Mechanics

MISFIRE

1998 Saturn SC2

Engine Performance problem
1998 Saturn SC2 4 cyl Front Wheel Drive Automatic 134000 miles

I have replaced the map sensor. TPS, IAC, ECM, computer, coles, spark plugs and wires, and timing sensor and the car still is misfireing and it is not out of timing. What are some other thing I can replace in order to try to make it stop misfiring. I have used an OB2 and it just pulls up multi misfire.
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Jese2005
October 31, 2009.




This is a tough one. Try replacing the crank shaft position snsor. It cost about $10 to $12 bucks. It is located above the back of the starter. Good luck. Not sure if this will fix it but it ia low cost. You tube has a video showing you where it is.

Tiny
SaturnGuy721
Dec 20, 2009.
By timming sensor do u mean the crank sensor?Also when u said the timming is good did u check the cam timming. When the crank sensor goes bad the car doesnt run or the car runs then gets hot shuts off doesnt run till it cools down I have worked over 16yrs for saturn working on these cars and never saw a bad crank sensor cause a missifire there ethier working at the time or there not. Also have u checked compression?Another thing that can cause a missifire is the injectors not squirting fuel or the right amount of fuel in the cyclinders u coud have a bad injector or bad wiring to the injectors. What codes are u getting?Also have u pulled the wires off the plugs one at a time to see if u drop rpm and have a dead hole not firing at all or just a random missifire?U could also have a plugged cat I have seen a plugged one cause a loss of power and missifires.U have already replaced alot of stuff and havent gotten the missifire to stop so lets take a step back and look at what we have and dont have before we replace anything else.

Saturntech9
Dec 21, 2009.
Yes I was talking about the crank shaft position sensor and I replaced it twice to make suren that it was not bad. I will try the cat. But it has good compression in all 4 cylinders ranging from 190-192, fule pressure is stady at 40 psi. It has new injecters and I took the tank down and cleaned out the lines and the tank and pump with new strainers. It only misfires on cylinders 3 an 4. It does crank up and run and the rpms tak out at 4000 but it wont pull it's own weight when I put it in drive and stalls out. I was thinking of replaceing the injecters one more time to see if that will help but I hope you can give me some more good feedback.

Well if u already replaced all injectors then I think ur good there then u should check and make sure none of the wires to the injectors got crossed. Also I would check ur sparkplug wires make sure u got wires not crossed on the emission label it shows the orders the wires go on the coil and on the engine looking at it from left to right the cyclinders are 1 2 3 4 sometimes something like that will trip u up. Also I would check ur coolant temp sensor they go bad alot and the connector that goes to it they turn green from the sensor cracking and leaking coolant Into it that can cause alot of weird stuff to happen. Since u replaced ur ECM and injectors already the only thing to really check there is the wires comming from the ECM to ur injectors do u have a nod light that is the little light that u plug in instead of the injector and if it flashes while it's running u know the wires are good if u don't have one u can use a blub test light one side is power the other side should be the ground trigger test to see if u have a power with the key in the run postion then hook the test light to ur power side side of the battery then start the car touch the test light to the ground trigger side and it should flash then we know ur wires are good to the injectors. Also what codes are u getting?Let me know what u find.

Saturntech9
Dec 23, 2009.
Thanks for your help I got it fixed. I replaced the injectors before I cleaned out the tank and it ran for about 30 miles and then quit, but I diden't think nothing about it after I cleaned the tank. There was sand in the tank like someone pored dirt in it. It runs grate now but do yo thin I need to replace the pump. The strainers had a film on it and the pump was rusty.

I have seen that sand in the tank before in customers cars I think it's just from sediment sucked up at gas station when there tank was low and got gas. As far as the pump goes if u think u got all the sediment out then u could just let it ride and see what happens if u want. If I spent all that money already I would let it ride and see what happens but that's up too u. Glad to hear u got it figured out. If I had known there was sediment I would have asked u to check those injectors that's what happened to the cars I had the injectors plugged with that crap. Well if u have anymore questions let me know. Also u have urself a very happy holidays.
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Saturntech9
Dec 24, 2009.
You too and thanks agan


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