I'm experiencing what feels like surging as I'm accellerating my car. At times during the surge, the engine pulls well, then seems to go flat, then repeats.
The engine shows no codes at all, and mileage hasn't been affected at all. It idles well, and WOT seems ok. I notice the problem most in the 1.5-3K range, since that's where most of my around town driving is.

Could the problem be the KS or TPS? Do both of these always throw a code when broken, or can they go bad without throwing a code?

 

KS can go without lighting a cel, TPS would throw a cel. Go to a local auto store for a free scad.

 

MAF, TPS, Fuel pressure, but not the KS.

 

sounds like and EGR issue. or the TPS. but a TPS with a flat spot will not throw a CEL

 

Have never had a light with this. There are also no codes are in the computer, so I guess I'll just check the individual components...MAF, TPS, etc. Thanks all.

 

I have the exact same problem with my JDM spec 2.5 Cefiro. I have found it is more pronounced on hills with the OD off holding about 3500rpm. I have so far replaced the fuel filter & am thinking of doing the fuel pump next. But firstly I am going to pull out all the coils & check them for tracking & check the spark plugs also. I have been told that as the coils break down they can give a surging effect

 

Let me know what you find out. When you say tracking...are you looking for signs that the spark is jumping where it shouldn't? That should be easy enough to check. I'll add it to the list.

 

Yes, spark jumping. Well I pulled all the coils out, no signs of tracking as far as I could tell. Pulled all the sparkplugs & found they were all well & truly worn out so I replaced them & siliconed all the coils. Put it all back together started it up, went for a drive & then the "check engine" light came on. Stopped the car & then it wouldn't start again, just cranked over & over. Eventually got it started again & drove it home. The upside is the surging doesn't feel as prounounced now, the downside is my wife won't drive it anymore as she doesn't trust it. Gonna have to do a fault code on it I think. Thinking possible oil surge or fuel pump issues

 

Wow...I checked the front three spark plugs and coils and all looked fine. I did notice some serious carbon that had built up on the tops of the pistons, so I blew out the engine with a few high rpm runs. That definitely helped with the surging. Maybe I had so much carbon in there that it was detonating on some cylinders and causing everything else to freak out. I tested the TPS and all is ok. Will see how it runs this week. Hope you get yours running 100%.

 

Well just per chance (the wife normally drives the car) I checked the oil level & it was on the low mark. Stuck a litre in & now the light doesn't seem to come on as often. Probably coincidence I think, or maybe another reason the light came on in the first place.

Tried to do the diagnostic screw on the computer thing but then realised Cefiro's (or mine at least) don't have them, damn!!!

 

If you're burning oil, it may gook up your EGR valve and throttle body more often. Those may be causing some of your problems.

 

Nah, I don't think its burning oil as its way past its oil change due date. I was meant to do it last weekend but with all the other dramas I just haven't done it. This weekend me thinks.

I have just replaced the water temp sensor so I will see if that makes any difference

 

Well the water temp sensor fixed the "check engine" light but ironically enough the car is still doing the original problem with the surging. The new thing is it is feeling a little powerless which is a bit perplexing. Will change the front crank angle sensor this time I think

 

Hmmm. Your surging still sounds like mine. Any codes now that you've changed a few things out? I still need to check my MAF sensor, but haven't been able to do the voltage test at the CPU. The voltage test for the TPS worked well...but I just can't seem to get good voltage at the MAF terminals. Maybe the readings I'm getting are telling me the MAF is messed up. I'm wondering if those $200 scanners would diagnose problems like this. That's just a little more than a couple of hours of labor and would be well worth the investment if it works.

 

I had THE same problem, car would pull then let go then pull then let go..I had a CEL...Knock sensor and Vehicle Speed sensor...replaced both, and the problem was gone

 

Sounds like a fuel pressure issue. Check it with a FP gauge.

 

Oooooo knock sensor looks like a pain is the *** to do. Might try the cam end crank angle sensor tonight otherwise into the shop for a fault code. For $40 it might answer my questions. The upside of working for a Nissan dismantler is I have access to stuff I can "borrow"

 

whats a tps? is that like the tps reports in office space? i'm having similiar probs check engine light = knock sensor, erg malfunction or something, and fuel regulator something after the tank sprung a leak recently... j/k bout the office space

 

Its a piece of cake, it shouldnt take you more than 10 mins . . . with proper tools.

 

Yeah I did a test run on an engine we had on the floor & I can get my hand in there ok.

GOLDMAX, how did you get on?

 

tRUkbOY...It wasn't me...I've never changed the KS. Check back threads...tons of good hints on how to do it.

 

Nah I just meant in general. Did you get your car sorted?

 

No...the problem still comes and goes. Still need to check out the fuel pressure and a few other things. I actually wish I had some bad codes so at least I would have something to start with!

 

Problem solved! Cleaned the MAF sensor screen - the surging is gone and the power is back! Free fix and very easy to do! I am totally amazed at how simple a fix this was. The MAF screen had a light layer of black soot on it from 8+ years of driving. Thanks njmaxseltd for suggesting looking at the MAF.

I highly recommend doing this. I cleaned mine with rubbing alchohol and Q-Tips. Warning...I've seen earlier posts that say to go easy on the cleaning or it will cost you the replacement of this part which is very expensive.

 

Seriously!?!?!?!?!? I'm blown away at something so simple. Your A/F meter must have been solid with black soot. I'll check mine tonight & relay the result.

 

Pulled my A/F meter out, didn't look to bad actually. Instead of cleaning it I just borrowed one from work - made no difference I'm afraid

 

It actually seemed to fix the problem the day I did it. The next morning it seemed flat again. Still no codes. I ran thru the AT code reading routine last night, and everything there seems fine there. I've found in the past that just checking the AT codes will help resync the tranny to the engine. Will see if it keeps doing it today.

 

Trukboy...you get your car fixed? The cleaning of the MAF screen AND resyncing the tranny box totally fixed my problem. It's unbelieveable what a difference it has made....seems to be similar to what others report when they replace a bad KS. The resync was the key to the final fix....now the fire is back! Engine pulls strong and the transmission shifts well...especially when you blip the trottle to evoke a downshift or two. Much more in sync. The car is actually enjoyable to drive again. Is yours an auto or 5speed?