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

[meandad]

Have an 86 GM 5.0 65K miles with a bad miss , sputtering, jerking . It 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. PCM shows no codes. FYI, This is a Canada Car, and the engine compartment layout more like an 88 Lincoln than a 86 GM. Did all the cheap/free things first. Checked battery voltage -OK, checked charging voltage- OK Checked Timing -right @ 10 deg, checked compression – 145 +- 5 all cylinders, checked vacuum – AOK, reseated salt and pepper shaker connectors, , cleaned Throttle Body , vac tested EGR and cleaned, cleaned IAC (helped Idle but not much else), removed and cleaned all ground and power connections in engine compartment, checked fuel pressure – OK, 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 , .

CHANGED Plugs, Cap, Rotor, and Wires. PCV Valve, Screen and Grommet, Checked coil input – OK , Checked coil resistance , was iffy so changed Coil, changed throttle position sensor & set, Changed distributor complete with Ignition control module, and PIP sensor , Seafoamed engine and ran 2 bottles of injector cleaner in gas.

All of the above was done over a three week period and still runs badly. I don’t want to continue throwing parts at it. Would appreciate any suggestions?

[GoodSamaritan]

Welcome to GMN!<br><br>My first thought about sputtering at part throttle would be the TPS (throttle position sensor). But if you're feeling it all through the throttle range, that might not be it.&nbsp; It's an easy thing to test. It's right on top of the throttle body and only held on with two screws. Most auto parts stores can check them for you for free. <br><br>If you're getting a rich condition across multiple cylinders, you may want to look a bit closer at the oxygen sensors. <br><br>Having said that wait for Lincolnmania to reply. He is the guru when it comes to these cars. <br>

[sly]

also... check the vacuum hose from the MAP sensor (located on the firewall above the heater core... or general location) if that's leaking... it'll cause no end of crap.

[88grandmarq]

Have an 86 GM 5.0 65K miles with a bad miss , sputtering, jerking . It 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. PCM shows no codes. FYI, This is a Canada Car, and the engine compartment layout more like an 88 Lincoln than a 86 GM. Did all the cheap/free things first. Checked battery voltage -OK, checked charging voltage- OK Checked Timing -right @ 10 deg, checked compression – 145 +- 5 all cylinders, checked vacuum – AOK, reseated salt and pepper shaker connectors, , cleaned Throttle Body , vac tested EGR and cleaned, cleaned IAC (helped Idle but not much else), removed and cleaned all ground and power connections in engine compartment, checked fuel pressure – OK, 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 , .

CHANGED Plugs, Cap, Rotor, and Wires. PCV Valve, Screen and Grommet, Checked coil input – OK , Checked coil resistance , was iffy so changed Coil, changed throttle position sensor & set, Changed distributor complete with Ignition control module, and PIP sensor , Seafoamed engine and ran 2 bottles of injector cleaner in gas.

All of the above was done over a three week period and still runs badly. I don’t want to continue throwing parts at it. Would appreciate any suggestions?

You say there were no codes... what do you mean? you got a constant code 11 or you got no response from the ECM when you checked for codes?

If you got no response from the ECM, I would check and repair the EEC connector and check for codes again, you should at least get a system pass code (code 11)

I would also replace the engine thermostat and for giggles replace the fuel filter.

[meandad]

Welcome to GMN!<br><br>My first thought about sputtering at part throttle would be the TPS (throttle position sensor). But if you're feeling it all through the throttle range, that might not be it.&nbsp; It's an easy thing to test. It's right on top of the throttle body and only held on with two screws. Most auto parts stores can check them for you for free. <br><br>If you're getting a rich condition across multiple cylinders, you may want to look a bit closer at the oxygen sensors. <br><br>Having said that wait for Lincolnmania to reply. He is the guru when it comes to these cars. <br>

Already changed the TPS, new one measures within the spec like it's supposed to. I thought the Oxygen sensors would only be read after it warmed up. Thanks for the reply John

[meandad]

You say there were no codes... what do you mean? you got a constant code 11 or you got no response from the ECM when you checked for codes?

If you got no response from the ECM, I would check and repair the EEC connector and check for codes again, you should at least get a system pass code (code 11)

I would also replace the engine thermostat and for giggles replace the fuel filter.

I should have said I got nothing but code 11. I just checked the cold and hot resistance on both the temperature sensor, and the Manifold temp sensor. they are both within range, and increment as they get hotter. Also checked the EGR sensor, and it's output voltages are also within spec. Also pulled off and reseated the PCM connnector. All no help. I was going to change the fuel filter but was afraid to mess with the fuel lines. They are not in good shape. It was replaced about 5 years ago anyway. Also when I checked the fuel pressure, it was fine, and the fuel was water white. Thanks for the reply.

[meandad]

also... check the vacuum hose from the MAP sensor (located on the firewall above the heater core... or general location) if that's leaking... it'll cause no end of crap.

I was thinking about changing the Map sensor. I don't have a scope to check it. The vacuum to it is fine though, as is the
vacuum in general. Thanks for the reply

[gadget73]

try unhooking the vacuum to the MAP. If it runs better, replace the MAP. It should run much much worse, but the few times I've seen a bum MAP, it runs like its disconnected with the vacuum line on it, but runs normal with the vacuum line unhooked.

There is apparently some way to check the MAP sensor using a tachometer to read the frequency output. I've never tried this, but it makes sense to me.


http://www.ford-trucks.com/forums/10...ap-sensor.html

[meandad]

try unhooking the vacuum to the MAP. If it runs better, replace the MAP. It should run much much worse, but the few times I've seen a bum MAP, it runs like its disconnected with the vacuum line on it, but runs normal with the vacuum line unhooked.

There is apparently some way to check the MAP sensor using a tachometer to read the frequency output. I've never tried this, but it makes sense to me.


http://www.ford-trucks.com/forums/10...ap-sensor.html

I Didn't try unhooking the vacuum to the map sensor. I'll try it if it stops raining before I have to go to work. I've heard of the tachometer thing, but I think thats one of those "Is it working at all" deals rather than being able to see if it was in spec. Thanks for the reply

[88grandmarq]

I should have said I got nothing but code 11. I just checked the cold and hot resistance on both the temperature sensor, and the Manifold temp sensor. they are both within range, and increment as they get hotter. Also checked the EGR sensor, and it's output voltages are also within spec. Also pulled off and reseated the PCM connnector. All no help. I was going to change the fuel filter but was afraid to mess with the fuel lines. They are not in good shape. It was replaced about 5 years ago anyway. Also when I checked the fuel pressure, it was fine, and the fuel was water white. Thanks for the reply.

replace the the thermostat.

[meandad]

I Didn't try unhooking the vacuum to the map sensor. I'll try it if it stops raining before I have to go to work. I've heard of the tachometer thing, but I think thats one of those "Is it working at all" deals rather than being able to see if it was in spec. Thanks for the reply

Tried it. Ran terrible, and kept stalling. I'm running out of Ideas.

[cld783]

did you clear eec and let it relearn after all the new parts?

[meandad]

did you clear eec and let it relearn after all the new parts?

Good Point, No I didn't after Ichanged the distributor, but I did after most of theother parts. I'm really thinking of buying a better set of new wires. I could always use them on my truck if they don't help. Thanks for your reply

[85crownHPP]

Did it start doing this all of a sudden or gradually over time?
If there are any junkyards near you I'd go nab a MAP sensor to try. Also you can test TPS function with a multimeter by probing the wires with it plugged in, key on. Black is ground, one should read 5 volts steady, and the other should vary from 1 to 4.5 volts or so as you open/close the throttle.
Of course double check the ECM ground at the battery terminal clamp too.

[85crownHPP]

Also when I checked the fuel pressure, it was fine, and the fuel was water white. Thanks for the reply.

What do you mean "water white"? did you mean "water clear" ? If your fuel supply could be questionable Id get it out and some fresh in. Ethanol gas is supposed to "go bad" much quicker...