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McAnic_Chad

Sensor-Ship. F*#@! S#%*! Wut's Wrong With My Car??

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I have been having problems since I bought this car. It's a 95 626lx V6. I was having starting/stalling problems so I rebuilt the distributor system (New: Plugs, Wires, Internal Coil, Cap, Rotor, & three different used ignition modules with the cam position sensor built in) that made the car start from a not-starting-at-all state. Then the problems returned. I did the HEI Ignition Module Modification. The car ran for 3 days & went back to stalling/not starting. This time I noticed that the fans would come on when the engine would stop and not restart unless I let it sit. So I decided to un-plug the Engine Coolant Temp. Sensor & try to start it, & it starts right up. It'll run like this for about 30secs then it'll die unless I plug the ECT Sensor back in, & in some cases this will make the car stall immediately, but for the most part starting the car with the ECT Sensor un-plugged & plugging it back in seemed to be working so I kept it up until the O2 sensor was delivered. I put the O2 Sensor on & the car started right up. It ran good for a few days & now has started stalling again & not starting unless the ECT is un-plugged. I would like to put "Sensor-Ship" to an end & just drive my car worry free. I love this car & you don't see many of them I want it in a dependable working state. ANY HELP would be nice thanks.

Few details:

Duralast HEI Ignition Module mounted & grounded directly to frame

NGK Plugs (I forgot what prand wires there are but they're cheap yet brand new)

Bosch Cap & Rotor

Problems only seem to arise the day after I have pushed the car a bit or after about 3 days of nice n' easy driving & shifting.

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Well what you've been doing is throwing parts at the problem and X amount of dollars later no better off. You have to take some electronic readings. Multimeters are fairly cheap, certainly cheaper than an O2 sensor. There is a topic around here that I made recently I think that has the entire diagnostic process for testing the ECT. I would start there and take it one step at a time. Heated O2 sensor for a V6 diagnostics I believe is also available. If you can't find the info let me know and I'll either search for it or upload some factory manual scans for you no problem. I hate seeing people throw parts at a problem. I've done it, we've all done it, it's expensive, and usually just wastes money. It's a bad habit ya got break and the only way to do that is diagnostics.

Fans kicking on and engine shutting off sounds like an overheating issue for sure. I would have thought the ECT to solve that but since you've done that gonna have to take some reading to find out why. Diagnostics start with questions. Did both fans turn on/off at the same exact time or one and then the other?

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Yea, they both came on, & yes both at the same exact time. when it shuts off some times it'll sputter before it dies off & the fans will "clip" as if they want to start running while it's sputtering but won't stay on until the engine has died. They'll stay on for about 10 seconds after the engine is off. BUT THE CAR HAS STALLED OUT WITHOUT THE FANS DOING ANYTHING AT ALL FROM TIME TO TIME. The car doesn't seem to be over heating & it doesn't really appear to be either based on the temp gauge... & being that I can drive it sometimes for 3-4 days in a row without any problem is just making me think that the problem isn't the cooling system itself. Is it possible for the coolant level to be just high enough to keep the engine form over heating while driving, yet so low that the actual coolant isn't making contact with the sensor so that it reads properly? I haven't thoroughly investigated the coolant level. & sometimes it runs for a few seconds & shuts off & the fans click, sometimes it'll warm up (gauge reads just above 50%, in other words a little bit closer to the "H" than the "C" which is when the fans are supposed to come on) and shuts off right when it's time for the fans to kick in, sometimes it won't shut off and the fans will run like normal, sometimes it just won't start at all. The trend that I find most common though is, unplugging the ECT sensor will get it to start even if only for a few seconds. Most of the time when it stalls it will not start again unless I unplug the darn thing & the fans will stay on until it's plugged back in, & in some cases that'll automatically shut it off. Put it like this; on a good day, I'll turn the key it'll start and run until it's warm then it'll shut off I'll pop the hood, unplug the sensor, start it, plug it in and keep on moving. Bad days call for me to have my girlfriend use her car to push me back home. The issue that is confusing me is a lot of the times that the car isn't starting, I check for spark which isn't present. I unhook the ECT sensor & it's sparking like a champ. I will test the O2 & ECT sensors thogh. Even though they are both brand new. I purchase all of my auto parts form http://rockauto.com/ they are very affordable. My Ignition coil was 199.96 at Auto zone I bought it from Rock Auto for 17bucks. :-D!!! Yet I can totally understand why you hate to see people waste money on parts when they don't know exactly what to replace. I just figured that the more new parts I have the better off I'll be based on my budget... The car only cost me $400 on craigslist & the owner told me it just needed a major tune up. I was able to drive it 45 miles back home the day I bought it. It just ran rough until one day it died & didn't start agian. It smoothed out once I replaced the cap & rotor though. That's around the time that it started to stall when I drove so I did the HEI Mod. (this was before I noticed the fans) I'm pretty confident in my mechanical abilities, & I'm willing to take on a challenge. I'm trying to give you as many details as I can think of but this is all that is coming to mind at the moment... Feel free to, & please ask more questions.. I'll answer to the best of my ability.

P.S. sorry if this is long winded but I'm just trying to give you as much of it as I can & thanks for responding...

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Your issues sound about the same as my recent no-start, stumble/stall debacle as well:

http://www.mazda626....-solved/unread/

In my case, it was the distributor, which was only a year old, and the new one that replaced it was also defective. The last one I just got seems to have fixed the problems, as I could reliably duplicate them before, and it's running and starting great again.

In your case, you might simply have a weak ground to your battery. When the fans kick on, it hurts the discharge/recharge cycle time on your ignition, and it can't keep up, causing the engine to stall. The cooling fans suck down some amps. Check your battery and alternator voltages, and clean the battery terminals, even if they look ok visually. Disconnect and clean the cable at the chassis end too, they often get some surface corrosion here and prevent a solid connection.

You may also have a defective fan, fan wiring, or fan relay that causes an intermittent short circuit. This pulls the voltage down too low for your ignition to spark. Try disconnecting the cooling fan relays (instead of the ECTS) next time this happens and see if it starts right up. These are complex relays that have both NC (normally closed) and NO (normally open) contacts, and at least one of the fans runs at two different speeds; there are also discharge circuits (to keep relays from sticking due to back EMF) and A/C aux fan circuits that all feed into these relays, which is why they have so many pins and some diodes & resistors. Relays are partly mechanical devices, and something might be jammed up inside causing the circuit to get into a conflicting state (when the relay closes, some part that's supposed to break a connection elsewhere doesn't).

Also, the ECTS harness is shared with the CKP, which on your '95 is required for it to start...perhaps unplugging the ECTS simply jiggles the CKP harness and it makes a solid connection again, and the car starts/runs. Have you tried disconnecting and cleaning the CKP harness? This is a not-unheard-of problem on '95+ probes & MX-6's.

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Great info! & thanks. I'll try the relay. When you say CKP are you speaking of crank shaft positions sensor? Do you know of any other grounds I should check? I was looking to buy some new battery terminals the ones I have do look a little old now that I think about it. & the negative one doesn't make a perfect circle around the battery post so maybe there isn't good ground there. & also where is the ECU On this 95 626? A lot of guy over at http://probetalk.com/ are telling me that I may need to replace it.

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It is behind the cupholders in the center console. Just pop the plastic out from around the shifter after you pull out the ash tray, and you'll see it.

Doubt it's the ECU, but it's not unheard of.

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Yeah sounds more electrical than a bad ECU however it won't hurt to check the harness and pins for good connection. Anytime you mess with the ECU you should remove the battery terminals first. Says so in the factory manual so I'd follow that one.

As long as there is good contact to the terminal somewhere and it's not loose I don't think the terminal would cause the issue. The car has many ground points so do a good wiring inspection. If the previous owner lived on a bumpy road it's possible to get something loose over the term of the cars life. You never know. I believe we had a member over the summer that was having the fans constantly cycle on/off real fast. Can't remember what caused it and after searching can't find the post. Meh.

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We'll I had the HEI mod done & when I reversed it I was still having the same problem. I have no idea what this could be... The improtant parts of the distributor have been replaced. The ECT sensor has to have something to do with this because now it's nearly impossible for the thing to start without disconnecting it. But that itself is brand new too. What is the CKP? I'd like to inspect it.

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thanks, had to be sure. I'll take that harness off & clean it... Any thing special I need to know before or about cleaning it? any special types of chemical required? As you can see I am kind of an out with the old & in with the new type of person so if I can find a crank sensor for cheap I'll more than likely just replace it... It doesn't look as if it's too hard of a job. I'll start with the connecor to it & let you guys know what the results are. Thank you both.

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There's a recent topic around here about the ECT values being different for many of the 626's. You'll want to make absolutely sure that you have the right ECT by testing it. Also had quite a few distributor issues which would make sense for your issue too but having the wrong ECT sensor would make more sense. Perhaps that's why your new ECT isn't solving your issue like you would think it should. Could be a valid 626 ECT but for the wrong year or engine type which has completely different values that it puts out. All I'm saying is it would make sense if you have the wrong ECT. ;)

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Right, well what do I do to test it? it looks identical to the one that I took out, & before I ordered it I went to a local pick & pull & found that there were many diffrent ones that just wouldn't fit the harness.... My distributor has been rebuilt from the inside. the coil is brand new & I have about 4 different modules. Plus the HEI. No matter what configuration I use I get the same results. I would put my money on the CKP due to the fact that I replaced everything else ignition related. I will look into everything else you are telling me though.

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Hmm I actually don't have that part of the manual uploaded so I'll do that tonight for ya. Check in my photobucket 1994 scans tomorrow morning and read through the latest images to find the ECT testing procedure scans. :)

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Aw hell. It just happens that's one of the largest sections of any manual I own. 174 pages. Jiminny Crickets. You would, wouldn't you. lol. Only bigger section is the manual transaxle which is about 260 pages. This is gonna take a while.

In the mean time I've uploaded the 2 pages that should prove most useful to you. This is from the KL V6 fuel and emissions section. It's not relevant to the FS I4 guys just in case anyone was wondering.

img-327699-1-F2-105.jpg

img-327699-2-F2-106.jpg

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ECT test can probably be done on the car too, at least on the 99 it is. The leads are accessible, either probe the plug or just take the plug off and test right at the sensor connectors.. Just relate the ambient engine temps to the sensor temps (cold engine = room temp, hot engine roughly 180 - 200 ). Infrared temp sensor works great in these situations. :)

If the engine is cold (completely cold, like overnight), check the ECT resistance reading against the input air temp sensor reading. They should be pretty close (+/- 15%).. If the engine is warm, they'll be skewed. The IAT sensor should match up to the chart up above tho.

CKT sensor test shown below. Oh, and I had "cleaned" my CKT sensor plug as well, turned out that that was the problem. After I unplugged and replugged it about 3 times the car started starting. Never underestimate the crankiness of electrical connections..

Also - what part of the country/world are you in and what are the temp/weather conditions? May help explain part of your start/no-start conditions too, related to temp sensor..

ckt test.JPG

post-29803-0-13697400-1323274923_thumb.j

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There has to be a way to replace that crank sensor without removing the pulley. I refuse. lol Based on my own experience I've learned that there is more than one way to remove/install a car part.

Did you test it already? What were the results?

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There has to be a way to replace that crank sensor without removing the pulley. I refuse. lol Based on my own experience I've learned that there is more than one way to remove/install a car part.

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Another question, Why does my water neck have a second sensor on it that my harness will not fit. There is one that is towards the front of the car (black) and another, that the harness fits, towards the firewall. (Gray) They look as if they are shaped the same and are the same size but the harness only fits one of them.

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After I cleaned the connectors My car drove fine for about a month, then it stalled again so I figured I'd made a bad connection again so I cleaned it again, but this time, I started the car and wiggled the Crank Sensor plug that I just cleaned and the car shut off. I stared it back up, wiggled it again, and it shut off... Wire shortage. I searched and found where you could see some of the copper poking through the rubber. I haven't fixed that yet but I will get some butt connectors and fix the connection. But for now if it cuts out, I just wiggle it until it stays running. Gets me from A-B.

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Replace the wire using solder & heat shrink OR terminals and crimp tool. I would make sure to add a rubber grommet or small hose around the wire in the area where it's prone to rub. There are all kinds of creative ways to make sure the wires won't rub through again. Good catch. Now that you've found the issue you'll be able to fix it np. Good job.

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Don't sound so surprised. You're advice is 99.9% top shelf. I always assume you're right until (rarely) proven wrong. You're just that good. You make my brain work overtime to think of reasons why you could be wrong. Out of like the last 3000 posts I think I only stumbled upon one when I disagreed with you. Wish you would post more or maybe you choose your fights more selectively. I'm like a whack-a-mole and you're like a precision guided bomb. :P

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