EFI - Timing fluctuations and idle surge

[67EB_in_619]

Ok.. so I am not sure if these are related.. but here is what has happened. I recently got a SnEEC and plugged it in.. all seemed good but I noticed that my timing advance was dancing around a lot even just sitting at idle... between 17 and 23 IIRC. Since I wasnt having any driveability issues, I pushed it to the back of my head to look up later.

Then.. last night when moving the bronco around in the driveway... it died on me a couple of times (doesnt usually do that) and was a little hard to start... again, doesnt usually happen. So this morning I went out and wiggled some wires and started it up and let it run for a while.. the idle was surging a little.. coughing down and almost stalling, then vroom back up to 1200rpm for a few seconds.. then settle back in at 750rpm.

Like I said, not sure if these are related. The stalling issue is keeping me from driving it.. could be a loose wire someplace. or it could be related to the erratic timing being a symptom of something going bad in the dizzy etc.

Anyone able to shed some light? Is the dancing timing normal?

 

[sicaz66]

truck avenger!

 

[73stallion]

how many miles on the engine? first thing to come to mind is timing chain.

 

[la77]

I Have No Clue About The Timing. Mine Did That At All Times Until I Changed My Tps, Now Much Better. Check Your Tps Out And Make Sure It Is Working Properly And Set Somewhere Between 0.6-0.9 Volts. The Probst Book Says 0.6 And Everywhere Else I Read Says 0.9v With Throttle Plate Closed. If You Don't Know How To Check It Get A Multimeter And Check The Green Wire Comming Off The Tps (throttle Position Sensor) With Key On Engine Off. It Is Supposed To Go Up To 4 Or 6 Volts Or Something Like That At Full Throttle. Should Be A Smoth Steady Increase In Voltage As More Throttle.
Just Learned How To Do This Last Week.

That Is All If You Haven't Done That Already.

 

[COBlu77]

Any codes? Fuel pressure consistant? Have to ask, because both issues could be numerous things. If you're not getting codes, then I'd start by checking the harness grounds, then the distributer, then TPS and IAB. Then as a last resort pull the distributer and look at the gear to see if it's missing teeth or slipping.

 

[roundhouse]

The timing on mine also goes allover the place at idle, you put the lighton it and its all over the marks.

The surgeing sounds like a vacuum leak somewhere.

 

[67EB_in_619]

about 85k miles on the engine but I put a new double roller chain on it about 5k ago. Fuel pressure is good.. .. grounds look and feel solid... injector harness to body, main harness to body, battery to frame, frame to body... but I will double check them all.

I just replaced the dizzy about 200miles ago.. so I am wondering if I got a bad one... thats why I was curious as to what everyone elses timing advance looks like at idle...

I had been thinking vac leak too.. putting it in reverse results in a solid thunk.. after thinking about it.. the first time it stalled and died was after putting it in reverse... must have wiggled something loose. Looks like I start hunting for the basics before I blame the EFI!

Any other ideas.. keep em coming!

 

[67EB_in_619]

I will connect the SNEEC again this weekend and check the TPS.. that should (if i can figure it out) make it easy!

 

[surfer-b]

If you have a digital meter hook it to the green wire on the TPS, take a sewing needle and push through the wire and hook to the pos. meter terminal I have found this to work the best. ground the meter to black wire coming out of the TPS or the batt. itself, with KOEO set to .9v~1.0v most i have read set at .98v after setting the TPS leave the meter hooked up and start the motor the voltage should stay steady until the butterfly plate is open then the voltage will rise, if the meter does not hold a steady voltage with motor @ idle then the TPS needs replacing. NOTE the voltage will hold steady even though the engine is searching for idle if the TPS is good.