Power Surging During Acceleration (~3000-4500rpm)

[rx7racr]

Car: '95 Maxima, 5-Spd, 140k. New KS, Coolant Temp Sensor, Fuel Filter, recently cleaned TB + IACV. Still gets good gas mileage. No CEL. 93 Octane Fuel.


Under fairly hard acceleration, (only after the car's warmed up), I experience a noticeable, rhythmic series of power drops/surges as I pass through the 3000 to 4500 RPM range. It is certainly not a violent cut-out - it just feels like I'm lifting off the gas slightly about once every 1/2 second for as long as it takes to get through this RPM range. It commonly happens to me when in 3rd and I'm getting onto the highway.

This problem has persisted for nearly 8 months now - through winter and into summer - rain or shine. I'd previously gotten a Temp Sensor and Knock Sensor code, but I replaced both components. Other symptoms include a very infrequent but harsh power interruption that lasts less than 1/4 second and occurs below 2000 RPM when under medium/heavy throttle in a high gear. Additionally, the idle seems to dip somewhat every few seconds when stopped at a traffic light - but this is barely noticeable.

I've looked at a number of other threads pertaining to similar experiences, but the original poster typically does not include a final post summarizing the actual solution to the problem... ...so I can only narrow it down to one of the following:

MAF (incl MAF wiring)
Injectors
Coils
KS
TPS
EGR
SparkPlugs
FuelPump
Wiring/Grounds
O2's
One person even suggested that lubricating the throttle cable would clear this up (???)

Anyway - I'm left wondering if anyone out there has had this problem and could share a fix?

My end of the bargain: If you guys help me figure this out, I promise to post up the solution that finally works for me

Thanks a lot for the help!

[AndrewR2442]

My vote goes to the 1)spark plugs 2)coils 3)TPS 4)maf. The uneven idle points to coils or spark plugs more often than anything else. You can easily check all of these if you search for the procedures under the 4th gen sticky's.

Check your tps but DO NOT LOOSEN THE BOLTS. That's only b/c I have gone through a headache for about a year now. I unbolted my TPS when i didn't even know what it was. I thought it would be a good idea to clean the inside of that thingy attatched to the intake. Wrong.

I drove on the interstate for about an hour w/it fine. Then on the ride home my car would surge but under 0% throttle. I was set at cruise at 70 and it would jump around. Even when i thought i had it calibrated correctly i would get surges when set cruise on the highway (TPS warmed up). You have to have your tps sensor warm to get an accurate reading in Ohms. Check the sticky's for a good writeup...

[khantalha]

Originally Posted by AndrewR2442

My vote goes to the 1)spark plugs 2)coils 3)TPS 4)maf. ...

^ i agreee

[Snypa]

My guess is coils/maf.

[rx7racr]

Thanks everyone for the suggestions thus far. Today I double-checked the codes: just the 0505 came up, indicating everything's ok. My computer must be a liar.... :-)

Then I checked the TPS (after a 30 mile drive - so it was warmed up). Pin 1 on the connector had 5v. Pins 2 and 3 had about 540 ohms at closed throttle and between 4000 and 4100 at WOT. There didn't seem to be any spikes in resistance as I swept the throttle, so I'm thinking these tests suggest the TPS is OK.

Next I pulled each coil individually while the car idled. With each coil pulled, I observed a VERY significant deterioration of idle smoothness, a notable change in sound and the car shook a bit (especially when I revved it a little). Each coil seemed to make the car shake about the same amount, so I can't say I found any coil that I suspect as being bad. Also, the behavior of the engine when any one coil was disconnected was WAY rougher than my occasional idle interruption, and way rougher than any of the power surging I experience while driving. I'm thinking that if I were actually losing a coil, the harshness I experience while driving would be a lot more severe.

I also tightened the grounds for the KS and the one that appears to ground the injectors and/or coils. There was minimal resistance between these grounds and the "-" battery terminal.

Oh, and I forgot to mention earlier that the spark plugs I've got are only about 1yr or so old - so I wouldn't expect them to be failing yet...

I did notice, however, that one of the wires coming out of the MAF connector showed visible chafing - right down to the stranded copper core (which looked oxidized). Could this compromised insulation be altering the resistive properties of the wire, skewing the MAF readings?? That might be consistent with the fact that my problem never seems to occur until the car has warmed up. Perhaps the computer is running on Open Loop until the car is warm, at which point it begins interrogating the MAF....

thoughts?

Originally Posted by AndrewR2442

My vote goes to the 1)spark plugs 2)coils 3)TPS 4)maf. The uneven idle points to coils or spark plugs more often than anything else. You can easily check all of these if you search for the procedures under the 4th gen sticky's.

Check your tps but DO NOT LOOSEN THE BOLTS. That's only b/c I have gone through a headache for about a year now. I unbolted my TPS when i didn't even know what it was. I thought it would be a good idea to clean the inside of that thingy attatched to the intake. Wrong.

I drove on the interstate for about an hour w/it fine. Then on the ride home my car would surge but under 0% throttle. I was set at cruise at 70 and it would jump around. Even when i thought i had it calibrated correctly i would get surges when set cruise on the highway (TPS warmed up). You have to have your tps sensor warm to get an accurate reading in Ohms. Check the sticky's for a good writeup...

[rx7racr]

BTW - it was raining like a %$#@% this morning, and the issue persisted with the same intensity. It doesn't seem weather dependent...

(Any more thoughts? particularly on the MAF wiring issue I raised in the last post?)

[mowgli29]

this sounds similar to a problem of mine...but not quite the same.

My car has done this since I got it about a year ago. It did it stock, and it still does it now. For me, it happens when I'm cruising (usually between 40-60) and I let off the gas and then hit it again. Sometimes it does it, sometimes not. To me it always felt like the motor was rocking back and forth on the mushy mounts...especially because I almost had to hit the gas just right to get it to do this. It feels like it gets in a rythm of rocking back and forth and then after a couple seconds it will stop and you'll actually accelerate. It usually happens a bit lower in the rev range for me, but I can get it to do it above 3k.

Well I installed ES poly mounts and it's just the same. Sometimes it seems like it might be worse. Now I'm looking for another cause...

the problem persisted throughout the following:
-two different stock MAFs
-one modified MAF
-USIM+4th gen TB and TPS
-00VI+5th gen TB and TPS
-stock rear coils
-5th gen rear coils
-4th gen IACV dirty and clean
-4th gen and vq40 injectors

The only thing that hasn't been swapped are the front coils. I'll try it, but I have a feeling it won't change anything. And yes, I have a CEL, but the codes are EVAP related, because I never re-installed it after the 00VI.

One thing I've wondered about is the Knock Sensor. I currently have a resistor in there because (it think) the lower harness went bad. There was a point in time that it was loose and over the period of a couple days, I could tell when I had a "working" KS and when the resistor was not making contact, resulting in it feeling gutless. Is it possible that the resistor may be too loose and it causes the engine to stutter when I hit the gas abruptly?

I have no idea WTH is going on. I haven't pursued it because it doesn't affect performance. At WOT in 1st - 4th gears, it doesn't happen (ok well SOMETIMES when I slam it into 3rd at WOT). Mostly when cruising and I abruptly hit the gas. Mostly in gears 4 and 5, sometimes in 3.

I'm tempted to take the hood off and go for a drive to see if the motor is actually rocking...

[rx7racr]

^ I notice you didn't try alternate front coils - - are the rear more likely to go bad, or were the spare rear coils the only ones you had access to?

[rx7racr]

UPDATE 7/23/08:

I read in another thread that CRC's MAF Cleaner spray helped resolve a similar issue for another member. I'm not usually a subscriber to the "repair-in-a-bottle" philosophy, but I figured it was only a few bux and a few minutes. Well, I disassembled the MAF and sprayed the everloving crap out of it (being careful not to touch the delicate bits). I cleaned the intake temp sensor too. Reassembled the whole mess and fired it up - - the problem persisted with no change accept for a possible improvement in smoothness as I transition from off-throttle to on-throttle.

Tried some fuel-injector cleaner too - no observable difference except for a lighter wallet...

Troubleshooting will continue...

By the way, I tried to hook up an OBD-II diagnostic system (AutoEnginuity) to the OBD-II port in the passenger footwell. The software would not make a connection to the car's ECU - and I can't figure out why... ...I know there's a raging debate regarding whether or not a 1995 maxima is OBD-I or II, but I've got an OBD-II port, so I'd assume that means the car is OBD-II equipped....

Anyway - still only getting the 0505 code

Any thoughts would be appreciated! Again - I intend to post up the solution when (if) I finally find it!

[knight71]

Originally Posted by rx7racr

UPDATE 7/23/08:

I read in another thread that CRC's MAF Cleaner spray helped resolve a similar issue for another member. I'm not usually a subscriber to the "repair-in-a-bottle" philosophy, but I figured it was only a few bux and a few minutes. Well, I disassembled the MAF and sprayed the everloving crap out of it (being careful not to touch the delicate bits). I cleaned the intake temp sensor too. Reassembled the whole mess and fired it up - - the problem persisted with no change accept for a possible improvement in smoothness as I transition from off-throttle to on-throttle.

Tried some fuel-injector cleaner too - no observable difference except for a lighter wallet...

Troubleshooting will continue...

By the way, I tried to hook up an OBD-II diagnostic system (AutoEnginuity) to the OBD-II port in the passenger footwell. The software would not make a connection to the car's ECU - and I can't figure out why... ...I know there's a raging debate regarding whether or not a 1995 maxima is OBD-I or II, but I've got an OBD-II port, so I'd assume that means the car is OBD-II equipped....

Anyway - still only getting the 0505 code

Any thoughts would be appreciated! Again - I intend to post up the solution when (if) I finally find it!

I have the same exact issue, read this thread and a possible solution. I have to try this also, but I haven't found the time to do it..Please post back if this works for ya..read on..

Micro-second pauses in acceleration - Going through HELL!

[rx7racr]

just for kicks, the following are a list of other threads which seem related to this: I figure this list might help someone else who is searching for similar info...

Engine Trouble - Loss of power on Acceleration



Hesitation while accelerating

Hesitation

[rx7racr]

Originally Posted by knight71

I have the same exact issue, read this thread and a possible solution. I have to try this also, but I haven't found the time to do it..Please post back if this works for ya..read on..

Micro-second pauses in acceleration - Going through HELL!

Thanks a lot - I'll check that out!

[rx7racr]

(Judging by the dozens of threads I've searched ((very few with actual solutions, BTW)) It's sounding like MAF and/or Coils have the majority of votes... ...and there are a TON of people with similar problems!)

[rx7racr]

UPDATE - 8/3... More Troubleshooting has been done:

Still no codes at any point (0505 only)

Borrowed an OBD-II scanner that worked with the max. I was able to observe the following while driving:

TPS
O2 voltages (x3)
MAF
Short/Long term Fuel Trims
IGN Advance
Vehicle Speed
RPM
Intake Air Temp
Coolant Temp
Open/Closed Loop Operation (x2)

OK - so I wanted to see if the TPS, MAF, IAT or 02's (or anything else) showed any erratic behavior during the surging episodes. After a number of passes through the 3000-4500 rpm range, with surging observed, it did not appear that ANY signals on the scanner were acting strangely (spikes etc...). From this, I think it's safe to say that the MAF, TPS, IAT, 02's, ECT, VSS and Crank Position sensors were all returning smooth (non-erratic) signals. I'm not exactly sure what the values should be on many of these sensors, but nothing seemed to do anything strange during the surging.

I also paid special attention to the IGN Advance, as I had suspected that the surging could be a retardation in timing - due, perhaps, to a faulty KS. Throughout the surging episodes, the IGN Advance stayed about where it would at other RPM ranges (at similar throttle positions), and it never spiked erratically.

So... The only thing that seemed to change (a little bit) during the surging episodes were the 02 voltages and the Fuel Trims (short-term more). The 02's (one of them in particular) seemed to read much closer to 1v immediately after the surging. Also, the short-term fuel trims (one of them in particular) seemed to go negative after the surging.

If I'm reading this correctly, both the high 02 reading and the negative Fuel Trim seem to indicate that the car could be running a bit rich during the surging episodes. What could cause this? Well - COILS certainly could! If one or more coils weren't firing properly, unburned fuel would be ejected into the exhaust, richening it, and sending 02 values high. Fuel trims should compensate for this by going negative (i.e. leaning out the mixture slightly.).

So I looked at each coil. None of the coils showed any visible signs of arcing or overheating, and I didn’t see any browning of the coil exteriors. With my ohmmeter set on 20k, each coil’s primary circuit (terminals 1+2, as in above diagram) measured between 1.52 and 1.71. It might be significant that 5 of the 6 coils were between 1.52 and 1.63, with the remaining coil measuring 1.71. It might also be significant that I measured these resistances with the engine/coils cold (remember, my problem only manifests when the engine is hot).


Any Ideas?

I might try buying a bunch of coils off e-bay, or maybe 2 new coils and just start swapping them around…

[rx7racr]

here's a link to a recent thread describing known bad-coil symptoms, which says all resistance readings should be between 1.3-1.7 megaohms. These symptoms sound worse than I'm experiencing, but perhaps my problem is just the beginning stages of coil failure...

...anyway - here's the link

Defective Coil Pack Symptoms

[Slickismax]

I have the exact same problems. I have noticed that when my car does the initial stumble on acceleration at low RPMs with WOT my fuel gauge dances with the stumble, like the ECU is cutting fuel or something. I also have the same "surging power" with 3/4 throttle through all the gears really. It's done this since I bought it in '99, and I've never tracked the problem down. I've made a few small attempts, MAF, Coilpacks, KS, plugs, and nothing seemed to help al that much. In for a solution guys!

[mowgli29]

First off, I'm a 5spd, are any of you autos?

GREAT work with the OBD-II scanner rx7racr! That eliminates a lot of possibilities already, thanks!

If I can find the time, I wanna try and make a video of what my car does...I'm curious if it's the same thing or not. Sounds similar, but like I said, mine feels like the engine is rocking back and forth. Like I'm flooring it then letting off then flooring it really really really fast.

Slickismax, you talking about a fuel pressure gauge? That's rather intriguing...I can't think of why the ecu would cut fuel unless there is some other sensor malfunctioning...but could it be a fuel pump problem?

[knight71]

I wrapped my front 3 coils in electrical tape and the surging has been eliminated almost 95%. I will do the back 3 sometime next week, and post back. Try this for all of you that are having this issue. I followed this thread to resolving this issue..

Micro-second pauses in acceleration - Going through HELL!

[nismology]

Your fuel pump is tired.

[Slickismax]

Originally Posted by nismology

Your fuel pump is tired.

It's been doing this since I bought it...which was December of '99. I'm pretty sure the fuel pump would have given up by now.

[Slickismax]

Originally Posted by knight71

I wrapped my front 3 coils in electrical tape and the surging has been eliminated almost 95%. I will do the back 3 sometime next week, and post back. Try this for all of you that are having this issue. I followed this thread to resolving this issue..

Micro-second pauses in acceleration - Going through HELL!

I'm going to try that tonight when I get off work. I'll drive around some tonight and see if it fixes the problem. Could explain why the fuel is being cut, as it could cause a temporary, "micro-second" short.

[mowgli29]

Originally Posted by nismology

Your fuel pump is tired.

That seems like it would make sense...but then why does it only happen when I let off and sharply hit the throttle while cruising?