I'm just now revisiting this thread. I had finals earlier this week so I have almost 2 weeks off before summer semester begins... WOO HOO!!! I now have a little time to visit my DF friends a little.

Glad to see the problem's solved! As for mine, I'm going to change the wiring, cap, rotor, and plugs this weekend so this beast runs like it should for all potential buyers. I'm now a 3rd gen owner and I have to say... I love my "new" truck! I'm gonna miss my 2nd gen, but not enough to keep it.

As for the scanner, it reads O2 at normal to slightly rich for a short bit, then drops to almost nothing then almost immediately back up to slightly rich again. This happened while holding a steady speed while driving. I haven't looked at it recently, but the issue hasn't returned. Of course, I haven't been driving it nearly as much since I bought my '05. I typically didn't drive it too far very often; most trips were w/in 20 miles or less. When the issues arose is when I was on trips for 60+ miles in hot weather. Thanks for posting what you found. I'll just replace those things on mine this weekend.

Oh, and to you HeyYou, as for the CAT, the truck doesn't have one. Thank you for the suggestion though.

 

Update, it came back with a vengeance this week.

Disconnected the whole MSD system, running stock coil to troubleshoot. Definitely a spark issue though, as it bogged out on successive cylinder firings and read way rich.

 

Aim, correct me if I'm wrong but doesn't the coil bracket have to have good contact with the block for you to get a strong spark? I'm hinting at pulling it, filing/sanding it down and reinstalling it to eliminate a possible contact (ground) issue.
I know my negative wire on the battery looked fine a while back but I had a shoddy contact because it was a little glazed and I had to scrape the glaze off to get a good contact.

 

^ i don't think so. i think the pcm controls the ground to the coil via the wiring, and uses that as part of the whole ASD shutdown control.

 

It isn't the coil or the msd controller. Happened yet again today after I had deleted all that stuff.

Every time it happens, the a/f ratio reads way rich (high nines and low tens), and the engine rpms drop about 300 rpms.

Sometimes it bogs 3-4 times in rapid succession, some times it's 1-2 and they are several seconds apart. It happens in any gear and will happen with any amount of throttle, whether it's steady or accelerating. Every time it happens, it pops right out of it and runs fine again.

I wonder if maybe I have one plug wire that is going bad, or perhaps the crank sensor is losing signal intermittently.


Getting no CEL whatsoever to help diagnose.

 

Check the connection for the ECT sensor the PCM uses..... an intermittent connection there would give you those symptoms.

 

You are referring to the engine coolant temperature sensor, correct?

I'll check it, but I haven't had any weird readings on the gauge, and the 2001 only has the one sensor.

Thanks for the help, I'll take any I can get at this point.


There is a little info to add:

I hooked the snap on scanner up to it.
According to it, with only 13 key on starts since I last reset the pcm (this morning), I have 1 misfire on cylinders 3, 5, & 7, two misfires on cylinder 2, and 6 misfires on cylinder 6.

 

have you ever taken your injector connectors off? Because if you have, you MUST have those THIN WIRE clips that are at the BOTTOM of the inj connector pigtail (the things that fly off when you take the injectors off). They keep the connector SNUG to the injector.

I HAD THE SAME PROBLEM. I was getting a misfire on 4 cylinders and they all were a bit loose on the injector.

You just need to get new pigtails. fiveo sells them the cheapest. I think they are 4.95 each for EV1 connectors, like your truck.

 

you're sounding more and more like bad fuel.. got any crap in that tank?

 

Have all new EV6 pigtails, they are tight. Injectors are firing or there wouldn't be a rich condition every time it happens. I literally have an air/fuel ratio meter plugged in at all times with a readout on the A pillar gauge pod, so I'm skeptical it's an injector issue.

I'm also doubting it's bad gas, as I only, and I mean only, fill up at Chevron stations, and it's been three different stations that I've rotated over the 2-3 months this has been happening. I have tried other brands of gas like QuikTrip stations in the past, and have had obvious running problems with it before, but nothing like the situation I currently have. I know what bad gas feels like, and this ain't it. I would buy into the fact that it feels like what I imagine an object clogging the fuel pickup screen would do, but with the A/F ratio reading rich when it happens, I have to logically assume it's getting fuel. Cruising A/F is 13.9-14.3:1, when this happens I consistently see 9.8-10.3:1 on the A/F meter. That's unburnt fuel, and that leads me to suspect spark.

With so many misfires over several cylinders, I'm leaning toward something that delivers or distributes the spark. I have replaced the cap, rotor, plugs, swapped coils, swapped the coil feed wire to the cap, and deleted the MSD system completely. I need to pull the wires and test them individually, and test the sensors that would tell the coil to fire.