sputtering at low RPM

[blackestate]

Ok,
I removed the injector lines and replaced the glow plugs. Then I got this sputtering, or hesitation, what ever to call it at low rpm's. (Reminds me of then the old carburated cars would load up and try to flood out)
then along at about 1800 it surges quick, goes back to struggling, then at about 2100rpm it takes off fine.

What did I do? I also adjusted the valves after this issue came up. Made the car idle sommther, and have more power. but did not affect this.

thanks

[Brian Carlton]

See if you can isolate it to a cylinder.

Crack each injection line, one at at time. The idle should get noticeably worse each time. Your looking for the cylinder that has no change in idle quality or speed.

[blackestate]

that it idles great! and it will not do this without going down the road. It revs good in park, and also with the foot on the brake.
Is there anything that I could have bumped? I am to the point that I have no clue.
It is not when the trans shifts either. hmmm..

Thanks
Doug

[Brian Carlton]

I cannot fathom any scenario, caused by your work, where it idles "great" but stumbles off idle up to 2100 rpm, and the runs perfectly smooth above 2100 rpm.

[blackestate]

so if this is just another issue at the same time, what could cause this? injection pump? filters?
It does it both on SVO and diesel
Thanks again

[barry123400]

I have to wonder if you disturbed something in the fuel supply? Any bubbles in pre filter? Just kind of wondering if aerated fuel might produce a result like this. I might submerge the output return line from the injectors and watch for bubbles coming through and surfacing in the container while upping idle substancially. But I do not know all the symptoms possible with air being introduced into the fuel supply to the injection pump. Yet it was the area you were around when you changed your glow plugs. But they would not have caused this. For what it's worth after a problem is found it is usually understood. On one or two occasions in my life it made no sense at all after being found even. Absolutly defied apparent logic. I still have time in my life to experience the third time I suppose but do not look forward to the event. The fuel supply does sound disturbed to some extent here. You might be getting erratic amounts of air in the fuel being injected. At certain levels of performance because of the attempt of the pump and fuel in the lines to deal with the air introduced . The Injectors might not have constant volume of spray due to the compressive factor of the air etc. Just a wild guess by the way. Pretty easy to test and eliminate at least if nothing more obvious springs up.

[blackestate]

On my F-350 I have actually installed some clear hose in the return to look for air.

Another piece to this little puzzle. After working on this, the tachometer started working. This morning,the tach quit working and operation went back to normal.

This is a 85 CA model. So how would that affect this issue?
Also been following the low power thread on the 84. I adjusted the valves due to shaking at idle, so maybe the IP needs an adjustment.

Thanks for all of the help.

Doug

[barry123400]

Well that tach acting unusual does pretty well get rid of the air in the fuel ideal. I do not know the differences between the 85 model and all the earlier versions but there are some. Is there an electrical feed or cable to the injection pump?Minor computor in the passenger kick panel? Somewhere I read that the tach proceses through that. Really I know nothing about the 85 models other than there were changes in comparison to the earlier ones. If or when you find out the funtion of the electrical feed to the injection pump it may lead you somewhere. Locating the tack probLem might give you a clue as well. Might take someone with specific 85 knowledge here. Perhaps since it is a california model something in the more advanced polution control system just might be the cause perhaps. Again that tach doing what it did is perhaps signifigant here. Did you disturb the wire to the injection pump if one exists? At least make sure the connection is clean and tight Any chance a polution abatement device was being told to stay open or closed when it should not have been? I do not even know what is on those engines. Be patient as a lot of our members have extensive knowledge of the 85 california version and will post I hope. I probably think simular to yourself. If car was running well prior to changing the glow plugs then most likely it is something I disturbed. The question is what? It is most likely in the imediate area worked on. There is coincidence as well but just unlikely not impossible. One last perhaps stupid question. Was there any prior symptom that led you to change the glow plugs out other than a defective glow plug?

[blackestate]

I changed the glow plug because the light in the dash stopped working.
As for the tach starting to work, it is a sensor cable thing, I played with that cable before and got it to work. this is under the hood, and as I understand it, part of the sensor.

I will look for some electrical connections to the pump. I did not see any. There is a switch on top of the valve cover that is a "smoke limiter" that was unplugged, and after the valve adjustment, it was cleaned, and a little di-electric grease applied, and reconnected.
That is the only mystey smog thing I can think of disturbing. Will have to see if I can find a print for this and see what it does and where it goes.
Where do I find specific model schematics/manuals at? the generic haynes does not have it.
also the fuel gauge is acting funny. thought it was related to the SVO in the tank, could it be related also?

Need to locate prints...

Thanks for all of the help. I am sure with the guys here it can be found. They have done so much for me already!

Doug