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

[meandad]

Well computer's been reset. 2 days, and 9 trips later, the car still runs like crap. I think everything has been checked or replaced except the ECM and the injectors. I'm going to double check for slop in the timing chain, but it only has 65K miles on it. I'm into the more expensive stuff and running out of other ideas. Considering most of my expense so far has been my labor +300 bucks, I suppose I shouldn't complain, but this is getting old real fast, and I'm really not used to having any car kick my butt like this. Anyone have any other ideas. As always, I'm open and appreciative regarding suggestions

[gadget73]

pop the distributor cap and check for slop. Mileage means little if its the plastic gears. I doubt it is, and I doubt you have a problem but its easy enough to confirm.

Are you still getting the lean codes? Is the fuel pressure good? How about under load ?

[meandad]

Project On hold again, Had to solder the radiator back together in my truck. Temporary fix until I can get a new one.

[meandad]

Th saga continues....This is a good one ....Have been using the truck for a while, but had to use the car when the truck was laid up. Stumbling was still there, maybe a little worse. On the second day I'm 2 blocks from my house, and it starts to die completely. Won't restart, and can't see anything obvious with it. I thought it might be empty even though the gauge said 1/2 tank so I threw in another couple gallons of gas. Still no go. Had to have it towed home. Got a parking ticket too while I was away calling the Tow truck. Anyway. When I got home, It still would start and then die. I said, well its about time to change the fuel filter that I had been avoiding because the feed line was so rotten. I was afraid to touch it. First, I took out the computer to get the numbers off it because that was the only other component I hadn't changed yet besides the fuel injectors. I opened up the computer to take a look, and all the usual suspects that would blow out seemed fine. I put it back in the car, and made it last on the list. I then noticed the Vacuum line off that goes from the EGR to the oil fill tube. I can't believe I didn't see that line off when I got stuck. I think I must have pulled it off when I was messing around looking at everything after I got the car home. I put it back on and put clamps on both ends. Tried to start the car, and it fired right up. It sounded like it was running lean, but there was no miss or stumble to it. I took it out for a ride, and it ran great for a while. then I almost got stuck again. The miss/stumble started to come back again. Then it started sounding like it was starving for gas. I threw it into low, so it wouldn't have to shift gears, and barely got it home driving with two feet. I'm really confused now. I took out the passenger side fender skirt, and managed to get the 5/16 fuel line out in one piece that goes from the engine to the fuel filter. Bent up a new one with great difficulty, and put it back in the car using the original flex lines to the filter and the engine. I just cut them back a little, and used 2 steel to nylon compression fittings. changed the fuel filter at the same time. I just got the car back together, and cut open my vapor cannister that was full of water. I dumped out the carbon pellets, and let the whole mess dry in the sun yesterday. Glued it back together today, and put it back in the car. It just started pouring, so I can't try to start the car and check for leaks. Anyone have any Ideas what could have happened. I plan to put the fuel pressure gauge back on before I try and start the car. Any other Ideas how I should proceed.

[84merc951]

my 84 was having the same issues till i put a new timing chain in and that solved all my issues but that car isn't in the family anymore however my dads 86 cp is still having the same issues as you and its been about a 2 years process with that car. I actually replaced the ecu in the 86 and that did nothing but maybe it will for you. But now the egr is acting up again so im hoping thats what it is this time. The only thing my father and i have left to change is the injectors and dizzy. Hows your wiring harness looking? Also did you change the pcv and screen. I did that and it woke the engine alot and it seemed to take the hesitation almost out of the question till last week. keep us updated.

[mercurygm88]

I had a similar stumble that after 8 months I finally found that the vacuum line from the intake to the map sensor was dry rotted. I went through and replaced that line and the one to canister purge solenoid and haven't had any stumbling since.

[meandad]

Thank You, but they have all been replaced.

[meandad]

The timing chain seems OK, I just made myself and injector cleaner which will be next I suppose. The harness looks OK, Changed the PCV and screen a while back, It didn't make a difference. I'm really hoping it was just the fuel filter. Just need some good weather to check it further. Thanks

[meandad]

A Recap of everything that was Done. Same problem still there. Please read through

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.

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 – replaced it anyway –no help

Checked Coolant Temperature Sensor –Resistance correct with good transition when engine heats up- replaced it anyway –no help

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 twice

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


Also 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.

Removed upper intake, and changed all vacuum lines in Engine compartment

Replaced Both Oxygen sensors – No Help

Replace Main fuel Line, and Fuel Filter

changed VSS speed Density Sensor

Change Vapor cannister Purge Solenoid

The only things I can think of doing now are checking/changing the fuel injectors, changing the catalytic converters, and changing the ECM.

Any other Ideas would be appreciated. Thanks again to all John

[sly]

It almost sounds like it's running too rich (open loop) and never settling into closed loop. Check the Coolant temp sensor (the two wire one).

refer to this page for comparison chart. http://oldfuelinjection.com/?p=28

I'd also check the u-joints to see of they are binding up and not moving freely (this may require letting it free-wheel in drive on jack stands and seeing if there's any drive-line vibration... or just dropping the drive shaft and see if the joints will move without issue).

[Southern_Pride]

Get some mercury quikleen from your local marine supply store. Dump it in with the gas light on and drive a couple miles. It will clean anything out of the injectors. Worked on my 91.

[meandad]

coolant sensors

It almost sounds like it's running too rich (open loop) and never settling into closed loop. Check the Coolant temp sensor (the two wire one).

refer to this page for comparison chart. http://oldfuelinjection.com/?p=28

I'd also check the u-joints to see of they are binding up and not moving freely (this may require letting it free-wheel in drive on jack stands and seeing if there's any drive-line vibration... or just dropping the drive shaft and see if the joints will move without issue).

Yeah, I checked both the coolant sensors. They both have the correct voltages, and increment properly as the car heats up. I changed them both anyway. It made no difference.


The U joints are not an issue right now because the miss can be felt without the car being in gear. Thank you for your input anyway.

[sly]

the only other thing I can think of is pulling the main connector off of the ECM and putting it back on a couple of times (disconnect the battery first) to make sure all the pins have good contact. I'd look at it the first time and verify there's no corrosion on any of the pins and clean off any that are.

[meandad]

Been there done that twice, but thanks anyway. I have never had a car kick my butt like this one is doing. It might wind up being a harness problem or somwthing stupid like that. I hope the fuel injectors help, thats what I am planning on doing next.

[sly]

Have you done a compression test to see if the cylinders are all up to snuff?

I also wonder if the EGR spacer is leaking coolant into the engine. I eliminated this on my 88 by taking the coolant lines off the EGR spacer and putting the longer one to where the short one comes from. (can't for the life of me remember which or where right now.)