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Discussion Starter #1 (Edited)
Hello, I'm new to the forum, and a new owner of a 91 MR2 NA. When I got the car I was thinking it would be a fun project car, but she is driving me nuts. I was hoping someone might be able to help me, so here goes...

The car will start and warm up. Once it is warm it sounds like it will occasionally miss. The tachometer also seems to read low. I found the idle is supposed be be at 750-ish but is reading around 500 cold and 250-ish warm. I was able to eventually pull Code 14 ( No IGF Signal to ECU, 9-11 times in succession). Since it had a problem that I wasn't completely sure of, had 200k miles, and had been sitting a while I did the normal tune up items. I replaced the spark plugs, wires, distributor cap, rotor, and ignition coil. I also replaced the igniter since I saw in several other posts that it could be the issue. Sadly the issues remain. So I dug up the BGB that was recommended on other Code 14 threads, found the wiring diagram, and tested everything for voltage/continuity that it should have. I didn't find a problem so i went ahead and ran a new IGT and IGF wire from the ECU to the Igniter just in case. no change. the tac still reads low and it is still occasionally missing. i ask around my local area and was able to get my hands on an oscilloscope to check the signals on the IGT and IGF. Sadly it is an old one so I don't have the ability to record and post the graph. The oscilloscope showed that the signals were being sent the majority of the time but occasionally I would not see the IGF signal. After a few times this causes the car to miss, which I assume is the ECU shutting the injectors for a cycle but then the IGF comes back and it turns them back on.

At this point my only other idea is something is wrong with the distributor signals to the ECU since the TAC isn't reading correctly. I have read that if the TAC is slow to respond that it could be a capacitor in the TAC but it responds quickly and has a lot of travel when reeving the engine so i think the cluster is fine. I just don't think it is reading correctly as it doesn't sound like only 250 RPM at idle. I know that the igniter provides the signal to the TAC but the igniter only receives signal from the ECU which in turn gets it from the distributor. I tested the wires on the distributor and they tested fine and I pulled the distributor and tested the resistance of the pickups. Everything tested within specs and wires tested good with no shorts to ground that my MM could find. The distributor did have oil on the back of it though so I replaced the o-ring on it in hopes to stop that leak. Tested the car again and still no change. TAC did seem to read a bit better at first but then went back to low. Could oil cause a disruption of signal with out throwing a Code 12? (no NE or G signal to ECU within 2 seconds after engine has been cranked) I noticed that the shielding on the wires from the distributor are also messed up and its still leaking oil, could that cause it?

I'm out of ideas at this point other then just replacing the distributor to see what happens. If they weren't so expensive I would but the auto shop has them from $150-$300 depending on refurb or new, and at this point I'd rather not just throw more money at it.
 

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Discussion Starter #2 (Edited)
so i ran a temporary wire setup to the distributor and ecu but nothing changed. besides a new distributor i'm out of ideas.. i was able to get a video of the oscope. its a little hard to watch due to the way cell phones record video and the oscope screen works but it is visible what is happening if you watch it the top line is the command signal to the igniter/ IGT taken from the pin on the igniter. the bottom line is the return signal or IGF to the ecu taken from the ecu pin. you can see the problem by watching for the bottom line to go solid. below is the link to it on youtube. Any ideas what could cause it?

https://youtu.be/Mu10CbNVxg4
 

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it appears that it was the ground wire from the coil to the igniter had an issues even tho it checked out on the multi-meter. ran that directly to the coil and is running a lot better went on a test drive today and had only one misfire. but no code was thrown. i believe that is due to spark plug gap. the tool i have doesn't go small enough. Will pick a feeler gauge set and fix that this week and test it again.
 

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On another note, since your car has been sitting a while as you mentioned, you may want to consider draining/doing a flush if the gas tank. There is a drain plug to do so. The reason I mention it is my latest MR2 had been sitting for about 4yrs and the filter on the fuel pump had decintigrated and there was a rediculous amount of rust in the tank.
 

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The code is telling you no IGF signal, and that is what the problem is. This is the ignition verify from the ignitor. The wiring itself is not usually the problem unless it is damaged. The connectors are more likely. Separate them all, look for dirt and corrosion, and make sure the contacts are bright and have spring tension. The other possibilities are that the ignitor or ECU are not processing the signal properly. I understand that you have already swapped the ignitor, but you should make sure that it has the proper ground to chassis. I don't think that the plug condition figures into this, because the ignitor is only indicating that it generated a signal. If everything else fails, you can replace the ECU and see if that makes a difference.
 

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Discussion Starter #6
Took the car on a drive today and she ran great while she was cold. about three quarters of the way to work she started missing and continued to get worse untill i got to work. same issue on the way home worked fine when i first started and for the first 4 or so miles but the farther i went the worse it got. about about mile 15 she stalled on me. i was able to start it back up and get home but with bad misfire. i checked for codes when i got home even tho the light wasn't on and 14 had come back.

On another note, since your car has been sitting a while as you mentioned, you may want to consider draining/doing a flush if the gas tank. There is a drain plug to do so. The reason I mention it is my latest MR2 had been sitting for about 4yrs and the filter on the fuel pump had decintigrated and there was a rediculous amount of rust in the tank.
i originally thought this might be an issue but with everything else i have done i don't think it is. when she is cold she pulls fine all the way through the rpm band.

The code is telling you no IGF signal, and that is what the problem is. This is the ignition verify from the ignitor. The wiring itself is not usually the problem unless it is damaged. The connectors are more likely. Separate them all, look for dirt and corrosion, and make sure the contacts are bright and have spring tension. The other possibilities are that the ignitor or ECU are not processing the signal properly. I understand that you have already swapped the ignitor, but you should make sure that it has the proper ground to chassis. I don't think that the plug condition figures into this, because the ignitor is only indicating that it generated a signal. If everything else fails, you can replace the ECU and see if that makes a difference.
i don't think the wiring is a problem now. i have run new IGT and IGF wires to the ECU and have run a new wire from the igniter to the coil. With and oscilloscope on the signal wires i can see the IGF signal not coming from the igniter occasionally. Its an old scope so i don't have a way to record it besides the video i linked above. it seems to be related to heat

i ohmed out the ignition coil last night to verify that i hadn't damaged it in the process and it came out to .6-.7 on my meter. the BGB states that it should be .41-.50 so maybe that is now the problem?

Is there anything else that can cause the igniter to not return signal? can it detect if a spark plug has not fired like if the distributor was not in the right place to complete the circuit? If the igniter had low voltage on pin 5 would that cause it? i'ts the one wire that i haven't figured out a way to monitor when its happening
 

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Discussion Starter #7
Got the car off the ground to get under it. cleaned the EA ground and the main ground from tranny to chassis but still have the same issue. Any ideas?
 

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...i ohmed out the ignition coil last night to verify that i hadn't damaged it in the process and it came out to .6-.7 on my meter. the BGB states that it should be .41-.50 so maybe that is now the problem?
The resistance measurement is not the problem. What could be happening is that the coil or ignitor is failing when it gets warm. That is a common scenario. There is a bad internal connection that is usually continuous, but as the component gets warm the thermal expansion causes it to interrupt.

What to do about it? You can try warming the coil in a pot of water to see if you can get it to fail hard. This is easy to do, and you might get lucky. The ignitor you would have to test in the car. You could try heating it with a heat gun, and you could try substituting another. Having two bad ones is not that unlikely.
 

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Discussion Starter #9
sorry for the long time no post. had some other things come up. Finally got this taken care of. it turned out to be my distributor was failing. from what i can tell the air gap was correct when the engine was cold and as it got hot it would stop sending signals to the ecu correctly telling it to fire at the wrong time when the igniter couldn't complete a circuit due to the distributor not being in the correct place. car is now idling smooth and no longer is throwing a code 14. With that said i can drive her but she has no power to accelerate and now has a miss when under load/attempting to accelerate hard. i replaced the fuel filter since she was sitting for a while with no change. i might start a new thread for this issue after i do some more testing. i want to test compression and maybe see if i can get a setup to test fuel pressure and exhaust flow
 
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