98 Q45 hesitation and bucking with massive loss of power

[QCumber]

I have abbandonned the transmission post as I have pretty much eliminated that as a problem.

Here are the two symptoms that are still bugging the s**t out of me:

1) hesitation and bucking (only happens between 40 and 60 MPH)2) after 1/2 hour of driving, I lose power. Feels almost like I am towing something or riding the brake. If I goose all the way up it will run to 4k rpm and move a little but other than that it just put puts around like a golf cart that;s running out of battery.

#2 above almost inevitably gets triggered by shutting the car off for a few minutes and cranking it back up.

Here is what I have done so far:

1) Cleaned transmission pan, new filter and gasket - no problem there2) all injectors ticking properly3) plugs have even burn, cylinders look good and hold even pressure all around4) EGR moves up and down when you throttle up and down (I even took it out of the loop alltogether with no result)5) tried two different used MAF sensors off a couple of Maximas (same exact part) we have in the shop - same result5) Tested head temp sensor (I know someone on here said the Q didn't have one, according to Alldata it does exist and I was able to test it within operating parameters.6) Tested TPS and secondary TPS both operating within proper resistance7) replaced fuel filter (looked like black sand coming out)8) Replaced IAC assy - still no change9) ran out of hair to pull



I am really frustrate with this. I have been working on cars for a long while and have resuscitated many project cars when it shouldn't have been possible but I feel like a complete idiot at the shop day after day farting around with the same car...

I am contemplating swapping out the fuel pump but I have put a lot of money rehabing this car (body wise) just not sure how much more I want to put in it.

Thanks again for your time thinking about this.

[Q45tech]

What is fuel pressure at idle, at cruise and WOT driving under load at 4,000 rpm and 6,000 rpm. 34 psi> 43.4 psi?

Any codes on Consult II or OBD2 scanner?

What does Power Balance test show..........min and max rpm and average cut.

[texasoil]

does it set the CEL? What are the codes?

[QCumber]

I was meaning to run these tests at the shop this morning but halfway there the fan/water pump belt broke, so I am working on that now.

My guess is one of the pulleys is going bad at first glance. Is it remotely possible that a bad pulley or seized water pump could be causing me to lose power? That would seem very odd!

[Q45tech]

Do you not inspect all your belts every 90 days when you change your oil?

I always change belts and idler pulleys way before they could fail that's what preventative maintenance is supposed to do prevent failures.

Generally the symptoms you describe are ignition coil related common on these 97-01 Q41.

[maxnix]

I was meaning to run these tests at the shop this morning but halfway there the fan/water pump belt broke.

Is it remotely possible that a bad pulley or seized water pump could be causing me to lose power? That would seem very odd!

Why? A seized pulley is not a good thing and is a result of neglectful inspections at each OCI.

Since you are new, here's a serioius tip: You replace all belts at once to avoid repeat labor. You have all pulleys on hand so the bad one's can be replaced. Joe will restock unopened parts packages that are not abused.

Joe ships overnight.

http://www.infinitipartsusa.com

[Q45tech]

If one pulley bearing fails the others are never far behind especially after 100k might as well change all when you replace all belts, if you plan on keeping car 3 more years.

All about costs per 100,000 miles of ownership, how you allocate the ten thousand.

[QCumber]

I had just replaced all belts when I put the car back together less than two months ago.

I am going to replace the pump and all pulleys tomorrow.

I had inspected all the coil packs when I compression tested the cylinders, nothing out of the ordinary (equal all the way accross).

[maxnix]

I had inspected all the coil packs when I compression tested the cylinders, nothing out of the ordinary (equal all the way accross).

I noticed visually that there is a little semi-opaque window where my failed coilpack seemed to have a slightly blacker image like a failed fuse. Not definitive, but I thought interesting and possibly indicative of the failure.