1G New problem

[blaze12]

Ok guys now i have a new problem , when i start my car it idles a 3000 grand staying still then as soon as i let off the clutch the car idle jumps from 2000 to 2300
back and forth and back and forth . Does this sound like boost leak problem or do i need to adjust the TPS and ISC also i have put a new ecu in it and someone told me that 90 cars can only use 90 ecu is this true because i dont think mine is a 90 i think it is a 91.

 

[hyphyone]

sounds more like a vaccum leak

 

[blaze12]

well i checked pretty well for leaks

 

[Absit]

well i checked pretty well for leaks

What? Either you test for leaks or you don't.

 

[volcomsnow245]

Yea I was told the same thing I would confirm that with steve. That's his user name pm him he will know.

 

[vtec_ths]

Is your Fiav blocked off?

 

[scott90gsx420]

No 90's can use other ecu's the RPM gauge just wont work and i think you have to swap like 1 or2 wires for something.. I know one is to get the speedo to work idk if there is another one or not but the ecu's from a 91-94 will work in a 90. I can only suggest you google it cant tel you too but ya google and the search button are your best friend man this has been covered several times.

 

[steve]

Yea I was told the same thing I would confirm that with steve. That's his user name pm him he will know.

Or you could search my posts to see if I've said anything about running 91+ ECUs in 90 cars before.

Or perhaps what I might have written about idle surge, or boost leaks, or fast idle.

 

[blaze12]

I know that you have to do stuff to get a 91 ecu to work in a 90 car but is what is happening to me , would that happen from putting the 91 ecu in . Because then ill just go find a 90 ecu.

 

[scott90gsx420]

No ive never heard of that happening from the ecu swap.. Its one of the things you think it is .. But i can garrentee its not from having a 91+ecu in it.

 

[blaze12]

well could the ecu be bad , im thinking about just rebuilding my old 90 non eprom ecu. Does anybody know who rebuilds them well?

 

[snowborder714]

ECMTuning, Inc.

 

[blaze12]

yeah i sent them an email just wondering if there is anybody else that will do it. Also does anybody know what ecm charges for a rebuild and can you tell them what you want rebuilt or do they just replace everything?

 

[snowborder714]

It all depends on how much they charge by what is wrong. In the link I showed you, it tells you they charge by blocks of 10 minutes. Once they receive your ECU, they'll look it over and test it, and then will get back to you on what needs fixed. This way you have an idea if it's worth it to get it fixed or not.

Sometimes they can diagnose some stuff (leaking caps, blown drivers, etc.) via pictures, so that may be a good way to start.

 

[doayamaha]

you need to know if the ecu is from a 90 and or if your car is a 90 what does it say on the door tag. if you can't find either one, go to vfaq put bullet connectors on the 2 wires it tells you to switch, if it will fix the problem then good if not switch them back.

 

[scott90gsx420]

He knows about that man hes wondering if the ecu could cause excessive idel.. The two wires that need to be switched just make it so the tacho. meter works..

Also if rebuilding the 90 is an option do that there really hard to come by anyways..
Ive got a stock 90eprom that had all the caps and stuff changed in 2003.. Says so on the thing and you can see on the outside of the ecu case where it like burnt internally or something. And my tach still doesn't work .

Back on topic yes the ecu being bad could cause those issues.. But id try the other stuff first just to try and save money. If they all check out then its probably another faulty ecu.

 

[steve]

The two pins that need to be swapped anytime you cross the 90/91 threshold are 6 and 14. One is for the Idle Position Switch and the other for the MAF reset.

Needless to say feeding the ECU the IPS signal on the correct pins is critical to make the car idle correctly. On the other hand, even without the IPS working the car won't idle that high unless too much air is making it bast the throttle butterfly. That could be a leak, bad FIAV, bad ICS, or misadjusted BISS. All things discussed in many threads on the site and there really isn't anything new to say.

Even if the IPS signal is going to the right pin that doesn't mean it's working. It's common for people to forgot to reconnect the throttle body ground strap and without a good ground to the TB the IPS can't pull the bias voltage from the ECU to ground.

I've already told the OP how to identify exactly what ECU he has and a quick check of the VIN or looking at the door pillar and remembering that anything after the start of June 1990 is a 91 model year or later.

 

[blaze12]

well would a bad cts or 02 sensor do this . It also has a really unresponsive throttle response i mean when its bouncing back and forth between 2000 and 2300 i give it gas and it stays at the same rpms and then if i floor it , it will go up in rpms but after a couple of seconds. Sounds like TPS to me but i replaced that today and no help.

whats IPS signal steve?

theres a ground strap on the tb?

 

[steve]

whats IPS signal steve?

Try using the search.

theres a ground strap on the tb?

On a 91+ car

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On a 90 car

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[blaze12]

If i dont have the ground will these problems happen?

 

[steve]

Unsubscribing

 

[blaze12]

I understand that with out the ground the isc wont get its voltage sent back to the ecu but will that cause the problems Im having?

 

[AWDtalonPt2]

I had this same problem on my 2g. I rebuilt the throttle body and all was well. Not that it will work for you, just an idea.