Mis-fire under pressure

O

old96

Member
Greetings gentlemen, just bought a 1996 5 speed 4wheel Tacoma. One owner, lots of miles but never abused.
Runs well --- except there is an occasional mis-fire under both easy and hard acceleration and also an infrequent mis-fire at highway speed. New distributor cap, new plug wires, new plugs, new coil and some Sea Foam with no improvement. Looking more like a fuel injector/injectors problem. I purchased an Autel OBD II code reader which I have no idea how to work. Also have the Chilton book for this model and year. Help.
Tim
 
Welcome to the forum.
Check compression that will tell you more. Also figure out how to use that OBD II that will tell you more. You can also put the sea foam in your in your vacuum line that feeds the brake booster help clean things out better. Maybe try running some injector cleaner. That’s all I’ve got until you test compression and get the OBD II reading.
old96 said:
Greetings gentlemen, just bought a 1996 5 speed 4wheel Tacoma. One owner, lots of miles but never abused.
Runs well --- except there is an occasional mis-fire under both easy and hard acceleration and also an infrequent mis-fire at highway speed. New distributor cap, new plug wires, new plugs, new coil and some Sea Foam with no improvement. Looking more like a fuel injector/injectors problem. I purchased an Autel OBD II code reader which I have no idea how to work. Also have the Chilton book for this model and year. Help.
Tim
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OBD 2 is a cinch to run. Literally just hook it into the plug and let it read the diagnostics. If it’s throwing a code it’ll tell you the code number. I don’t know what all capabilities the Autel has otherwise.
Try injector cleaner like OR17TRD said. 21 years is a long time, I’m sure it could stand a cleaning.
Welcome to the forum.
 
Thank you for the reply's. My gut feeling is that the injector system probably need to be replaced. Obviously the OBD at idle will not see the problem. Someone told me that the older car /vehicles computers did not store the error codes, you had to read everything "on the fly". The newer car computers did store error codes that you could read from the OBD or download to your laptop. I'm not sure what my "on board computer" can do. Damn, I love my old flat head.
 
I would try a few cheaper things before replacing injectors. That would be something I would do if it was guaranteed to fix the issue. Also it might only be one that’s not working causing the misfire. Don’t just start replacing things. Lol
 
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If you've got a v6 throw the Chilton manual in the wood stove! It's junk! If it's a 4 banger maybe it'll help a lil bit... if you can, when the tank is on E get some race gas 100 octane or better only a couple gallons at most, (not great for cat conv...) but runs super clean and hot. It works miracles on motorcycle injectors.
 
It's a 4 cyl. I've got plenty of AVG gas (plane) 100 octane, leaded. Would kill the cat conv. quickly. Hopefully this weekend I can see if I can work/understand the OBD.
 
Love those old Chilton books! They’ve gotten me through many projects!

BIRDSLAYER said:
If you've got a v6 throw the Chilton manual in the wood stove! It's junk! If it's a 4 banger maybe it'll help a lil bit... if you can, when the tank is on E get some race gas 100 octane or better only a couple gallons at most, (not great for cat conv...) but runs super clean and hot. It works miracles on motorcycle injectors.
Click to expand...
 
old96 said:
Greetings gentlemen, just bought a 1996 5 speed 4wheel Tacoma. One owner, lots of miles but never abused.
Runs well --- except there is an occasional mis-fire under both easy and hard acceleration and also an infrequent mis-fire at highway speed. New distributor cap, new plug wires, new plugs, new coil and some Sea Foam with no improvement. Looking more like a fuel injector/injectors problem. I purchased an Autel OBD II code reader which I have no idea how to work. Also have the Chilton book for this model and year. Help.
Tim
Click to expand...


Hi Tim , did you replace plugs after seafoaming ? (dumb question I know,had to ask)

& from info you provide sounds some what intermittent & what's considered "a lot of miles" ?

Might want to check pump pressure at injector fuel rail...
 
200,000+, but mostly easy highway stuff. Never abused. When I say intermittent I mean the engine just quits dead, as it the electrics and fuel were shut off abruptly and immediately restarted. It's a bit violent, no sputtering, just on and off. May not happen for another 15 or 20 minutes.
 
old96 said:
200,000+, but mostly easy highway stuff. Never abused. When I say intermittent I mean the engine just quits dead, as it the electrics and fuel were shut off abruptly and immediately restarted. It's a bit violent, no sputtering, just on and off. May not happen for another 15 or 20 minutes.
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Check connection where harness plugs into igniter, these can work their way loose but appear tight (plug wears out )
 
As original stated, that's all new stuff. I don't think there is anything else to replace on the ignition system.
 
old96 said:
As original stated, that's all new stuff. I don't think there is anything else to replace on the ignition system.
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Regardless if it's "new stuff" From your description of sudden loss (on/off) of everything it almost has to be a poor connection somewhere, I had 1 brown wire in my connection that was bad & it,the connection & assorted wires looked perfectly fine & un disturbed & it caused what you speak of, I was lucky & was able to remove wired end out of connection, re splice & reconnect & all went away....
 
Turns out it took a 4 channel engine analyzer to solve the problem. Crankshaft position sensor was shifting plus the computer was dropping number 2 and 4 cylinder injectors at at around 2,330 rpm's. Items were replaced and it run great now. Nothing that at good mechanic and money can't fix.
 
old96 said:
Turns out it took a 4 channel engine analyzer to solve the problem. Crankshaft position sensor was shifting plus the computer was dropping number 2 and 4 cylinder injectors at at around 2,330 rpm's. Items were replaced and it run great now. Nothing that at good mechanic and money can't fix.
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good to hear , there;'s no school like old school...
 
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