6G Celicas Forums

Long time member, rare contributor.
I have a '99 celica that I have daily driven for 10 years now with very few issues.

About a week ago I notice that the engine seemed to have a miss or stall of some sort on my commute to work. I made a mental note to keep an eye on things, but it wasn't severe enough to pull-over.
Each day I have driven it since, the problem has gotten worse.

- The engine starts and idles fine.
- When below normal operating temperature it runs fine, though it is definitely down on power and seems to be rev limited to ~3,800 under load. With no load it will rev to 6,000.
- When the engine reaches operating temperature it begins to have the stall. It is as if the whole engine cuts, restarts, and repeats numerous times within a second. It does it so much, and so quickly that it creates a violent shake that I am worried is going to do serious damage. At this point I am driving as little as possible, but it is the only car I own.
- The problem only seems to happen when I am at constant throttle. The stop, start shaking does not occur during accelerating, coasting, nor idling (though it is down on power and weirdly rev limited at all times).


1. At first I thought it was a dying fuel pump that was becoming intermittent and not supplying enough juice, but the problem persisted after replacing pump and filter.
2. Years ago, I installed a secondary ignition control and coil (MSD), but left the stock parts in place with a bypass. The problem is identical running any combination of ignition control module and coil. The distributor cap passes any sort of visual inspection.
3. The air intake system passed a similar visual inspection, but I have not tried to look into the throttle body.
4. On a wild hair, I attempted unplugging the TPS. The car had the same issue, but with additional problems. Removing the TPS was the first time a dash light came on and is the only thing that shows up on diagnostics history.
5. There are no codes showing in current diagnostics.

At this point I am thinking the ECU took a dump, but I really don't want to replace it without some sort of lead.
I have also thought it might be the EGR, but that doesn't really add up.

Anyone that may know, please give any advice you can. I am near my wick's end and I can't afford to replace much more before I give up and park the thing for good.

distributor maybe?

Check the map sensor vacuum hose. I have had to Celicas and they each have shown different symptoms when the map was bad or the vacuum hose fell off or was leaking. But both cars had a problem with accelerating after 3 to 4 thousand rpm.

Thanks guys.
I have since replaced the disto cap and rotor, plugs, and plug wires. The dist itself feels very tight and timing checks out, so I can't really see how it would be causing the issue.

I will check in to the MAP sensor and related hoses.

A mechanic friend told me that he was sure there was something wrong with my Catalytic Converter. Reluctantly I decided to take a look. It hadn't been touched since the day it was installed at the factory and the bolts weren't even recognizable any more. I managed to grind the bolts down without hurting the flanges too much.
As soon as the last bolt was loose I tapped the cat with a hammer to break the rust seals. The cat fell to the floor pretty easily and all sorts of material started to fall out of the exhaust pipe. It was pretty weird and worrisome because the material was coming from UP Stream (toward the manifold, not the muffler). In the end, I figure about half of the catalytic material had broken into pieces and somehow migrated up the pipe. As best as I can tell the material never actually reached all the way back to the engine. The chunks and bits that came out of the pipe were enough to fill two solo cups!!

I drove the car with the cat completely removed and it seemed to help the problem quite a bit. This engine really does not like the lack of back pressure, but it was good enough to convince me that the cat was at least part of the problem. I knocked our what was left of the catalytic material in the housing and put it all back together (new gaskets and such, obviously).
Side note: Completely unmuffled, Celica sounds kind of awesome. Not nearly as Ridiculous-Bumble-Bee as I'd expected!

Once everything was put back together, the car absolutely drives better.
There is still a strange momentary dip in power around 3,500rpm, but it climbs past and takes off for 5,500 pretty hard if I keep my foot in it. I am going to keep investigating what might be causing the power dip.

Has anyone ever seen or heard of a cat doing this? I can't imagine what would cause it to disintegrate the way that it did. I'm not convinced that the cat was the orginal problem and I want to make sure that the right thing is fixed so that nothing more goes bad.

I'll have a brand new car one piece at a time if I don't get this solved!

If you have california emissions you have two cats, one hung off the manifold, that one could be broken.

Thanks for the help everyone.
The car is driving MUCH better, but there is still something a muck. I am keeping an eye on it and I am super sensitive to what I feel while driving every day.

Appreciate everyone's help!!! I will update again when I find more, but for now I am going to be trying not to buy any extra parts...