I'm going to post this in Audio & Electronics and Engine Tech. The reason is because the problem crosses electronic and engine tech issues in my opinion. If I'm wrong. So be it.

BACKGROUND
I'm a fair mechanic but I stink when it comes to electrical or wiring issues. I'm an electrical klutz.

I purchased a 94 GSR 4-dr to use as a daily driver. I was aware that it had some mechanical issues when I purchased it but I totally missed that it had some electronic (wiring) issues.

I've repaired all of the mechanical issues (frt rotors, pads, rebuild calipers, replace half shaft bearing, replace CV, etc.) except an intermittant misfire that occurs from time to time when the ECU is in closed loop (slow traffic). I replaced the rotor, coil, cover, o-ring, wires, wire loom and plugs (iridium IK-20). The problem persisted in slow traffic. I swapped out the MAP with a known-good one and the problem still persists.

I was intent on swapping the TPS as a next step when I noticed that my dome lights would not work. Then, I noticed that when I put both of my dome light switches into the ON position, the "Open Door" warning light comes on in the gauge cluster.

The only electrical work done to the car by the prior owner was an after-market radio put into the car by Mobel Tel.

SITUATION
I'm sure that the issue is engine management and related to a sensor failure or sensor wiring. However, I need to assure that the integrity of the wiring in the car is good before continuing to chase after the intermittant engine problem because the wiring itself could be the issue.

QUESTIONS
Is there a device that I can buy or rent that will allow me to test out the integrity of the wiring harnesses?
If it's a long and drawn-out test, I'd like to consider replacing the harness. Are these readily available?
Is there anything else that I ought to consider?

 

The thing to get is a multi-meter. Anywhere from $20 RadioShack to $200 Fluke. But then you'll have to learn how to use it.

You say you're a fair mechanic, so it can't be too hard. You just have to verify that any particular wire actually goes where it's supposed to go, isn't disconnected somewhere in the middle, and it doesn't touch any other wire or the chassis.

You'll also want the wiring diagrams for your car. Helm manual...

The engine management shouldn't have anything to do with the dome lights or the door-open warnings. Maybe those problems are unrelated, but it just means more than one electrical thing is connected where it shouldn't be.

 

Jim,

Thanks. I'll go by Radio Shack after work. Fluke can wait for a much brighter and richer guy than me.

Great minds think alike. I just went to Helms site before I got your response and ordered the 1994 book. Not cheap at $64 plus shipping, huh?

I did not think EM would be linked to the dome lights but thought that it might be indicative of some generic harness error or failure as you indicated.

Thanks for the help. Please come back if you think of anything new.

 

hmm....I don't think that the dome light problem is directly related to your engine problem but possibly a harness got crimped agains something and is getting crushed or something along the lines of that. If anything I would suspect that the problem lies in the interior harness because you mentioned the problem with the dome lights.

And going through and checking every single wire on your harness is gonna be a bitch, though replacing the harness will be a bitch too, and very costly on top of that.

Could you explain the this miss fire more, like under what conditions does it happen?

And hey those fluke meters are the shit, I have one,

 

I've got a tiny little $20 RadioShack one that I can throw around or take with me just in case.

But I like my Fluke 179... They both work, but it's like putting down your $3 department-store ratchet wrench & picking up a SnapOn.

Helm manual is pricey, but it's got a lot more detail than the $12 Chilton/Haynes/whatever...

The domelight problem isn't directly related, but it's a hint about what condition your wiring harness is in. Finding breaks & shorts is a PITA, but you're stuck with it unless you want to junk the car. You'll find the Helm book has pretty detailed troubleshooting stuff for any component. You don't have to really understand electricity; it'll tell you where to poke the leads of your meter.

You'll also want to get some other stuff like wire, alligator clips, & a handful of connectors. You might have to make up some jumper wires to do some of the tests.

 

My reply to Eddiebx did not post. Why?

Well here it is.
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Eddiebx,

Sure, I'll elaborate.

Let's say that I'm commuting to work and I've been driving on a State highway at an average speed of, say, 55 and I've encountered, say, 2 stoplights. When I come to a traffic backup and will have to inch forward for, say, 10 minutes, my car will not accelerate normally. It hesitates and balks. In order to accelerate, I must push the pedal to WOT or nearly WOT where it will then accelerate as though nothing was wrong at all.

This makes the problem look like it only appears in closed-loop ECU operation and not in open-loop.

Sometimes this condition will persist until the end of the commute and sometimes this condition will only appear for one or two back-ups and then end. The only consistent characteristic to date is that it never appears at the outset or in the first few minutes of driving. It seems that the motor must be at full temperature for it to manifest itself.

So, I'm inclined to believe that it's related to one of the sensors, wiring or the ECU in the engine management system.

The reason that I first tried a known-good MAP is that I once had a similar problem in my track car while at Road America. Replacement of the MAP fixed that problem and saved that weekend.

Next on my suspect list is the TPS but the dealer is telling me that I need to buy the whole throttle body for $700 because the TPS does not come separately. Looks like I'll have to get myself over to the junkyard to find one.

 

After reading my reply to Eddiebx, I'm now thinking that it could be the ECT sensor since it only manifests itself at normal operating temperatures.

I've got a Helms manual on the way. As soon as it gets here I'll locate where the engine coolant temp sensor is and test it for resistance and voltage.

 

Two things.

I don't understand why it is not throwing a MIL light from the ECU.

Finally, I just called my local junkyard about a throttle body. They want $250, will not separate and I have to pull it. Do you believe that price?

Is there a compatible TPS that I can take from a Civic or something to swap out the existing one?

 

hmm....one thing I would check right now is the output voltage of the TPS. At closed throttle it should be like 0.5v, and at WOT it should be 4.5V. Check that just to make sure your getting a good reading, and also make sure the voltage increases linearly, not that there are spikes as you increase the throttle angle. If the voltage is off, you can actually adjust your TPS by slotting those rivets that hold the tps onto the TB and rotating the TPS. I believe the middle wire is the sensor output wire on the plug.

Other sensor that I have found to cause that sort of mysterious bogging would be the IAT, and the knock sensor, if you happen to have a spare one laying around it might be worth a shot to swap out. I don't believe the ecu makes any major corrections based on ECT but I could be wrong. But I do know the IAT and the knock sensor have correction tables.

One thing to keep in mind is, sometimes when you have a bad solder joint, the continuity of the joint will deteriorate with respect to temp. For example I have had a bad solder joint on my IAT wire and I would throw an IAT code every time the car warmed up, I couldn't find the problem for months till I realized that it could be the joint itself. Just a few things to keep in mind while troubleshooting.

If I think of anything else I will post, sorry I am in the middle of studying for a big exam,

Oh yeah I forgot, you can use mostly any honda TPS off of any car, so I would suggest you go find yourself the cheapest TB and pull the TPS off that.

 

If you decide it's a TPS/throttle body issue I have a GSR TB at my house... someplace. Came off my car, so I know it's good.