86 GM 5.0 with bad miss/sputtering/jerking. some Help would be nice

[meandad]

yeah, the codes I'd expect, but it shouldn't run noticeably different otherwise if things are working as they should. Most of the smog equipment operates that way. It sets codes when missing, but you really shouldn't have any other indication that its not there. If it runs funny with the stuff present, then its probably screwed up.

other random thoughts, have you tried unhooking the green line to the EGR valve? It also shouldn't make any obvious difference in how the car runs but if the EVR gets sticky, it can yank the egr valve full open when its not supposed to be and that makes it run bad. Also, thinking about it merc91 has a good point about weak ignition causing the rich running problems too.

Yeah I just disconnected the air pump on a suggestion. It was free and worth a shot. The EGR I have actually removed and capped off, The weak ignition I can believe but have already replaced the PIP sensor, Ignition control module, Coil, new plugs, and put in a set of low resistance Ford racing wires. I am going to try the MAP sensor, then repost everything that has already been done to the car so as to give everyone a fresh start.

[meandad]

OK Here's the Latest - Please provide Input - Must have Input - grabbing at straws

OK here’s the latest on my poor Car. ****Please tell me if you disagree with any of my findings and why. I will not get insulted. I think I included everyone’s suggestions and what was done to date.

Subject:

86 Grand Marquis 5.0 65K miles This is a Canada Car, and the engine compartment layout more like an 88 Lincoln than a 86 GM.

Symptoms: bad miss , sputtering, jerking
occurs at light throttle the worst, but can feel it at all speeds.
Occurs when Cold or Hot, but slightly better when hot.
Car has good acceleration.
Pulled plugs twice after coming home, they are all wet like a rich
condition. Not real wet but wet


Things Done Already

Checked PCM Codes - shows no error codes. Only code 11
Checked battery voltage 12.5-OK
checked charging voltage- 14.5 OK
Checked coil input Voltage 12.5 OK
Checked coil resistance , was iffy so changed Coil,
Checked Base Timing -right @ 10 deg with spout disconnected
Checked Timing –advances normally with spout connected
checked compression – 145 +- 5 all cylinders,
checked vacuum 20 - 24 – OK,
cleaned Throttle Body
cleaned IAC (helped Idle but not much else)

Checked Manifold Air Temperature Sensor –Resistance correct with good transition when engine heats up

Checked Coolant Temperature Sensor –Resistance correct with good transition when engine heats up

EGR - vacuum tested and cleaned, also tried running with EGR capped off, Checked EGR sensor - voltage within specs with smooth transition.

reseated salt and pepper shaker connectors, and all sensor connectors

removed and cleaned all ground and power connections in engine compartment, Including ECM Ground

removed and reseated computer connector

checked fuel pressure 35-40 and fuel clear / clean – OK, Fuel pressure holds fine after engine is shut off

checked (listened to) all the fuel injectors I could get at 6 out of 8 sounded fine but couldn’t reach the 2 deep under the manifold- I don’t think it is actually an injector problem since the condition of all the spark plugs is the same. Maybe something controlling in injector dwell / Timing

Disconnected the Air Pump (removed the Belt) Ran car around to see if the computer would learn anything new. Still ran like crap. Computer knew right away that the Pump was disconnected. Code reader came up with 94 and 44 which are both Thermactor pump errors – reconnected pump back to code 11 on the PCM


CHANGED:

Plugs , Cap, Rotor, and Wires (all twice) currently has Ford racing wires
with standard copper plugs

PCV Valve, Screen and Grommet

Ignition Coil

Changed distributor complete with Ignition control module, and PIP sensor

changed throttle position sensor & set - resistance is within specs with smooth transition,

Changed MAP Sensor – No Difference

Replaced some burned harness wires to the WOT relay, and replaced relay

Seafoamed engine and ran 2 bottles of injector cleaner in gas.

Made sure and reset computer and gave it time to learn after changes


Items I did not change or check, and Why:

Engine computer – Last resort also it seems to report proper error codes when I disconnect things otherwise reports code 11

Engine thermostat – Condition exists with engine either hot or cold and everything seems to heat normally- can’t see a reason to change the thermostat

Oxygen sensors – Computer should only look at them after warm up, and Condition exists with engine either hot or cold

Did not change the fuel filter because the lines under the car are so bad, I thought I might open up a can of worms – Also Fuel pressure was between 35 and 40 and fuel was clear as water and smelled fine.

[Southern_Pride]

Unplug the o2 sensor. Maybe one shorted out and is backfeeding the ecm.

[86VickyLX]

There was a time with my car where it would keep eating computers. It would kill them in the same exact way every time. You'd start the car, it would idle like shit, the exhaust out the back was black, running really rich. KOEO tests showed everything ok. When I tried to run a KOER, it wouldn't do anything. However, I could get the engine to run right, and run a KOER test by doing this. Start the car up, as it starts running, I would shut the key off and then turn it back on to run, if done correctly the engine will start running again. After that, as long as I didn't turn the engine off, it ran great. But I'd have to do that everytime. I went through about half a dozen computers until I gave up and just replaced the wiring harness. Upon further inspection, the starter relay was the older style (non diode suppressed, very bad for EFI cars!!!!), and some strange wiring that wasn't supposed to be there. The first computer I replaced was a remanned unit, so it had problems in the past. A remanned computer from Ford is easy to spot. It's painted black.

[gadget73]

Are the injectors the correct grey top units, or did someone maybe replace them with the wrong ones?


also, the fact that the O2 sensors don't give you codes for the engine running rich when it so obviously is tells me there is a problem there. Agreed that they shouldn't be used until warmed up, but if I'm not terribly mistaken about Ford's fuel trim strategy, it will use past data to figure fuel tables even in open loop mode. Basically meaning if the O2 sensors are shot and making the motor run really rich when the ECM is looking at them, it stores that info and may make it run rich even when not reading the sensors. Could be worth unplugging both of them and unhooking the battery to force a return to factory defaults. No O2 should give a somewhat rich condition, but if it runs better that should probably indicate something. I've never actually had a bad O2 sensor give a code. They always pretend to be just fine, but they make the engine run pig rich. When the sensors set codes, its almost always because something is legitimately wrong with the motor, not the sensor.

[86VickyLX]

Technically speaking, the bad O2 sensor codes are the thermactor codes. With everything working/not clogged. When code 44 or code 94 comes on, it means the O2 sensors are sluggish on response or may not be warmed up completely.

Ditto on unplugging the O2 sensors and resetting ECM seeing how it acts then.

[meandad]

Everyone is ganging up on the O2 sensors. I will unplug them clear the ECM, and see what happens.

[meandad]

Also the injectors are original grays. I have had this car since it was brand spankin new Thank you everyone for your 2 cents

[meandad]

OK most of the snow is gone so I figured I'd disconnect those pesky O2 sensors. How the Hell do you get at the connectors ? They're
behind the engine with no slack. Is this a from under the car job ? Or is it just a job for someone with little hands ? Any best way ?
I disconnected the battery and reset the ECM anyway since I don't think I did it after changing the MAP sensor. I'll try taking it to work
tonight. See what happens

[1990LTD]

Either/or. I wasn't able to get at them from above whatsoever. Breaking them loose was hard enough but unplugging the harness = definitely not.

[gadget73]

they're not really easily reached. You can probably get them from up top best but there isn't much slack in those wires. Be advised, the 86 has specific oxygen sensor plugs that don't fit any other year. same sensor, just a funky plug.

[1987cp]

Don't both O2 sensors go into a common bit of harness that then plugs into the main harness with just one plug? If I'm remembering that right, the single O2 plug up top should be lots easier to get to.

[mcninetyone]

My first guess would be that the AIC sensor is bad!!!!

Have you checked into that??

[meandad]

What is an AIC sensor ? Do you mean the IAC sensor ? If so, I cleaned the IAC, and it helped the Idle, but not much else. I was told the sensor wouldn't cause my running problems. If I heard wrong let me know. For an update...I reset the computer after changing the MAP sensor, and it made a big difference. Still stumbling, but now it's much much less. It is also now doing it on deceleration which it wasn't before. Whats left is beginning to feel transmission related. It's hard to tell. I ordered the Intake Temperature sensor, and the Coolant temerature sensor because they were fairly cheap, and easier to get at than the O2 Sensors.. Pretty sad isn't it ? Anyway, If the weather holds up, I'm going to change both temp sensors, reset the computer, and try it again. After that I have to change the oil , so while I'm under there, I'm going to change the transmission filter, and check the TV cable adjustment. I'll update again after I try it. Thank you everyone again for your input.

[86VickyLX]

Sounds like vacuum lines are weak and rotted. Deceleration is where the highest vacuum is made in the engine. It's possible that vacuum lines are being pulled shut due to increased vacuum, causing an issue right there. I had this issue with the MAP sensor line, it actually would pull it closed on decel.