87 f-150 300 6 cyl missing and dies at idle?
#1
87 f-150 300 6 cyl missing and dies at idle?
Ok I'll try and give as much info as I can about my problem
I hope someone can help me.
I have a 1987 f-150 300 6 CLY that starts right up and then
dies after a few seconds unless the throttle plate is opened slightly.
It also stumbles off idle and has a miss.
If I play with the throttle a while I can get it to settle
and idle sometimes. If I remove a cap from the intake manafold
vacuum it will idle but still misses.
Intake vac is about 16-17 in and does not fall at high rpm so cat is ok?
The TPS tests good.
I have cleaned the (idle bypass sol.) and it seems to be functioning
Should this seal completely when no signal is applied?
When I take the SOL off the valve will close completly but when I put it
back on I can see the SOL plunger pushes the valve open slightly.
Plugs look ok slight spot of redish area otherwise clean.
KOEO 11 pass 11 pass
CM 87 Fuel Pump CKt 33 EGR
Pressure tested ok I dont remember valu but it was good
EGR is probably junk.
(KOER was done with vac leak it was the only way to keep it running for test)
KOER 41 No HEGO switching detected always lean (SOMETIMES)
44 Thermactor Air Injection system inoperative (ALWAYS)
I havent measured the out put of the O2 sensor yet but it
shouldnt be in play when the engine is cold anyway.
The air pump was shot even before I got the truck.
Anyway any ideas here ?
I just realized I forgot to test the ACT sensor I will check that if I can find it.
Thanks for any help.
Ken
I hope someone can help me.
I have a 1987 f-150 300 6 CLY that starts right up and then
dies after a few seconds unless the throttle plate is opened slightly.
It also stumbles off idle and has a miss.
If I play with the throttle a while I can get it to settle
and idle sometimes. If I remove a cap from the intake manafold
vacuum it will idle but still misses.
Intake vac is about 16-17 in and does not fall at high rpm so cat is ok?
The TPS tests good.
I have cleaned the (idle bypass sol.) and it seems to be functioning
Should this seal completely when no signal is applied?
When I take the SOL off the valve will close completly but when I put it
back on I can see the SOL plunger pushes the valve open slightly.
Plugs look ok slight spot of redish area otherwise clean.
KOEO 11 pass 11 pass
CM 87 Fuel Pump CKt 33 EGR
Pressure tested ok I dont remember valu but it was good
EGR is probably junk.
(KOER was done with vac leak it was the only way to keep it running for test)
KOER 41 No HEGO switching detected always lean (SOMETIMES)
44 Thermactor Air Injection system inoperative (ALWAYS)
I havent measured the out put of the O2 sensor yet but it
shouldnt be in play when the engine is cold anyway.
The air pump was shot even before I got the truck.
Anyway any ideas here ?
I just realized I forgot to test the ACT sensor I will check that if I can find it.
Thanks for any help.
Ken
#2
My basic assumption comes from your OX sensor code. I tells a great deal about the root cause.
An alway lean is telling that the engine is detected as running rich.
Just the oppisite of what you may think.
It means the computer fuel tables are shifted lean and not the engine.
How does it get to running rich?
A. air leak into the intake, after the throttle body.
B. fuel regulator diaphram leaking into it's vacuum hose.
C. fuel pressure to high.
D. leaking injectors.
E. possible air leak into the exhaust ahead of the OX sensor.
Any one or more of these conditions are detected by the OX sensor to the point it no longer can switch in it's normal way because it it always out of range to much fuel in the exhaust gas (cool).
A cold start should go high idle then come down as the engine and exhaust heats up.
If this is not happening to begin, there may be more than one fault present at the same time..
Cold start opens the IAC to provide air. If there is a leak besides, it may close down and not contol the idle because there is no other way to do this.
At the same time the fuel is rich because the ECT and ACT has signaled the EEC to do that due to the cold temp.
This is all accomplished at the time the ignition switch is goes from OFF to RUN, then to crank.
Make a good investigation of every area where hoses, gaskets and mating surfaces could be open to air.
An alway lean is telling that the engine is detected as running rich.
Just the oppisite of what you may think.
It means the computer fuel tables are shifted lean and not the engine.
How does it get to running rich?
A. air leak into the intake, after the throttle body.
B. fuel regulator diaphram leaking into it's vacuum hose.
C. fuel pressure to high.
D. leaking injectors.
E. possible air leak into the exhaust ahead of the OX sensor.
Any one or more of these conditions are detected by the OX sensor to the point it no longer can switch in it's normal way because it it always out of range to much fuel in the exhaust gas (cool).
A cold start should go high idle then come down as the engine and exhaust heats up.
If this is not happening to begin, there may be more than one fault present at the same time..
Cold start opens the IAC to provide air. If there is a leak besides, it may close down and not contol the idle because there is no other way to do this.
At the same time the fuel is rich because the ECT and ACT has signaled the EEC to do that due to the cold temp.
This is all accomplished at the time the ignition switch is goes from OFF to RUN, then to crank.
Make a good investigation of every area where hoses, gaskets and mating surfaces could be open to air.
#4
Originally Posted by Bluegrass
My basic assumption comes from your OX sensor code. I tells a great deal about the root cause.
An alway lean is telling that the engine is detected as running rich.
Just the oppisite of what you may think.
It means the computer fuel tables are shifted lean and not the engine.
An alway lean is telling that the engine is detected as running rich.
Just the oppisite of what you may think.
It means the computer fuel tables are shifted lean and not the engine.
Originally Posted by Bluegrass
How does it get to running rich?
A. air leak into the intake, after the throttle body.
A. air leak into the intake, after the throttle body.
so that may be why I got that code.
I'll check the other options as well.
Originally Posted by Bluegrass
A cold start should go high idle then come down as the engine and exhaust heats up.
Originally Posted by Bluegrass
If this is not happening to begin, there may be more than one fault present at the same time..
Originally Posted by Bluegrass
If there is a leak besides, it may close down and not contol the idle because there is no other way to do this.
Originally Posted by Bluegrass
At the same time the fuel is rich because the ECT and ACT has signaled the EEC to do that due to the cold temp.
Thanks for the input I will get back to it soon and see how far I get.
Thanks
Ken
#5
Originally Posted by Steve83
Read this diagram & its caption.
Then try to determine if it applies to you. IIRC, there was another recall that affected many 4.9L EECs.
Then try to determine if it applies to you. IIRC, there was another recall that affected many 4.9L EECs.
I have alway thought this truck ran RICH attaching a trailer with it running would burn your eyes like crazy lots of (I assume unburnt fuel fumes) but no black smoke though.
That EEC "training" procedure may be useful.
This truck doesnt get driven much 5-10 times per month 10 mile or less trips.
Thanks
Ken
Last edited by kpyro; 02-19-2007 at 09:06 PM.