G50: Rev limiter & smells like burning plastic

[ejXa q45]

my Q has seen better days , and in the pass month i have been working on it once a day for a few hours but this is the part that i can understand. the car is fine for the most part under no load in park and in neutral it revs up fine but in drive it will not go over 2000 rpm or so .it wants to but, cuts out before it dose it starts off real slow then it start to move and then it cut outs it smell like plastic burning and i see a small amount of smoke when the hood is opened maybe its the KN sensor or o2 sensor help me

if anyone had the same problems or knows whats going on please comment

[ejXa q45]

also i took off the throttle body and saw that the EGR valve tube that connected to the inside the intake manifold was clogged with carbon so i cleaned it out but still no luck

[Q45tech]

Rev limits below 6900 rpm, are some type of fail safe as explained totally and in detail in FSM.

First one measures the fuel pressure before proceeding to any diagnosis

What scares me for members is how really, really, really basic a 90-95 Q system is, I pray for members who have difficulty now in their future later model vehicles they acquire over the next 20 years.

It won't get easier.

Dual fuel injectors, dual spark plugs and coils, 100's of new sensors.

[maxnix]

One wonders why the most general amalgam of mechanical problems posted are without a history of maintenance?

Only the best maintianed cars have seen better days once they are shipped from the factory.

Must proceed in a well reasoned diagnostic regimen.

Fuel pressure vs. RPM graph due next.

[redmanfx]

Could also be the Throttle Position Sensor. Mine did the same thing at 3000 RPM. Check the codes, I bet it's either the TPS or knock sensor.

[texasoil]

The G-50 knock sensors will not turn on the check engine light before 96 models with OBD-II. They WILL set a code in th eECM memory and ity will slightly lower WOT performance and economy. Knock sensors will not cause driveability issues at all.

[qship96]

faulty knock sensors will NOT light up the MIL on 96 obd2 q either.

[bmwkiller]

...it will not go over 2000 rpm or so. ...it smell like plastic burning and i see a small amount of smoke when the hood is opened

I had almost the exact same problem, though my wouldn't go over 3000 rpm. Same smell of burning plastic too.Turns out mine was the crank position sensor. Appearantly, when I did the timing chain guides, I had unplugged the sensor and didn't get it fully connected again. The plug came off and suddenly I was limited to 3000 rpm. Plugged it back in and everything was perfect. The burning plastic smell went away too. I looked everywhere for something that was rubbing up against a belt or the exhaust, but found nothing. Never did figure that one out.

[elwesso]

have you checked your ECU codes????

[ejXa q45]

i do not think it there is anyi will check and get back to you i pulled a few connectors when running so had a few codes for the wires i pulled ..

[ejXa q45]

what page # is it on i wont to know more i have a 94 fms

Rev limits below 6900 rpm, are some type of fail safe as explained totally and in detail in FSM.

[ejXa q45]

i got a new maf from ebay. i installed it ,but i did not fix the problem well it fix it a little bit but not completely.i have a smoother idle but it will jump up and back down between 1000 and 1500 when i backed out of my garage then put it in drive hit the gas, but then the slip and tcs light went on... so i think i need a new TPS the q is still in fail safe mode an it will not go above 2000 rpm help i replaced all these things or cleaned them transmission coils packs plugs fuel filter cas maf cleaned throttle body EGR tubes and unit acc valve fuel system all visitable connectors

[ejXa q45]

tested the fuel line pressure today . it was about 35 psi after start up. and when i rev the Q up it hit 45 to 50 psi . i used a psi gage that i got from home depot and also pickup some fitting as well to make my own fuel pressure gage. it leaked a little but, all an all i think it worked well. next time i will use plumber tape to seal all threadsmy question is what is the psi supposed to be when runing and when rev up .

[maxnix]

It is probably specified in the FSM, but I think maximum is 43.5 psi.