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Category: Toyota
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1994 Toyota Celica ST: 000 miles..wouldnt start..towed..spark plugs

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My 1994 Toyota Celica ST (268,000 miles) keeps skipping while I am driving and idling rough. This didn't start happening until it wouldn't start one day (at this point it was not skipping). I had it towed to a repair shop and they said that oil was seeping past the valve cover gasket and was causing the spark plugs to not fire correctly. The shop replaced the valve cover gasket, spark plugs, O ring and tubes. The car drove fine for a couple of days, then started skipping and idling rough. I changed the distributor cap, rotor button, and ran a bottle of fuel injector cleaner through the car. The car drove fine for a couple of days again, but started to skip and idle rough again, so I changed the fuel filter. The car drove fine for a couple of days and then I filled up with gas and it immediately started skipping and idling rough again. This time I took it to a shop and the mechanics checked the fuel injectors, vacuum hoses, and the fuel pressure (they were all working fine). They found that the original shop put in the wrong spark plugs, so they changed those plugs and put on new plug cables. The car had been driving great, but I filled up with gas again today and on the way home the car started skipping again. The last 2 times it seems to happen after I fill all the way up with gas. Any thoughts on what the problem could be?

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Being that this problem comes and goes and based on the inputs you have provided here I am thinking fuel contamination, we have seen a lot of issues in certain area's of the country lately where the ethanol was mixed too heavy or water contamination in the tanks that causes issues like yours. This can be frustrating because it can be difficult to figure out for some mechanics and is commonly overlooked. Ultimate the solution here if that be the case would be fuel tank removal, draining, cleaning.

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Customer: replied 7 years ago.
I filled up at 2 different gas stations (probably 60 miles away from each other). It is likely that the problem could be common enough to effect both stations? Would the problem be resolved if I was able to get through this tank of gas without removing the tank, or would residue remain in the tank?
Water for example (if that is the type of contamonation here) will not easily pass through the pick up screen in the tank, so the contamination stays mostly in the fuel tank, refuel this car 100 times at 100 different stations and it will still be there, aditives also will not resolve this. The only time I see "residue" in a tank as you mentioned is when oil is contaminating fuel. The best way to clean this out is as I stated with tank removal, it is near impossible to clean it effectively otherwise.
Customer: replied 7 years ago.
I guess what I'm confused about is why it doesn't happen until I fill up completely. If the tank of gas was bad and had water in it, wouldn't the problem continue until that tank of gas was depleted? For example, last time I filled up the car, it started skipping and idling rough almost immediately. But it ran fine on that same tank of gas after the new spark plugs and wires were put in.
The fact that refueling causes this and the fuel pressure is good is what tells me to go after fuel quality/contamination, I am not saying that this is water, I am saying that this is contamination, it could be water, diesel, e85, mud, anything really can be contaminated in the fuel tank. Certain chemicals and contaminants float while others sink when gas is mixed, it sounds like what ever is causing this is mixing when the fuel tank is toward full level, I would have the fuel pump removed and the pick up screen and the tank closely inspected.
Customer: replied 7 years ago.
How rough is this on my car while I drive it? I typically drive about 120 miles a day. Is it something that should be looked at ASAP, or (as long as the car keeps driving), can it wait until the weekend?

On a 1994 model the main concern is running the engine too lean and altering combustion chamber temperatures, 268,000 miles on this engine is quite a feat so this engine is already pretty worn, as long as the check engine light is not coming on and flashing then there is no major damage being done.

Another thought that came to mind for me earlier stood out as a timing alteration but your fuel statements tell me to have you check the tank first. If you need to wait until the weekend then just be sure to monitor the condition carefully, if this only happens full then consider only filling the tank half way this week.

Customer: replied 7 years ago.
Peter, you've given me some great info and I really appreciate your time. How extensive of a process is it for a mechanic to take out the fuel tank, drain it, clean it, and check the pick up screen? Not sure if your able to provide this info, but do you know approx how much a repair like this might cost?
A typical charge for this would be 3 hours times the shops rate. Most times parts are not needed for this issue but if so that would depend on what is needed. I deal with fuel contamination on a regular basis at work and usually there are no long term issues or repeat issues as long as this is properly addressed the first time.