Rough idle, bogs down sometimes at stops, sometimes while driving, then would kick in all of a sudden and be fine

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 three days then back to the same issue.

I next thought fuel since it was stuttering in and out and very apparent under acceleration. Since this car did not 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 mad, replaced the fuel pump. It ran better, but did not solve the problem.

I rechecked the spark on the car and it was okay, 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 bad under acceleration and bumpy idle.

I was then thinking catalytic converter. I drilled four holes in the converter to see if that would help but it really did not. 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 $350.00 to replace it.

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

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

I am not sure what to do now, the only thing left on the fuel side is the fuel pressure regulator, which is like $140.00 from the dealer, and like $95.00 online. I am 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 two 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 thirty miles I had to drive home. Help!
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Monday, October 22nd, 2007 AT 1:28 AM

29 Replies

Tiny
RASMATAZ
  • MEMBER
I would say it is the ECU that is bad because I have seen this problem before I would try a used one. Here is the location.

Check out the diagrams (below). Please let us know what happens.

Cheers
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Monday, October 22nd, 2007 AT 5:00 AM
Tiny
RISH57
  • MEMBER
Okay, 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 carburetor cleaner, but it was not 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, thoroughly cleaned the intake hoses and checked for perforations in anything in the area and found nothing besides 175,000 hoses that all seemed to be intact. I saw two wires in the MAF, 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 proprietary threading that sent me from hardware store to store and even a plumbing and air conditioning specialty store that did not have a thread that matched the one I had. That is what made me just replace the fuel pump and filter rather than spend hours driving around looking for stuff that did not work.

I had at some point a repair manual, but it is in a POD storage unit so I am kind of 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 will have to see the next few days how it acts and such to say for sure.

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

Also, I do not 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 will go back to modulated which will be less and within specs.

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 will 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 before I installed the new injectors it did not take so long to start the car. I have also noticed this is only after it sets for a while. If it has 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 will 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? What 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.

It 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
Okay, yes I replaced that when I did a tuneup, however, I noticed a similar 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 a lot of stuff that does not fix the problem.

Diagnosis was one fuel injector was clogged; fuel pump was checked and okay; Had chain shop replace all injectors, clean fuel injection system, replace fuel filter. Exact same scenario after repairs: rough start, drove home okay; 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/I have seen this problem (dirty fuel in tank) before. Just got car back today; was hard to start again, but once started runs okay. Fingers crossed.

Note: this was a problem at day one (1996) when bought used 1993 Sentra (70,000 miles). One day after purchase, could not start. Selling dealer replaced all fuel injectors which fixed problem. Also replace fuel pump at about 100,000 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 100,000 more miles later, the injector problem has come back. Hopefully, problem is fixed, and will not come back again.

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
My car has still been running okay 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 am going make a T-fitting to the end of my fuel pressure tester to see if my fuel pressure regulator is okay. At this point is the only thing that has not been replaced.
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Thursday, October 25th, 2007 AT 11:48 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
Going to 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 am heading up to the hardware store now to get a fitting and do some readings, just not sure how exactly I am checking without 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
Okay.

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 do not think it has ever been changed and I am at 175,000.
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Monday, October 29th, 2007 AT 4:40 PM
Tiny
RASMATAZ
  • MEMBER
Pressure looks good-track down an excessive back-pressure on the exhaust system-options remove oxygen sensor, slap on the pressure gauge and read off while at idle-nothing over 2psi. If so it is an indication of restriction catalytic converter 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 do not believe it I tried the ECU you said finally and I have been running the car it has never run better I think we got it! I will report back if it does it again wish me luck.
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-1
Monday, October 29th, 2007 AT 10:11 PM
Tiny
KAHNE
  • MEMBER
  • 1994 NISSAN SENTRA
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 194,000 MILES
I recently changed my spark plugs and valve cover gasket, on my 1.6 motor. Every since then at low rpm's the car wants to sputter or have no power like it is not getting gas, then it is followed by what I think is white smoke. But by reading your site white smoke is coolant but this definitely smells like oil coming out of the exhaust. But holding hand over tailpipe leaves no oil residue. The plugs I bought and metal rings you screw onto the plug before putting in motor and we either lost one or one did not come with the ring so we took one off the old plugs, only problem being they did not seem to be made to come off. So we used pliers and forced the ring off and then onto the new plug. The ring was completely intact but was bent some while trying to get off the old one. Was wondering if the plug or maybe we did not seal the gasket well enough could be causing this problem?
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Thursday, August 2nd, 2018 AT 6:35 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Test all the spark plug wires resistances and make sure it is in there and clicks when its set in. Also, test the coil primary and secondary resistances. Did you torque the plugs?
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Thursday, August 2nd, 2018 AT 6:35 PM (Merged)
Tiny
KAHNE
  • MEMBER
Wanted to add that it only sputters at low rpm and then all of a sudden it seems to get it's power back and drives fine at around 35-40 mph. It is just after the sputtering it smokes big time. It does smoke some without the sputtering but I notice the big clouds of smoke while or after it is sputtering. Could the plug be causing the smoke?
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Thursday, August 2nd, 2018 AT 6:35 PM (Merged)

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