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91 MR2 N/A Rough Idle, Running Rich, No Accelleration

21130 Views 9 Replies 6 Participants Last post by  gstar
Hi Guys,

I have a 91 Mr2 auto N/A. I bought it very cheap but it has a issue I just cant seem to solve. The car starts up but right from the startup runs very rich and rough idle, engine shaking to the point sometimes that my mirrors vibrate. The car has no power, I have to floor it just to get it around my driveway. The rough idle seems to get better when the rpms are higher, and on warmer days I notice a huge improvement, where it will hold an idle better without stalling or getting close to that point. So far I have replaced spark plugs with ngk's (checked them and they are black from rich), brand new ngk wires, checked compression on all 4 cyllinders which is good, timing is good, oil is good along with all other fluids, brand new distributor cap and rotor, replaced actual distributor, replaced ignition coil and ignitor, replaced ECU, confirmed fuel pump working by shorting terminals, replaced EGR VSV, tested EGR seems fine along with EGR Modulator, looked for vacuum leaks cant seem to find any, removed intake, brand new O2 sensor and tested with multimeter to confirm working correctly. Also, when revved to 2000-2500rpm the engine revs bounce up and downand speedo guage does same. I cant get a CEL code by shorting terminals, and the check engine light will go on and then turn off. Anyone else had this issue, i am now completely stumped on where to go next.

Cam
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Chech the map sensor. Unplug the vacuum line to it and cap it with your finger. If it doesn,t change how it is idling its probably that. If it gets worse or dies when you do that then probably something else.

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Hello all,

My name's Chris, I am the new owner of this MR2 in question.

In my troubleshooting I was able to find that it is something to do with the EGR system and it will be easily fixable once my parts come in. The problem of acceleration is more caused by the transmission not being sent the correct voltages for normal solenoid operation. I have replaced the engine harness and can be sure of no shorts in the wires. I have also replaced the solenoids themselves.

I have been checking fuses and relays, all fuses seem to be working but the a/c fuse has no power on either end. The efi and ign relays work fine but the are getting 70 ohms? Not quite sure if that is normal. The grounds are at 23 ohms. I have tried hooking the grounds directly to battery with a jumper wire with no avail.

The CEL flickers only when the transmission wire is plugged in, the purple wire is the only one that seems to give issues. I suspect the speed sensor, as I get a jumpy speedometer. I have the BGB but I still cannot find the sensor. The transmission will drive fine in manual shift mode(1,2,D) and will reach 65 no problem. The solenoid wires are all getting ~8V of power through them. The BGB says that they all come straight from the ECU to the connector...

I am no electrical genius but I am handy with a multimeter and could check the right wires if need be.

ANY help or feedback would be greatly appreciated.
 

· Registered
Joined
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23 Posts
Hello all,

My name's Chris, I am the new owner of this MR2 in question.

In my troubleshooting I was able to find that it is something to do with the EGR system and it will be easily fixable once my parts come in. The problem of acceleration is more caused by the transmission not being sent the correct voltages for normal solenoid operation. I have replaced the engine harness and can be sure of no shorts in the wires. I have also replaced the solenoids themselves.

I have been checking fuses and relays, all fuses seem to be working but the a/c fuse has no power on either end. The efi and ign relays work fine but the are getting 70 ohms? Not quite sure if that is normal. The grounds are at 23 ohms. I have tried hooking the grounds directly to battery with a jumper wire with no avail.

The CEL flickers only when the transmission wire is plugged in, the purple wire is the only one that seems to give issues. I suspect the speed sensor, as I get a jumpy speedometer. I have the BGB but I still cannot find the sensor. The transmission will drive fine in manual shift mode(1,2,D) and will reach 65 no problem. The solenoid wires are all getting ~8V of power through them. The BGB says that they all come straight from the ECU to the connector...

I am no electrical genius but I am handy with a multimeter and could check the right wires if need be.

ANY help or feedback would be greatly appreciated.
This problem has been solved. The +B amd +B1 lines were broken in the harness causing a fluctuation of voltage. Aprox only 3v was being sent to the ecu, the ecu was not able to feed the ECT. Very simple and cheap to fix. Just check the feeds from the fusebox to the ecu for resistance. The rich conditions were due to EGR vsv being broken. Hope this helps!
 
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