Firing Order..1995 Grand Am 3100 M

[JoeMechanic]

Hello dudes and dudettes..I just finished replacing the engine on a neighbors 1995 grand am 3100 M with a 1996 Buick Skylark 3100 M(bone yard).My question is 2 fold..what is the firing order #1 and #2 are the crank and cam sensors as well as the ECM the same in the 1996 skylark?.I ask because the engine does not run smoothly...it shakes at idle and when you put it in gear shakes alot and almost stalls.I installed new plugs and wired it before I installed it..I just want to double check the wiring.I found the firing order on another web site as 123456 coil pack is marked 52 36 41 from the front of vehicle(packs are mounted on a bracket on rear bank of head).If this checks out what else should I look for?...No SES light so far..otherwise engine runs and sounds good except for this shaking...could be a miss?..throttle response is crisp and engine revs to 1500-2000 rpm's well?..thanks for any advice,Joe.

[geoffinbc]

Yea you got the firing order correct. Yes the cam and crank sensors are the same in that era. You may be running into an idle relearn problem. Is the engine smooth at 1500RPM?

[3100 MPFI]

Make sure that you didn't crosswire the spark plugs. It is easy to do on that engine, and I have done it MANY times.

Cylinders 1, 3, and 5 are on the REAR head, and cylinders 2, 4, and 6 are on the FRONT heads. Make sure you didn't cross them first.

[JoeMechanic]

Are you postive that 135 is Rear bank and 246 Ft ?

I think Alldata online might be incorrect..I am pretty sure 135 rear bank and 246 is front.I will double check my wiring job (did this before I installed motor).I will also put back the original coil pack module assy.I left the one that came with the bone yard motor on motor since it looked good..I am suspecting a dead 1 of the coils.The way the engine runs it seems that 2 cylinders are not firing correctly..thanks for your help,Joe.

[JoeMechanic]

Correction..Alldata was correct..135 Rear Bank with #1 marked closest to passenger door or blower motor.246 Front Bank...Coil Packs is 52 36 41 looking at it from front of vehicle.Looks like I have it correct so the coil pack might be the culprit..I will put back the original and see what happens,Joe.

[3100 MPFI]

Just so you know, I just had a problem with a misfire in my 1990 Grand Prix STE, and the DIS module was the culprit, and my DIS was NEW. Swapped in the spare unit from my 3100 (with the 3100 coils as a just in case), and problem solved. Also, make 100% sure you didn't swap 2 of the wires on the coils just to be sure. I have a feeling you have already double checked all of that, but never hurts to check again.

[JoeMechanic]

No,I triple checked and its not because of wrong wire on wrong coil or plug.135 rear bank and 246 front bank wires installed correctly.You though have me thinking that possibley the wiring that plugs to the ICM might be plugged to the wrong side of ICM.When I hooked it up I just plugged in the wires closest to the ICM and they plugged in without a problem perhaps the wire coming from crank sensor is plugged to wrong side of ICM?..hmm...let me go check that,Joe.

[3100 MPFI]

They can't be cross connected. All 3 plugs are different sizes.

Are the wires new? Are they on good? I had a set of cheapies that didn't click on good. I also got a yard set (that were 8 or 9mm) and they had a misfire to them.

Did you check the proper gap? Just because they SAY they are pregapped, that does not mean they really are.

[JoeMechanic]

Wires are new 5 year 50,000 mile warranty from my

wholesale supplier warehouse down the street from me.Plugs are AC Delco's and I alway's check gap prior to installing ANY Spark Plug.I did however find a major problem arg!!...I just checked the Fuel pressure and its below spec my about 5-11 psi Ignition On Engine OFF.It is supposed to read between 40.5 or 41 psi and 47 psi according to alldata online specs.I am getting a reading of 36 psi steady engine off.When I start it up its 35 psi engine on..unplug regualator vacuum hose and it goes to about 43 psi engine running.Alldata states that its normal for it to be lower than spec at idle and assume then that regualtor is functioning properly.When I goose the engine it responds well and guage jumps from 35 - 43 psi..so I know the regualtor works fine.I can't hear the pump working with Ignition ON so I know its about had its last day.I will double check tomorrow with a better guage(snap On) than what I am using(harbor freight tools)but It does work fine I believe.Next step if to pull all 6 plugs back out,unplug ICM(so I don't get a zap surprise)and check engine cylinder compression.I think I have this car almost fixed..the damn owner and his lack of maintainence is part of the problem.I should have known after getting the job..Oil in old engine looked as though it wasn't changed in a year black as coal,front tires going flat often(thank god I have a compressor)trans fluid burnt(changed that also)drove car with broken valve spring for about a year(I heard that once and forgot about it and didn't confront him about it)..found bad rear shock mount and shock after first teast drive(changed that) found bad inner tie rod bushing(press fit) driver side along with broken sway bar link..put it this way I better charge the dude at least $500 labor now..all I got so far os a crisp $100 bill..he paid for all of the parts thus far..this car should have been junked IMO..162,000 miles straight mint no rust body though..nice dark green original paint..nice car.

[JoeMechanic]

Boy will he be surprised when I tell him he needs a new pump..but I'll wait until I finish doing the compression test to make sure the valves and pistons are sealing properly.Who know's maybe he'll sell me the car cheap if he doesn't want to dump anymore into it..it drives very nicely(probably better than in last 5 years) he has yet to drive it.