'98 S70 Base 5-spd intermittent bad running & VERY hard starting

[iSparky19]

Videos of issue.

Video 1

Video 2

 

1998 S70 NA 5-Spd

Head gasket just replaced, head tested and shaved.

The problem is intermittent and I can’t find a pattern.  I started it up this morning, 41f/5c outside, started perfectly runs perfectly.  Went out at lunch, 71f/22c, that when the video was taken.  It will also happen when it's cold, sometimes hot, sometimes after just running it.  

Parts replaced:  Cam sensor, Crank sensor, coil, timing belt, rear O2 (not that it matters), .

Tested:  MAF (get CEL when unplugged), input to coil, fuel pressure, IAC buzzes at key turn, TPS, probably more, but I forget.

When it’s having the starting issue, the starter will sometimes NOT stay engaged, but pull itself back in, as if it thinks it’s started but hasn’t.

In the first video.  It “starts” but it runs like crap.  My foot was giving it half throttle, and it wouldn’t rev above 2,500, rough and sounding like absolute crap.

When I went to the engine, I was actuating the throttle cable by hand about a quarter turn.

Second video, you can hear the engine stop turning while starting as if it were flooded.  But is it possible for the injectors to flood it that much in a short time?  Also, I’ve tested fuel pressure while it was acting up and it was normal.  Were it dumping fuel in, I would have thought the pressure would have gone down.  I am turning it off between starts, it's not shutting down on its own.

It feels like the timing is wrong.  But that can’t be the case, since it can run perfectly fine, and all timing is ECU controlled.  On the “can run fine”, when it starts normally it will idle, run, and pull normally.  No hesitation, no hiccups, it’s smooth as anything, it will pull strong all the way to 5,500 (I stop after that).

On top of all that, NO CEL!

I am at a loss on this.

[Zappo]

For the first video, was the engine still warm when you started it up?

It does act like it is flooding.  If it starts and runs normally when it is cold, your issue could be the coolant temp sensor.  I have had one go bad where it always reads cold, so the car would run fine cold, but would start to surge when it got warmer.

Another thing you can check is the wiring to the throttle position switch.  If some of the wiring is damaged, it won't run correctly.  Easy test is to grabbed the wires and lift up while the engine is running and see if the idle changes.

Have you confirmed the timing is correct?  If the timing belt jumped for some reason, it can cause poor running.

 

[iSparky19]

>For the first video, was the engine still warm when you started it up?

Cold.  Second video was also cold.  However, I started it in the morning when it was even colder outside and it started right up.  Ran perfectly fine.  

>Another thing you can check is the wiring to the throttle position switch.  If some of the wiring is damaged, it won't run correctly.  Easy test is to grabbed the wires and lift up while the engine is running and see if the idle changes.

Tested the sensor and the wiring.  Getting signal from computer and sensor is giving correct output.  Wiggling the wires doesn't change the output with the rubber pulled back and tested from the wire end.  

>Have you confirmed the timing is correct?  If the timing belt jumped for some reason, it can cause poor running.

Can't be the belt.  If it skipped a tooth on cams/crank it couldn't unskip the tooth randomly later to start and run perfectly fine.  I did check that, though  

[Chuck W]

Have you looked at the ECT sensor and its connector? Corrosion on the connector could cause a bad signal to the ECU and cause hard starting.

[bmdubya1198]

That's a weird one. I'd also suggest the ECT sensor, are you sure it's reading properly? Bad coolant temp values will majorly screw up the fuel maps and cause these sorts of issues.

Did you check for any codes? Even without a CEL, you may still have codes stored.