Hey guys, my fiend has a 98 maxima and recently he ran into some wierd problems which shop can not find why:
1) his car has sounds like it backfiring in the intake;
2)cylinders # 1 and 6 don't work.
3)no ECU codes at ALL!!!
Mechanick has checked the timing chain, timing itself, changed the 1 and 6 coils and wires. The car wouldn't start. If anybody has any idea of what could it be, your help would be appriciated!! Thank you!

 

First find your friend another mechanic.
Do a compression check, make sure there is no internal engine damage.
A Haynes shop manual or a good mechanic should be able to trouble shoot the car.

 

Coils and wires? No wires on a VQ...

Make sure the injectors are firing, and check the plugs as well (swap out from a known working cylinder to confirm).

Backfiring in the intake means what, the exhaust valves may be stuck closed and the exhaust gases have nowhere to go, hence out the intake during the intake stroke.

 

guys i know this guy too, they did compression check, everything is fine, checked all sparkplugs (all work), all coils (all work) but no spark on 1st and 6th cylinder

 

check your maf

 

also check injectors

 

If you're sure that all coil packs work, then no spark on 1 and 6 has to be either an issue with the wiring harness, or the ECU. I believe that's the entire circuit for spark; ECU, harness, coils, plugs.

 

well.....it if its not SPARKING it couldnt be the injecters....if the coils and plugs are good i agree with pmohr check the harness first....then the ecu

 

sell me the car....


or just check the coils, it's probably that.

 

and the usual clean TB, clean IACV, check all fuses

 

As I told you before, the coils are new, and it started right after tune up....that might help you....

 

Tune up? What was done? Go back over the work, check every electrical plug. Make sure you didn't bend the pins in the coil packs sockets. If the pins are bent, they woun't make a connection... hance... no spark.
Check both crank position sensors, check the cam position sensor.

If this started right after the tune up work was done, then something that you worked on is causing the problem. Go back over the tune up work.

 

CPS crankshaft pos sensor, camshaft pos sensor. One or both, possibly.

 

as of today car is still in a shop and it doen't start, checked almost everything,
changed: ecu, camshaft pos sensors, sparkplugs.
also was checked: maf, harness, fuses, fuel pump, coils, chain cover was removed and chain was checked
everything seems fine and car still won't start =((

 

got to be a dead battery then. jump it

 

check and see if you are actually getting fuel in the cyclinder. Since you've check all of the thing we have suggested, theres not really much of anything else to check.

BTW- what has changed since the tune up? you still havent answer that question. if it started after the tune up, what have you or anyone else done to it that would cause it not to start? Its hard to help when we are only getting half the story.

 

sparkplugs, fuel filter, fuel pump, battery was changed on tune up

 

3.5 Liter that biznitch

 

similar situtation happend on a friends I30 after the shop told him he needs a "clean injection system" treatment where they pour some **** down his fuel tank. the car start mis-fire/shaking. it last almost two weeks and ran fine after.

 

ok here is end of story:
the car was in one shop for like a week then they said take ur car we can't find a problem, took it to a different shop, they fixed it, they said it was improper timing!?
and here is my question how can timing get messed up if a car runs fine and then one day just won't start?

 

I think the lesson here is always take it to a good mechanic. You've pratically got a new car after changing all those parts out, most you could have done yourself. Most likely they crapped something up to cause the timing to be wrong.

You should mention that mechanic on one of those mechanic threads they have around maxima.org as a mechanic to avoid.