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It's the '93 GS guys. Millenia ZE, curveneck IM, and same issues at startup as previously mentioned.

Idle issue - I'm thinking IAC related, as unplugging it made zero difference at startup. The car will bog down and stall at idle, unless I keep it revved up for a little while, basically the time it takes to warm the engine up briefly.

The new issue is a CEL flashing only when revving the engine. The rear end is still torn apart, since I'm swapping the brakes between the 2 cars again, so I have not been able to take it for a drive yet. The CEL is gone the moment I drop the throttle off, and only returns when I rev it to ~2.5k+

Throttle response is sluggish, but was not prior to parking the car. I brought it down from a surging, 2K rpm idle, to a smooth 800 prior to parking it for the winter. Beyond running it semi-regularly in the driveway, and keeping fuel in the car, nothing has changed.

Any ideas for these 3 issues? I'm betting #1 and #3 are tied together, #2 is brand new as of today.

trouble idling screams vacuum leak to me, or possibly a bad vaf. are you sure the car wasnt in diagnostic mode when you started it? my car can barely idle in diagnostic mode. it might also be worthwhile to reseat your spark plugs. if youve taken them out recently its possible they arnt sitting 100% properly. after i did a compression test at school my car was misfiring like crazy and couldnt idle. turns out one of the other students i let put the plugs in didnt tighten them properly.

did you have a chance to try the iac with the coolant temp sensor unplugged?

as for the cel with revving its possible you car is experiencing knock. might be worthwhile to tap into the knock sensor and monitor the readings on a voltmeter while revving. the signal should be steady, if it fluctuates its detecting knock or faulty.

It could be vacuum, that was a royal nightmare to deal with last year... No telling if I got it perfect or not, but I believed I had. I have another VAF to test, I'll give that a shot next chance I get to work on it. Currently swapping rotors, pads, and calipers between the cars -.-

Definitely NOT in diagnostic mode, I will give the spark plugs a shot before I swap the VAFs, good call. I need to get ahold of a compression tester, neither car has been tested since I've owned them.

I haven't yet, wow, you already suggested that to me too... fail on my part, thank you.

I was worried it might be knocking, hopefully not...

I've got a list of stuff to check now, thank you Mike. I'll check it out soon!

Edit:
Okay, so I had jumped ten/gnd earlier today and forgotten about it... Definitely stopped the CEL issue.

Still throwing a code for the coolant sensor(only have 1 tapped in, the other is just loose), but here's where it gets interesting.

Out of curiosity, I swapped the black coolant temp. sensor pigtail for the green one... CEL went away, even with the black one unplugged. Anybody have an explanation for this? The other effect of swapping them was the idle jumped about 200 higher, and held steadily for the first time this year. Is it safe to assume that the black pigtail is somehow damaged? It would explain the surging idle with it plugged in, as well as the fact that the CEL went away the moment I swapped them... If the ECU wasn't getting proper signals from that sensor, it would explain the surging at least.

Side note, the car held a fairly stable idle at 100-200 RPMs while in diagnostic mode... Unplugging the IAC on the TB dropped it down considerably, I was just surprised it held that low without stalling.

The idle is steady at 1000 currently, I'll drop it down to 800 tomorrow when the neighbors are less irritable. Having no exhaust on a KL won't make you many friends.

what do you mean by pigtail? are you talking about the wiring harness for the engine? or you cut/spliced in a new plug? if you believe the plug is bad you can verify that with a voltmeter, however any major cracking or degradation in the wiring would be a fairly obvious sign of a poor connection. i have noticed the where the wires meet the plug they tend to crack and the shielding tends to wear away over timer. or are you saying you took the plug from the one sensor and plugged it into the other and the cel went away? if thats the case im pretty sure the plugs are different and they shouldnt be interchangeable between the differnt types of sensors. perhaps your ecu only expects readings from 1 sensor and youve had the wrong one plugged in all this time?

by having the one sensor loose im assuming you mean your coolant neck isnt drilled/tapped for it yet? this would explain a high idle as the ecu would think the engine is cold and produce a high idle to decrease warm up time. if you want to know for sure take the cap off the fill neck and dip the sensor in the coolant. idle should be around 1200rpm when warming up then drop steadily to 650ish when at full operating temp.

what are you using to control everything? im assumig mx3 ecu and probinator chip?

I feel wiring harness is not specific enough... but yes. I did not cut/splice anything either.

The plug itself is not damage visibly, that was my first thought as well. Are the two coolant temp. sensors different styles? Only one was plugged in to begin with, as the other is not tapped. The ECU has thrown a code for the second coolant sensor from the day I purchased the car. The CEL didn't go away when I swapped the plugs, only the surging changed.

At this point, the only CEL is for the second coolant sensor; Aside from that, the idle is smooth as butter!!

The ECU is chipped, from what Anthony told me, but I do not know who made/installed the chip. I'll crack it open to take a peek Monday, I should have done that forever ago. Unfortunately I haven't had the car drivable very much since buying it... Thankfully that is over after I bleed the brakes tomorrow. Well, that is until I swap the springs and struts from my '92.

ok... cel im assuming is code 69? your sig lists both a 92 and a 93 which both came with both coolant sensors. the klze engine as far as i understand it never came with the second coolant sensor. the way the chips are programmed they need that 2nd sensor to function properly despite what year or if the car had one in the first place (94+ like mine). your lucky in that your harness is already wired for the 2nd plug, otherwise youd have to add a wire into the ecu and make the connection yourself. the 2 sensors look almost identical, and the plugs are very similar, it is only the grooves in the plugs that are misaligned to not let them plug into one another. that being said my new beck/arnley sensor didnt come with the groves and although i havnt tested it, id assume it would plug into either plug on the harness.

by you having a cel im assuming your coolant fans are on most if not all the time? the 2 delphi sensors i had would send an improper signal once the car was half warmed up and caused the fans to come on and cel. you can test your sensor by fallowing this http://www.mx-3.com/manuals/showimg.php ... E2-014.gif as far as i understand these sensors can fail 2 ways. 1 is to be completely out of spec and throw the cel, the 2nd would be the sensor just reports an inaccurate reading, like telling the computer the coolant is 5C when its really 70C but not throwing a code. i would start by buying 2 new sensors. your in the states, there probably cheap enough there. then either drill/tap in the 2nd sensor onto the neck, or if your lazy and dont have a tap just drill and then JB weld the sensor in place. i have done it this way and it works fine. just make sure to not get any shavings or jb weld into your cooling system. also let it cool over night before starting the car. id also verify the sensor is working properly before welding it in place. you can do this by letting the car warm up with it sitting in coolant in the fill neck. no cel, ideal idle and your gold.

there is also no point in opening the ecu to look at the chip. both of mine from 2 different programmers were not marked in any way, they are just standard computer eprom chips...

The code is 09, I'm not familiar with a code 69...?

I forgot the plugs are different, the black one was a royal PITA to remove from the sensor. The green went on and off smoothly, so there's one problem solved.

I'll have to add it to the list, that's one more expense tacked on. With all the stuff I need to fix, it's a miracle I can buy anything new anymore! I'll tap it in, after I buy a new sensor.

The fans are both on most of the time, although the second fan did turn off after driving(prior to the car being parked).

Unfortunate, I'd like to verify that the ecu is chipped at least. I know that a few of the people who made them labeled theirs, so I will take a peak just in case. If not, at least I'll have made an attempt.

Thanks again Mike, I'll test that sensor before I update this again.

When Code 9 is present, the PCME substitutes fixed calibration values for the various representations of engine coolant temperature used internally. The engine may idle roughly and may be hard to start. Timing and fuel delivery calculations will be skewed somewhat since the coolant temperature will be only an approximation. As well, to safeguard against overheating, the PCME will also activate the cooling fan constantly.

Memorization:

This code is memorized in the PCME non-volatile memory.

Things To Check When Diagnosing:

Use the above table to check the coolant sensor itself. It is probably the cause of the problem

As always, check the connector to make sure there's no corrosion or grease or dirt in it.

Disconnect the sensor and check the R/DG wire for +5V with the ignition on. If it is absent, check the wiring to the PCME and the PCME itself.

69 is for the sensor that only came on 92/93 mx3's. 09 is for the sensor that was used on all years. from what ive just read the 69 sensor is just for the computer to know when to turn the fans on and the 09 sensor is what is used for calculating fuel mixture and timing. its funny because ive noticed a difference in mileage with have the 69 sensor faulty. im gonna replace the 09 sensor aswell and see if it helps. i also know for a fact it will affect the idle.

Thank you Mike, you've taught me a lot about this... I'll get the IAC working in my '92 again, after I pick up a sensor for the '93.