Crusing in 3rd gear at a constant speed I get a surging around 2500 - 3000 rpm. What is the cause of this?

any other rpm and it seems fine... WOT is fine too...with lotts of power.

could it be something with the ECU?

any suggestions?

 

Could it be the common grounding issue with FD's? Add some more grounding wires from your battery to the chassis.

 

Look at page F-228 in the manual. It states several possibilities;

-injectors
-spark plugs
-pressure sensor
-igniter
-ignition coil
-throttle sensor

Page F-194 states;

-pressure regulator
-oxygen sensor
-knock sensor

Probably doesn't help much, but the manual was close. If it's any consolation, mine does it too, but I attribute it to the PFS PMC, as thats when it started.

Frank

 

is your "CHECK" on? if so, find the code on it.
if not, check the turbo swing valve and the vacuum hoses on it.
check the soleniod that controls the swing valve to the 2nd turbo.

 

solenoid

 

Cleaned the gounds already. I have about 3-4 extra ones... I will reset the ECU (pettit) and see what happens.

I am sure it's not a turbo problem...

 

i dont think its your turbo either. check with flyrx7 he knows his ****..

 

Good morning, surging is usualy a sign of a lean condition. Don't freak out though, we are talking lean under vacuum, not boost. Huge difference. What engine management are you running, I can make my Power FC do this if I lean out the cruise tables and leave o2 feed back on, it hunts around trying to make a mixture it thinks is ok, hence the surging.
jay

 

Hey Jay,

Thanks, but I am running the Pettit ECU... non-adjustable mixers... I will add some injector cleaner to the tank as well.

 

Ok , Check fuel rail pressure first.
If you have a digital multimeter, you should be able to read o2 volts by grounding the black lead of the meter and back probing the o2 connector with the red lead of the meter. Set the meter on volts, wel, milli volts if you can. I believe around .75 is stoich , lower is lean, higher is rich. That will at least give you an idea if it's lean or not. If it is lean, you have to see why. Air leak in the on the engine side of the throttle body, low fuel rail pressure would be the main culprits.
Jay

 

Mine did this, and I tried every trick in the book. It only went away when I upgraded to a PFC.
Good luck.

 

The problem with this though is, if cruising (when the problem occurs) you are in open loop and the ECU is regulating the mixture by going full rich/ full lean/ to find the mean-best A/F ratio. So checking the o2 will just be jumping around anyhow.

WOT would be a different story though.

Frank

 

my small coupler from the ypipe to the cross over tube was leaking and it caused similar stutter. the leak was not visible.

 

mine was doing the same thing....but it would happen in any gear and get really bad when the lights or fan were on. I changed the plugs and wires and the problem went away. gl

 

Well sort of right, cruise is actually closed loop, where the ECM looks at the O2 feedback to adjust mixture. Full throttle is open loop where the ECM strictly uses tables. Now, when you are crusing, you should see swings AROUND stoich, I believe somewhere around .70v. if you are swinging around that (say .85 high and .65 low) for example, everything is ok. However if you are swinging around say .5 (.35 low, .65 high) for example you are lean. It does sound like a lean surge although I know RX's have more tricks (problems) up their sleeves. Good luck.

 

Damnit! I always get that mixed up!

Frank

 

Ok then... tonight I took my 7 for a spin again... and found out that 2nd and 3rd gear had this surging effect
around 2500 - 2900 rpm. But strangely 4th and 5th gear were fine at the same RPM.

I added some fresh gas in with some Amsoil Fuel system cleaner/ cleaned the grounds around the firewall and re-set the battery.

Took my seven out again and it seem to run allot better.
Still had a little but it was barely noticeable...

Weird or what? 3rd gen gremlins?

 

forgot to ask this question: Since I reset the Ecu... removing the negative battery cable and step in brake for 30 secs. Then reconnect.

I have heard that this is only a cure for a couple weeks then I might develope the surging again...Is this true?

 

Only if it's something the ECU is going to relearn, but if it's something you fixed it won't comeback (boy, that's profound, huh?)

Frank