Ok, breif history. After rebuilding I drove around for a week with no problems then there was an oil leak. On my last trip before dropping the bedplate and replacing the o-ring I hit the revlimiter at 7,200rpm while I was at 11psi. After that on the ride home the car stalled a couple of times and I had to crank it about 3-4 times, after that the last few stops before I got home, along with the 3-point turn in the yard before backing into the garage it didn't stall and seemed to run fine.

So, now the o-ring has been replaced and I get the car running. It drove fine while it was warming up. Went about 5 miles and once it hit opperating temp it immediatly started bucking and wouldn't accept any throttle. I had to drive the whole way home at idle. I could crack the throttle ever so slightly (maybe 2-4%) but anymore and it would jerk and buck violently and the exhaust would pop. During these episodes the WBO2 goes way lean. In the morning after it has had time to get cold again I'll see if the problem is still there or if it is actually dependent on engine temp.

Any ideas?

EDIT: By operating temp I don't mean when the water temp needle gets to the position that it always sits at when its warm. I mean when the idle oil pressure gets to about 25psi. You know how the Oil pressure at idle stays pretty high untill its completely warmed up...

EDIT2: Car is still running on the stock ecu. SFMU and 42# injectors. Hahn turbo kit. Has the Hahn FCD and the missing link.

Bump. TPS, idle air? Shift hard and pull something loose?

Yea, I was thinking maybe the TPS just took an instant shit... I didn't mess with the car today, had to go to my best friends funeral... been kinda out of it since his death last wednesday night. Ima try and find my spare tps that is probably lost in the abyss that is my garage...

OK I just got done running it in the garage and while it was cold it was running fine and letting me free rev it. After about 7-10 minutes, once the idle oil pressure dropped below 50psi (getting pretty warmed up) it won't let me rev past 1,500 rpm... It just sputters and shit like its on a stutter box almost. Which sensors are not used in warmup but are relied on for normal operating temp operation? Please help, I leave for college on the 3rd of jan and need my car.

EDIT: I wasn't able to find my extra TPS but if its not used during warm up but is after its at operating temp then I'll go buy one or if anyone can tell me how to test it, i have a multimeter and test light... just not sure the proccedure. Never had an electrical problem before these last few weeks.

Ok, Thanks for all the help. I guess I'll just bite the bullet and tackle the MegaSquirt install... I've been dreading it for a few months now... The two suggestions I got from Dino were o2 and map and they'll be cut out of the picture when the MS... later.

Think maybe the coilpack is getting hot and then the output is breaking down?

take off the hrc black box. now. now... did i say now?

Originally posted by grain
take off the hrc black box. now. now... did i say now?

what?

Originally posted by grain
take off the hrc black box. now. now... did i say now?

OH? Whats the problem with it? I'll do that and see if anything changes... I was just leaving it on cause I figured it didn't hurt and it was already installed before I got the missing link...

Ok, to avoid the MS install since I don't think i can get it installed and tuned well enough for a 3 hour trip to college by the 3rd, I installed a new front o2 sensor and then a new map sensor but neither fixed the problem... What else could it be? could it be the rear o2? I havn't had a cat for 2 years and never had a problem...

Did you tr what Grain said?

yea, nothing happened.

Reset the ecu.

Originally posted by greygoose
Reset the ecu.

Done that many times. No change.

Any more possibilities other than Front o2 or Map? I've replaced the front o2 and the map, The problem only occurs once operating temp is reached. While its cold it runs perfect absolutely NO problems. I've removed the HRC black box thing also. I've reset the ecu after every change. I leave for school tomorrow... Would a bad rear o2 cause this? Its kinda important...

Replace your Coolant Temp sensor. Check and validate: Throttle position sensor, Idle air controller, and EGR functions. Check and make sure your thermostat isnt broken.

Well I've had a migrain for the past 3 hours and havn't been able to fall asleep for 2... then out of nowhere it hit me, check the coolant level idiot. So I did. The resevoir is bone dry and the coolant level is about 3/4ths the way up the upper radiatior hose at its highest point... please tell me this is my problem! I'll find out for sure when I wake up, that is if I ever fall asleep... However, I'm afraid I'm just having false hopes... But thats all that has changed since the last time it worked perfectly... I know it was full before... *crosses fingers* (oh yea I don't believe in that shit)

Originally posted by djtrickee
Replace your Coolant Temp sensor. Check and validate: Throttle position sensor, Idle air controller, and EGR functions. Check and make sure your thermostat isnt broken.

Ok I replaced the Coolant temp sensor and nothing changed. And the IAC is fine. I don't have an EGR. I checked my friends tps and mine with the ohm meter set on RX1K and on mine it went from 4 ohms closed to 1 ohms open. On my friends it went from 5 closed to 1.5 open. Does this amount of difference matter? or does that rule out the tps? AHHHHH WHAT THE FUCK???!!!!

Originally posted by CarbonFiberRST
4 ohms closed to 1 ohms open.

It should be way higher in resistance than that. There is 5 volts going to the TPS sensor, with 1-4 ohms of resistance it would be pulling between 1 and 5 amps, which is many orders of magnitude higher than any sensor should pull. Were you reading the multimeter correctly?

Also, do you have a datalogger? If you do, watch the value of EVERY sensor and look for something which is out of wack.

crank or cam sensor?

Originally posted by ner947

Originally posted by CarbonFiberRST 4 ohms closed to 1 ohms open.

It should be way higher in resistance than that. There is 5 volts going to the TPS sensor, with 1-4 ohms of resistance it would be pulling between 1 and 5 amps, which is many orders of magnitude higher than any sensor should pull. Were you reading the multimeter correctly? Also, do you have a datalogger? If you do, watch the value of EVERY sensor and look for something which is out of wack.

I think its the values I said times 1000. I said I had the ohm metter set on RX1K. does that mean resistance=X(1,000) x being 5 - 1.5 for my friends and 4-1 for my sensor? So its 5,000 ohms closed to 1,500 ohms open? I really don't know... I'm using an Electro-Tek multimeter from wallmart that cost $10. I had it set with the dial turned counterclockwise 2 clicks from the off position where it says RX1K and then on the Read out I'm using the numbers on the uppermost readout or whatever thats green and it ranges from infiniti-0.

EDIT: Also, I took the reading from the two upper most pins on the tps as it is mounted.

Originally posted by CarbonFiberRST
EDIT: Also, I took the reading from the two upper most pins on the tps as it is mounted.

Yeah, it sounds like you got the right value so chances are the sensor is working fine, but the resistance doesn't tell you anything about the wiring.

Originally posted by .bs0d
crank or cam sensor?

The engine would not run at all if either of those sensors were malfunctioning.

Originally posted by ner947

Originally posted by CarbonFiberRST EDIT: Also, I took the reading from the two upper most pins on the tps as it is mounted.

Yeah, it sounds like you got the right value so chances are the sensor is working fine, but the resistance doesn't tell you anything about the wiring.

Originally posted by .bs0d crank or cam sensor?

The engine would not run at all if either of those sensors were malfunctioning.

Ok, well can you offer any advice from what you've read in this thread? I'm clueless... There was no problem other than an oil leak. I dropped the bedplate and fixed it, then I put it back together and this problem created itself...

Like the new title says. I have MS controlling the injectors and once the car warms up I can't rev above 1500-2000 depending on which msq I load... This is exactly what it did before, it even goes lean (not as lean but 18.0ish or leaner) but while it was warming up i was able to rev it to 3k-4k rpm. Unbelievable...


EDIT: Could the timing cause this? I mean, it doesn't make sense, its fine while warming up then once warm it does this... (I've never verified the timing...)

I richened up the bins where this problem occurs and instead of it going full lean it will do the same thing but read in the 14afr range... So I guess it must be ignition related? Also, fuel pressure should drop slightly as vacuum increases? I have the aeromotive 1:1 and with the vacuum source is connected it is at 40psi at idle then drops some as I open the throttle. With out the vacuum source connected it stays right on 43psi at idle and when reving(I'm assuming this is correct).

How likely is it that I'll be able to figure out how have MS control ignition and fuel at the same time? are ignition maps as vehicle specific as fuel maps? the only sensors left to replace are the cam positioin and the crank position... along with the ecu but I'd rather save the money...

EDIT: The car idles fine with the MS I had it idling for 15min while I was fiddling with it... the afr goes from 14.5ish-15.0ish and the rpms stay around 950.

K, fixed the problem... I'm an idiot and it was the crank position sensor. So anyway, I guess it CAN run with that sensor malfunctioning. I know for a fact that it won't even get spark if its not plugged in at all. I guess this thread can die now. I drove around for about 15min and it needs lots of tuning but atleast its driveable.