Rpm Limit

[datbmac]

I have looked up here and haven't found what my issue is so here goes. Today i finally finished up putting my car back together. Then comes the issue; at idle runs fine no loping no surges, but when you apply about quarter throttle, rpms starts to surge and at full throttle it hits a wall at 2500 and won't go any higher. Need some help please. The only mod is an Apexi N1 turbo back.

 

[95TalonOwner]

Did you do a boost leak test?

 

[Bud92gsx]

Did you do a boost leak test?

+1 boost leak

 

[Dhan]

Off topic, but what is the normal idling RPM for a stock turbo'd 4G63, assuming there's no problems or vacuum leaks?

 

[GsXdSmKingGsX]

off topic, but what is the normal idle rpm for a stock turbo'd 4g63, assuming there's no problems with vacuum leaks?

800-1,000

 

[Dhan]

800k-1,000k

Interesting. Mine always hovers around 1,100.

 

[datbmac]

Ok I will do that when I get back to the shop tomorrow.

 

[DSMTyson]

Interesting. Mine always hovers around 1,100.

Turn your BISS to get your idle where you want it. Assuming you have no boost leaks of course.

 

[Absit]

800k-1,000k

My tach doesn't even go to 800k.
Desired idle speed in a M/T is set to 750.
Don't just start turning the BISS (the second S stands for "screw"), adjust it properly.

 

[Dhan]

My tach doesn't even go to 800k.
Desired idle speed in a M/T is set to 750.
Don't just start turning the BISS (the second S stands for "screw"), adjust it properly.

I don't have the shop manual for my '90 yet. Is 750rpm what it says? There's actually a good article on vfaq about the BIS screw that I was looking at, not sure if that's the problem though.

Sorry to jack your thread OP.

 

[Luis77321]

it could probably be a sensor... i dnt know which one it is.. my buddy had the same problem..

 

[datbmac]

Today i am somewhat closer to the problem with the maf unplugged it will rev to the limit but with the sensor plugged in it gets to 2500 and surges. Soo right now the problem could be the sensor so I'll get another to test and see how it goes.

I don't have the shop manual for my '90 yet. Is 750rpm what it says? There's actually a good article on vfaq about the BIS screw that I was looking at, not sure if that's the problem though.

Sorry to jack your thread OP.

It's cool I want to learn as much as possible

 

[datbmac]

will a knock sensor code cause the above symptons

Will a knock sensor code cause the above symptons?

Problem solved maf gettin another soon I hope.

 

[datbmac]

Well i got the mass air flow but it didnt solve the problem. I didnt know what else to do so I started rechecking the mass air flow connector and I was checking for power on the pins in the connector and saw that i didn't have power on pin 7 of the connector. So I got a wiring diagram and saw that it leads to pin 16 of the ecu. Then I went to the ecu and backprobed pin 16 and had no power there either so I took the ecu out of the car and started ohming the resistors on the main board and they all checked out so I started looking at the ecu part numbers and saw that the ecu I have is md166260 which is out of a 91 fwd turbo. Does it matter about the ecu or do I need a 90 awd turbo ecu?

 

[Gasolinebaptism]

That is really goiong to make the difference to an ECU more than AWD/FWD is AT/MT.
That ECU will work fine in your car, the only modification needed to have it in your car would be to swap pins 6 and 14 on the harness side... I believe those two anyways.. But considering that your car starts, that's already been done.

This people telling you to do a boost leak test aren't joking.. Here's an easy one.
Fire up the car, let it idle on vacuum, grab a can of starting fluid and spray it on the intercooler couplings where they connect with the pipes. If the RPM's increase at all, you have a boost leak at that spot.

 

[datbmac]

The ecu is an automatic because it has the numbers e932 on the eprom. Didn't notice until I actually looked at the eprom.

 

[Geier]

Boost leak/bad ECU.

 

[Gasolinebaptism]

The car is still going to run. And it shouldn't pack at 2,500. even though it is an auto.
Have you done a BLT?
Put the ECU back in and run the test I outlined for you.

 

[datbmac]

Ok maybe I should give a detailed update of my car situation there were numerous problems to begin with first was the head gasket fixed that then was the no start which I kind of fixed that have to get a relay. Then was the rpm issue; at first you had the feather the throttle to rev but I also had a wiring problem that caused the parking lights to come on when the dome light fuse is plugged in at the same time. I fixed that and now it will rev up without feathering the throttle but under light throttle it will do the rpm surge thing but the car will run with full power and boost just won't rev under light throttle and trying to ease off under light throttle it will buck and jerk really bad as soon as it gets to 1500 rpm; and if there was a boost leak wouldn't the car run super rich and not have full boost.

 

[Gasolinebaptism]

Well the turbo can also easily suck way more air past the MAF then it's designed to read, and without other tuning software you'll hit fuel cut.
Just go buy a can of starting fluid and do that test. It'll take 5 minutes. Get the easy stuff out of the way.

 

[GettinPaper]

This happened to me bro, my car would run fine, and when i would drive her she would not go above 2500rpms and would just idle surge badly. She wouldn't go anywhere.. first thing i did was replaced my ecu with an eprom from a MT AWD 91. And fixed her perfectly Check your ECU and see if it needs to be replaced.

 

[Gasolinebaptism]

It's one of two things. a boost leak or an ECU. I'm simply saying the BLT will take 5 minutes and there's a lot less hassle than buying a new ECU. Not to mention it's cheaper as well.

 

[datbmac]

Ok I will do the boost leak test but it will have to wait until next week because school is out. But in the mean time should I get go ahead and get another computer to absolutely make sure that its not me problem too?

 

[stojo07]

I have looked up here and haven't found what my issue is so here goes. Today i finally finished up putting my car back together. Then comes the issue; at idle runs fine no loping no surges, but when you apply about quarter throttle, rpms starts to surge and at full throttle it hits a wall at 2500 and won't go any higher. Need some help please. The only mod is an Apexi N1 turbo back.

I know you said only mod is an Apexi N1 turbo back but do you have any sort of air/fuel adjustment? If you have the APexi s-afc then you may have the wires switched around. If you do you should be using the pink and orange instead of the yellow and white

 

[datbmac]

No I don't have any type of tuning on my car as of yet. I guess the main thing about the ecu wiring is checking to see if every one is in the right place.