Surging.

[onlinebiker]

I've an annoying one on my 99 SC2.

I got the car with a rod thru the engine. ($300) and bought another 99 with a rusty undercarriage, and swapped engines.

All went easy.

It starts and runs well - but a bit noisy - body rattles which quiet down as it heats up. Good compression 190+ cold. Spark plug readings as textbook perfect.
Very good acceleraton off the line. Decent gas mileage. No SES codes.

I notice a slight surging in overdrive between 45 and 55.

I suspected it might be a knock sensor - but a new one made no difference.

I suspect the ECM has been changed as my reader says ""ABS not supported" although the car does have ABS (Not hooked up) - and it shows a fault for the keyless entry - and the car does not even have power locks.


Any thoughts?

[bluesl2]

The surging issue may be EGR related, try swapping the valve off your old engine then driving it. How old are the plugs/wires?

[onlinebiker]

Originally Posted by bluesl2

The surging issue may be EGR related, try swapping the valve off your old engine then driving it. How old are the plugs/wires?

Not sure - but wires appear new. Plugs do not show errosion - so I assume they're fairly new as well.

Will try another EGR. I have a few...

[onlinebiker]

Am now getting a p0326. Still feeling the hesitation.


Live data on my scanner shows erratic advance under all conditions. At steady speeds the advance is between 11 and 34 degrees btdc. ..

Thoughts?

[onlinebiker]

Update. I had to run to town. So once the car was full warm - the advance ran between 40 - 44 btdc at 62mph and 55 mph. No surging.

Grrrrrr....

It's easier when stuff just breaks.

Easier to find...

[OldNuc]

The surging as the engine warms up is an incorrect air flow through the throttle body. It is usually a wear issue and time to go shopping for one with good bearings and now visible wear. This is a mechanical failure unless you or a previous owner have playing with the static air adjustment screw.

[onlinebiker]

On the way back from town it started doing it again. Full hot (192f) the advance drops down to 10 to 25 degrees....

I have opening day of deer season tomorrow - so I guess the problem goes on hold.

[OldNuc]

I suspect the bearings are way gone or you have a good air leak between the throttle body and the cat outlet.

[onlinebiker]

Originally Posted by OldNuc

I suspect the bearings are way gone or you have a good air leak between the throttle body and the cat outlet.

Ok.. I have spares. Any good way of testing one?

[OldNuc]

Hold the throttle body only straight out in front of you and wind it full open and see if you can feel any motion in the throttle shaft only back and forth towards you. There should be a rubber cap on the static air adjustment screw Inspect throttle bore for any wear.

No wear or motion allowed.

[onlinebiker]

Originally Posted by OldNuc

Hold the throttle body only straight out in front of you and wind it full open and see if you can feel any motion in the throttle shaft only back and forth towards you. There should be a rubber cap on the static air adjustment screw Inspect throttle bore for any wear.

No wear or motion allowed.

Thanks!

I dunno when I will get to it. I have 5 deer tags - my SO has 2, and my sister has 2. I expect to be busy butchering deer for the next couple weeks. Fortunately it is cold enough to hang them outside. I have my car gantry (with Saturn wheels) set up for hanging deer..

I'll post a picture when we get some hanging...

[onlinebiker]

I got caught up on hunting and got some time to wrench...

I checked the throttle body - and there was very little play on the axis to body fit... I checked another one from another 99 - and it seemed to have none at all - so I swapped the body - with the TPS and air....

It did not change at all...

My INNOVA 3160 tells me that the flat spot is caused by spark being retarded - under 20 degree btdc...

I changed the knock sensor and no change.

What else could be causing it to retard?

[TomM96]

I dunno the Ig timing determinants, aside from KS... maybe mixture?

FDryer should chime.

I wanted to complement the designer's choice of material for the fenders on the
tow rig (seen in another thread).