Scan tool needed

[tbondo]

I was wondering if anyone has a brand or knows of a live action scan tool that offers an adapter for an OBD1 92 mx-3? I currently don't have any codes but my car (fresh KL-DE swap) is not running/idling properly. I'm leaning towards bad TPS sensor but I don't want to just start throwing money at it without knowing for sure.

[MrMazda92]

Have you adjusted your TPS lately? It's tough to get it just right, but if it's part of the problem then proper adjustment will go a long ways. I went from a 2,000 RPM unstable, surging idle to a smooth 800 with no more than TPS and throttle stop screw adjustments.

A scan tool wouldn't tell you much if you aren't throwing codes anyways, sorry to say. There are multiple threads with good info on adjusting it.

[mikeinaus]

mrmazda is right. i used a scan tool at school on my car. obd1 is very basic and it doesnt tell you much more then the codes. theres a few basic tests you can do with the scanner but unless your throwing codes the refresh rate (how often the computer recieves data) is too slow to pick up any errors that the ecu wouldnt know about.

what is wrong with your car? my car had a weird idle where it would randomly idle at 1000rpm and idle properly at 650rpm maybe 1/2 the time. it may be a problem with your coolant temp sensor. i noticed when my coolant sensor was unplugged my car idled properly, it also idles normally since ive replaced the sensor. the car also didnt throw a code with the original sensor.

[MrMazda92]

You know Mike, that may be my problem I've been blaming on my IAC... I didn't think to replace the sensor, I always forget to K.I.S.S. *facepalm*

I drained the coolant, flushed the system with water(let it idle to heat it up and push it through the system), drained and refilled with 60/40 at the time. I never checked the sensor itself.

Wow, that makes me mad!

Thanks for the reminder...

[mikeinaus]

a good way to test is to just unplug it. your car will burn alot of gas on a basic map but it wont be sending the ecu improper readings affecting idle. the sensor works by telling the computer if the coolant is lets say anywhere from -30C to 120C, any readings in those ranges and the computer wont throw a code. lets say the sensor is reporting 70C then jumps to -5C for a few min then to 20C i dont know if the ecu would be smart enough to know its faulty, and would just affect the idle to a cold start scenario.

[tbondo]

Thanks for the quick lesson on OBD1. I have tried to adjust the TPS but like you say it can be tricky. I'll have to try again along with checking the coolant sensor. I have it parked for the winter but maybe if there's a nice day I can go out and tinker a little.

[Daninski]

Actually adjusting the TPS is fairly easy it's just time consuming. Using a feeler gauge and ohm meter about 20mins. Adjusting in small increments is the ticket. You could also have a sticking EGR, that will cause rough idle as well.

[MrMazda92]

Do you mean unplug the sensor, or the IAC?

I've had my IAC unplugged for over a year now, otherwise I idle at ~2k

[mikeinaus]

Plug in your iac unplug your coolant sensor

[tbondo]

I don't believe it is the egr as I have taken it apart, cleaned, and tested by sucking on vacuum lines. That seems to be functioning. I'm leaning towards a sensor and I will have to try all the options everyone has provided. I have seen comments about a 4 cyl tach vs a v6 tach and don't understand that. I actually did the swap from the B6 4 banger (still using B6 tach supplied with car) to the 2.5 KL-DE. Can someone explain how the tach would matter?

[mikeinaus]

Cluster shouldnt affect performance at all. I don't even think you need a cluster to start the car. Is it just idle problems? Can you describe what's wrong with it better? Is it misfiring? Knocking? Hesitating? Stalling?

[tbondo]

I questioned the cluster comment as well. I didn't see how that would make any difference. Before I parked it for winter it had a high idle. Everything ran smooth just high. After warming to operating temp it would hover around 1500-2000 rpm. I tried to adjust the tps according to a chilton manual, but that didn't seem to help. I could have had it adjusted improperly as well. I've never done it before.

[mikeinaus]

An easy way to test it is to put the car in diagnostic mode and touch the throttle. The cooling fans should turn on as soon as the throttle is lipped and turn off with it at rest. Is there any vacuum leaks? That's the main cause of high idle.

[tbondo]

I don't believe there are any leaks but I could be wrong. During investigation of this I tore all vacuum lines off just to make sure they were routed properly. I will try the diagnostic mode test. Should it be in diagnostic mode while adjusting the TPS?

[tbondo]

Well the time came to start working on the car again and after some more tinkering on things I have had no luck of any change. I adjusted the TPS as close as I could get to chilton specs, ran with the IAC plugged in and unplugged (wiring harness), and the same for the coolant temp sensor. The only thing these attempts did was signal the ECU to throw a code. The engine still idles at 1500-2000 rpms and drives down the road in 5th gear due to high rpms. I also have a sputter or hesitation when I get into the throttle a little heavier. I'm almost at my breaking point as I have been fighting these same issues since I completed my swap over a year ago. If there are any experienced 2.5 swappers out there in the central minnesota area willing to help, I'm willing to pay.