97 Nissan Pickup wierd problem....

[fallen4shell]

Ok...here's the deal: my dad has a 97 Nissan Pickup with the 2.4L engine. Ever since he got it it has not run great...not really bad, but just not as good as expected. When you are taking off it almost feels like it is holding back for some reason...it doesn't miss, but it just doesn't accellarate smoothly either. It surges during steady acceleration...at any speed. The check engine light comes on often and the code is a PO304 which signifies a cylinder 4 misfire, but it is most definitely NOT a dead miss, and I really don't feel a miss at all. It's more of a surge....almost seems like it could be transmission related, but then there is that code so I dunno.

He has taken it to his mechanic who specializes in foreign autos NUMEROUS times and I know that the mechanic has tried several different things including, but not limited to, replacing plugs, wires, cap, rotor, injectors....at least on cylinder 4 if not all. I'm sure he checked basics like fuel pressure, vaccuum leaks, etc and I believe he also tried a new EGR valve. He is a good mechanic and my dad has used him for years with no problem so I honestly don't feel that it is a mechanic incompetency issue. I have tried doing some swapping of the plugs and wires myself, just to see if I could get the misfire code to set for a different cylinder or somethng, but it is always PO304. I have also tried unplugging various sensors and things(TPS, MAF, MAP, IAC, O2, etc) to see if any of them would affect the running problem (surging) but nothing did.

The mechanic, and my dad for that matter, have basically just given up on ever fixing this truck, but it just drives me nuts that it is so predictable, but so elusive at the same time.

Has anyone ever dealt with anything like this before?

Let me know what you guys think.

[zanegrey]

check timing
check and recheck oil pump timing.

check compression on all 4 ..
also check fuel and air filter.
clean out breather element

check fuel tank for contamination.
check and clear strainer on fuel pump.

remove and check temperture sending sensor.

oil change and filter..

[fallen4shell]

Originally Posted by zanegrey

check timing
check and recheck oil pump timing.

check compression on all 4 ..
also check fuel and air filter.
clean out breather element

check fuel tank for contamination.
check and clear strainer on fuel pump.

remove and check temperture sending sensor.

oil change and filter..

compression is fine. Fuel and air filter have both been replaced and adequate air flow through breather inlet has been verified. The surge is too rythmic to be trash in the fuel...it's very predictable. Bad gas can give some wierd problems, but they are usually not predictable and/or repeatable. We have put gas treatment to no avail just for good measure, but again, I don't think that's it. The PID on the coolant temp sensor reads fine. An oil change, while always a good idea, is not going to fix a surge.

I am pretty sure that the mechanic verified proper timing. Just out of curiosity, however, did you have a particular reason for suggesting oil pump timing (as in...some past experience) or were you just throwing out some random ideas for me to try?

[Terry_Lee]

might check intake gasket

[fallen4shell]

I have checked the intake gasket as well as the rest of the engine for vaccuum leaks and found none. The truck idles smoothly so it doesn't really seem like a vaccuum leak.

[flyguy123]

Any exhaust leaks? Maybe your TPS is starting to fail.

[Stitz Love]

I asked a friend of mine (a qualified mechanic) what he thought about your situation.
He replied...
"I'd be interested to see the truck on a data logger since I believe it's OBDII, it should have this capability. See if it's switching to closed loop when warmed up. How's gas mileage? I'd also shoot a laser temp sensor at all the cylinders (exhaust) and make sure their all around the same temp."

I hope this helps you.

[fallen4shell]

I worked as an auto mechanic for 5 years. It is OBDII and at one point I know that I did hook it up to a scanner but I don't think it showed much...the scanner I was using though could only acess it via "global OBDII". I remember looking it over pretty good and everything seemed to be in order other than the cyl 4 misfire code. I'm SURE I would have noticed if it wasn't going into closed loop.

I also know the mechanic who my dad uses on a regular basis and I have complete confidence in him. He has spent much more time with the truck than I have and I know that he has a Snap-On MODIS scanner so he undoubtedly got a better data readout than I did and after several weeks and several trips back to him (trying several different things) the problem still exists. It does seem to get pretty poor gas mileage.

Unfortunately, I don't know what all he tested and did to the truck. It's been over a year since he has messed with it and probably 8 months since I tinkered with it. Having left the Mechanic business for the time being I no longer have access to a scanner nor have the time to really spend with the truck. My dad has simply accepted the problem as an inherent flaw and has given up even trying to get it fixed. The truck starts and runs so he just drives it AS IS.

Given that it is a Cylinder 4 misfire code....there are some pretty basic checks that I am sure the mechanic went through. Spark, fuel, compression, etc....the basic things that a cylinder needs for combustion. The main reason I posted onto this forum was in hopes that there might possibly be a common (yet elusive) problem that throws that code on these engines....such as maybe inherently weak valve springs or something of that nature. I have often found that regardless of how strange the problem seems SOMEONE on these forums usually has had it before.

[zanegrey]

try posting on these two sites .

http://nissan4wheelers.com/n4wheel.html.

http://www.tnt4x4club.com/main.php

i know they are for the 4x4 sites but it is the same engine type.

they have more traffic on these sites and more let's say experts..

good luck.

[GBClark]

To 97 nissan PU weird problem, Do Not overlook a partailly plugged exhuast system. Either in the converter( most common) or muffler!!

[fallen4shell]

Originally Posted by GBClark

To 97 nissan PU weird problem, Do Not overlook a partailly plugged exhuast system. Either in the converter( most common) or muffler!!

Have you run across this problem before on this engine? Seems like if the exhaust were plugged it would throw misfire codes for more than just one cylinder or at least random cylinders.

[ttfox88]

im just throwing a wrench here what about transmission or even the diffeencial. i had a 240 that did that to me it was the trans and differencial.

[xv750rider]

Maybe I'm going out on a limb here, but it may be a broken vacuum hose.
I have a '91 with the KA24E engine with OBD1 so I coudn't get a code. The engine ran O.K., but it would idle funny and run badly. The fuel economy was terrible! I did some digging and found a broken vacuum hose above the EGR valve. I know it seems simple, but it's worth a check!

[jazdaddy]

Have you checked the valve Seats?

[doctorIntraining]

Ironically, I have the exact same problem with my '97 Nissan 4x4, 2.4 Liter pickup. Did you find a resolution to the problem?