2G FI Help

C

C. Ludwig

New member
Here's the problem:

Car ran great next to last event last year. Then stored the car covered outdoors for two weeks before going to Gateway for our last event last fall. It rained some while the car was stored. It did not get directly wet but there was alot of moisture in the air and condensation everywhere. We trailered the car to Gateway in a downpour on an open trailer. And then it was drizzling the first morning.

So we start the car Saturday morning in St. Louis and it fires right up and settles into idle. I let it sit for probably 15 minutes warming up (temps were in the 40s) while I was getting dressed. I grab the bellcrank on the throttle body to rev it and clean it out and it lean bogs and dies. Fires right back up and when I try to rev it it just leans out and wants to die. Can slowly rev it to about 4k but it misses badly. Open the throttle quickly and it bogs and dies.

Ohm checked:
air meter
TPS
injectors
wiring harness that runs from computer to injectors, OMP and CAS

Swapped known good parts:
both coils
plugs
wires
CAS
computer
fuel filter

Short story is we worked on the car for 8 hours in the rain at Gateway that miserable day for nothing. Packed the car up, got drunk and went to see Jackass. I've been in the process of moving all winter and the car has been in covered storage since we got home. I was hoping (no real expectation) that the problem was related to the moisture and would cure itself when everything dried. Yeah right! I can dream anyway. Well we get the car out for annual tech Saturday (in the rain no less!) and it still has the problem. In my mind it has to be electrical and it has to be fuel related. The injectors were rebuilt and flowed last year and they ohmed out good when we checked them. We had a clean fuel filter but swapped in a new one just for kicks. Pressure is good. I'll be in my new garage soon and will be able to really have at it but would like to get some ideas before. Anyone???? Thanks!

Chris


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Chris Ludwig
08 ITS RX7 CenDiv
 
Chris,
Sounds like you've checked most everything!
Just a couple thoughts,
I'd check the variable resistor
Water in the gas
Did something crawl up the exhaust and die
Air flow meter resistance through the full motion of the flapper
Test light setting of the TPS

Good luck, and let us know what it turns out to be!
B
 
Bad fuel is a possibility. My first go-kart racing experience was cut short in much the same way due to water in the alcohol. Hmmmm. Will check.

Chris

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Chris Ludwig
08 ITS RX7 CenDiv
 
I have had the same kind of issues with bad fuel.. Made no sense, but when I stuck the pick up line into a jar of okey dokey fuel, viola! problem solved. Then I looked in my tank..........!

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Stop it! You guys are getting me excited.
biggrin.gif
Guess I'll find out Friday when I can work on the car.

Chris

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Chris Ludwig
08 ITS RX7 CenDiv
 
What year 2nd gen. If it has the electronic OMP then i would check or replace it. It sounds like it has failed and is going into limp mode.
 
It has the S5 setup with the elctric OMP. I've been through the OMP limp mode deal and that was different. When I first put the car together (started as an S4) I didn't connect the OMP. Took me days to figure out why the thing wouldn't rev. This is different though. When the OMP was unplugged it would rev but would miss badly. Now it won't rev under hard throttle at all. If it's not the fuel then I'll ohm the OMP to eliminate that.

Chris

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Chris Ludwig
08 ITS RX7 CenDiv
 
Chris,
Check the solenoid resistor.It's part of the injector control wiring. It sits below the AFM. Could have gotten soaked when hauling in the rain.You might put a timing light on it and check the ignition advance.
Good luck
B
 
I assume you've pulled the codes?

What the heck does S5 stand for? Never heard this designation before.

Jeff
 
Haven't pulled the codes. Don't have the neccesary equipment to do it, meaning I don't have a cluster in the car to use the SES light. Base timing is good and there isn't a resistor pack on the S5s.

S4 designates the 86-88 models and S5 the 89-92s. S1-3 is used for the 1Gs.

Chris

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Chris Ludwig
08 ITS RX7 CenDiv
 
Originally posted by C. Ludwig:
Haven't pulled the codes. Don't have the neccesary equipment to do it, meaning I don't have a cluster in the car to use the SES light.
Click to expand...

Before I realized the SES light flashed the code I used and analog volt meter in the test connector to read them (An LED with a 100 Ohm ressitor would do it as well). I assume you had the power disconnected as I once went through several sessions before realizing I had uncleared major codes(I think do to a compression check). Unplugged the power for 5 seconds and the car was back.

Jeff
 
Opps, Better make that a 1k ressistor to limit LED current to 10-12 mA. The green test connector has 12V power (black/white) and code number ECU 1F (yellow/black).

12V -////(1k Ohms)------(anode) LED (cathode) -----ECU 1F

LED will flash slow and fast for 10's and 1's digits.

Hope this is clear - Jeff
P.S. if not [email protected]
 
Thanks Jeff. And everyone else. At least I have a direction to look now. Have been pretty put out by the whole thing. Will let you all know what I find out today. Cross your finger!
biggrin.gif


Chris

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Chris Ludwig
08 ITS RX7 CenDiv
 
Well, swapped the fuel, and tested the OMP and no dice. Because of time constraints that was all I could do last weekend. We have Saturday set aside to figure out the problem. Gonna start all over and check everything from top to bottom. Geez!
smile.gif


Chris

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Chris Ludwig
08 ITS RX7 CenDiv

[This message has been edited by C. Ludwig (edited March 07, 2003).]
 
Chris,
I don't know much about the S5 ,but here's a few things I'd try!
Put a timing light on both leading plug wires and look for a consistent spark as you open the throttle. You can check the the advance above idle at the same time. You can check the fuel cut from the TPS sensor. Maybe the fuel cut is stuck? Check the AFM ohms through the full movement of the sliding cone with the factory spec..Check all the connectors in the FI circuit.Relays? What do the plugs look like? Wet or dry? Put a vacumn gauge on it and check for a big leak.Could your fuel test port plumbing be messing you up?
good luck,
B
 
Just a quick thought, my first guess would be TPS. I/ve had them Ohm out OK but not be worth a damn. Use a screw driver or rod to listen to the secondary injectors. These should come on around 5000 and above while reving. TPS problems will easily keep this from happening.

Jeff
 
Well...hmmm. Started all over yesterday. Checked everything. Put new plugs and wires in it just because it was time. Deccided it's definetly a fuel problem. Everything checked out. Car still did the same thing. But the more we ran it the better it got. Currently it's cured for the most part. Still stumbles a bit below 3000 which really isn't much of a problem. So it just cured itself? We're pretty stumped and can only assume it was bad fuel that is finally being purged. ODD!

Chris

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Chris Ludwig
08 ITS RX7 CenDiv
 
Solved! OMP sensor. Actually the stepping motor of the OMP seems to have frozen in place. The stepper motor actually ohms out good but it was stuck in the low volume position. Since I'm running pre-mix anyway I pulled the sensor and wrapped a zip tie around the plunger and viola!!!

Chris

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Chris Ludwig
08 ITS RX7 CenDiv
 
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