I have searched the threads and internet for days and started a thread about this earlier this week with no response. I thought I'd give it another shot. I can't figure it out and about to go crazy! I never had the problem before I took everything out to replace my head gaskets. Now that everything is back in the car starts up right away no problem. No high idol or stalling issues.

However while car is in park or neutral if I were to raise the rpm's the car will not go past 2k without doing this up and down up and down idol. It will not hold steady. It gets to 2k and then goes up to 2500 back to 2k then up to 2500 repeatedly. I tried driving down the street and there's hesitation when I press on the gas then it picks up speed until 2k rpm all of a sudden it bogs down like it's flooding with gas. No backfire occurs unless I rev the engine quickly. Why is it doing this?

I adjusted the idle screw on the IAVC with the tps unplugged of course. Idol speed changes accordingly. Note: when tps is uplugged there is no up and down idol problem.

So then I go through the process of testing the tps. Pin 1 reads 5 volts as it should so that I know is ok, BUT, the tps continuity is at 3.2. No matter how far I rotate the tps it still reads the same 3.2. It also doesn't matter if the throttle is in a closed or wide open position I still get 3.2.

I hope someone can help me with some ideas. IAVC, TB, EGR tube are cleaned. Engine temp switch and sensor and also front o2 and rear bank o2 sensor are all reading the correct contiuity.

Please help!!

 

The RPM issue your having is related to the intake box check your MAF sensor. The rpms won't go past 2500 and it won't go up above 2000-2500rpms it's your MAF. The MAF won't let your car rev past the 2500 or above.

 

It sounds like the TPS is bad if the car oscillates from 2000-2500 by itself.

 

sounds like a vacuum leak to me. Are you noticing bad gas mileage now?

 

I'm not getting any gas mileage right now lol, I can only drive it a block and then I come right back because of the refusal to go past 2k rpm.

I will test and clean the maf sensor. I bought a new maf sensor 2 years ago and have only driven it barely 1000 miles since because of overheating problem it had. Also 4 years ago I had replaced so many emissions parts because of codes that kept popping up. I'm familiar with working on cars following instructions from the repair manuals but I was new to this car and not really knowing what I was doing. I just went with what the scanner said and replaced or repaired everything following the step by step instructions from my Chiltons.

The tps was one of the items I had replaced 4 years ago and I didn't know anything about checking continuity or tps relearning (if it even applies to 4th gen Maximas). So with all this in mind the overheating probably came from my inexperience working on this type of vehicle. None the less it wasn't doing this idol up and down thing until now. A friend of mine who is a master mechanic and is now impossible to reach checked the car for no start problem 2 years ago and said I needed to replace the maf, I did and it started right up. Even now it starts up no problem but the idol is what it is at the moment.

Would it help if I also mentioned a short hiss about 1 second long when pressing on the gas? I used my vacuum pressure tester and to test for vacuum leaks and the needle laid down comfortably at 19 steadily. I hope these clues help. Anything else I need to check? Any extra info anyone might need don't hesitate to ask. Thanks for your help guys! I'll let you know what I find out about my maf.

 

The maf sensor has been cleaned and is fine. Not sure what else to do at this point except to replace the tps and see if that does it. For some reason it doesn't feel like it's the tps even though the idol doesn't go up and down when unplugged. It idols at 900 and I could rev the engine as high as I want to and maintain the idol at one spot for as long as I want to without a problem.

What else could it be? I'm thinking I need to do the idol adjustment with IAVC, TB adjustment screw and TPS. Any thoughts?

 

If the car wont rev past 2500 rpm its classic MAF issue. Get one from the classifieds. Dont think TPS is your problem at all. Its the MAF.

unplug MAF with car running. The car should bog down.

If u unplug the MAF, and the car stay the same or doesnt bog down then your MAF is toast/.

 

Ok I disconnected the MAF with car running. The engine almost died then the idol went real rough for a few seconds then found it's way back to idle and launched the cel. From what I've read I think from here in the org or fsm I don't recall, the ecu or ecm whichever it's called would find an alternative to keep the car running. The cel was expected once I disconnected the MAF I'll clear that in a moment or two.

 

CEL is not gonna turn off until u complete a driving cycle. Prolly 60 to 100 miles.

U say u already checked resistance across TPS??? The resistance was supposed to vary from open to close. resistance across pin 2 and 3 in open supposed to be 4000 ohm, closed is 0.5k ohm.

Think we found your issue.

 

I think you're right. Yup I have 5 volts going into the power pin on the tps and continuity is what I'm supposed to be reading on pins 2 and 3 right? If so I get 3.0 if have the ohms set to 20k. It's rotated as far as it can go towards the battery side of the car. At closed position (almost closed) it shows 3.0 and if I rotate the tps the other way it's still 3.0. It will go to 3.2 while rotating but that is as high as it will read and then rest at 3.0 once I stop rotating it.

Quick question on that, on top of the throttle body where you're supposed to insert a feeler gauge to configure the tps, is that supposed to move when I turn the tps? If not mine does and the idol goes up as I rotate the tps away from me toward the passenger side of the car. It's actually opening the throttle plate. I'll post a video if I'm not making any sense.

 

I figured out the problem. It was the TPS after all it was not installed correctly! I didn't know there was a wrong way to install it. Inside the tps is the silver piece with the end of it pointing outward and inside the throttle body where the tps goes there is a silver bar. I initially had the end piece of the tps immediately engaging with the silver bar. This caused the bad reading and up and down idle once it reached close to 2k rpms. I tilted the tps so the end piece is on the opposite side to see what would happen and sure enough the ohms ranges were available for me to adjust unlike the constant 3.0 to 3.2 I had gotten initially. The up and down idle issue is gone also. Only thing I need to figure out now is why a short 1 second hiss from the tb area happens when I press on the accelerator fast. I wanted to see how she responded by revving her a few times.
Again thanks the all the info and any suggestions on that last issue I'd appreciate it.

 

"idol goes up and down at 2k rpms"

Billy Idol??

 

Hey little sister...

Yeah the car would drive like complete @$$ if it was a MAF issue you wouldn't be able to get it down the block w/o hating your life.