Hi and thanks in advance for your help. My truck is a 1986, a 2.8 engine with 52K on the rebuilt engine. It had been developing a bucking issue, and after some work, I have some improvement, but still a bucking problem that is less dramatic. Below details what I've done.

The koeo codes showed 14 and 18. I could not get codes on a koer as it would not idle. This is what led me to replace the ignition module. What I got was a good cold idle, but after she warms up, she still idles good, but popping the accelerator gives me a shimmy that must be the bucking when the truck is driven.

Replaced oxygen sensor. More to this below, but I admit that I had a heck of a time. Had to heat up this one to get it out. Then, I found that the lower part of the sensor froze in the threads, so I used a rethreader and got the new one in except for a 1/8 gap. Does that mean the sensor heater won't ground?

I tested the voltage to the tps and got the 5 that I'm supposed to.

Replaced the oxygen sensor. I tested the heater voltage wire and got 12.7.

Swapped out the map sensor. No change.

So, I know the 18 code is loss of pip signal.. I've read that the pickup on some distributors can go out, and I have one that I believe is good. Not really adept at testing these things, but I'm willing to try...

So, I read a great description of a WOT test, and the engine starts... I'm not sure how this relates to a miss or what bad wiring may be involved...? Can somebody explain this?

Okay, that's where I'm at. Regarding the o2 sensor... those threads are good now, but may not be in the future. I'd like to find another Y-Pipe, but can't locate a new source. Would anybody know of one? It would sure set my mind at ease.

Thanks again. This is the truck I use for our pet sitting business and it would be great to get her going soon without a big expense at the mechanic's shop.

Tony

 

An update on how this is going...

Much better, with a little drama. I took voltage readings on the tps, and it checked out okay. Not so with map sensor; 5.1 at the wire and none at the connector. Quick trip to the junk yard took care of that. Still had the same shudder at idle and revving the engine (all rpms). I had popped the battery cables, but still received the code 18. Now, it would not idle for key on engine running codes, so I went ahead and swapped out a few good parts that I had (a new IAC and an extra coil--easy jobs). Yeah, no diff, but I expected that. At this time I put in new plugs and wires. Still, no diff. While I was scrounging for my extra parts I came across a new distributor from an O-Really switchout from five years ago, and what looked to be a pristine ignition module. Put those in, idled much better. Timed it to 12 btdc with the spout connector off. Did a road test and runs great warm. Here's the deal...

It does some bucking at first. Bucking went away on the road test, and it idled nicely.

Came back and ran the codes. Got code 11, the all is good code!??? Yeah, but I had done some cable off battery time, and the road test was barely twenty miles.

I'm at the point where I want to revisit the O2 sensor. I had to do some rethreading as the old one had heated part of the casing of the old sensor in there and I had a bit of a gap left. I understand that the O2 Sensor generates voltage from the heat. I've tested the voltage from the white wires a few days ago. One (the heater wire), had 12, and the other, the ground, had nothing of course. But... mebbe the ground is not grounding because of the gap and it has to heat up more to generate a signal??? I wonder if anyone can suggest the best way to test it. I've got a multimeter that can do the job, or I have one of those Harbor Junk light testers. I'm asking as I don't wannna blow anything in the computer. Oh, btw, I do have another computer, not a big deal to switch out, but I don't think it's necessary.

So, just throwing it out to those of you who are wiser than me. Which is pretty much everybody...

Thanks for listening. If nothing else, I hope this helps somebody.

 

im not sure I understated the gap? do you mean its not seated all the way?

 

Thanks for the question. Yup, not seated flush with the y-pipe; there is a gap, nothing leaking, but I'm concerned about it grounding for the cold start heating element (the white wires of the O2 sensor. You see, the casing of the old O2 sensor had welded in there. I made some good threads with the rethreader tool, but after a few tries to tap all the way to the base, well, the threads started looking thinner. Not wanting to have to deal with trying to find a new y-pipe or chancing a lousy helicoil job, I got the new O2 sensor in there and this gap, about as thick as a spacer, was as close as I could get.

 

if its not leaking and you got 12v I would say its grounded.

 

Hey, thanks for the reply. I'll move on from that and take a look at the fuel system as the source of this intermittent issue. Just drove her about 10 miles and for the most part, she's doing great. Still getting code 11 on the reader, but there is some kicking on the warm-up side.

 

what is code 11? its either spark of fuel to me im kinda guessing fuel meaning an injector ? if missing just cold to test spark you could pull plug wires one by one off the coil?

 

Thanks for your suggestions. Code 11 is "all is groovy."