Been chasing ghosts here for a month now. When starting my truck, it usually wont start unless you give it a little gas but when its cold it will most likely start right up. idk if thats got anything to do with my misfire....SO you can sit there and rev the heck out of it in neutral with very little to no misfire. It idles fine, but once you take off and accelerate a bit it stumbles pretty good. full throttle is little to no misfire. Ive done plugs, wires, cap, rotor, fuel filter, air filter, a bottle of fuel injector cleaner and i believe the guy before me did a fuel pump as well. Now i know the first post is gonna be about timing, i know, but im not fully convinced yet. Ive been sifting through all the misfire posts and cant seem to find one that matches up. Any ideas guys?

 

well... when that happened to me, It was my injectors.. but adjusting the timing is waay easier :p

 

I am guessing you are talking about your 88. It probably has the old style injector connectors. While it is idling, try wiggling the injector conections. By misfire, I am understanding missing on 1 or more cylinders.

They can be brittle and look like they are connected to the injector and may even be on the injector, but it doesnt take much to break the connection.

 

thanks! yes its on my 88...im gonna go check it now...tonight ill get my hands on a timing gun and look into that as well!!!!

 

It has a little wire like c-clip that holds it on to the injector. I said to wiggle but should of said to give a slight tug and push on the connector. May need to use a pair of needle nose pliers or something similar.

I had a problem of it running great and going down the road it would start to cut out. Guess the wind was pushing it off or if I floored it, the spark would jump the gap and run fine. That was my theory. Took me awhile to find it.

 

I have had the same problem. Check you O2 sensor heating circuit. If your O2 is not warming up and the ECU goes into closed loop it stumble and runs like crap. At full throttle you force the ECU back to open loop and it runs fine.

 

Where exactly can I find this said heating circuit..? Near the 02 sensor itself?

 

2 of the wires going to the O2 sensor are for heating it and 2 are for reading the sensor. Depending on the year and what has been done to the truck the colors will very. Just check your wiring to the O2 sensor for splices or burned wires.

 

Ok thanks!

 

I've had a failing TPS and 'out of limits' Coolant Temp Sensor cause this issue as well.

Best wishes on finding it.... I've been chasing a 'smaller' 'miss' for 2 years... bout to give up! lol.

 

Also before you do anything make sure your valve lash is within spec. Out of spec valve lash will make the engine seem like it has a miss and run like crap.

 

Good pointing out! And yes, I had that issue when going to the new CAM (261) with crappy condition adjusters... Replaced the adjusters and got it to 7 and 9 as engnbldr says... Seems ok on my end, as I've checked it many times... BUT, can't hurt and it's an easy check- to get back in and MAKE SURE.

Pretty sure my miss might not even be a miss as much as an "EFI" or "IGN" component that's just A TEENY bit off... Could even be my FPR or leaking CSI or something the like(had RC service my injectors 8K ago, with an "EXCELLENT" passing grade on all 5, including CSI... but NEVER KNOW, lol.) Still think it's a weird 'spot' in my AFM or IGN or fuel pressure issue... The hunt WILL continue, but I can only check EVERYTHING SO MANY TIMES, right? (Plus, my "MISS", if that's what it is, is more of a very slight erratic 'puppupup-pup-pup-pupupup' at Idle and low RPM once hitting closed loop temps.. So doesn't sound too similar, but still, can't hurt to mention everything that causes 'gremlin-drama', right? lol)

Sorry OP.. not trying to get answers for me... just sharing to show "I can relate", lol.

still watchin!

 

ok so its been forever but im back...and the misfire is still there. i had my 02 sensor unplugged aslo have my pcv valve unplugged with a bolt in the vacuum line...the truck ran great! the misfire was barely even there. once the truck warmed up it was gone. now i hooked up the o2 sensor and adjusted my timing (which was off a tiny bit) and the truck runs like CRAP! Im lost...misfires until 3500-4k rpm than runs great but it wont even hit rev limiter it just kinda sputters.

 

Have you checked your maf ? I have the 3vze and i had a similar problem. It was the maf connector was corroded and causing it to not send a strong signal to.my fuel pump. Now im not asking for sarcasm or anything else. Just maybe worth a shot.

 

Auxiliary air valve is another option. Had this problem on a bmw 525i. Acted the exact same.

 

yup put a different air box top that came off a buddys truck that ran great...no change. ill check the iac tomorrow...

 

Yeah cause that iac goes sometimes. It has to open wider when you shift from park or neutral to drive. Its not a real hard fix, not sure on price. Usually they can be cleaned but if its been in mud or water, its probably filthy!

 

IAC seems to be ok....idk what to do here...if i don't get this figured out my yotas gotta go its gotten to the point were the truck doesn't just misfire any more it just runs like a turd!!!!

 

Do you have any codes?

I had this same problem with my old 22re and i couldnt ever figure it out. Only thing id say check is coolant temp sensor and the TPS. After that maybe check your mechanical timing to see if your timing chain skipped.

Oh and i love my 3vze hehe

 

Have you considered, a worn cam lobe?