S10 missing and hesitation

[87S10]

Replaced my 2.8 in my 87 S10 with a 3.1 ,freshly rebuilt,new complete fuel system tank ,pump and filter. Timing is dead nuts on 10 degrees BTDC and during warm up period,the RPMs are low with an intermediate miss but after warm up the miss is gone but on the initial take off,the motor will surge,like it's starving for fuel. What I have noticed when lightly tapping the throttle at the TB is a hesitation and when observing the fuel delivery from the injectors at that moment of hesitation,it's obvious the fuel delivery drops off. I've tried raising the fuel pressure but no matter what I try,this hesitation keeps haunting me. At this point I'm stumped as what to do to fix the problem,just can't keep throwing money at cuz I'm unemployed at the moment,any help sure would be appreciated.

[geoffinbc]

Have you measured the fuel pressure? Are you using the stock 2.8L injectors? Is it the stock ECM? What plugs are in it? Are you sure the EGR is working correctly and not stuck open?

[87S10]

I have raised the FP at the regulator by means of shimming under the spring till the plugs indicated a rich condition,same outcome. Injectors,ECM are stock and plugs are Delco. EGR system has been completely gone through with cleaning,works perfect.Sometimes it runs perfect but for the majority of the time it just misses and hesitates off idle. With the exception of the ECM and Spark Box,all sensors have been replaced..........Thanks....Jack

[geoffinbc]

Then it sounds like a misfire from the ignition if the fuel adjustments don't change anything.

Check all your plugs again. Take them out and inspect the insulator on the outside and cylinder side of the threads. Cracked ceramic is very easy to miss and will cause intermittent misfire. I chased a misfire on my Trooper for a week because of a tiny hairline crack I could not see until the plugs were a little dirty and went through a few heat cycles.

If that checks out then try another set of plug wires.

What happens if your floor it does it misfire really bad under load?

[60dgrzbelow0]

Start the engine late at night, with no exterior lighting around... if it is not pitch black around you when you try this, just cover the outer areas of the engine compartment with the hood up with blankets, a tarp or something to obscure any 'light pollution' whatsoever... and let the vehicle idle while you look around both sides and the front and back of the motor for little signs of "Blue Lightning" where the coil energy is either shorting out or bleeding off. If you don't see anything at first... be patient and have a Buddy slowly raise and lower the engine RPMs to see if the problem only reveals itself in that way. Don't completely enclose yourself to the point of asphyxiation and keep your hands away from any pulleys and belts, etc. You'll have to remain in darkness under the hood long enough to allow you eyes to adjust well enough to pinpoint the spark leak(s). You'd be surprised at how often this little trick works. With a little patience...this technique can save you hours of chasing the "Wire Gremlins" hither and yon!

[87S10]

Then it sounds like a misfire from the ignition if the fuel adjustments don't change anything.

Check all your plugs again. Take them out and inspect the insulator on the outside and cylinder side of the threads. Cracked ceramic is very easy to miss and will cause intermittent misfire. I chased a misfire on my Trooper for a week because of a tiny hairline crack I could not see until the plugs were a little dirty and went through a few heat cycles.

If that checks out then try another set of plug wires.

What happens if your floor it does it misfire really bad under load?

At WOT on a roll,this motor pulls very strong for it's size but from a stand still at WOT the motor boggs and shuts down I'm gonna check the plug wires tonight as suggested in the dark,then check the plugs thoroughly a second time. I'm beginning to think that maybe the ECM fuel programming for the 2.8 is at fault here,don't know

[87S10]

Guys .. I have got a serious problem here that keeps occurring melting the rotor cap where the spark is transferred to the cap terminals. Has anyone run into this or can someone recommend a fix.

[geoffinbc]

What brand are you using? Pick Up a Delco Cap they seem to last the longest

[87S10]

What brand are you using? Pick Up a Delco Cap they seem to last the longest

Hey BTY...........no it wasn't the quality of cap more like some spark surge or something. Ended up changing out the whole distributor and replaced coil with a MSD street series,problem solved ,no more hesitation,miss or bogging when going WOT. Thank you for taking the time in trying to help me solve this