As the title says when I try to start the car up in the morning SOMETIMES not all the time the RPMS would shoot up to 1200 or so as normal then automatically go back down to 0 causing the car to stall. The other day when the car was running it was hesitating A LOT while it was running only when the temperature of the car was cold. The car runs fine, drives fine, etc. I just have this little annoyance sometimes that I want to get taken care of. I showed it to my mechanic, he said no vacuum leaks nothing looks out of place, and he said it may be my MAF Sensor. I don't have a MAF sensor but I'm using the '97 MAF which is hooked up to a Cattman Combo Hybrid Intake with a JWT Air Filter the one with the velocity stack. This is hooked up to a '00 VI with a '00 Throttle Body. Can I use the '99-'01 MAF the ones that are sold on courtesyparts.com? Does this sound like it may be an MAF issue, how do I test my MAF to see if it is good or not? BTW, no codes at all.

 

It sounds like it could be a bad ECTS. The readings from that sensor are what the ECU uses in open-loop conditions to determine the air/fuel mixture. On the VQ30, the ECTS is only 20 bucks - I imagine that the one for the VQ35 may be identical or very similar.

 

Sorry to say man I dont think you are going to get a lot of help in this forum. You should post up in the all motor. That is where the VQ35 wizards hang out most of the time. I have cold start issues to, but not like yours. They are related to my pathy TB and the fact that there is no coolant line running into my TB anymore. Hope you can get it fixed.

How do you like the 00vi on there?

 

'00VI is nice good high end. I'm also upgrading to the PF TB. Why do you not have a coolant line running into your TB? Is it because you chose not too? I don't want that to happen I want the coolant lines running. Where is the coolant line btw? Is it the line at the very top?

 

No the coolant line is on the bottom of the stock TB I think. The pathy is not set up for a coolant line. The only issue is that if the engine is too cold you will need to hold the idle up with the gas pedal right after start up for like 15 seconds. Its not a big deal. You dont even have to make it idle very high. Just enough to make sure it doesnt stall. I think the benefits far out weigh this one fall back.

 

Has there been proof a PF TB is beneficial?

 

You will have to cruise the all motor forums. I went on Stephen Max's advice when doing the swap. Apparently its only beneficial if you are running a VQ35, a 00vi, or a MEVI. It really doesnt do much for a stock VQ30.

 

I replaced the fuel filter, will see how she starts tomorrow morning.


Anyway I can troubleshoot the MAFS?

 

It doesn't do much for a modified 3.0 either.

 

HarrisH, what base fuel pressure are you running at? I have a feeling it's much lower than the 53 PSI the 3.5 injectors should be seeing. Low fuel pressure = improper atomization = hard starting and other issues...

 

I have VI fuel injectors I believe they are 290 CCs.

 

Ahhh...i see. That just throws my theory out the window...

 

Yeah I'm using a '00VI upper and lower manifold thats port matched to the VQ35 heads. The FPR is the '00VI FPR, the Fuel rail and injectors are also from the '00VI. The fuel pump is the Walbro fuel pump.

 

Wow. What a strange fuel system combination. I'm willing to bet that at cold-startup the motor is getting too much fuel with the walbro. Any particular reason you're using that fuel pump?

 

How is that a weird or strange fuel system combo.? Everyone that has the VI on either a 3.0 or 3.5 has the exact same setup except for the differences of the stock fuel pump or the Walbro. The fuel system is essentially the same as in the 3.0 only difference is the 20CC larger fuel injectors. I've had the Walbro for some time now and I just recently started noticing this issue. So I doubt the Walbro has anything to do with it, otherwise it would be doing it from the moment it was in the car.

 

I would check for vac leaks and connections. You have no EGR correct? Any CELs?

 

My trusty mechanic also said that it MAYBE the MAF sensor. Since it measures the air coming in sends a signal to the ECU which then dumps in the according amount of fuel. He said to disconnect the MAF in the morning right before my cold start and see if the car starts, if it starts up fine then it's the MAF that's bad or on its way bad. I would assume the latter of the 2 since I have no driveability issues, CEL codes, etc. What do you guys think? Good idea? Anyone ever tried something like this?

 

No vacuum leaks, connections all look good. Yes I do have EGR, no no codes. I also had my mechanic check for vacuum leaks he couldn't hear any. Vacuum leaks would be more consistent I would presume and cause a lopey idle.

 

IACV might be dieing. Swap with another max and see what happens.


And the MAF thing--it is true for 5th gens. If it starts better w/o it connected, it is hte prob.

 

If it was the MAF that went bad you wouldn't be able to rev past 2500 RPM.

 

No, that means the MAF is dead. But a slowly dieing maf still runs.

 

Any other symptoms, how often do these go out, again it would be hard to diagnose while swapping because this only happens after the car has been sitting over night.

 

Usually you have hesitations and the car doesnt feel as strong when the MAF is dieing. As for the IACV, the more I think about it, I dont think it is it because you would have the starting probs more often.

 

Can you describe the hesitations in detail, would the RPMs fluctuate, it does pull quite strongly thru the powerband. I've started it maybe 30 times today and it started up absolutely fine, and idled absolutely fine.

 

Also the ECTS measured within spec when the car was at operating temperature. I haven't had a chance to check the resistance with the car cold since it has not been sitting over night.

I'm overly concerned because I don't want this problem to escalate into something bigger.

Let me try to describe it in detail, on Monday, I started the car after it had been sitting for about 48 hours. The rpms shoot up to 1200 but the car was hesitating very very badly. While the car was hesitating the RPMS WERE SMOOTH. So I turned it off, I turned it back on the RPMS shoot up to 1200 then right back down to 0, this happened 3 times. On the 4th time while the RPMS were going up as the car was starting I hit the gas a little and then let off the gas and the car idled SMOOTHLY at 1200 RPMS without ANY hesitation.

After that initial start in the morning the car was turned on and off on a number of occasions and always started up on the first try and idled very smoothly.

Today after the car had been sitting overnight I go to start it and the RPMS shoot up to 1200 and the car idles steady. Me being me, I turn it off and start it up again GRRRRRRR same Sh8! RPMS shoot up to 1200 and shoot back down to 0, this happens 2 times, I believe on the third try it idled smoothly I don't recall stepping on the gas or not. But that's the best way I can describe it.

 

Perhaps the car can feel stronger? Hesitations is what I'm trying to figue out, when I go over bumpy roads or uneven surfaces I guess the throttle response is changing either because of my foot or whatever else reason and consequently I hear a different exhaust note. For e.g. If I'm going from a smooth standstill it'll go VROOOOOOOOOOOOOOOOOMMMM shift, VRRROOOOOOMMMMM shift, etc. If I'm going partial throttle from a stop on an uneven surface it'll Go VR VR VROOOOM VR VR VROOOM. Can that be described as hesitation?

 

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Yeah that sounds like hesitations under a load.

 

So then it's probably the MAF, if it is I'll be SUPER DUPER excited if it resolves the problem.

 

Also this usually happens when the car is cold... but shouldn't the rpms fluctuate as well?

 

I am know mechanic but when my boy gti vr6 does that his rpms fluctuates

 

MAFS do more than you would imagine! I'd wiggle some wires on the MAFS and see where the RPMs go to next...How many miles on your MAFS?

 

UPDATE:

I don't think it's the MAF here's why.

I started it up this morning, seemed to hesitate a tad bit but did start up first try. I took out the key after 2 seconds, started it up again rpms shootup almost stalled but bogged down to 300 or so then went back up. I disconnected the MAF it started the same way, RPMS went up then bogged up then down then stayed smooth, but SES light came on (duh!). Started it up again with MAF harness in again same thing, RPMS shoot up bogged down a little to 300 then went back slowly. I will check the ECTS resistance. Please don't say it's a dirty TB because mine's as clean as can be.

 

I just cleaned up the TB surprisingly it was dirty but not that dirty some black liquid did come out, and I also sprayed some into the IACV hose. It does seem to start up A LOT better, but I won't know the cold start for sure until tomorrow morning.

 

Clean the IACV and clean the hose.

 

Ok well here's another update

I started it up this morning it was quite chilly actually here in New Jersey. It did start up on the first try of the key. But me being me I took the key out and started to start it up 2 times more. The second time as well as the third time the RPMS shoot up to 1200 and then bogged down a little to like 700-800. But the car DID NOT stall and I started it up atleast 5 times withing 10-15 seconds.

Perhaps I should clean the IACV and TB some more?

 

vacumm leaks ,huge vacumm leaks and little vacumm leaks my car did this recently when i put a vias on.

 

I don't know about vacuum leaks, would they not affect idle? I showed it to my mechanic he didn't hear any vacuum leaks.

 

Is the TPS adjusted correctly?

 

dubbya said just to give it gas for 15 seconds and it goes away.

 

check the egr gasket.. mine slipped when i had the IM off and when i would start my car it would instantly rev up, drop to 0 and die