watut

Hey guys. I recently replaced my father's IACV and ECM, followed by a idle air volume re-learning on his 2001 Infiniti i30. The car idles perfectly now. However, now when driving at low speeds the RPM will randomly go up ~500 and go back down. Kind of feels like the car is trying to downshift but decides not to. Any advice?

Any advice/ideas?

maxiiiboy

For the RPM to go up, the engine must be getting more air, or more fuel, or both.

You my want to go through pages ES-21 to ES-25 0f the FSM - they describe the fuel injection system, its operation, and the inputs/sensors that affect the amount of fuel injected. In particular, I would go through the diagram EC-21 top to bottom, and consider/test each sensor listed there: POS, MAF, coolant temp, front O2, TPS, .... ,etc.

A bit laborious but I can't think of anything better right now .... I would focus checking all connections as your problem looks very intermittent.

One more thing: you said you replaced the ECU. With what kind - new/OEM or aftermarket/junkyard? In the latter case, how do you know it's good?

foodmanry

iTrader: (15)

Automatic transmission? Sounds like it is slipping from first to second...

watut

Thanks for the replies guys. Sorry should have specified, it is an auto transmission. the ECM was from the junkyard, refurbished.

The car shifts fine into all gears but only does this when cruising in gear or when slowing down and turning.

2damax

So you will be cruising, then the car will put itself into neutral and rev up and back down and then go back in gear? Or will it stay in gear and jerk you forward and slow you back down? If it is the first one, does it slam back in gear or is it smooth throughout the whole process?

george__

iTrader: (1)

sticky gas pedal

watut

It stays in gear but the rpm will jump up say from 2000 to 2500 and quickly back down to 2000. It stays smooth and doesn't jerk throughout the process.

2damax

I don't see how the RPM can jump with the car in gear and the car doesn't jerk or anything. I must be missing something simple here. Hopefully someone chimes in that has dealt with this before.

maximasicilian123

The only time I ever experienced Rpms going up and Down is at idle with a bad maf sensor. And when in gear the car will not go past 2nd or 3rd in a automatic. U might wanna have that checked if that helps

watut

The car goes through all the gears and will go past 2500RPM no problem. Drove the car today and it does feel like it jerks/lurches forward when it acts up.

Today the SES light finally came on with P1320(coils) and P0158 (o2 sensor). Can any of these cause this issue?

I printed off pages EC-21 to EC-25 0f the FSM to trouble shoot when I get a chance in the next few days.

george__

iTrader: (1)

Fix the ignition coil man!

watut

Could the coils cause this issue?

I remember my 01 Maxima throwing the coil code, then it threw the misfire code(s) after. Should I wait until it throws me a code for a speciific coil/cylinder? As he is not in a position to buy 6 new coils from the dealer $120/each at this moment.

More information here. Seems it only acts up after warming up. If I try to rev it up in park or neutral - it will go to 1500-1750 and jump around there (won't freely rev higher). If I push the gas pedal harder then it will rev higher but won't hold steady at higher rpm. If I try and hold it at a higher RPM (say 2500) it will drop back down to 1500-1750 and jump around there. Hope this makes sense.

Do you guys reckon this can be a vacuum leak?

Video - YouTube

Here's what it does if I try and hold it at any rpm at idle, it goes down and jumps around here