Throughout the summer I had a long-crank-cycle before ignition, and no significant engine problems prior to that. The failing aftermarket pulley/harmonicbalancer had been recently replaced but not before the deteriorating belt bashed up my crankshaft position sensor (CPS). So to solve the long crank and the bashed-up CPS, I replaced it myself with a new OEM CPS sensor. And the car cranked quickly, as expected.

And, by coincedence or not, the hesitation in acceleration and gear-changes began to occur. Same afternoon. And over weeks of use, advanced to cutting off at intersections and sometimes while underway on the highway.

My mechanic replaced all plugs, chose a rear-coil and a front-coil to replace. Still no improvement. Must be the ECU, he says. So I've spent my spare-time from Fall to now trying to swap out my ECU with another used ECU. The numbers printed on my own ECU were not legible, so I ended up with some near-fits I bought from helpful people on the .org, but nothing that matched any portion of the more-legible plastic label on the side.

Before I beat myself up further on an ECU...would that be my culprit at all? Would any variation related to a new Crankshaft Position Sensor be causing my engine to run erratically? What about similar owner's problems with their MAF? (An MAF code was thrown by one of the mismatched ECU's but I couldn't trust that implicitly due to the mismatch of the ECU.) How often do ECU's fail on 4th Gen, anyway?

Any feedback would be so helpful to get my car running again...

Thanks,
Charles

 

Reset your ECU manually and see if that MAF code gets thrown again or if any others get thrown and check back in.

 

ECU's do not fail often on 4th gens. When you accelerate, can you go past 2000RPM?? If not, replace or clean your MAF. Hope you kept your original ECU.

 

How is your idle? Is it really erratic?

When my MAF completely died my car wouldn't even move 2 feet without stalling. But before that, it had a really erratic idle and would go up and down a lot most of the time coming to a near stall, and when I hit the gas from a stop nothing would happen for like 2 or 3 seconds and then my car would jerk forward. It will also sometimes randomly lose power almost as if it was a misfire at a steady speed.

A easy way to check if its your MAF is to unplug the MAF sensor while your car is at idle and if your idle steadies and is stable then it is definitely the MAF. That is how I diagnosed the problem.

 

Chris, Trini, Leo:

Many thanks for the input. I spent today wrangling with it. Using the near-fit ECU (alleged to be compatible, but not my original one) and no change to my Crankshaft Position Sensor (CPS), I cranked and drove a couple of miles without major incident. Sluggish, no codes for the initial time. Then out on the highway it skipped and threw the engine light. OBDII showed three codes: #6cyl misfire, MAF, and aux emissions control. And progressively it got where it would not pull out of the parking lot until I reset the ECU and left the engine off for several moments.

After this "rest", I drove the couple miles home, and attempted to bring the car to it's pre-problem status of late Summer, for a baseline. I disconnected the Crankshaft Position Sensor and plugged in my original ECU. Long crank as expected, started, and drove dare I say normal for a mile or so. Then missed, stuttered. Coaxed it into Autozone, would not move two feet for a moment or so, "rested", ran the OBDII. Three (new) codes, (none of the previous ones): Crankshaft Position Sensor (naturally..), EGR solenoid valve, and fuel tank pressure/EVAP.

History: In winter of 2008 I had replaced the EGR solenoid with another used one and had not really thought much about it in the meantime. It never gave me noticeable trouble, it just kept the Check Engine light on all the time until I replaced it and the knock sensor in 2008.

A helpful post on the .org recommended another independent mechanic here in Atlanta with Nissan training. I plan to head there today (Tues 12/28) for a second opinion. Please post your thoughts in the meantime. I really appreciate the bi-coastal tech support.

CP

 

Listen, I don't understand your troubleshooting process at all...you are just making the problem more worse than it is. Why would you not try to clean the MAF or replace it?? Also, you put back in your original ECU and disconnected your CKPS?? Its obvious that this will make the car crank for a very long time without starting. It needs that sensor to read TDC.

If you continue like this, people may not be able to diagnose your problem properly and help you out.

 

Yeah not to be rude, but I agree. I think your problem is surely a MAF related problem. Esspecially if its the original sensor. Trust me, I went through the exact problems and the MAF isn't exactly cheap either so I kept finding ways to avoid that sensor until my car wouldn't even start anymore.

A dead MAF can literally kill your car, my car wouldn't even run with it connected at one point and I had to disconnect the MAF to get my car even started.

Please try the easy suggestions first, clean your MAF, disconnect it while your car is running to see if it stabilizes.

 

Have a 95 Maxima. Replaced plugs, injectors cleaned, Coils are fine, fuel filter replaced. When I go into 3/4 throttle car seems to load up but goes no where but if i ease off the throttle it seems to take off, the Maxima also stalls & turns off intermittently. Been fooling around with these hesitation problems for about 6 months. When the car is idling and I unplug the MAF meter the car dies. Is this normal or is the MAF on the way out? NO CEL codes either. Help!

 

if the car doesnt rev past 2500 rpm then your maf is toast. Get the autozone maf and u good. Try cleaning the MAF first with MAF cleaner.


Test TPS per FSM too. Download the FSM from fallenone's sig.