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Discussion Starter · #1 ·
well the saga continues....when COLD the truck has all kinds of power. when warm, it spits and hesitates and doesnt have power...this is only when hte 02 sensor is hooked up. i can unhook it ( currently what i am doing) and it runs great, and has lots of power. i stil get an occassional hiccup. what can this is? TPS is new and adjuted correctly, coil ,AFM and plug wires all test good....thanks <IMG SRC="smilies/usa.gif" border="0">

[ 09-27-2001: Message edited by: dallas ]
 

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Before the engine warms up, or if the computer senses a major problem(i.e. no o2 sensor) it runs the engine in "open loop"
, a preset set of instructions. When the engine warms up, it goes into "closed loop"
opeation and uses inputs from the sensors
to control fuel mixture and timing. if you dont get any codes during self test,you may have an "in range" failure of one of the sensors, meaning the ecu doesn't see a problem with it. It seems like you have been fighting this for awhile, sometimes they are a bitch to diagnose. You may want to break down and take to the dealer.
Are you absolutely sure that there isnt crack in the intake hose between the VAM and the throttle body?

[ 09-20-2001: Message edited by: zags ]
 

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cold engine injector thingy.

have you cjecked it to see if it is stuck open. is your truck running really rich?

what else is going on. give more details! <IMG SRC="smilies/biggrin.gif" border="0">

zags, i left you a few messages on that one post for the newbie. did you catch them? <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0">
 

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dont you have a cam and header and such???
if so then your truck is running to lean. open up the top of the AFM and turn the lil gear wheel one or two teeth CounterClockwise.
my truck has the same problem yours did but im gonna fix that this weekend. thanks for bringing it up because i could not tell any one exactly what it was doing.
 

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If your engine is stock, (No header, etc), your problem may be a leaky exhaust valve. This will make the O2 sensor crank down on the mixture, leaning the cylinders that don't leak. Check your valve adjustment, check your compression. Good luck.
 

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Discussion Starter · #6 ·
its NOT running rich, and i just rechecked my valves. they were at 7/11 and thats where i set them again. i HAD the AFM cranked 2 teeth, and backed it off, but i'll try it again. no leak in the intake hose, and no its not running rich. it is leaning out once it goes into closed loop mode. i hope its not a leaky exhaust valve, i dont wanna put on a new head, i just pulled it for 2 stuck plugs and i really dont wanna mess with plugs or anything involving the head again. <IMG SRC="smilies/rolleyes.gif" border="0"> the motos only has about 25k on it. and when its in closed loop and runnin poorly, SOMETIMES it will temporarily fix it self and run great, but its gotten to the point now where thats not too often, so i'm driving with the 02 unhooked. keep the ideas comin. thanks..BTW how many turns backed out is the AVERAGE on the air screw on the AFM? 2? 3? thanks
 

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<FONT COLOR="Red"> I think you have a dead sensor somewhere, so you need to pony up the bucks for a FACTORY shop manual for the year vehicle you have. Then simply follow the detailed tests for each of the sensors the manual outlines. It can be a little time consuming but this has ALWAYS worked for me.. </FONT c>
 

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Discussion Starter · #8 ·
alrighty, i can get one of those no problem....BUT what sensors are there that are related to this? my buddy can tell my over the phone what the FSM says, BUT i need to know what sensors are up to no good <IMG SRC="smilies/confused.gif" border="0"> thanks guys, ya'll rock <IMG SRC="smilies/usa.gif" border="0">
 

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Originally posted by Fightin' mad fireboy:
<STRONG> BUT i need to know what sensors are up to no good <IMG SRC="smilies/confused.gif" border="0"> thanks guys, ya'll rock <IMG SRC="smilies/usa.gif" border="0"></STRONG>
<FONT COLOR="Red"> Since you mention unhooking the O2 sensor changes performance once the engine is up to operating temp, I'd say that you should start with the sensors that monitor coolant temps that are outlined under the "emission controls" section.

I had a similar problem where my air injection (smog pump) stayed in "bypass mode" after the truck heated up. The problem turned out to be one of the coolant sensors that only has a single wire running to it. Most of the sensors I have checked are single wire units that either make or break continuety at a given temperature. The really bad news id that this sensor was like $86 from the dealer....I had to visit Pic-n-Pull..
</FONT c>
 

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Discussion Starter · #10 ·
alright, as far as i know there is one coolant temp sensor for the gauge, and thats in between the head and intake about 3/4 of the way towards the firewall. i replaced that about 8 monhts ago, BUT there is on directly ontop of the thermostat housing that is suspect....are there any others?
 

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Originally posted by Dallas Whedbee:
<STRONG>alright, as far as i know there is one coolant temp sensor for the gauge, and thats in between the head and intake about 3/4 of the way towards the firewall. i replaced that about 8 monhts ago, BUT there is on directly ontop of the thermostat housing that is suspect....are there any others?</STRONG>
<FONT COLOR="Red"> The sensor for the temp gauge won't have any impact on the rest of the system. On my 83 there were two sensors towards the front of the motor. Your manual should have a page that shows the locations for your particular year and equipment level (mine did anyways). I simply started by checking the sensors in the order dictated by the manual. It's so simple! I like to have both a DVOM and an analog style meter on hand for these tests. </FONT c>
 

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Discussion Starter · #13 ·
in my FSM cant find the EFI sensor that it ontop of the thermostat housing. i believe this is the only other sensor that can lean out my truck after it warms up. anyone with an 86 know of any other sensors? thanks guys i'm gonna go get that part this after noon if ya'll think that that is it <IMG SRC="smilies/usa.gif" border="0">
 

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Originally posted by Dallas Whedbee:
<STRONG>is your 83EFI? did you convert it?</STRONG>
<FONT COLOR="Red"> No.. an 83 is what I have actual experience in performing the tests I'm telling you to do. I do not have an 86 FSM, but I do have an 85 FSM that shows the test and expected results for the "Water Thermo Sensor" on page "FI-68"...oddly enoungh, the test procedure for the O2 sensor is right on the facing page (FI-69). How 'bout that? Now there just HAS to be a similar test outlined in the 86 FSM? <IMG SRC="smilies/confused.gif" border="0"> Look under the "fuel injection" chapter instead of "emission controls".

DO NOT replace any parts UNTIL you have tested them, otherwise you stand a very good chance of just throwing your money away.
</FONT c>
 

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Discussion Starter · #15 ·
i tested the thermo sensor ONTOP of the t-stat housing AND the thermo switch next to the cold start injector switch, replaced them both and it runs better over all, but when i hook the o2 up it still looses power and hesitates in between 2k and 3k rpms once it warms up....maybe its not leaning out and its my Cold start injector that is stuck on? HELP! i'm so damn pissed off at my truck now.... <IMG SRC="smilies/pissed.gif" border="0"> thanks
 

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<FONT COLOR="Red"> You DID test the O2 sensor right? Were both of those thermo sensors bad (failed test)? </FONT c>
 

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Discussion Starter · #17 ·
the o2 is new ( 2 months) yes its a bosch, BUT it was doin all this b4 i replaced it and was gives me the same code 05 b4 and after i replaced it. i counldnt get the same reading twice on those thermo sensors, so i got them, they were at cost, so it wasnt too hard to take <IMG SRC="smilies/eek.gif" border="0"> i am thinkin maybe my CSI is stuck? i'm gonna unhook it and drive around today and see.......i swear i'm gonna send you $$ or take you out to lunch or sumthin when this is fixed.....thanks bro <IMG SRC="smilies/usa.gif" border="0">
 

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Originally posted by dallas:
<STRONG>the o2 is new ( 2 months) yes its a bosch, BUT it was doin all this b4 i replaced it and was gives me the same code 05 b4 and after i replaced it. <IMG SRC="smilies/usa.gif" border="0"></STRONG>
<FONT COLOR="Red"> I'd still check it.. I've bought parts that were "dead on arrival" before. If you don't get the specified signal, I'd start tracing the wire from the O2 sensor back and looks for shorts or breaks.

The other thing I'd try is (after it warms up and runs poorly) to try removing the wire from each of the thermo sensors to see if it runs as good as it does with the O2 sensor unhooked. This would tend to indicate a possible circut fault in the O2 wire somewhere. So, check that O2 sensor preferrably using an ANALOG meter. You will need to see the needle swing to 7 - 9 volts in pulses (I forget the # per second)..

Don't forget to thumb through the diagnostic tables in your FSM in the front of the EFI section, since they may help point you to some other cause.
</FONT c>
 

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Discussion Starter · #19 ·
okay, will do, i ran it without the CSI hooked up today, ran AWESOME for 20 minutes then slowly....slowly slipped back into its problems. doenst sputter hear as much, only did it once instead off all the time, but its DOGGY. i coundt get in the freeway, its like the timing is way retarded, but its not.....i just checked my EGR valve too....its clear and holds vaccuum
 

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<FONT COLOR="Red"> One other tip I can offer is that whenever I install any new engine electical component, I always remove my battery ground to dump all codes and computer settings (not like this will solve your problem, but will make each subsequent test equal to the last). </FONT c>
 
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