Nayehi

First I want to thank all of you who take the time to answer posts on these forums. I have been lurking here for a cpl years now searching for this and that and have found a wealth of info. ie, I would have had the car in the shop to replace the starter until I found it was a 30min job. people like you make these forums work.


Since I’ve had my 99 (3 yrs), if I let the fuel get below ¼ tank, a rather sharp left turn or a left turn at a um, higher speed would cause the car to miss/“stutter” and start cutting out especially uphill. A couple months ago, it suddenly began getting worse. Even with a full tank it will stutter (ie. hesitate) sometimes has a miss at idle. Going uphill causes the problem (which is bad since I live in the mountains) but pulling out from a stop is the worst. And if I really need to get on the go pedal it has even backfired. Seems that any time the engine suddenly needs more fuel, the problem gets worse. And it just seems down on low end power. Cpl times I wasn't sure I'd make it home. Oh and if I turn the overdrive off, it kinda helps. Which sorta makes sense; the lower gear and higher revs would reduce the sudden need for more fuel. I have tried different fuels, reg, prem, 100% gas, etc. have replaced the fuel filter and cleaned my K&N air filter and I have checked for fuel leaks.


The ECU is throwing 10 02 (O2 Sensor Heater), 03 04 (Knock Sensor) and the famous 03 02 (EGR). The check engine light has been on when I got the car. It ran fine with a hwy mpg of 30+ and the codes sounded pretty benign, so I just drove it. Probably not the best decision I ever made so don’t jump on me. I was really short on cash at the time. I should mention that I am on a fixed income and not able to throw money at a problem (plus I really dread cutting that bolt lol). I do plan on correct these problems but I need to tackle the immediate before I find myself call a tow. Hopefully replacing the O2 sensor will get rid of the knock sensor problem.


Sounds starved for fuel to me so I’m thinkin fuel pump. But could it be the EGR tube completely blocked? As always, I have searched the forums here and most hits I found pointed to the fuel pump. Just wanted you guys’ input. Also I have learned that the fuel pump is rather easy to replace and that there maybe is a filter inside the tank? Pump=$150 So what do you guys think? Anything else I should check/do before I ****** out the back seat? I don’t have any way that I know of to test the fuel pressure and flow so would it be worthwhile to have that done first or just go for it and get gas on my hands.


Didn’t mean to be so wordy but want to give all the info. TIA
Tony

asand1

iTrader: (1)

Pull the sender/pump and check the hose segments for cracking.

DennisMik

iTrader: (2)

I'd like to start by suggesting something cheap - the fuel filter. The pump may be trying but a plugged filter holds it back.

Nayehi

Thanks, man. I'll do that. I had the car on a lift and checked for leaks as best I could with the pump running.



Thanks for the reply. I realize my post was very wordy, but I had in there that I have replaced the filter.

asand1

iTrader: (1)

There are actually short segments of hose above the pump inside the tank that can leak pressure.

njmaxseltd

iTrader: (19)

EGR, O2 and knock sensor will not cause a back fire or hesitation.
The EGR system on our cars plugs up, no flow.
If you were low on fuel pressure, you'd be throwing lead codes.

You have a 99, notorious for bad coils. A back fire is almost always associated with ignition. Consider replacing the coils or at least trouble shooting them.
Lower RPM's will show a misfire much better then higher RPM's (od/off).

Your engine is an air pump, the more revs, the more air, the more fuel you need.
Your theory of a lack of fuel makes no sense when you say it runs better in the higher RPM's. (od/off)

Nayehi

Thanks I will defo check that as well.


Thanks for the reply. Yeah as I said, I thought those ECU codes were benign. Wasn't sure about the EGR though. Didn't know the symptoms of that. Lead codes? Can you clarify? I looked for ECU codes for fuel pump/fuel pressure. Must have missed that one.

I tried to make my post as clear as I could as to what my problem is and give as much information as I could. Perhaps I should have been less descriptive and more specific and also included my level of experience.
*note to self: keep posts under 500 words

Let me clarify. First, I’m no expert and I certainly don’t pretend to know everything. I value the input of others especially Maxima owners. Asking for help and advice is how I have gained the knowledge I have. I have been working on my own (and others) cars for over 35yrs and I was a NASCAR Late Model Stock Car inspector for 10 years. I understand the theory of an internal combustion engine (although I’ve never really understood how they keep an 8000hp Top Fuel Dragster motor from flying apart ). My suspecting the fuel pump/pressure is not only based on the symptoms but also my personal experience

My immediate problem is the stutter/hesitation (same thing). I have to feather the throttle when pulling out from a stop or going up a steeper hill to keep the car from stalling. The more throttle required, the worse the problem and the more I have to feather the throttle. The miss/backfire only occurs occasionally and may actually be a separate problem. I agree that normally those are ignition related but I suspect they may be related to the hesitation as those problems started along with the hesitation. Or maybe not; I’ll find out when I get this fixed. As for the revs with OD off; the lower (or higher depending on how you look at it) gear ratio reduces the amount of go pedal needed to accelerate so the hesitation is not as bad. It's the gear ratio that helps, not the higher revs. I never had or didn’t mean to imply that I had a theory of lack of fuel, rather the lack of fuel pressure necessary to supply the additional fuel needed to accelerate. And of course I mean the additional fuel needed for the air/fuel mixture that the ECU calls for when said throttle is pressed given the altitude, ambient temp, MAP, TP, and etc... . Hope that clarifies my post.

Thanks again to all who have and will reply.

MOHFpro90

iTrader: (11)

I read most of this, but thought I would throw this out there: If it hesitates/misses under load, its ignition related.

Out of curiousity, have you checked to see if your FPR is bad?

njmaxseltd

iTrader: (19)

I mistyped a word in my previous post.

Lead should be LEAN.

If your f/p was low, you would be throwing LEAN codes for both cylinder banks.

As I said previously, your 99 is notorious for bad coils. Been there, done that w/mine.

Your hesitation or misfire is felt more under load because of a weak spark. (it gets blown out).

What you describe is ignition related.

You should know these basic things with your 35 years of experience.

Replace the coils on your 99 and you should see a huge difference.

aackshun

iTrader: (3)

Going through coil pack problems riiiiiight now, made road coursing really boring on the straights

cashoit

O2 Sensor wd def cause a lean mix.

Misfires should be throwing codes. Clean MAF and TB. Since u 99, check coils as well.

Nayehi

LOL yeah i said I was gonna keep it under 500 words from now on. I checked the FPR. Was OK.


No codes other than those I mentioned. I think its the heater on the O2 sensor?, not the sensor itself?.

Ahh I should have caught that LEAN. I nevar mak typos. And you'd think I would know after 35 years, huh? My reply sounded a bit more self-important than I meant it. Didn't mean to imply that I had 35 years of experience, just been working on my own stuff for that long. Not my career path, more of a DIYer.

Honestly, personally speaking, every car I have had or worked on with hesitation issues has been fuel related, not ignition. Hesitation, not misfire. Misfire is obviously ignition.

Having said all this, I got a rent-a-fuel-pressure-gauge from az today and checked. Sure enough, it's NOT the fuel pump. Or any fuel pressure issue for that matter. Drove the car with the guage attached and with the hesitation, 40-50PSI. Oh well, I said I didn't know everything, though sometimes I think I do lol. Guess I'll start troubleshooting the coils and ignition tomorrow having ruled out fuel. If it is the coils any particular brand to stay away from?

Anybody else got anything I would be happy to hear it. Every model year seems to have its own quirks. Thanks again.

Nayehi

Tore into the coils today and decided to change the spark plugs while I was at it. The car had not two but three different types of plugs in it. 4 Bosch, 1 Bosch Platinim and 1 Denso. The latter two were in terrible shape; I needed a ruler to check the gap and the Denso.

So on the advice of a member, I cleaned the contacts on the coils (both ends) tested them and replaced the plugs with NGK Laser Platinums. One coil tested slightly different, other than that they seem fine. May have already been replaced? Didn't notice branding or numbers on any of them. Drove the car several times over cpl hours and the problem seems to have been corrected. Gonna clean the EGR in the next few days and reset the ECU. Found out a lot about our engines during this endeavor.

Thanks to all who replied and put up with me. No wonder I've been in so many relationships lol.

shadygrey

is this a problem with a 95/96 as well? I'm having similar issues where I'd be cruising along fine for about 5 mins, than the car would start to stutter as if its not getting any fuel. I replaced the fuel filter and cleaned TB already. CEL light has not come on at all.

mbxrb

iTrader: (1)

I have the same problem with my 98,but I know it's my fuel tank that has rust,because when I changed the fuel filter the fuel was redish in color.