1993 Nissan Sentra 1.6L 175K - Random Stuttering Problems

Tiny
RISH57
  • MEMBER
  • 1993 NISSAN SENTRA
Car has been acting very randomly with the same problem going in and out with increased frequencies.

Noticed first that I would be driving around and suddenly the car would bog down. Sometimes at stops, sometimes while driving, then would kick in all the sudden and be fine.

My first thought was.1. Spark 2. Fuel 3. Air

I first went the cheap root and replaced the spark plugs and air filter, they needed to be changed and new it should be done anyway. Ran better for about 3 days then back to the same crap.

I next thought fuel since it was stuttering in and out and very apparent under acceleration. Since this car didn't have a fuel pressure fitting on the rail (blarg), and I had spent many days trying to find a fitting, I gave up and replaced the fuel filter first, not better. Got pissed, replaced the fuel pump. Ran better, but didn't solve the problem.

I rechecked the spark on the car and it was ok, went ahead and re-gaped the spark plugs, replaced the distributor cap and rotor and it seemed to idle better, especially after adjusting the throttle cables, but still was crap under acceleration and bumpy idle.

I was then thinking catalytic converter. Yes this is ghetto, but I drilled 4 holes in the converter to see if that would help but it really didn't. Plugged the holes with some liquid steel and back to the drawing board. Yes I plan on replacing it soon. Granted I can get it running right.

I was fed up. Went to the junk yard and found a fuel pressure relay and tried switching it out. No better.

Fed up more, I took it into the dealership to have diagnostics ran on it. They told me it was fuel injector #2 and wanted $350 to replace it.

I got online, ordered genuine fuel injectors and went ahead and replaced all 4 of them this weekend. After adjusting the throttle cable back down to normal, the car was running great like it was b4.

I drove the car somewhat aggressively to a friends house, stopped the car once after driving 20 miles, drove another 10 miles after that and all was good. After the car sat for about 2 hours, came out, started the car, and it was idling rough again and doing some weird crap again. Only this time it would actually accelerate fine when pedal depressed pretty far down but still not running right.

I'm not sure what to do now, the only thing left on the fuel side is the fuel pressure regulator, which is like $140 from the dealer, and like $95 online. I'm not sure what to do next. It almost makes me feel like the actual ECU is bad or something. If it was anything else major, I would imagine that the codes ran at the factory would have told them something else they would have mentioned to me, like O2 sensor, etc etc.

I imagine after it setting to 2 hours in cold rainy weather it had plenty of time to cool down if it was heat problem, and if was just cold, that it would have gone away the 30 miles I had to drive home. HELP!
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Monday, October 22nd, 2007 AT 1:28 AM

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Tiny
RASMATAZ
  • MEMBER
The engine is it a GA16DE?

Look for vacuum leaks. Find the Idle Air Adjusting unit remove and clean it, also the EGR valve.

Do a resistance check on the TPS closed and wide open throttle position.

Also check the heated wire in the mass airflow sensor

You need to check the fuel pressure regulator with and without vacuum while engine is running.

Also check the primary and secondary resistances of the coil
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Monday, October 22nd, 2007 AT 5:00 AM
Tiny
RISH57
  • MEMBER
Yes, the engine is the GA16DE.I'll start looking into some of that on my lunch break today
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Monday, October 22nd, 2007 AT 8:53 AM
Tiny
RASMATAZ
  • MEMBER
You need to recheck the fuel pressure with a gauge-

There's is no schrader valve for fuel pressure hook up. Tee-in between the fuel filter at firewall and the hose that's coming from the TB.

TPS disconnected: do below

Check the closed and WOT resistances on the TPS.

At closed throttle should be 0.5kilo ohms, at wide open throttle should read 4.0kilo ohms.

Also might want to clean the vacuum timing control solenoid.
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Monday, October 22nd, 2007 AT 5:00 PM
Tiny
RISH57
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OK, so today I did the following:

1. Took off and cleaned the Idle Air Adjusting unit.
2. Checked the EGR valve
3. Checked vacuum hoses mostly around the EGr side of things
4. Checked the heated MAFS wires

The IAAU was dirty, and I got quite a bit of gunk out of it using carb cleaner, but it wasn't ridiculously dirty. Reinstalled it, cleaning all the connectors with connection cleaner and applied dielectric grease to the fittings.

I also took off the air intake syetem and cleaned it all out while checking the EGR valve. I manually was able to push the EGR diaphragm up and down with no binding multiple times. There seemed to be another EGR looking valve posterior to the EGR valve.I have no idea what it was. Thought it was the EGR at first, but just looked like it.

I took off the intake system, throughly cleaned the intake hoses and checked for perforations in anything in the area and found nothing besides 175k hoses that all seemed to be intact. I saw 2 wires in the MAFS, one small and one big, both of them were intact.

I tried like mad to find a fitting months ago that would accept my current fuel pressure gauge put there is some sort of proprieitary threading that sent me from hardware store to store and even a plumbing and a air conditioning specality store that didn't have a thread that matched the one I had. That's what made me say the hell with it and just replace the fuel pump and filter rather than spend hours driving around looking for stuff that didn't work.

I had at some point a repair manual, but it's in a POD storage unit so I'm kinda flying by the seat of my pants here. I have an OHM meter, but quite frankly, I have never really understood how to use it.

So far after doing that stuff this afternoon it seems to run better once again like all the other stuff I have done but not quite there. Rather then getting all excited, I'll have to see the next few days how it acts and such to say for sure.

One thing that it odd, it that ever since I installed the new fuel injectors the car has a hard time starting. B4, even with the rough surging and idling, the car started easy. Now it turns for about 5-8 seconds and I have to depress the gas pedal a bit to get it to start, then it runs ok.

Also, I don't know where the "vacuum timing control solenoid" is.

And, how does running the car with and without vacuum check the fuel pressure regulator?
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Monday, October 22nd, 2007 AT 11:32 PM
Tiny
RASMATAZ
  • MEMBER
And, how does running the car with and without vacuum check the fuel pressure regulator. You cannot without the pressure gauge-this is where you remove the vacuum hose from the regulator the pressure should increase to about 8-10psi. Then vacuum hose connected it'll go back to modulated which will be less and within specs.

BTW to check for a back pressure in the exhaust system remove the oxygen sensor hook-up a pressure gauge and read off it should be 2lbs or less anything over you'll be looking at the Cat again.
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Monday, October 22nd, 2007 AT 11:53 PM
Tiny
RISH57
  • MEMBER
Car is still running pretty solid after the cleaning of the Idle Air adjusting unit. So far.

However, my car still has a hard time starting ever since I replaced the fuel injectors. So question: would the computer have stored some sort of different fuel curve and so forth since the car was dogging for so long? And if so, would that entail me turning that knob on the back of the ECU?

Once the car starts it runs fine.B4 I installed the new injectors it didn't take so long to start the car. I have also noticed this is only after it sets for a while. If it's been running for a while, I turn it off and restart it, it start up normal.

Yes, I plan on just cutting off the schrader valve attachment dohickie and putting in a T-fitting to test some stuff in the next few days.

After replacing the fuel pump, filter, and the fuel injectors, I almost feel obligated to change the fuel pressure regulator. I guess I'll figure that out after I test the fuel pressure.
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Tuesday, October 23rd, 2007 AT 11:20 PM
Tiny
RISH57
  • MEMBER
And again, where is the vacuum control solenoid. And what the hell does it do?
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Tuesday, October 23rd, 2007 AT 11:22 PM
Tiny
RASMATAZ
  • MEMBER
The valve timing control solenoid is part of the valve timing control system its purpose is to provide optimum valve timing.

Its is located at


http://www.2carpros.com/forum/automotive_pictures/12900_valve_timing_control_solenoid_sentra_94_1.jpg

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Wednesday, October 24th, 2007 AT 12:24 AM
Tiny
RISH57
  • MEMBER
Ok, ya I replaced that when I did a tuneup, however, I noticed a similiar solenoid on the posterior aspect of the air plenum on the same side (passenger) of the car
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Wednesday, October 24th, 2007 AT 1:36 PM
Tiny
MKAROC
  • MEMBER
Good news and bad news: Bad news - I just went through the same problem; have had intermittent problem that comes and goes; Good news - you just saved me from doing alot of stuff that doesn't fix the problem.

Diagnosis was one fuel injector was clogged; fuel pump was checked and OK; Had chain shop replace all injectors, clean fuel injection system, replace fuel filter. Exact same scenario after repairs: rough start, drove home OK; hard to start the next day; problem came back; took back to shop; one of the new injectors was stuck completely open, gummed up with fuel crap; shop took fuel sample, which was much darker than expected; they drained tank and put in new gas;shop said they/ve seen this problem (dirty fuel in tank) before. Just got car back today; was hard to start again, but once started runs ok. Fingers crossed.

Note this was a problem at day one (1996) when bought used 1993 Sentra (70k miles). One day after purchase, could not start. Selling dealer replaced all fuel injectors which fixed problem. Also replace fuel pump at about 100k miles. The car has been intermittently hard to start over the years, especially when raining. Also has always run sluggish until gets up in RPM. Eleven years and 100K more miles later, the injector problem has come back. Hopefully, problem is fixed, and won't come back again until car and I are both dead.

I will post status after a few more days of operation.
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Thursday, October 25th, 2007 AT 9:06 PM
Tiny
RISH57
  • MEMBER
I'm glad this forum on this topic is expanding. It's always good to post even when the problem is fixed so that others are helped.

My car has still been running ok this week, with still exception to the harder starting. And yes, once started, will easily start if started very soon after setting. I am awaiting to hear your results.

I remember specifically when I replaced the fuel pump that I looked around in the tank and it was very clean. When I get a chance I'm gonna make a T-fitting to the end of my fuel pressure tester to see if my fuel pressure regulator is ok. Hell, that at this point is the only thing that hasn't been replaced at this point.
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Thursday, October 25th, 2007 AT 11:48 PM
Tiny
RISH57
  • MEMBER
My grammer sucks ;). That must be my point ;)
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Friday, October 26th, 2007 AT 3:41 PM
Tiny
RASMATAZ
  • MEMBER
Did you tee-in and got some readings with and without the pressure regulator-let me know what it is.
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Friday, October 26th, 2007 AT 9:03 PM
Tiny
RISH57
  • MEMBER
Gonna be doing that probably on Sunday, will report back.
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Saturday, October 27th, 2007 AT 1:01 PM
Tiny
RISH57
  • MEMBER
So when I T-Bar in the fuel fitting, I basically need to just pull any vacuum fitting or is there one specifically I should be pulling to get my reading?

I'm heading up to the hardware store now to get a fitting and do some readings, just not sure how exactly I am checking w/o the fuel pressure regulator.
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Monday, October 29th, 2007 AT 1:15 PM
Tiny
RASMATAZ
  • MEMBER
The fuel pressure regulator is attached to the fuel rail-you disconnect/reconnect vacuum hose. When the vacuum hose is connected it modulates the fuel pressure with out the hose and plugged it raises the pressure to about 8-10psi. Vacuum hose with fuel in it, the regulator is bad.
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Monday, October 29th, 2007 AT 1:52 PM
Tiny
RISH57
  • MEMBER
OK.

So the fuel pressure with everything connected was 34-35 psi, when I took the vacuum hose from the fuel pressure regulator off it ran at 44psi.

So, that is normal or abnormal?
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Monday, October 29th, 2007 AT 4:38 PM
Tiny
RISH57
  • MEMBER
I should add that I have a catalytic converter on the way. I don't think it's ever been changed and I'm at 175K.
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Monday, October 29th, 2007 AT 4:40 PM
Tiny
RASMATAZ
  • MEMBER
Pressure looks good-Track down an excessive backpressure on the exhaust system-Options remove oxygen sensor, slap on the pressure gauge and read off while at idle-nothing over 2psi-if so its an indication of restriction-Cat perhaps. No gauge disconnect exhaust manifold tie it to the side and retest-did it improve?
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Monday, October 29th, 2007 AT 7:00 PM
Tiny
RISH57
  • MEMBER
I don't have a pressure tester of that nature, nor do I have the tool to take off the O2 sensor. I kinda figured it was time to replace that thing nontheless and it's on order.

I do have to admit, the car after setting at work tonight for 5 hours started right up. It's so come and go with it starting easy and hard, very unusual. All I know is snow is right around the corner and I got to get this all figured out by then, that's for sure.
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Monday, October 29th, 2007 AT 10:11 PM

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