Hi ALL,
Ive been lurking here about 4 months now and I now have a problem I hope you can help/point in the right direction. Oh its a 1990 4runner 3.slow 127k (rebuild at 90k by previous owner)
Last week when I got off work the runner had what I thought was a dead miss, felt like it was running on 5 cylinders, did it all the way home (14 miles) next morning was the same then it went to doing it intermittently, smoothed out after warm up and only noticeable when barely giving it gas (a jerking hesitation) So far I have checked wires/good, pulled plugs/good/not fouled (plugs,wires,cap,rotor replaced 11/07 at 123k) Today we did the seafoam intake cleaning through the brake booster vacuum line/no difference, although throttle response is better and engine is smoother when not missing (or whatever you want to call it)
I'm thinking its got to be fuel related or electrical ? injector ? fuel filter ? I'm kinda lost so any help is appreciated,
I cant post at work but I can read it, also I'm in the auto industry and can semi work on the runner at work, THANKS

 

Check the tps, throttle position sensor, might be worth a shot. other than that no suggestions

 

Thanks for the response Mike !
I did check TPS today and its good, changed fuel filter/no change. Could the timing be off ? It seems to be getting more and more prominent, This is driving me CRAZY!

 

Me is guessing fuel or spark. Check the cap, if there is a small crack there could be moisture getting in. does it act like an engine after being washed and the dizzy not covered?

 

No cracks in the cap, I'm not sure how it would run if dizzy got wet like that (never happened to me)
I think I'm getting closer, reset ecu, checked timing/right on, although you could see idle was moving up down with timing light, didn't realize I had bosch plugs in it so I replaced them with NKG's, threw in a can of BG MOA, it smoothed out but still slight hesitation/miss still there although its not jerking like it was, and it seems like I've lost some power under load? I may go and replace the wires as well ? any suggestions are surely welcome.

 

plugged cat? or MAF?

 

I have the same problem and found that I had no compression on number 5 cylinder. Turned out to be a burnt valve. I would check that also mine was doing the same things that it sounds like yours is.

 

Kinda sounds like an EGR sticking open?

 

Just came inside from trying to figure out the exact same problem, only all I did was change my battery and when I put the new one in I went to go out and now I have a definite miss, most prominent when starting from a stop.

Was running perfect before. Pretty pissed off right now.

I will definitely be watching this post.

 

I don't have the cat anymore but I will check out the EGR and do the mod if its bad, I hadnt thought about the Maf for a miss/stumble but i'll check it out as well. I think the timing is retarted, A friend told me these engines like 16 degrees off dead center ? does that sound right (I havent searched timing here yet as Ive been super busy at work home too)
Thanks to all for your help and direction !

 

Do you have access to a cylinder compression tester? I'd give that a shot.