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Kia Sportage start rough problems

I have a 1995 Kia Sportage it has a rough start up feeling like it has no power and feels like it is back firing at me it used to be inconsistent even on the highway when ever it got to lower rpm.
But ever since I changed the plugs battery wires TPS sensor and fuel filter it only back fires and has no power for the first little bit of driving… What does anyone think I can do to fix this? It also has low power getting from idle to going kinda like at stop lights.

Perhaps you could give us a clue about why you replaced that particular collection of parts. How many miles on the car?

Over 100k
I changed the fuel filter and plugs because it was back firing and having bad pick up speed but it still does…and yes the parts were higher quality not any Amazon or anything cheap idk why it’s back firing timing marks are good… honestly that’s the first time I’ve ever heard of this problem it feels like miss fires or putting bad… I think it’s getting bad mixture and not back firing but just using a bad mixture

The throttle position sensor was because it had delayed reactions such as 5-7 seconds of flooring it before it actually revved up to 1000 and more rpm…

So it helped that it just still has slow acceleration essentially when it’s stopped such as a stop light or leaving the drive way…

Leaving the driveway it back fires and some times at stop lights but it hasn’t yet on a stop ever since I changed the TPS just back fires now on start up … I have a feeling like it could be a vacuum issue or sensor … Maybe transmission but I don’t think so because of the back fire

Backfiring, a term also used to describe erroneous explosions into the exhaust system, generally is caused by extreme temperature in a combustion chamber due to a vacuum leak resulting in extra lean metering, carbon deposits in the combustion camber that retain heat and ignite the fuel, and valve problems… valves not properly closing due to sticking or carbon buildup.

Were this mine, based on the symptoms, I’d start looking very closely at the valves first. I’m betting you’ll find your problem there. Hook up a vacuum gage and the needle will probably wobble so wildly it’ll make your eyeballs spin.

Unless this engine is modified, in which case you need to offer full disclosure as to what’s been done.

Okay well thank you I’ll try to vacuum test it tomorrow see if that’s the thing.

Do you think it could be a cat converter? Also or just a maybe?

I’m guessing a compression or ignition timing problem. Timing is pretty easy to check if you have a timing light. Make sure the base (idle rpm) timing is close to what it should be, and that it advances more or less like it should with increasing rpm.

Hopefully OP has replaced the engine air filter recently. If OP thinks there might be an exhaust restriction, clogged cat, etc, good idea to check the idle intake manifold vacuum, another simple thing to do. It should be 17 to 22 in Hg. If it is bouncing around rather than holding steady, Google to figure out what the bouncing pattern means.

This car might not have OBD II, but it probably has some sort of diagnostic software that posts diagnostic codes. If so, first task is to check those.

OBD 1 doesn’t scan anything … And the timings fine I already checked

There’s an off-chance it could be caused by an evap system problem. When this occurs, try loosening the gas cap to see if that has any effect. Don’t drive any length of time like that, only as test.

Have you ever had the timing belt changed in the time you’ve owned it? Do you know the last time it was changed - not guess, know?

This engine is a single cam non-interference engine that is now 22 years old with 100K on the clock. The timing belt should have been changed at least twice in its lifetime by now. If the cam slipped a tooth it would likely show these symptoms - mis-fire and /or back-fire and low power.

I’d be checking the cam timing and the belt.

I don’t know when or if it’s been changed just bought it a few months ago but I checked the timing and it looks good timing marks are level

The CAM timing marks look level or the spark timing marks?

And since you don’t know when or if the timing belt has been changed - it is due now.

Whenever somebody buys a car whose maintenance record is unknown, it is vital to assume that NO MAINTENANCE has ever been done.

1 Like

Good way to look at it