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04 Chevy Blazer won't gain speed

So I’m kind of panicking here because I’m a single mom with two kids and this is the only way everyone (including myself) gets to school.

The car was working fine going into town, but then again I live in a mountain community and the ride into town was mostly downhill. It was acting strange when I put it in reverse, it didn’t start to back up on its own, but I figured maybe there were some rocks under the tires preventing it from going.

The problem hit when I was on my way home going up the grade. The car wouldn’t go over 40mph, no matter what I did. This has never been a problem before. The engine has to work hard (4000 RPM out of 6), but I can keep it at the speed limit (65). So I figured maybe the seat was further back than usual (boyfriend has some long legs) and I just wasn’t reaching the gas pedal. I got to the top of the hill and decided to kick it into speed. Once again, engine jumps into high RPM, then made a grinding noise and got slower. Insert panic.

I did a little poking around and most things suggest checking the fluids. It’s always had the fluids changed regularly and been serviced properly, it’s one of the reasons I bought it. Admittedly my oil change date is a few months past, I’ll be doing that asap. I checked the transmission fluid: still pink, but low.

Anything else I should be checking for, please tell me. I’m afraid to take it to a shop without arming myself with more information because I don’t want to get taken advantage of.

Thanks for your help everyone!


When you checked the transmission fluid, was the engine up to temperature and was the engine idling?


Is there a check engine light on? If so, have the codes read and post them (in exact form like “P0123”). Many auto parts stores read these for free or maybe you can borrow a code reader so you don’t have to drive it much until you start to get a handle on the issues.

No check engine light, but from my understanding the vehicle isn’t constantly diagnosing itself so I might have to drive it for a while for it to come on?

Tester - yes, the engine was still hot from my drive and I had it on and idling when I checked the transmission fluid.

The computer is constantly monitoring - its the only way everything works. But it doesn’t turn on the light everytime something hiccups - so yes, sometimes you have to drive it a while. It might have “pending codes” and many scanners will pick those up so it’s worth it to get a scanner on it.

Honestly, given the symptoms your next drive should be straight to a shop. Given what is happening you may end up producing more damage by driving it around. And certainly try to make it one of the downhill drives to the shop.

How low was the transmission fluid? That’s the first thing to put in order and be sure to then have the leak found and fixed. Trans fluid doesn’t get used up so if it was low then it’s leaking.

Aside from the transmission fluid, you want to have the fuel pressure checked and if a basic static check shows ok that isn’t enough. You want someone to check it while simulating load. (E.g. - as in revving the engine for a while)

You also want to have it checked for exhaust blockage. This can be done pretty quickly and easily by someone with a vacuum gauge who knows how to use one.

How old are your spark plugs and wires? I’d want to have a look at those too.

Concur w/above, this needs immediate att’n at a good shop, or risk an even more expensive problem (& possibly dangerous). It can be very difficult to read the transmission fluid level accurately on newer cars. It has to be done exactly per the manufacturer’s direction. Involves having it at the proper operating temp and going through some shifting procedures, step by step, before reading the level. Find your owners manual, then ask a good shop to follow the directions there to determine if the level is low or not.

Alright, it’s going to the shop first thing tomorrow. All downhill, Cigroller :slight_smile:

George - I’ll dig out the owner’s manual too.

Thanks everyone. Wish me luck.

Report back and we’ll be happy to - try - to help you sort it out if you’re not confident you’re getting a straight scoop from the shop. (Happy to get reports back either way). And if you do come back with any error codes pulled from the computer make sure you get the exact code(s) number - like “P0123”

If you didn’t add trans fluid yet, make sure it is either marked Dexron or Dexron VI when you do. The Dexron might be marked “Dex/Merc” but should say it meets Dexron III specs someplace. (Dexron III was the “official” spec when this came off the line. Now Dexron III “sort of” doesn’t exist anymore. GM and most trans shops will recommend Dexron VI as being better. I had a GM from '00, and I didn’t agree, though it had a different transmission in from yours too.)

Offhand, sounds like a transmission problem and the low fluid in an automatic is always a reason for concern.
If the transmission is low then it’s leaking; either externally from a seal or gasket or possibly through a leaking radiator transmission fluid cooler.

You guys are going to be surprised by the problem.

After a drive down the hill to the shop last night, the catalytic converter was glowing red in the dark. Engine couldn’t breathe, who knew.

I’m thrilled it was a simple fix, although I’m predicting a transmission replacement some time in the near future. The thing has 140k miles on it with original transmission, guess I’m doing good all things considered.

Thanks everyone for your help!

Have you ever had the trans fluid and filter, gas filter, air filter and transfer case fluid replaced? Maintenance can avoid repairs.

Congrats on getting the problem resolved @Habanero84 . Simple fix yes. Inexpensive fix? If you live in an emissions testing state, maybe not so much. But the important thing is the fix is known.

Thanks so much for the report back.

I’m actually not surprised - the glowing cat is the most common way for an exhaust to be clogged these days. Think only positive thoughts about the transmission and if you haven’t serviced it regularly make sure it goes to a locally owned, non-chain transmission specialty show to have them check it over and put things in order. You probably have a leak and should have it serviced. You can often get a lot more than 140K on it if you do the fluid & filter regularly.

Cat replacement was about $300, not bad all things considered. Emissions aren’t a concern in my county.

I usually have the car brought in and maintained regularly, but they don’t do the transmission unless you ask. I had them flush the transmission fluid and replace it today when I had my oil done. Nice small town local place, haven’t steered me wrong yet. I don’t think there’s a leak in it, I think the last time it was serviced they just didn’t put enough in. There’s never any drips or puddles under my car, and the fluid levels are usually consistent.

Car feels much peppier now that it can breathe, what a relief.

I hoped they checked for a misfire which can ruin a cat in minutes so it doesn’t happen again. Also, generally just drop the pan on the transmission instead of flushing. Hopefully it’ll be ok but my trans shop never flushes a transmission.