Diagnose My Ride

November 8, 2006 9:13 AM

Why is my Mazda losing power?

I have a 2000 Mazda Protege (1.8 L, automatic, 43K mi, a lot of that in the past 18 months). I had a lot of work done on it in May including brakes, new radiator, and transmission flush. Jiffy-Lube check-up in late August. Oil's fine, fluid levels are good.

A couple months ago it started having trouble with acceleration. I press the gas and the engine revs, but not all of that power is getting to the wheels. Once it gets up to speed, it will stay there, but the process is slower than it ought be. The engine sounds healthy--no knocks, no rattles, no skips--it's just working too hard.

I haven't been able to afford to take it to the shop, and the problem has been worsening slowly. There's a slight delay in response, and the RPM are high even when I'm not accelerating--if I cruise at 70 on flat ground the engine will rev at 3000. The car is eating gas, of course, and I worry that I'll damage the engine further by running it high so constantly.

I'm all but broke, and don't want to spend a penny more than I have to on diagnostics and labor. At worst, I'd like some scenarios to present to the mechanic. At best, I have DIY-car-repair friends I can work with. So tell me, (1) what are some likely problems, and (2) could a team of very intrepid laymen repair them?

posted by hippugeek to travel & transportation (9 comments total)

Either the transmission fluid is low (go and pop the hood, don't take Jiffy Lube's word for it), or your transmission is dying.

At 43K miles, I'd bet on the former. Dexron III or whatever your car uses is available at better gas stations everywhere.

Possibly the "transmission flush" created a leak somewhere in your transmission fluid system. If you add more fluid and this magically solves your acceleration problem, the next thing you need to do is find the leak.
posted by jellicle at 9:39 AM on November 8, 2006

I'd find a reputable garage to look at this instead of Jiffylube, if at all possible, if this requires professonal intervention. When you park the car, do you notice any red liquid pooled underneath?

If its not a leak, it could very well be a vaccuum sensor malfunction that is causing the transmission not to shift properly. I have a feeling that this may be the case here.
posted by dr_dank at 11:03 AM on November 8, 2006

Transmission flushes (as opposed to a simple "drop the pan and drain" process) are fairly notorious for causing problems later down the line. The process can dislodge metal bits (which would normally settle into the pan) and lodge them deep in the tranny's guts, causing problems like yours.

Hopefully, it's just low on fluid.
posted by Thorzdad at 11:24 AM on November 8, 2006

If you had the tranny flush in May odds are your tranny is fine. We drove the hell out of two Protoges, 91 and 92. They are solid cars. The acceleration problem could be a bad fuel injector. The first thing I would try is a bottle of fuel injector cleaner. If that doesn't help, you might have to spring for professional help. I don't think fuel injectors are something that the typical shade tree mechanic can muck with .

Also, try a tank of premium gas. Sometimes the additional detergents in premium gas will help flush out the system. I doubt it will help, but it's only gonna cost you a couple of bucks extra to try.
posted by COD at 11:25 AM on November 8, 2006 [1 favorite]

Thanks for the suggestions--I'll try the premium gas and fuel injector cleaner next time I fill up.

A dying transmission is, of course, my biggest fear. It's not just low on fluid--I've checked it myself several times, hoping that was the issue. Haven't seen any leaks under the car.

Vacuum sensor sounds very possible, and isn't something I'd thought of--thanks.
posted by hippugeek at 12:29 PM on November 8, 2006

I recently had a problem wherein my Toyota truck was down on power and wouldn't kick down to a lower gear. It turned out to be an cracked intake boot- unmetered air was getting into the engine. Look closely for cracks. Even small ones can cause problems.
posted by wzcx at 12:37 PM on November 8, 2006

I know very little of cars, but my '93 Volvo 240 recently had issues that sound a lot like these. It took forever to get up to speed, burned through gas, and had the constant low hum of trying too hard. The overdrive refused to engage, keeping the car in 2nd-to-highest gear even at higher speeds.

It turned out that a solenoid had burned out, which (somehow) prevented the car from knowing which gear was needed to properly maintain speed. The part and labor cost between $300-400, if that helps with panic perspective.
posted by TG_Plackenfatz at 2:15 PM on November 8, 2006

First of all, I'd carefully and quickly check all 4 wheels after a short drive at highway speeds, to be sure I didn't have a bad brake component, or wheel bearing. If any wheel is noticeably hot, check the brakes.

You can learn a lot about the condition of the internals of your transmission by paying close attention to the odor and color of the fluid, and the condition of your transmission filter. If you feel handy, you could drop the transmission pan, change the filter and pan gasket, and replace the transmission fluid, all for about $40, if you do the work. Transmission fluid should not be discolored, or have a burnt smell. There shouldn't be visible metal or significant discoloration in the old filter element. If you find either of these indications, you probably have internal transmission problems. But you could have a very simple problem, too, like a crushed line to the transmission cooler, driving up internal temperatures.

The problem you describe could be caused by many components, including expensive ones like a bad torque converter, or slipping clutches. There is no point economically in "fixing" a lot of external things just because they individually don't cost much, if they are not the problem. At 43K, I'd think it's a bit early to be having major internal transmission problems, but if something has gone wrong, waiting to fix it will likely cause other parts to fail, too.
posted by paulsc at 3:19 PM on November 8, 2006

Check your spark plugs, too.
posted by Mr. Gunn at 9:14 AM on November 9, 2006