P201 P301 codes & compression test

Went into town today, about 15 minutes away.

On the way back I got a flashing check engine light with a rough idle. Noticed that if I gave it a lot of gas it would stumble.

Got it home and let it cool. Checked over the injector harness and the wires look OK. Didn't go any further with that.

Pulled the plugs. #1 (one with the codes) had a glob of carbon or something bridging the plug gap. Otherwise it looked good.

#2 and #4 also had some material in the gap but it was splintery and apparently wasn't enough to throw a misfire.

Did a compression test.

Cylinder , Dry, Wet
1, 150, 155
2, 190, 200
3, 155, 160
4, 185, 195
5, 195, 200
6, 190, 195

I cleaned off the plugs and checked the gap (still .035 on all six).

Going to put it back together shortly. I'm assuming the gunk on #1 plug was causing the misfire codes and they'll likely be gone, but I'm curious what that substance is and where it's coming from.

Also, do my compression numbers indicate anything? She has 176k on the clock and I"m not the original owner.

Spark plugs are cheap but I'd worry about that cyl 1 comp test!

I should also mention that, other than the crud on 1,2&4, the plugs looked the same across all six - nothing to indicate a problem.

RCP Phx said:

Spark plugs are cheap but I'd worry about that cyl 1 comp test!

Click to expand...

I would be changing them since I have them out, but it's too late to get to the part store tonight.

They're just over a year old with maybe 10k on them. Put them in July of last year at 165k. (I've started recording the work I do on our vehicles - starting July of last year )

What brand are they?

Also what year are we talking about?

2001

I think they're autolites. 985s if IIRC.

I got it back together. Codes are gone while idling in the garage. Going to go for a ride and see what happens.

Well, it runs better than it has in awhile.

I didn't have any complaints, but now it's noticeably peppier.

I went to move it around in the driveway, and the P0201 is back as is the rough idle. So I still have a problem.

So I pulled the fuel rail.

My intention was to swap the #1 and #2 injectors, but I got distracted and set them down together and forgot which was which. So I pulled 3 and 4 and swapped the two sets.

I figured if I have a bad injector, I'd get a P0203 or P0204 code and if I have a harness or PCM problem I'll still have a P0201.

Well, I still have a P0201.

So guess there's an electrical problem somewhere between the PCM and the injector.

Are there any common failure points in the harness I should check first? Everything from the plug through the plastic wire enclosure across the manifold looks good...

A little long but it describes a very common problem. https://naxja.org/forum/showthread.php?t=1145993

I'm done for the night.

I have a neat little test light that has two LEDs and allows you to check both power and ground. You ground the clip and the probe glows red on hot. If you clip onto the hot of the battery, then probe glows green when it touches ground.

So I pulled injector 2's plug. One lead glowed red indicating steady power. The other pulsed green indicating the PCM was grounding it.

Injector 1 was the same, but I found I could change idle by wiggling the plug.

I can feel both injectors pulsing.

I got thrown a bit because my code reader (Innova) doesn't seem to clear these codes even when the problem is fixed. I had P0201 and a new P0202 from pulling the plug on #2. Both stayed after clearing codes even though #2 was plugged back in.

Shut off the car, cleared the codes, and they both stayed gone.

The plastic on the injector plugs is getting a bit fragile. A couple of the lever latches broke off from finger pressure and I had to slip a screwdriver down to release the catch.

So I think I'm going to order a set of injector plugs and solder them in at all six positions. I have a feeling the #1 injector plug is my problem and I don't see any reason to expect the rest of them to be in any better condition.

Thanks for that thread. I will go over the whole harness.

I have new injector connectors on order. Should have them Thursday so this will be a project for next weekend. I'll pay particular attention to the area between 5 and 6.

Appreciate your help RCP Phx