DJ99

Greetings.

I don't post much here because I usually don't have issues with my 30 year old T100 with 65K miles!

Here's the issue:
I was having a slight misfire during idle and sometimes at speed. A while back I did locate some bad plugs and grounding out/sparking around the plugs. I fixed that by replacing the plugs which were worn out and badly gapped. I also replace the roter and cap and wires at that time. FYI - I had to make 100% sure to adjust the plug connectors in the boots to make sure they were all where they should be. I didn't expect that. I used boot grease, etc.
The misfire was better, but not entirely gone. I decided to replace the injectors since they are a little old and only rehabbed once by myself. I decided to finally do the EGR delete at the same time. I removed the EGR and pair valve, EGR modulator and capped everything off as per the instructions. I installed the 5.7ohm resistor in the gray egr heater plug. I removed the plenum and swapped out the old injectors for new - they came with new seals. No problem. I got it all back together with new plenum and throttle body gaskets and at cold idle it runs 1200 just fine and sounds great when throttled up. When the thermostat opens, it starts to bounce slowly up and down around 800-1000 continuously. I believed it to be the iacv or it's hoses on the throttle body so I got new hoses although they weren't really bad and checked the flow. I also got another throttle body and swapped it in and have the same idle issue. I have checked everything I can think of for vacuum leaks and nothing appears off to me. My intake tube from the air meter is solid. There are no codes. Timing is 10BTDC with the jumper and around 8 without. Does this sound like a vacuum leak to you? Any ideas I can troubleshoot before I take it to a professional?
I will appreciate any ideas you can throw at me!

DJ99

I thought I would post what I found. I watched a video of a 22re guy that had 3 out of 4 bad injectors. His symptom was warm idle bouncing. I replaced the newly replaced injectors with my original factory models which I individually cleaned and tested and all is well. I hadn't suspected them as the cause. What I learned through this experience is to not try to do too many "fixes" at the same time to avoid having to chase down an issue without knowing which "fix" caused the problem. I have learned a lot more about my 3VZE now that I will never need to know.

old87yota

Yes, just because a part is new, does not mean it is good.

I am glad you got your problem worked out!

Robert m

iTrader: (2)

What and where did you get the new injectors?

DJ99

I got the injectors off ebay from f**l i*******r s**p. In retrospect, the price was too good to be true. They were supposed to be refurbished - cleaned with new rubber. What I got looked brand new, but they did not function like the original denso - in fact not at all. It was too late to return them but I asked anyway since they were not at all working right and maybe not even the right part. They offered me $8 as a "sorry, not sorry", but I told them I would just post my experience here instead. I checked the negative reviews and found I'm not the only one.

DJ99

So I went back to the original injectors with professional cleaning and the problem(s) persisted. I moved on to the intake gaskets. They were replaced and still the problem. The compression and leak-down tests seemed OK, but there was still the issue. I finally yanked the heads and there it was - a puddle of coolant in cylinder 5! I'm in the process of replacing the head gaskets with a valve cleaning and tune up. They are surprisingly in very good working order. This truck only has 65K miles in 30 years. The original head gasket was replaced maybe 25 years ago "just for good measure" by the local dealer. I now with they hadn't touched it.

DJ99

So my misfire at idle and bogging under load persisted. After ruling out just about everything, I thought I would hone in on the question of what the heck is the "fuel pulsation damper"? I found a great article online that described my issue perfectly. The article stated that sometimes the screw loosens and can allow the damper to stroke too far downwards causing a lean condition - like a misfire at idle and especially under load. I removed the damper and took the cap off and although the damper was not leaking, the non-adjustable adjustment screw was completely loose under the cap. I replaced the damper (aftermarket - not denso, and no screw) and those nagging issues are now gone. I have learned a lot from the process.

Jimkola

Odds are the headgaskets were done under the VO6 campaign eons ago. I doubt the original ones from 1993 lasted this long.

scope103

The FPD damper screw has nothing to do with adjusting the stroke of the diaphragm. It's attached to the diaphragm and moves in and out with it. When the fuel rail is pressurized, the screw sticks out a little farther. It's a quick and rough way to tell if the rail is pressurized.

But, whatever you did, I'm glad it fixed your problem.