1993 Toyota Corona terrible fuel consumption/smoky


Asked by dustincarlo Apr 03, 2014 at 11:09 PM about the 1993 Toyota Corona

Question type: Maintenance & Repair

Hi! I use a 1994 Toyota Corona as my daily commute. It has a 3S-FE 2.0 liter engine So far it has logged 275K kms without much issues. Recently I had the engine overhauled and replaced the following; Timing belt, tensioner bearings, con rod bearings, piston rings, In/Ex valves, valve seals, water pump, and spark plugs and all seals and gaskets. However when it was completed, I noticed that black smoke is being emitted from the exhaust pipe and the fuel consumption was so terrible. I had the spark plugs inspected and they were covered with soot indicating the presence of unburned or excess fuel.

I already had the coil replaced and still emits black smoke. Also I tried inspecting the fuel rail regulator but it seems to be in order. No CHECK ENGINE signal encountered. What did the mechanic miss here? Please help?

10 Answers


Your engine is running way too rich- black smoke means unburned gas- is it a carb? should be able to adjust it- is it injected? something ain't right- and the people who did all that work should be held responsible for getting that thing to run right-

4 people found this helpful.

Yeah if its a carb, you can adjust the mixture whether it's too lean or rich, i your case it's to rich, It's not to hard, just look for a screw on the base of the carb and back it off a tad, But make sure it's not the idle screw. But if injected might be a bit harder, best bet is to just take it back to the guys you got the overhaul at and get them to do it, hopefully still under warranty.


Thanks guys. The car is a port injected model and the guy who made the overhauling also remains puzzled. I thought its has something to do with the O2 sensor but it appears it does not have one. Damn car has been running at 10 kms/liter before, now it dropped to 3 kms/liter! and its not even a V8. Hoping somebody can crack this case soon. Ciao

2 people found this helpful.

May I ask why you had it overhauled if you hadn't had any problems with it? The timing belt is regular maintence. Usually the rest is done if there is a specific problem. Anyway, there could be any number of things wrong here. Hopefully the cylinders were honed and still within specs. If they were too worn they shouldve been bored & oversize pistons installed. The piston rings have gaps in them that should have been staggered when installed. If they werent, oil can get by. If u went thru the trouble to replace the valves then the valve guides & seats shouldve been machined or replaced. The valve springs shouldve probly been replaced also. The cylinder head shouldve been surfaced also if within specs. if not within specs or warped it shouldve been replaced. Did you have it done by a reputable shop? You need to find out all of this info from them so you know what the real deal is. Then they need to fix it at no charge to you. Also you could have your timing checked by someone else to insure that part was done right. Im betting there is a problem with the piston rings not sealing for one of the reasons I mentioned or the valves not seating or sealing.

1 people found this helpful.

hI Kim, thank you for the reply. I had the engine overhauled because it already clocked 270K kms and it was not as perky as before. Since the timing belt needs to be replaced, I had the mechanic inspect every component and he also discovered broken conrod bearings. Every routine engine check was carried out. Some of the piston rings needs replacing but the bore is smooth and not worn out. I agree with all your advises and every precaution was observed concerning piston ring positioning, valve clearance..etc. Despite all that the car continuously gulps fuel like a high displacement V8 engine with exhausts like a bad diesel engine. I also noticed that the engine has power and acceleration and it does not overheat. Oh yes the shop will fixing it at no charge but I think they ran out of options and dumfounded. Sigh

1 people found this helpful.

OK. If its over fueling there are a couple things to check 1st. 1 Is your fuel pressure regulator. The simple way to check that is to remove the vacuum hose from it & smell it. If it totally smells like fuel then replace the regulator. I'm thinking the likely suspect tho is the camshaft position sensor. It controls your fuel. I can supply you with the location & specs if you need. 1St inspect the wires & connectors for it. Then you use an ohmmeter to check the resistance. If its not within specs then replace it. Same thing with the crankshaft position sensor. It controls your spark.

4 people found this helpful.

Oh ya, a shop should be able to put a fuel pressure guage on it to get an accurate measurement.

1 people found this helpful.

I've been meaning to ask you- What is this car really? In the title it reads 1993 then in your question it says 1994. None of the year, make, model or engine size add up. First of all, they did not make that model or that engine in either of those years.


Hi Kim, my apologies for the confusion. The car is really a 1993 Toyota Corona (T-190 series) with a 2 liter 3S-FE 4-cyl engine. A photo is provided for your reference.

Hi Dustin, bump! Did you find a solution? I got similar problem. Though mine didnt get overhauled, happened just after replacing the computer box cuz it got burnt. Thnx

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