either, a vacuum leak will cause irratic idle but will smooth out as the rpms go up. if it wasnt doing it before u did the t-belt, then it has to do with whatever u just did. one of the coils isnt hooked up,ignition wires are not on correctly. if u dont have a check engine light on then its in the ignition,any sensor failure would throw a code.its also a sign of a plugged cat,u can tell by having someone rev the engine and holding ur hand behind the exhaust tips...although i would think it would do that even if it were not warmed up.

deanshark

I've driven it a couple thousand miles after the t-belt and everything change. It just started doing this a couple days ago. Also when I hit the gas it feels like it wants to go but something is pulling it back.

python

iTrader: (4)

check ur cats,take it to an exhaust shop to eliminate that. no check engine light? any misire?

deanshark

No lights. No misfire.
Other then my hand over the tail pipe, is there any other way I can check the cats? I can't afford to bring it in right now. The muffler shops all charge just to check unless ya have the work done there.

curiosul

If you do that, don't keep it for too long or you'll mess up the mufflers (I did that twice in a matter of 2 days - 250$ ... )

Banshee365

Do you know anyone near you with a '93 LS? I'd swap ECM's to put that possibility to bed if at all possible.

deanshark

Nope, noone I know has one. I just figured it might have been a known problem or something. Thanks for the advice. I'll check everything out when it gets a little warmer out.