Ignition problem 98 Yukon SOLVED!

[redwing4900]

It looks like there are a few ignition issues popping up around the forum, here is mine. 98 Yukon 5.7L new spider injection, rebuilt engine with 32k miles on it, 210k total. It had new plugs wires and cap and rotor after the rebuild. I overheated the engine about a month ago because of a radiator leak. I replaced the radiator and it seemed to be ok until I noticed a hesitation especially in 4th gear at low rpm. It wouldn’t start one day later and I found the cap and rotor were VERY corroded. Replaced them both then it ran fine for a week. The hesitation came back, this time it was giving me a code for the module in the distributor I can’t recall the code or the part name (maybe cam position sensor). I went to change this sensor, and one of the bolts broke off so I had to remove the distributor completely to get at it. After I replaced the module, finding a part of the old rotor up I there, I was pretty sure that when I reinstalled the distributor, the alignment was correct, since it fell right in and I had lined it up the way it was (I thought), but when I went to start it the codes started flying and it wouldn’t run. It was about a month ago, I had a cylinder 5 misfire which I never had before, but I figured it was because of the extreme corrosion on the cap and rotor. Since I don’t want to go out and work on it in the blind, I figured I would bounce this latest issue off of the forum.
Do you think it could be the ignition module or engine ground Or something else? That’s where I figured I would start clean up the engine contacts, double check the timing make sure it’s correct. I was wondering if the overheat could have caused the wires to go bad, and figured I could change them and the plugs. Is 30,000 miles an appropriate time for changing wires and plugs? I thought they would last a little longer but maybe it’s time since the corroded cap may have caused some overload to them.
Sorry for the ramble, but I’m trying to include all that happened here. So what do you think? I will re test tomorrow and have some codes and pass along what I find.
Thanks

 

[east302]

I’d start with getting the codes and going one by one on them.

You’ll need the CMP Retard set on the distributor. That usually trips the P1345 code and has to be reset when the distributor is removed. You’ll need a good scanner (GM Tech2, Snap-on, etc.) or a Bluetooth OBD adapter and an app (DashCommand or CarGaugePro) to read it. Spec is zero degrees (+/- 2) at 1,000 rpm.

To get it close, twist the distributor until the driver side screw tab is hitting the upper intake.

I’ve never had much luck with aftermarket caps, Delco is usually the way to go on them.

Swap the plug from 5 with another cylinder and see if the misfire moves. Repeat with the wire from #6, it’s probably the same length.

Also see what the #5 plug looks like.

 

[Eman85]

Besides just dropping in did you mark the rotor position and distributor body position before removing? As stated you'll need a scan tool to set the CMP of the distributor.
For testing a suspected miss in the ignition the cheap fast fun and easy way is with a spray bottle of water. Have someone power brake the truck lightly to laod the engine and mist water around the plug wires. If you have a bad wire it will begin to miss. Also look at the plug porcelin, look for any carbon tracks or cracks. Look in the end of the wire in the spark plug boot, if it's black it's bad.

 

[redwing4900]

Great responses which I have come to expect From this forum, Thank you. I did mark distributor position which makes me suspect that may not be the problem. I will give the spray bottle a shot if I can get her running.

 

[exp500]

If you are using a bluetooth OGD scanner, you need the "advanced options or GM Advanced PIDS" depending on which App you are using, some apps are paid $ for advanced.

 

[redwing4900]

I finally had some time today to look things over and found the pictures fuse blown that was in the ENG-I slot 20amp. I checked the timing and it appears correct now as it turns over without sputtering and coughing. Still no start. I have rechecked the previously blown fuse and it’s not blowing now. I’m going to check for spark now. Maybe the coil is bad? I don’t have a clear procedure for checking the coil for resistance. is there a way to check the cap? Maybe the new cap got overloaded? for resistance. Does anyone have that? The reason I ask about the cap check is because after I cleaned the corrosion off of the old one it wouldn’t work so I replaced it fired right up. Thank you

 

[redwing4900]

Also no codes are showing up

 

[exp500]

Put a spark tester in Coil and Dist Cap. test both for full hot spark.
These trucks hate cheap dist caps. burn holes in them. Use GM/Delco/ Delphi or United DCR-820x only.
Also in parts Use Only GM/Delco/Delphi - CPS, ICM, Coil. GM/Delco/ Ignition wires or better. NGK/Delco plugs.
Glad it's running!

 

[redwing4900]

Thank you for the response. I had an off brand cap before but this time it’s a Delco. It’s not running yet. Still working it out

 

[redwing4900]

Also I just remembered that the cps is a master pro. Woops

 

[exp500]

Put your scanner on live data, monitor RPM while cranking. Might help. Shows CPS at least has output.
Also use Dielectric on connections/plug wires.

On ICM, you can unplug and put test light to ground testing white wire while cranking. Light should flash. Spark signal to ICM.

 

[redwing4900]

I shot the connections on the coil and ended up getting a new one, tests were in my Chilton manual. After I replaced the coil, a small adjustment to the distributor(more advance counter clockwise), it started and ran rough and gave me code 1345 crankshaft position/camshaft position correlation. I was going to try to rotate the distributor one tooth counter clockwise so I could capture the correct timing, but the cap was hitting the plastic intake manifold cover…! Frustrated, I packed up I’ll get to it in a couple days. I remember that when I initially set the timing, it was turned all the way in one direction trying to avoid hitting the manifold and fuel lines. Has anyone else dealt with this? Thanks again for your responses I hope the coil and the fuse did the trick. I’ll follow up with what I find with the timing adjustment.

 

[east302]

To set the CMP, you aren’t re-stabbing the distributor or moving it to another tooth. Once it’s installed, loosen the hold-down bolt and twist the distributor by holding the cap until it’s at zero degrees per the scanner. Tighten the hold down and you’re set. Usually, that puts the cap screw tab nearly hitting the intake, but you’ll need a scanner to get it set correctly.

 

[redwing4900]

Yes I was thinking that it was a tooth off because it ran so rough after I did the re stab. I’ll retime it tomorrow I hope it works. So the code 1345 is because it’s not timed correctly?

 

[exp500]

In your scanner, look for something like CMP RETARD. Setting is "0" += 1degree above 1000 RPM.
As east302 mentioned - This should be verified first.
Update your scanner PIDS, I know the Torque app must be Torque pro and sometimes that doesn't work right without adjusting. Which APP are you using?

 

[Eman85]

If you marked the body of the distributor and put it back in the same spot you can't be a tooth off or it wouldn't run unless you swung the body to a different spot.

 

[east302]

Yes I was thinking that it was a tooth off because it ran so rough after I did the re stab. I’ll retime it tomorrow I hope it works. So the code 1345 is because it’s not timed correctly?

The P1345 will set, among other things, if the CMP Retard (cam/crankshaft correlation) isn’t adjusted following distributor removal.

If you moved the whole distributor up a tooth (you wouldn’t be the first to accidentally do that) then I’d try to put it back to the previous tooth and first position that matches your original marks. Then twist it until the tab hits the intake, tighten down the clamp and try to start it.

Here’s a worn out one at zero degrees, note that the tab nearly hits the upper intake:

 

[redwing4900]

That picture is exactly what I needed to see, thank you. I was working on the Yukon today moved the distributor back to it’s original position (1 tooth) i have the cap on there just like it’s pictured, and it started but it’s still not right. I’m getting a misfire code along with maf codes. I’ve changed 3 things so far: eng-i fuse, coil and cps. Someone mentioned that it must be ac delco but i have a master pro. Could this possibly be the problem? The engine sounds like i need more advance but it’s pegged for advance (counter clockwise) and that’s why i was trying to get creative by moving it one tooth over. When i retard the timing it won’t start. My read out tool doesn’t tell me what the timing is. I have to borrow a neighbor’s sensor to see where it’s at but i can tell it’s off. This is a picture of my old rotor that must have caused the corrosion mentioned before under the cap.
I’m stumped…thoughts?

 

[redwing4900]

By the way this was not an ac delco part the middle fried off and was laying in the distributor. Sounds like I’m answering my own question regarding ac delco versus cheaper doesn’t it I could change the cps back to the original one that was in there or get an AC delco cam position sensor and see if that does anything. My only issue with that is the timing is still wrong.

 

[east302]

Do you mean the timing (controlled by the computer) or the CMP Retard (set using a scanner)? There’s no adjustment for the former and- unless you got really lucky- you’re off on the CMP if you don’t have a scanner to read it. But, it can be off up to 14-degrees or so without throwing the P1345 code.

The GM manual has the diagnostic tables for each code. I’d run through those before replacing any other parts. The manuals for a 98 can be downloaded here…

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

A subscription to alldatadiy.com has the same information in a digital format.