idle and rev drop issue

Hello all.
I have a '93 3000GT VR4. the last 2 days it's been acting funny. after driving it for about 15 minutes, parking it, then going to drive it again 10-15mins later the car wont start right away. it'll start, idle irratically (300-1,200rpm) and then die a few times, unless it rev it to 2-3k for a few seconds, but after that it still revs in the 300-550 range.

also

when i was in my car a second ago, I reved it to 2000rpm and kept it there, after a second or two it would drop to 1,500 and then back to 2,000. it did this for like 5 minutes straight before i came inside. Ive noticed this before too but always figured it was just because it's turbo'd and they work a little differently. i noticed my a/f guage will fluctuate with this too. the guage drops to nothin when it drops to 1,500 rmp, then regesters again back to 2,000.

things to know about the car

in the last 500 miles it has had the following work done:
-new thermostat
-new harmonic dampener
-new timing belt
-new T-belt tentioner
-new accessory belts
-new fuel filter
-ran fuel system cleaner through full tank of gas in the 300 miles


does this look like i need a new fuel pump? when i go full throttle 1st-3rd gear, it runs rich between 3k and 6k (havent had it over 6k yet) so i know the current pump can deliver when it is pushed. Any suggestions?

I had the same problems. My ecu went, got a new one and this problem stopped. I also replaced the fuel filter but that had no effect. And I just replaced wires and plugs b/c the engine was sputtering, the wires were the problem there.

I took my car to a dealer and paid $90.00 for them to tell me that it would cost $1,400.00 for a new ECU to be installed. So I went to Autozone and ordered myself an ecu. When it came in it took me no longer than 15 minutes to stick her in and go about driving.

Could be your TPS too.

$1,500 for a new ecu?!?

that's alot... considering i just bought the car and put $700 into it already for repairs.

anybody parting out a '93 VR4?

yep, thats to cover labor and $400 for the warranty on it. Yea its b/s but thats a dealer for you. By the way the ECU was $209 at Autozone

o good. i thought u meant the ECU was 1,500. I dont mind installing myself. thanks for clearifying.
-Josh

Well could be as simple as an IAC (idle air control)...can't just jump right to ECU. That's always the last resort.

Make sure your MAS sensor is plugged in (wouldn't run w/o it so it probably is), make sure there's no bent pins on the connector.

My first thought would be IAC, it's basically what controls idle and it seems to be a common problem with these cars. They go for $30 used on Ebay, which is where I bought mine, which fixed my same problem. Autozone wanted $200+.

The engine shouldn't rev itself back up to 2000 RPMs turbo or no. Could be ECU, more likely IAC.

another issue now. today when i was driving too and from class, when i coasted with clutch all the way to the floor, and in/out of any gear it rev'd itself to an idle of about 1,800 and when i stopped moving, it would drop back to normal (~600) I will be looking into this all this weekend. thank you all for your help.

-Josh

Sounds like the same issue to me...but this time sounds more like the ECU is confused...

this is nuts. it's beginning to really worry me.

I pulled the IAC, cleaned it well, and reinstalled it. also, while I was in there i pulled the Y-pipe off my stock BOV for a little more volume...

now i finished up and started it... everything sounded perfect, it was prrring like a kitten. pulled it out of the drive way and went down the street. but now when i let off the GAS it runs super rich! I have augogauge electronic Phantom series A/F guage.. it went FULL RICH... but it only runs rich for a few seconds. while it's running rich, it's also running 2.5k RPM now in NEUTRAL. So i watch the mixture because i'd never seen it soooo high (not even when i hammer on it @5k) and it slowly works it's way stoich and then lean and then almost nothing and now the idle is around 300RPM and i have to give it gas to keep it from shaking me to death and dying. I drove it around a little bit and noticed a few things:

1: It revs high (2-2.5k) when neutral until I drop to 10MPH, then it idles really low. (something enguages at 10mph perhaps?) it did this at 10mph on the dot the 5 or six times i tried it.

2: when it's idling high, I think i can hear something adjusting in the engine bay, the sound corosponds with the mixture and RPM changes.

3: after the idle drops to 300 range, the lights dim as it's about to die, and sometimes it would run itself rich again to recover but it'll jump around a bit.

4: when it is idling high, and the mixture drops to lean, i cna tap the gas the littlest bit and it runs really rich again but the idle does not change much.


all this time i can't help but think it looks like it's running a shitty program or something because everything happends the same every time. I dont understand why, if it's this funky, it does the same thing every time. (the 10mph idle drop, very pattern-like mixture fluxuations)

I only hope it's nothing too spendy... if it is my rents are gonna take it (they loaned me the cash instead of a bank) and sell it and get me some shitty cavalier... that's not acceptable but the cost of maintaining this thing is gouging me deep...

anybody want to buy a '93 VR4? $7,000 and it will drive home with you just needs some love. i'll even throw in the $2.5k system.

Okay, don't jump to selling it yet.

First pressure test your intake. Fix all leaks, make sure all pipes are securely attached, and all vaccuum hoses are attached in their proper locations. Do a visual inspection of your MAS plug and MAS for loose connections or damage.

Then unplug the battery for 10 minutes and let the ECU reset itself.

A few questions, did this start out of the blue, or did it happen after somebody did some work on teh car?

When was the last time you changed your plugs, which plugs did you replace with?

When was the last time you changed your fuel filter?

What is your mileage at now?

i;ve only owned the car for a month. it runs great for a couple days, then somehting happens. I replaced the fuel pump less then 300 miles ago w/ oem one from dealer. when i got the car, everything went to shit. I am guessing the 120k was never done because everything on the 60list has gone to shit in the last month. I replaced the thermostat last weekend, and it ran fine for 2 days, then i started with the starting/stalling issues. then the next day it was revving high at idle while moving and now it's doing that to more of an extreme. I have 150,000 miles on the car. I also don't think the plugs and wires have been changed since their original 60k because nothing else was changed. i took the battery off all night and hooked it up today and it's doing the same. triple checked all my hoses (even tore it apart and put it back together again just to make sure)

I mentioned i removed the y-pipe from the Bypass valve (bov). I was told this wouldn't be a problem but ever since I did this it's been running rich too but as mentioned, i already checked everything I can. right now I am gonna go pull the ecu and inspect for damage. hopefully the caps are shit because i already have the equipment to make quick work of it. Thanks for helping me out. I know i need to do plugs and wires but frankly, w/ the $1k of repairs I've already done and the fact that i just bought the car... I'm broke and I can't ask my rents for money because they will not hesitate to take it (they are less patient with these things and my dad hates imports so he's begging for a reason)

-Josh Evans


I just took the ECU out and inspected it. no leaky caps. the thing looks new inside. no smells or anything. on now to the mas, reinstalling the BOV y-pipe and checking everything... again.

as far as running rich was it doing it that bad before you moded the BOV,I know in my talon that the BOV was routed into the intake and the computer would tell the car when the BOV opened and would close off intake from outside air I don't know if this applies to your car or not but that made the talon run real rich sometimes

i put the y-pipe back in. now the idle is a little low (but i'll adjust it as necessisary) now i dont run rich, but i run lean. and it stumbles under mid-full throttle a bit... feels like a ton of lag... but it doesnt rev high anymore, and it doesnt run rich....

so before it was all too rich and too high... now it's too low and too lean.

CRAZY CARS

EDIT - It did not run rich before i removed the pipe. also i found the rubber gasget thing on the throttle body from the intake tubing was half-stuck in the tube ... it was a biatch to get on propper.

Well there you go. First off you have a MAS so you can't run an open BOV without a fuel controller or you will run rich.

2) that gasket was off, causing a boost leak -> erratic idle.

You can do a visual inspection all you want, but until you pressure test you wont eliminate all your boost leaks. I feel for you on not having the money to maintain teh car, but plugs aren't all that expensive, go to Napa and get some NGK coppers for around $15. If money is an issue, stop buying parts at the dealership, the prices suck, the work sucks, everything about them sucks.

All the parts for the 60k can be found at www.thepartsbin.com for $300-$400

Anyway, pressure test and change your plugs, I think it would make a difference.

Oh yeah, you mentioned you had an A/F guage, if the problem persists, can you try and mention how rich/lean it goes. Some numbers might help. Good luck.