Engine Problem

[Stymee14]

My 1984 Supra will start and only stays running if I press the gas pedal. If I rev it up and let off the gas pedal, the car will cut off. If I start it and don't press the gas pedal, it will idle real rough around 600 rpm (barely running).

I normally ran regular unleaded in the car which it ran like a top. When gas prices decline, I put in a batch of Super unleaded. I noticed the car hesitating shortly afterwards. Now, it's to the point if I drive it and stop at a light, once I take my foot of the gas pedal, the car dies! I have to restart it, constantly give it some gas to keep it running.

I didn't want to waste time and money and was hoping someone had a similar problem that could turn me on to a fix. Do you think sediments/water may be in the gas to have partially clogged the fuel filter or some of the fuel injectors???

I ran the Super unleaded out to a 1/4 of a tank then refilled it with regular unleaded, dumped some STP gas treatment in the tank the last fill up.

[erock]

theres a couple of things that might be a issue check the fuel filter to see if clogged. or if running now might have been bad gas. I had the same problem with my supra and it cost me about 1.5k in parts to replace the whole fuel system ( tank pump cratel fuel lines and filter). but try the simple stuff first. fuel filter, timing, air filter ect. see hwat that does for ya

[Stymee14]

Thanks,

I feel like a dog chasing his tail. First thing I did was install new fuel filter. The filter that came off seemed to be pretty clean so I sort of ruled that out which didn't fix the problem, I installed all new spark plugs/ wires (didn't do the trick), I replaced all vacuum hoses (emissions- didn't do the trick), I have a spare non running supra so I took the Idle Speed Control valve off and installed it (didn't do the trick), I installed a new O2 sensor (didn't do the trick), I cleaned the throttle bore with carbuerator cleaner (made sure it was safe for O2 sensors and catalytic converter) which didn't do the trick. I noticed my catalytic converter was glowing red (overheating) so I thought that was the problem, I installed a new catalytic converter and this also glows cherry red (overheating). Last thing I have done was drain all the gas out of the tank by unloosening the gas tank drain plug, put fresh gas in the car (didn't do it) and performed a compression test (which I need to put everything back together and do again because I don't trust my readings). I was getting about 180 PSI out of 1 and 2nd cylinder, 40 psi out of 3 and 4th cylinder and like 20 psi out of 5 and 6. A guy told me to stuff a rag in the cylinders and if the rag blew out of the cylinder, I had good compression in which it did for cylinders 1 through 6!!!

It is extremely hard to get it running. Once I get it running, I must keep my foot on the gas pedal just slightly in order to keep it running (taking my foot of the pedal and she dies)!! During warmup, the engine lopes but once it gets to operating temperature, the rpm hand seems to remain constant (doesn't lope like warming up), I was thinking about installing new spark plugs (since I have the old one's out from doing compression test) and replaced old gas with good gas and install new wires. I did notice that the spark plugs that came out of cylinder 4, 5 and 6 had a good amount of carbon buildup but spark plugs out of cylinder 1, 2 and 3 seemed in good shape (were new plugs).

I have been thinking about this problem and it seems that the fuel isn't being ignited properly due to the catalytic converter getting hot (probably burning off the unburnt fuel in the cylinders). Once I get the car over, mashing the gas the engine appears to be super strong. If I get it up around 4K rpms, it doesn't die down, it will remain there. I'm going to do compression test again to see if I yield better results, no way that engine will work off of two good cylinders!!!! I was thinking about tearing it down, removing intake manifold and building everything back up (replacing fuel injectors, new distributor, re-time the car, taking throttle body off of my 85). This is my last go around or I will be selling both 84 and 85. Thanks for your help once again, any help is appreciated.

Originally Posted by erock

theres a couple of things that might be a issue check the fuel filter to see if clogged. or if running now might have been bad gas. I had the same problem with my supra and it cost me about 1.5k in parts to replace the whole fuel system ( tank pump cratel fuel lines and filter). but try the simple stuff first. fuel filter, timing, air filter ect. see hwat that does for ya