Cant figure whats wrong with it going to sell it.

I have been trying to figure this PO301 out for about six months now.

new plugs
no vacuum leaks I can find
coils are good fuel is good? put some injector cleaner in it.
pulled the injectors after 135k to have them cleaned the guy said they did not need it $100 down the drain
when the check engine light came on I reset it and it would go 130 miles or so then came back on. Now it will come on in 10 to 15 miles used to come up 301 then random mostly 301 now.

2002 prerunner 4 door will just have to dump this thing on craigs list for 4k. I am all out of ideas would make me sick to take this to a repair shop and dump 800 into it to tell me it was a sensor. any ideas from anyone????

 

I don't recall what year they switched to coil on plug, but if you have plug wires, check them for cracks. That's the first thing I would do. That, and check if the little tops of the spark plugs are screwed on tight.

Also, is the check engine light solid, or flashing about once per second?

 

What other codes has it been throwing? Are the others also all misfire codes (P030X)?

 

how is it running.before you put more money in it you should check compression and do a cylinder leak down test.also you could perform a top engine clean.i think the stuff that some of the people use here is seafoam.just do a search for sea foam

 

The truck comes up with 301 all the time and 300 every 5th time or so. the coils are one each per plug. I have herd of the sea foam they have it a wally world. I used lucus be for in it seemed to keep the engine light off longer? I will have to try a compression check.

cold be the coolent sensor saying the truck is cold and making it to rich? well will havt pull it in the garage and run a compression check @ 135k it still should have good compression my moms honda @ 380k still runs strong.

Larry

 

might try NGK I have autolite in the truck now.

 

It seems to be focused on cylinder# 1, I would put OEM plugs back in, put 100-200 miles on it and see of the engine light comes back. I'm also wondering if the coil pack may be weak on #1. Maybe somebody knows the answer to this, can you swap the coil pack to another cylinder and see if the code moves with the coilpack?
Send a PM to Chris4X4, he is scary smart when it comes to tacos.

 

yes you can swap coils out and see if the code moves with it thats a good idea

 

I moved the coil to 4 and the problem stayed with #1 what should the compression be?

 

I'd say a good rule of thumb would be about 150 psi for a strong motor. Also, they should all be within 10% of each other.

 

Get the autolite's out of the truck & spend the coin on the iridium denso's that are supposed to be there. My certified preowned had these pieces of shit in there & they made the truck run weird. They are also shorter tip where the spark was farther up in the combustion chamber than it is with the correct denso plugs. I did not have cel but truck runs much better(normal) with the denso's. 67.00 for plugs sucks but the way it ran with fuck plugs was much worse.


edit - oops, you said 2002 so the denso iridiums aren't stock that year but would still ditch the fuckolites for some proper denso factory spec plugs. They shouldn't be 67.00 either.

 

Were can you get these plugs. I looked on line at checker and autozone they have NGK and bosch What should I use? 2002 Taco

 

OK I have been trouble shooting this truck on and off for six months. #1 miss fire. cleane all the injectors plugs coils.

I got it. I think the vavlve is stuck open on # one. all the cylinders have about 130psi and #1 verys from 60-90psi. one time I was checking the pressure and it stopped making pressure for a few turns. it was going wow wow wow then smooth as it was still turning. I had all the plugs out to turn easier. this lead me to belive the valve was stuck open

ok what should I do if I put some sea foam in the oil will this unstick it? because when it first started it would happen on and off. I thinks it just needs some cleaner. I really don't want to pull the head. do you think this is a job I can do.

completed jobs... how hard is the job to pull the head and install new belt?

replaced valve body in th350
replaced heads on a chevy 400 sb
installed cam
removed and install a rabbit engine and clutch
replaced a 79 olds diesel with a chevy 350
removed and installed 72 vw motor after replacing cylinders
dissembled and ship a kx500 threw the mail to Japan, then reasembled
did a valve adjustment on a 84 benz diesel

how much would this job cost me if I had it done?

 

it seems you have the mechanicl knowledge and know how.if you have the time and a place to do it then you should.remove the head yourself and take it to a engine shop to have the head work done.removing the head on this motor is a fairly simple job.you will save a few hundred dollars doing this youself you could use your savings to replace your timing chain depending on milage or put a cam in it and get alittle more power.but in my opinion i would try the seafoam cleaner before tearing it apart.

 

If you have, or have access to a leakdown tester, use one of those. It's an easy test, and it tells you where you're losing compression. For example: piston rings, head gasket, intake valve, or exhaust valve.

Also, pull the PCV valve out while it's running and see if smoke comes out of the valve cover.

Another trick to diagnose exhaust valves, is while it's running, try and cover the tailpipe with a sheet of paper. If it flutters like it's getting sucked in, you've lost an exhaust valve.

 

when I had my injectors cleaned for no reason the truck had 138k the injectors flowed like new the guy said he looked up some fixes for the same problem one mechanic had a stuck valve on #2 and gave it a whack with a hammer. I laugh when I herd that, I think its a good idea now. well going to try it and report back on what happens.

were can I get a good Manuel to fix the head or has anyone seen this on the web

well, wish me luck