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My final troubleshooting thread

S

SJon85

Veteran CEG'er
Joined
Sep 11, 2009
Messages
906
Ok, this is my last effort of trying to get my car running, here is my giving up pic thread...
http://www.contour.org/ceg-vb/showthread.php?69138-I-m-giving-up.

The main problem is the car is dropping spark from 24 to 1 degree, seems to be happening only around 2k and 3k rpm but also runs pretty rough under 5k rpm. Also after running the car and driving around a little it will die after you give it some gas everytime.

The original wiring harness was giving me problems with the front o2 sensor not having power because several of the clips were not latching together, got that problem solved with the stock 3L uim on and the car was running great. Since my wiring harness was pretty messed up I decided to pick up a used one that appeared to be in good shape with all working connectors and installed my ST220 uim at the same time. Now with the ST220 uim and new wiring harness I am having the dropping spark problem. So here is what I have nailed it down to...

1. UIM couldn't cause a spark issue
2. Swapped out the coil pack and plug wires with some that I know for sure work just fine
3. If cam or crank sensor were bad the car wouldnt start at all
4. I believe the wiring harness is fine, but I did have to do some modifications to it which I believe should be working just fine.

To make a long story short the current wiring harness on the car is an 01-02 mtx cougar harness(which is correct for my car), however I did have to remove the crank and cam sensor wiring from an 01-02 atx cougar harness to install on the current mtx harness, I did that by using a very small flathead screwdriver and pushing the wiring pins out of the connectors, and pushing them by hand back into the their appropriate places. After I did this wiring change I am also throwing a fuel rail pressure code now, which I haven't looked too much into, besides making sure the fuel sensor is plugged in and doesn't have any leaks anywhere.

Before I switched out the cam and crank wiring I had the 01-02 mtx harness with just the two crank sensor wires soldered together and had the same issues. Didnt have the fuel rail pressure code with this setup tho.

So who thinks I should spend even MORE money on this car and send the better part of my 3 wiring harnesses to svttour along with $100 and hope that fixes my problems. OR should I replace the cam and crank sensor with some new autozone sensors at the cost of $50 even though those were never changed or messed with?

Thanks in advance to anyone who can help me, because otherwise the car and all its mods are going to be forgot about and put into storage for about 2 years.
 
logic says you should put your original harness back on.

Your car should then run ok as it did before.

If it does.. this will prove that the problem is in the new harness and not with your accessories. ...G.
 
gorman said:
logic says you should put your original harness back on.

Your car should then run ok as it did before.

If it does.. this will prove that the problem is in the new harness and not with your accessories. ...G.
Click to expand...

Unfortunetely the stock harness is pretty much toast and looks like spaghetti with some connectors cut off. The harness I have on their "should" work just fine, and only had one problem being that the crank sensor was soldered in, and then I installed the complete wiring for the crank sensor and still have the same exact issue. Since I have spent $100 on harnesses already I really dont want to spend another $100 on a harness just to find out its not the harness, but I guess that is about my only option, just want others opinions and see if I can test anything else first.
 
oh well .. just tried to narrow the list of culprits. .

I don't know about your original UIM; the ST220 UIM only has 5 fixing studs.... does your new UIM have a vacuum leak perhaps ?

How do you know that you are losing spark between those angles ? G.
 
99.9% positive I dont have any vac leaks, it idles at 750rpm and has no throttle hang or anything like that as well as the air/fuel gauge seems to be reading right where it should. I thought the rough running was because of the tune, so I datalogged it for Joey and he said thats what my spark was doing, and when driving it you can feel the spark missing, especially at cruising throttle around 2k and 3k rpm its really bad and generally runs like crap in the lower rpms, but after about 5k rpm it takes off like a rocket and doesn't have any spark issues up there.

As far as the wiring harness it would only make sense that that is the faulty item here, and should probably just send it out to svttour, but i guess its more of a personal call of do I take the chance of wasting another $100 to get nowhere on this car? And I am sure you meant 6 fixing studs instead of 5.
 
Your #3 premise is incorrect, there are all sorts of gray area around crank and cam sensor inputs. While it should not generally start, that is not a given. Simply weak signal could start at lower speeds but act up at higher.

The timing SHOULD move around, mine does it all over the place on dead stock motor and realtime live data output. Now with a tune, dunno.

You are also still describing a vacuum leak, worse down low and better up high. Live data on O2 sensor will pick up on that.

One indicator of weak spark or improper would be darker colored plugs since weak burn does not keep them clean.

A $10 voltmeter (should be in EVERYBODY'S box) will verify wiring harness condition. After that all you must do is guarantee quality of the connectors which is not hard.

Engine die after a throttle rack can be IAC not properly holding idle air bumped up, or carbon buildup around butterfly edges.
 
Thanks for the input amc49, heres what I can answer right now since I am currently away from the car this week.

When you say act up at higher speeds, I am guessing you mean the RPM? Say I am in 3rd gear at 1k rpm and go wot, the car will stutter/miss for a while and not run healthy at all until about 5k rpm when it then hits a certain point where it knows what its doing all the sudden and pulls like crazy all the way to redline. So high rpms it runs great, but just cruising and giving it a little gas in lower rpms it will skip and jerk the car like crazy, and that will happen worse and worse the closer the TB is to closed.

As far as the timing moving around, I dont know much about the tuning process at all. But when Joey told me what the datalogs looked like I think he was saying that in those lower rpms it will just instantly drop from 24 to 1 degree of timing, which he suggested was a wiring or ground problem.

As far as a vacuum leak, I have my aem wideband gauge hooked up with the datalogging. Which I think Joey had to add more fuel to the tune when I installed the ST220, but I am going to email him right now and ask how much and I know at one point he said it was pulling 15% more fuel for bank 2 so I need to clarify those things with him. Also sprayed carb cleaner around the entire intake and didnt pick up on anything.

I will pull the plugs when i get back to the car and see what color they are.

I have tested for power at the cam and crank sensor with the key in the on position, neither of the wires on each connector have power which I dont know if they should or not?

IAC is brand new from autozone and seems to be operating just fine, in fact when I do a cold start I can give it gas and it wont die, and sometimes it will be idling and just die out of nowhere. Seems to me the IAC is fine, but I could be wrong.

THANKS for the help guys!! Really dont want to be buying a carport for this car and not see it everyday.
 
SJon85 said:
Thanks for the input amc49, heres what I can answer right now since I am currently away from the car this week.

When you say act up at higher speeds, I am guessing you mean the RPM? Say I am in 3rd gear at 1k rpm and go wot, the car will stutter/miss for a while and not run healthy at all until about 5k rpm when it then hits a certain point where it knows what its doing all the sudden and pulls like crazy all the way to redline. So high rpms it runs great, but just cruising and giving it a little gas in lower rpms it will skip and jerk the car like crazy, and that will happen worse and worse the closer the TB is to closed.

As far as the timing moving around, I dont know much about the tuning process at all. But when Joey told me what the datalogs looked like I think he was saying that in those lower rpms it will just instantly drop from 24 to 1 degree of timing, which he suggested was a wiring or ground problem.

As far as a vacuum leak, I have my aem wideband gauge hooked up with the datalogging. Which I think Joey had to add more fuel to the tune when I installed the ST220, but I am going to email him right now and ask how much and I know at one point he said it was pulling 15% more fuel for bank 2 so I need to clarify those things with him. Also sprayed carb cleaner around the entire intake and didnt pick up on anything.

I will pull the plugs when i get back to the car and see what color they are.

I have tested for power at the cam and crank sensor with the key in the on position, neither of the wires on each connector have power which I dont know if they should or not?

IAC is brand new from autozone and seems to be operating just fine, in fact when I do a cold start I can give it gas and it wont die, and sometimes it will be idling and just die out of nowhere. Seems to me the IAC is fine, but I could be wrong.

THANKS for the help guys!! Really dont want to be buying a carport for this car and not see it everyday.
Click to expand...

Wait, u mean u havn't looked at the sparkplugs yet? That would've been one of the first things i'd've checked. Recheck gapping and see what happens. Might be a good idea to buy some cheapos first. $1.99 each or sumthn.
 
Have you swapped the PCM yet? I would pick up an ELM327 interface and start datalogging. Chances are you will be able to pinpoint what is causing your problem. The elm327 lets you monitor the voltages of pretty much everything and will build you a spark table based on what it is seeing from the pcm.
 
Don't get me wrong, I have checked the plugs several times including putting cheap ones in. To be honest I have been having soo many problems that I can't remember what all I have done, but I think I did inspect the plugs a little while ago when I had the wrong iac on, at that point all the plugs looked light brown in color and gap was fine.
 
I have some low milage Cam and Crank sensors. If you want to eliminate those from your equation let me know. You can just have them.

-Adam
 
Thanks to Adam, crank and cams sensors should be on there way tomorrow!
 
Yes, since weak cam/crank sensors have a "hall" effect, they can weaken and wear out not giving the proper signals.

I assume your fuel system is returnless? So the fuel pressure code is probably just the rail pressure sensor either malfunctioning or faulty. You should setup a fuel pressure gauge so you can watch the pressure through all the different symptoms. If I remember right, the fuel pump has a variable output when it is running to raise and lower pressure based on demand. If your frankenstein harness doesn't allow the PCM to receive a fuel pressure sensor reading which could make your car stumble.

Right now the cam/crank sensors are a good place to start. Especially with a random no spark. Good luck and keep us posted!
 
amc49 said:
Your #3 premise is incorrect, there are all sorts of gray area around crank and cam sensor inputs. While it should not generally start, that is not a given. Simply weak signal could start at lower speeds but act up at higher.
Click to expand...
.

I can attest to this, I didn't even have my cam sensor plugged in and it started with no problem when I did my 3L build, I thought I plugged it in and then found it unplugged later! I hate to see such a great car put away for a while... Best of luck man!
 
Ok guys, took me long enough to get back to working on this. I got the cam and crank sensor from Adam, but only the cam sensor will work on my car as the crank sensor on my car has slightly smaller pins on it. So now I need to find the correct crank sensor. Anyways the cam sensor didnt change a thing, checked the spark plugs and they are all the normal light brownish grey color, and unplugged the MAF while it was idling and it caused it to not run unless the TB is open. The fuel pressure light went away though!
 
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