Finally!! Got her going! 3 weeks of nothing but working on my1986 vette vette vette! It had its ups and downs, Tears of joy and sorrow and frustration, but she is road worthy again.You allknow what I mean[8D]Went on a 200 mile test drive too make sureThe only thing that caught my attention, other than the glorious Black86' was a surging at part throttle. She's fine at Idle and Fine at Full throttle, but in between out on the highway she surges. Example: cruising at 60mph you give it 1/2 throttle keeping the pedal steadyto speed up, andthe engine surges until you give it more gas then it downshifts ( Auto Trans )and...VRRMMMM it takes off. She doesnt knock ping or miss, and it only stalled once when going down hill to a stop sign.My instincts tell me its the fuel pump, most everything else is new,but what do you guys think? I know MECH259 has the answer.....

 

That might be a little harder to diagnose without looking at scan tool readings. Have you checked codes? Make sure your TPS voltage is steady @ idle around a 1/2 volt. Use an analog volt meter to watch voltage sweep on throttle, particularly at where cruising speed is. Might also try unplugging vacuum line to EGR valve to see if surge goes away. Try those things.

 

Got it Im going down to check it now!

 

I checked the Voltage going to the TPS sensor at closed throttle. It was 0.8 , So I adjusted it back down to 0.5 or 1/2 a volt. I havnt taken it out for a test cruise yet but if this doesnt fix it then Ill try the EGR vacuum next.How will the car runif the EGR Valve doesnt have a vacuum source?

 

It will run ok, just might get some detonation on a warmed up engine. BTW, .8 v is acceptable, as long as it is rock solid, no fluctuation.

 

Still the same problem.( surging at mid RPMs while drivng, Ok at Idle and full throttle)I removed the vacuum hose from the egr valve under the intake pleneum, and there was no change. Actually it didnt feel like any suction was coming from the hose at all. The motor was at 180deg when I did this. Does this mean that therelay under the throttle body, behind the thermostatthat the hoses go to are bad, or should I check something more simple, like the Gap on my spark plugs

 

There wouldn't be any vacuum at idle, the computer only opens the egr solenoid when egr is needed. I think Mech wanted to see if you were getting egr when it wasn't wanted. Make sure that the egr valve isn't stuck slightly open. Sometimes you can get a little carbon build up in the valve and it won't close all the way. Checking fuel pressure can't hurt. You would want to run the gauge out of the hood and tape it to the windshield so you can watch it while driving.When you checked the TPS did you do a slow sweep from closed throttle to w.o.t. watching for voltage spikes? If not, do so. And finally try spraying carb cleaner around your plenum, intake runner and intake manifold gaskets and see if it bobbles. If so change whatever gasket is sucking air.

 

Also, spraying carb spray around intake will change the idle if you find a vacuum leak. Really like to see what the O2 voltage is doing, probably staying on the lean side (>.100 volts) and also look at your MAP sensor readings. You can also unplug your Mass Air Flow sensor to see if idle improves any cause it will go into a backup setting, won't be good, but if it seems to perform a little better, the MAF will be suspect.

 

Im heading to San Diego today in the Vette, from Oklahoma, I have to check into my new Duty station. ( NAVY ). Tommorw when I arrive Ill post how it did on the trip! Wish me luck!