Nico Friends:
Am beginning the process of diagnosing a rough starting problem on a '97 Maxima. The car has only just recently developed this problem. It eventually will start, however, and then runs great! It runs smoothly; no stalls, no loss of power at accel, etc.
While the starter is turning, the engine sounds like it's misfiring. Flooding? Choking? Can't tell. Though I occasionally now get a pronounced fuel smell. Problem seems to have gotten worse with colder weather, or with very damp weather (<- though that bit may be apocryphal)
Quick Inspection:
- No obvious fuel leaks under hood.
- No obviously damaged vacuum or fuel lines.
- Tested with stethoscope, all 3 front bank injectors are popping. Cannot get to rear bank yet.
This weekend, will get in there and start diagnosing further - How to maximize my evaluations?
So far, I'm thinking:
- Fuel Pressure Regulator
- Ignition Coil(s) - but car runs great, once running...
- Ignition Coil Shrouds
- Bad Injector(s) - rebuild? replace?
- Need to replace all Injector Seals?
Does it seem reasonable to assume that:
- the fuel pump is probably OK, given that car runs really well once it is running?
Have read lots of notes and tips here - including how to dx a bad fuel regulator valve. Don't have a fuel pressure gauge, though; will a vacuum test on this regulator be an adequate test?
Any other ideas? Many thanks in Advance, Lou
Maxima GLE, about 140K
Maxima Intermittent Rough Starting - Diagnostics
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MinisterofDOOM
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Re: Maxima Intermittent Rough Starting - Diagnostics
If it were an injector problem, I would expect it to run rough anytime BUT startup/idle. UNLESS it's a flooding issue from a leaking injector...that might become less troublesome at higher revs where you've got more air/fuel moving anyway.
Coils...I don't see why coils would only affect startup. My bad-coil experience (not with Nissans, granted) is that it doesn't really matter what you're doing in the car...heavy throttle, idle, casual driving, even cruising...it all suffers the same.
Fuel smell is not uncommon in winter with 90s Nissans. The rubber lines under the hood tend to crack and leak, and it often happens so that it's only (or at least mostly) noticeable in the cold. Far more common on older VG-engined cars, though. My old '93 would get VERY strong fuel smell in the winter, but I never found a drop of gas or a line that looked suspect.
A common source of rough-start symptoms with Maximas of your era is the EGR. That'd be my prime suspect, even if it's a little weird that it doesn't cause problems after startup.
Coils...I don't see why coils would only affect startup. My bad-coil experience (not with Nissans, granted) is that it doesn't really matter what you're doing in the car...heavy throttle, idle, casual driving, even cruising...it all suffers the same.
Fuel smell is not uncommon in winter with 90s Nissans. The rubber lines under the hood tend to crack and leak, and it often happens so that it's only (or at least mostly) noticeable in the cold. Far more common on older VG-engined cars, though. My old '93 would get VERY strong fuel smell in the winter, but I never found a drop of gas or a line that looked suspect.
A common source of rough-start symptoms with Maximas of your era is the EGR. That'd be my prime suspect, even if it's a little weird that it doesn't cause problems after startup.
Re: Maxima Intermittent Rough Starting - Diagnostics
Mr. Minister, tks for those notes...
As a general question: Is it good maintenance practice to re-seal the injectors? (I see parts lists around indicating sets for this.) Or to replace their O-rings? Sorry, don't know all the anatomy yet; haven't pulled the injectors on this car.
(Now, gimme a Mercedes diesel - that's another story!)
My thinking re the injectors was roughly the same - as the fuel smell is so pronounced, and a new finding...If it were an injector problem... UNLESS it's a flooding issue from a leaking injector...that might become less troublesome at higher revs where you've got more air/fuel moving anyway.
As a general question: Is it good maintenance practice to re-seal the injectors? (I see parts lists around indicating sets for this.) Or to replace their O-rings? Sorry, don't know all the anatomy yet; haven't pulled the injectors on this car.
(Now, gimme a Mercedes diesel - that's another story!)
Will check the EGR valve - hopefully some HowTo tips on this forum. Many Thanks!A common source of rough-start symptoms with Maximas of your era is the EGR. That'd be my prime suspect, even if it's a little weird that it doesn't cause problems after startup.
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NutriaforBreakfast
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Re: Maxima Intermittent Rough Starting - Diagnostics
Just some suggestions here
- Fuel Pressure Regulator
Fuel pump and regulator are fairly easy to check with FSM and Chiltons
You can borrow the Actron equipment from Auto Zone to check pump output
and vacuum of the fuel regulator
- Ignition Coil(s) - but car runs great, once running...
Pull one coil at a time while the engine is running to see if there is a spark.
I actually grounded a coat hanger wire to the spark plug to see if
a good spark was produced. Checked the plug in to the coil to see
if there was 12 volts twice -once when engine was hot then cold.
- Ignition Coil Shrouds
NOt sure about this
- Bad Injector(s) - rebuild? replace?
Recently replaced the # one bad injector. The bad injector would click using a
mechanics stethoscope. I had to take off the plenum to check the ohm/resistance
of the fuel injector-it had a bad coil/electrical problem. I ended up replacing 3 on
the same injector rail because I had too hard of a time getting them out and was
afraid those other 2 might fail soon. Courtesy Nissan wanted to charge me $400
labor just to change one coil (labor only).
- Need to replace all Injector Seals?
The injector seals will get hard with age. If there is no gas leaking they are
probably ok.
EGR valve should be closed when the motor is closed and open when the engine is hot.
When its hot you can push it up manually and it should sound like the motor is going to die.
I can stick open or closed.
- Fuel Pressure Regulator
Fuel pump and regulator are fairly easy to check with FSM and Chiltons
You can borrow the Actron equipment from Auto Zone to check pump output
and vacuum of the fuel regulator
- Ignition Coil(s) - but car runs great, once running...
Pull one coil at a time while the engine is running to see if there is a spark.
I actually grounded a coat hanger wire to the spark plug to see if
a good spark was produced. Checked the plug in to the coil to see
if there was 12 volts twice -once when engine was hot then cold.
- Ignition Coil Shrouds
NOt sure about this
- Bad Injector(s) - rebuild? replace?
Recently replaced the # one bad injector. The bad injector would click using a
mechanics stethoscope. I had to take off the plenum to check the ohm/resistance
of the fuel injector-it had a bad coil/electrical problem. I ended up replacing 3 on
the same injector rail because I had too hard of a time getting them out and was
afraid those other 2 might fail soon. Courtesy Nissan wanted to charge me $400
labor just to change one coil (labor only).
- Need to replace all Injector Seals?
The injector seals will get hard with age. If there is no gas leaking they are
probably ok.
EGR valve should be closed when the motor is closed and open when the engine is hot.
When its hot you can push it up manually and it should sound like the motor is going to die.
I can stick open or closed.
Re: Maxima Intermittent Rough Starting - Diagnostics
OK, Now this has become a real crisis - car absolutely will not even turn over!
Based mostly on advice here, so far:
I've replaced the Fuel Regulator Valve and verified the function of the EGR valve; EGR responds to vacuum, and moves full throw. I also cleaned the Mass Flow Sensor while things were apart; it looked perfectly intact and clean, fwiw...
After all that, the car is even more difficult to start. Symptoms are a severe, rough shaking, misfiring kind of behavior, thought it eventually starts. Feels really profoundly bad when this happens, as if the car is firing out of order (!); if it were a carburetted motor, I'd say it is behaving as if completely flooded.
Once the car does start, however, it's like a racehorse - it really runs great for a 140k+ car. (So it can't be the fuel pump - ( or can it? )) Through all of this, the CEL is not on.
Then, this morning, more starting problems... Tried about 5 start attempts, then plugged in the ODB diagnosis device - I've had codes for the knock sensor and an O2 sensor, on and off, for a couple of years. I've cleared all codes in the past, just to be sure they aren't spurious and, eventually, these two codes return.
This morning, though, after clearing codes, the starter will not even turn over! ( I doubt I've burned the starter...? )
What's up now? Can anyone offer some suggestions?
Based mostly on advice here, so far:
I've replaced the Fuel Regulator Valve and verified the function of the EGR valve; EGR responds to vacuum, and moves full throw. I also cleaned the Mass Flow Sensor while things were apart; it looked perfectly intact and clean, fwiw...
After all that, the car is even more difficult to start. Symptoms are a severe, rough shaking, misfiring kind of behavior, thought it eventually starts. Feels really profoundly bad when this happens, as if the car is firing out of order (!); if it were a carburetted motor, I'd say it is behaving as if completely flooded.
Once the car does start, however, it's like a racehorse - it really runs great for a 140k+ car. (So it can't be the fuel pump - ( or can it? )) Through all of this, the CEL is not on.
Then, this morning, more starting problems... Tried about 5 start attempts, then plugged in the ODB diagnosis device - I've had codes for the knock sensor and an O2 sensor, on and off, for a couple of years. I've cleared all codes in the past, just to be sure they aren't spurious and, eventually, these two codes return.
This morning, though, after clearing codes, the starter will not even turn over! ( I doubt I've burned the starter...? )
What's up now? Can anyone offer some suggestions?
Re: Maxima Intermittent Rough Starting - Diagnostics
Resolution?
Turns out this whole syndrome of problems was down to a slowly-degrading starter. Having assumed this was a fuel delivery problem, and having replaced the fuel regulator valve, I finally did kill the starter. Assumed this was due to burning it out with all the start attempts.
In any case, after replacement - ALL symptoms are gone, and the car starts every time.
In all my 40+ yrs working on cars, have never had a starter behave quite like this... !
Turns out this whole syndrome of problems was down to a slowly-degrading starter. Having assumed this was a fuel delivery problem, and having replaced the fuel regulator valve, I finally did kill the starter. Assumed this was due to burning it out with all the start attempts.
In any case, after replacement - ALL symptoms are gone, and the car starts every time.
In all my 40+ yrs working on cars, have never had a starter behave quite like this... !