89 octane 10% ethanol gas versus plain 87 octane??

Ok,

Why does my engine give me more frequent hard starts and stalling on 89 octane 10% ethanol unleaded gas and run fine on plain 87 octane unleaded?

I messed up and pushed the wrong button at the pump the other night, and Voila! the frequent stalls and hard starts return...

87 Cherokee, 14k on rebuilt 89 4.0L, .060 bore job, high end performance bearings, rods, rings, pistons, head and intake ported and polished... Bosch 19lb injectors, new air filter(soon to be homebrew cold air with K&N 4 1/2 by 8", 3" inlet, insulated per Dr. Dyno pattern), good grounds all around, CPS tests fine(but then again is there a sure test for this?), new OEM fuel pump and tank flush a couple months back, TPS is new, IAC is new, sensor in distributor new at rebuild, O2 sensor just replaced with new exhaust(possible leaky exhaust manifold gasket or crack in manifold), plugs are Champion brand and gapped right per mechanic, wires good, cap and rotor are fine, no melted wiring on exhaust....did i miss anything?

Doing vacuum test on wednesday and another fuel pressure test to see if the regulator on the rail may be bad, tested good after the fuel pump was replaced. Also after a 100 mile road trip yesterday the fuel pump became extremely LOUD, once the jeep cooled off it was quiet again??

Just looking for some input, seems to be ethanol blend at the moment, but still have some stalling probs and hard starts on 87 unleaded at times, but not as bad...

Cory

Alcohaul has a lower BTU rating and doesn't always burn as well as gas does when in use, even if blended with gasoline.

Isn't there 10% ethanol in the 87 grade?
Because there is only two tanks under ground; the 87 and 93 grade, the 89 is a mix of the two.
All the stations in my area has a sticker stating 10% ethanol all grades.

The higher grade fuel the harder it is to burn on a 9-1 engine as most are the 87 burns best. When you put the higher grades in you just burn more money and not get any additional performance. The higher grades in performance engine are use to prevent detonation.

All the stations in my area has a sticker stating 10% ethanol all grades.

Click to expand...

That's beacuse we all have to use 10% here in the Chicago area Ronnie, as well as "winter blend" and "summer blend" (almost makes it sound like Starbucks' doesn't it?), csr lives in a place with better air quality so they don't "need" it.

We have 87, 89 with 10% ethanol, and 90-91 super. I usually run the 87 cause it runs better, but is usually 5 cents a gallon more then the 89 with ethanol...trying to promote the clean air and help the locals out who produce for the ethanol i guess.

Thanks for the answers, those ideas were pondering in my head but i was unsure.

Got my K&N cone filter today, pipe is getting the fab done on wednesday(adding the nipples and standoff), air box....well, not exactly sure on a design yet, will start with Dr.Dyno's enclosure.

Thanks again,

Cory

Hey, did you ever figure out that dying problem you had a few weeks ago?

Nope on the dying problem, still happens and is ticking me off to no end.

Doing vacuum and fuel pressure tests on wednesday. I CANT stand it anymore, NO mechanic I have taken it to can figure it out or replicate the situation when i take it in...how can they fix something that "aint" there when they look at it. Its a piece of shit that has drained my damn savings account and ive about had it...its always one more part, or one more test, or drive it off the damn cliff. Right now watching it get crushed in a metal yard would be satisfying!

Im about to give up and cut my losses and go back to regular "reliable" Ford, GM, or Dodge 4 wheel drive pickups, havent ever been stranded in any of them that I have owned!! Nor do they have the patented "problems" that jeeps seem to be famed with.

There, I feel better now.

Cory

EGR? Wifes 87 had a sticky EGR valve that would stall at stop lights and sometimes on low speed corners (made things intersting when the power steering died). Would occasionaly idle really bad.
Almost the same symptoms, when I once left the plug off of the EGR solenoid. Read somewhere the EGR solenoid is defualt open, which means with no power, it´s always supplying vacuum to the EGR, which can´t be good.
My old 86 FSM recommended a coating of heat grease on the rod and periodic cleaning of the EGR piston and seat. Supposed to scrape them clean (carefully) and not use solvents.
Another thing to check is the bend of the cable bundle, near the back of the fuel rail. Don´t hear it mentioned much anymore, but was once a common problem to have frayed or fatigued wires there, which caused intermittant problems. The wires that run under the engine from the front of the fuel rail are also prone to cooking on the exhaust manifold and/or rubbing on things.
The electrical plug was loose on my MAP, motor would crap out at the oddest times. The vacuum plug/stopper for the MAP at the TB shrank over the years and would leak a little vacuum and pop out on occasion, I coated it with a dab of silicon.
Just a couple of possiblilities for intermittant problems that I´ve seen.

Ive thought about the EGR at times. When idling, i can reach down and move the rod toward the fender and it will stumble and die if i dont let it go, didnt try the other way to the engine though. I figured it was working ok.

All the wiring is good, will check out the MAP on wednesday along with the EGR, vacuum, and fuel pressure tests. The mechanic is going to love me...

Thanks 8mud.

Cory