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2002 Xterra SE, Shock Blue, AT/4x4
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Discussion Starter #1
I am running out of ideas and could use some help.

Short story, my 2002 X, 3.3 NA is a flood car (surprise!!) and new to me. Now, it bogs badly when hitting the gas after many new and used parts (see long story below). Not really driveable. Occasionally I will hear a pop in the intake. I have to advance the distributor to get it to stay idling. Timing belt is new and I checked it twice. The tooth count is perfect. Fuel pressure is below spec, but not much around 32 psi at idle, new fuel filter too. Cranking compression was ok, except for #3 was 95 psi (added oil for a wet test- 225 psi, telling me rings are suspect not head gasket or valves). P0300 multiple misfires. Put in a used distributor, no change at all. Starts fine cold, really struggles on a hot restart. Will idle all day, no overheat but it does heat up quicker than I would expect. My next move will be to remove the fuel rail and check injector operation including spray pattern as water or debris may be clogging. Any thoughts?

Long story, bought the 2002 Xterra sight unseen from South Dakota. Worked a trade deal for a car I was selling for somewhat equal value. The X didn't run at all, owner said his trusted mechanic stated it needs an ECM for a no spark condition. The owner was concerned about potential cascading repairs, so he decided to sell. It's really clean, and in Shock Blue was hard to resist so we made the trade and he even hauled it to my house in MN. Turns out he was right, the ECM was bad (I confirmed no spark or injector pulse) -but it was due to being soaked from a flood of some sort. It's possible he didn't know this when he bought it in the Fall, his kid drove it for 4 months before it croaked since corrosion takes time. I replaced the ECM, TCM, body module, radio and amp (RF system), and air bag modules-all had rust and corrosion on circuit boards. Cleaned the connectors as good as possible which weren't too bad. I drained the fuel tank, some water in the fuel. Fuel pressure is ~32 psi at idle (low but not awful). New plugs and wires, cap/rotor seem ok. Changed all the fluid- yep, water. Milky ATF and oil too. The water out of the diffs preceding the oil was like Evian, very clean and clear. Strange. Flood cars are the worst and I would never have bought it had I known but here we are. I am trying to avoid replacing the engine, but I am afraid Thanos has snapped his fingers and replacement is inevitable.
 

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2001 Xterra 4WD Auto 3.3L NA V6
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Water in the trans can mean eventually having to replace or overhaul it. The glue is water-soluble and has been weakened. No telling how long before it finally gives.
 

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Struggling to restart on a hot restart always seems to point to too much fuel in the mix. I wonder where the ECM is getting engine temp condition relative to start injector impulse timing? I suppose it would be coolant temp but I don't know the Nissan theory of operation. I suppose one of a possible number of inputs could be triggering the ECM to call for cold start conditions.
 

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03 XE A/T, SC coming soon
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Struggling to restart on a hot restart always seems to point to too much fuel in the mix.
this is a symptom of excessive timing advance(typically sounds like the starter motor is trying too hard)


I wonder where the ECM is getting engine temp condition relative to start injector impulse timing? I suppose it would be coolant temp but I don't know the Nissan theory of operation
coolant temp sensor but this actually gets more interesting. If a Nissan ECM has an open/shorted temp sensor then when viewing the data monitor with consult, the ECM will provide an “inserted value” based on run time. This may or may not be the case with generic OBD2 scanners
 

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2002 Xterra SE, Shock Blue, AT/4x4
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Discussion Starter #6
I understand the hard to start with over-advanced timing, and you're right. I have the timing advanced, but if I don't have it advanced it won't hardly run and definitely won't idle. It did run normal for a time after replacing the ECM early in the process, so I took it down the road to shake it down. I got about a half a mile before it fell flat on its face (maybe finally entered closed loop?). Barely made it back home. Feathering the throttle didn't get much more than pops in the intake and a loud "bwahhh bwahhh" from the air filter. Telling me it's running lean.
After messing around with a lot of things, I am still stumped. I replaced the MAF sensor, and the scantool still shows that it appears to be ingesting more air than it should according to the manual further telling me it's lean. The calculated load is higher than book spec too. The temp sensors seem to operate normal. I think my next operation is to pin test the ECM while running. Should be a fun test in flexibility and breathing while partially inverted.
 

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I would check the Fuel Pressure Regulator. It sounds to me like a bad FPR diaphragm. Due to the leak you will have:
1) bad fuel pressure
2) p0300
3) possible bogging on acceleration
4) Difficulty restarting

1) is due to the fact that it's allowing fuel to escape the system directly into the intake which lowers your fuel pressure.
2) Is due to unmetered fuel entering the air intake and causing a rich condition
3) Likewise, unmetered fuel entering the system. When the RPM increases so does the vacuum, s more unmetered fuel is entering the intake
4) After you shut off the engine the remaining fuel pressure in the system forces fuel through the FPR into the intake where it will leak into the cylinders and cause a flooded condition.

To test your FPR simply start the vehicle and pop the small vacuum line for the FPR off of the back of the intake manifold. If the FPR is bad you will get fuel dripping out the vacuum line.

IF it is the FPR, it's about a $120 part. You will have to remove the intake manifold to get to it, so it's a prime opportunity to replace your valve cover gaskets, inspect and replace any questionable coolant rubing or pipes under the plenum, and if it's due, change the timing belt as it is easier with the plenum off. Also highly recommended is replacing the thermostat bypass hose at this time. It's an elbow shaped hose that comes off the top of the thermostat housing. The only way to change it is to remove the intake.

These vehicles have a lot of "while you're in there parts".
 

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2002 Xterra SE, Shock Blue, AT/4x4
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Discussion Starter #8
I would check the Fuel Pressure Regulator. It sounds to me like a bad FPR diaphragm. Due to the leak you will have:
1) bad fuel pressure
2) p0300
3) possible bogging on acceleration
4) Difficulty restarting

1) is due to the fact that it's allowing fuel to escape the system directly into the intake which lowers your fuel pressure.
2) Is due to unmetered fuel entering the air intake and causing a rich condition
3) Likewise, unmetered fuel entering the system. When the RPM increases so does the vacuum, s more unmetered fuel is entering the intake
4) After you shut off the engine the remaining fuel pressure in the system forces fuel through the FPR into the intake where it will leak into the cylinders and cause a flooded condition.

To test your FPR simply start the vehicle and pop the small vacuum line for the FPR off of the back of the intake manifold. If the FPR is bad you will get fuel dripping out the vacuum line.

IF it is the FPR, it's about a $120 part. You will have to remove the intake manifold to get to it, so it's a prime opportunity to replace your valve cover gaskets, inspect and replace any questionable coolant rubing or pipes under the plenum, and if it's due, change the timing belt as it is easier with the plenum off. Also highly recommended is replacing the thermostat bypass hose at this time. It's an elbow shaped hose that comes off the top of the thermostat housing. The only way to change it is to remove the intake.

These vehicles have a lot of "while you're in there parts".
Satito, thanks for the insight. I had checked the FPR function about a month ago, and though my fuel pressure was a bit lower than spec (33 at idle, 40 vac disconnected) the FPR seemed ok. No fuel out the hose, and I know exactly what you're talking about. I even pulled the fuel rail a couple weeks ago and actuated each injector into a jar to watch the spray pattern, which all seemed to be ok. I picked up a used fuel pump from a junk yard (because Im cheap and it's easy) that Im going to test and install today. I did the timing belt earlier this summer, and it was probably the original at 130k- cracked and stretched. New NGK plugs and wires too. I installed a different distributor and no change, but it wasn't a known good part so it could be crap too. But I do get good spark. Im probably missing something basic and overthinking what's wrong. The whole flood car thing could keep me chasing my tail. It's a second car for me, so now that hunting season is done, there's no pressure to get it going right away. And I know what you mean by "while you're in there", but Im trying to minimize my expenses just in case I shove it off for parts.
 

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Did the problem start before or after the timing belt was replaced (just to rule out that it skipped a tooth)?
Have you tried the relearning procedure on the throttle position sensor?

Another thing worth checking is your EGR system. If the EGR is stuck open or getting stuck, that can really cause an engine to have starting, idling, and acceleration issues. Carbon build up is very common in these systems.
 

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Discussion Starter #10
Did the problem start before or after the timing belt was replaced (just to rule out that it skipped a tooth)?
Have you tried the relearning procedure on the throttle position sensor?

Another thing worth checking is your EGR system. If the EGR is stuck open or getting stuck, that can really cause an engine to have starting, idling, and acceleration issues. Carbon build up is very common in these systems.
Satito, I appreciate your input! I forgot about the EGR, I'll check that..
I bought it not running (see initial post), and once it fired up after ECM replacement, I drove it into the garage and replaced the timing belt. It ran ok, but not great. Water in the fuel too. That's the magic of buying a non-runner is you have no idea if there was more wrong. I have done several of these belts, and I always check my work. The belt had the hash marks on it, and I even counted the teeth and it was right on per the manual. It's on. I did replace the fuel pump yesterday, and checked the FPR. It was good at about 32 psi idle and around 40 when hitting the throttle-no fuel spitting out the vacuum hose. Since I disconnected the battery, that must have reset the ECM. I fired it up and ran mint! For about 5 minutes... This tells me the base engine is probably ok. Then once it warmed up it started getting boggy again. I noticed the MAF and Calc load is still high, but the IAT was showing 120 F. That seemed too high since it was about 20 F outside. My O2 sensors are garbage too, so Im guessing once the ECM hits closed loop it corrects to what the O2 sensors are saying. I might be chasing a wiring gremlin too such as poor ground, maybe the junction by the ECM plug. I already made sure the grounds on the intake were good. For the record, it does throw the blinky MIL P0300 off idle too.
 

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Is it still having start up problems or has that been solved?
If it's an issue after warming up it could be the fast idle control aka wax pellet is giving you trouble. Some times the arm gets bent (or someone bends it to try and "fix" an idle problem) etc. Take a look and make sure it's at the 90 degree angle it should be at.
 

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Discussion Starter #12
Is it still having start up problems or has that been solved?
If it's an issue after warming up it could be the fast idle control aka wax pellet is giving you trouble. Some times the arm gets bent (or someone bends it to try and "fix" an idle problem) etc. Take a look and make sure it's at the 90 degree angle it should be at.
The wax pellet armature was indeed bent, but that's a non-issue with the starting. It still has the high-current draw hot start, it could be the starter since the one in there was submerged in water for who knows how long.

Something I noticed is the rear O2s (post cat) go 0 volt lean above 2200 RPM. They are responsive at 2100, and then flatline above 2200. Is there some kind of fuel cut for some reason at 2200?

My MAF is still reading high (about double the book values). I pin tested the voltage at the ECM and they were within range. I even swapped out with another ECM, and it was the same. No difference in running. The PCV seems to check ok. I don't think these have EGR valves, I cant find anything in the book and I definitely didn't mess with an EGR tube when I took the intake off. Right around this time frame, Nissan was messing around with valve timing for cylinder dilution, which is what EGR does. The early/mid 2000s 2.5L had this system, basically keeps the exhaust valve open a tad as the intake valve opens sucking a little exhaust into the incoming air charge. The problem was the catalysts were fragile, came apart, and sucked in catalyst fines during the dilution time. Essentially slowly dumping sand down the engine, taking out the rings.

I also have new front O2 sensors and fuel pump coming this week, the existing B1S1 is running high voltage at start, and not very responsive hot. The used fuel pump is unknown, and leaks back after sitting awhile. The original sending unit was junk anyways, so all is not lost. Pressure is good, but maybe flow restricted. IDK, seems like cheap insurance anyways. Easy to do.
 

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It's possible your rear o2 sensors were damaged during the sumbersion. Water may have made it's way up the tailpipe to the sensors.
 

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With regard to the EGR...

It is possible that the computer it came with was not the original (replacement for the flooded unit) and both it and the computer you swapped in are expecting to see an EGR.
 

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The wax pellet armature was indeed bent, but that's a non-issue with the starting
this is correct


It still has the high-current draw hot start, it could be the starter since the one in there was submerged in water for who knows how long.
a damaged starter would likely show issues at all times. Starter struggling when warm can be a symptom of excessive timing advance. Make sure the gun is dialed correctly, that you’re using the correct mark and that the balancer is accurate. A timing belt installed incorrectly could possibly cause this


Is there some kind of fuel cut for some reason at 2200?
that’s a big negative.


My MAF is still reading high (about double the book values). I pin tested the voltage at the ECM and they were within range
don’t ever use this value. Using nissan diagnostic equipment we monitor A/F alpha to monitor mixture feedback. This is much more useful but can be affected by fuel issues as well as airflow issues. Generic scanners should have a data value for mixture feedback as well


Nissan was messing around with valve timing for cylinder dilution, which is what EGR does
although this is correct, many VG33 engines used by nissan had variety of different emissions equipment installed depending on the model year and what specific emissions standards were required. Some did it or didn’t have EGR and there were two different catalyst options as well. If yours didn’t have an EGR tube to mess with while removing your intake then your likely isn’t equipped and that can be totally normal. Mine has it and if you were to use a donor ecm from an EGR equipped truck, the only issue is you’d expect EGR codes but otherwise no issues.

I replaced enough qr25 motors for catalyst ingestion

good luck with the xterra
 

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Discussion Starter #16
this is correct




a damaged starter would likely show issues at all times. Starter struggling when warm can be a symptom of excessive timing advance. Make sure the gun is dialed correctly, that you’re using the correct mark and that the balancer is accurate. A timing belt installed incorrectly could possibly cause this




that’s a big negative.




don’t ever use this value. Using nissan diagnostic equipment we monitor A/F alpha to monitor mixture feedback. This is much more useful but can be affected by fuel issues as well as airflow issues. Generic scanners should have a data value for mixture feedback as well




although this is correct, many VG33 engines used by nissan had variety of different emissions equipment installed depending on the model year and what specific emissions standards were required. Some did it or didn’t have EGR and there were two different catalyst options as well. If yours didn’t have an EGR tube to mess with while removing your intake then your likely isn’t equipped and that can be totally normal. Mine has it and if you were to use a donor ecm from an EGR equipped truck, the only issue is you’d expect EGR codes but otherwise no issues.

I replaced enough qr25 motors for catalyst ingestion

good luck with the xterra
Thanks, I need some luck! I have fixed a lot of cars, never a flood car. I would say the chances the O2 sensors were submerged is 100%. I found the water line on the bare steel vertical supports behind the radio area. It was up to the radio. Also, the exhaust had a lot of water in it. I just want to cover my bases with fuel injection before I consider replacing the engine.
The ECM that was in it when I got it had been soaked, lots of green corrosion and such. The used replacement was as close to a match as possible. The 3rd one i just threw in for giggles was out of a 2003 I scored out of a junk yard for $10. It set an A/T communication error and an EGR position error. I compared the ECM pins one by one and expected both those codes before I put it in trying to be as safe as possible..
My MAC scantool gives mediocre data, and has a graphing feature which is really handy. The Short Term Fuel Trim is all over the place, mostly positive. So it's trying to give it more fuel. And the O2s going lean and lean misfiring in the intake steers me back to a fuel problem.
The timing I know is advanced, but not a ton. The timing belt is as perfect as it can be with an aftermarket belt. I'll install the front O2s that I know are bad, and the fuel pump and see how it goes. I don't want to sink a ton of money into a flood car, but if I can at least get it running well I'll drive it for awhile.
 
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