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Full Version: Help: Check engine light on, code 71
6G Celicas Forums > 6th Generation Celica > Engine/Transmission/Maintenance
Jules88
Hi, I have a '94 Celica ST automatic, with about 170,000 miles. The check engine light is on and it's code 71. I already cleaned out the EGR, but the check engine light came back on after I reset it. So I got another EGR used from Pick a Part, and the light is back on again. Could it just be it needs a new sensor?
Also, smoke comes out of the tail pipe when I give it gas, and it smells really bad. Is it unrelated to the check engine light being on? I've considered having the engine rebuilt, but I want to make sure before I spend that much money. It has good compression. I bought valve seals but the person who was going to do them said it would be best to just rebuild the engine. And the person I bought the car from said he recently rebuilt the engine. So I just don't know..
I'd appreciate any ideas on these problems. Thank you!
Box
There're 4 components within the EGR system, at least in OBDI. The valve, the modulator, the solenoid, and the sensor. All need to be tested in order to find what's causing the code. The code is triggered when the computer senses that the exhaust temperature is too low. Usually the sensor can be cleaned. Also over time the EGR tube and the ports get caked with carbon. Sometimes all it takes is removing the EGR tube and cleaning it along with the ports on the intake and side of the motor. The tube between the bottom of the modulator and the EGR tube is really susceptible to clogging. Recently had to clean mine out the other day. Google "7A-FE EGR Test" and you'll find out how to test everything.
Box
Also on the other issue. Is the smoke blue or black, and does it smell of fuel or oil? The 7A-FE is notorious for stuck oil rings that'll let oil into the combustion chamber and will cause burn off. Not too big an issue as long as you keep oil in it. You can try doing piston soaks and running detergents through it in hopes of alleviating the problem by breaking the rings free. I was lucky and was able to break my rings free by running Marvel Mystery Oil in the crankcase, and doing a piston soak with the Marvel.
Jules88
Thanks for the advice. The smoke is gray, and there is a lot of it everytime I accelerate. People are saying it's oil. If that's the case all I have to do is use that Marvel oil you mentioned? Because they are trying to get me to rebuild the engine, and I really don't want to do that.
Thanks again.
Box
You can give it a shot. Personally I wouldn't rebuild it unless the performance of the engine has been hampered. What you should do is piston soak it overnight with the Marvel, then run it with the Marvel in the crankcase. All else fails you can switch out to a heavier weight oil to slow the burn.
Jules88
Alright I'm going to try that tomorrow, thanks a lot.
stephen_lee
apply vac to the port on the egr valve(either with a lone vac hose to a port on the intake mani that has vac, or suck on it) at idle, if the engine stalls, the egr port and valve are functioning. the solenoid hardly goes bad. im betting if it passes the valve test its the modulator (20$ at autozone IIRC)

smoke on accel is usually piston rings allowing oil to burn off. if it burns oil and has decent mpgs id bet its rings. valve seals only show a puff of smoke at startup and thats it..
BonzaiCelica
Ok so since this is the most recent check engine code thread soo :

My beams redtop is throwing a light and the only pinouts i have on my diagnostic box connected are +B, Tt, E1, Ts, AB.

My car is a 99 but even then the diagnostic box is part of wiring harness so what gives?
richee3
There should be a TC pin in your diagnostic box. The BEAMS grounds the TC pin rather than jumping TE1 and E1.
BonzaiCelica
Thx but i failed before i even posted here. I connected e1 and +b and it arked a sparc and the paper clip got hot. Afer that i believe the check engine light went away. And to top it off today i disconnected the battery and forgot that that resets all codes. So now im screwed.

I tried to turn it on and it wont turned over. While its trying to turn over it makes a bicycle horn noise so ill check the coil packs and spark plugs, injectors.
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