surge/lunge

[greyface]

I did a search for lunging and surging and got a few hits, but all report surging at startup, idle, or when stopped.

My problem happened while cruising at highway speed. I was running at 65mph and it felt like someone hit me from the rear. It's happened twice in the past 6 months. The first time it happened, if I recall, there was a single popping sound... Almost like an exhaust backfire but not as loud. The second time it happened there was no noise, just the surge. Any ideas? Thanks.

85 FJ60
Chevy 5.7L TBI V8
H55F 5 speed transmission

 

[jgordon]

do a search under my name with rpm and miss, if I get a minute I'll try to find it. My symptoms were a miss/hesitation, then a surge/lunge when the engine "found itself" again.

Mark where it happens, is it at a certain rpm? Mine happened frequently enough that I was able to figure out where it was and anticipate it. Never quite got used to it. EGR valve bypass helped a lot, as will (I'm told) a carb rebuild.

 

[mtb_rider]

Notice that he has a 5.7 with TBI, so gotta think Chevy, not F motor. Did it slow down at all, or just gain speed? I assume it was just a quick surge, and went back to normal on it's own?

 

[greyface]

Did it slow down at all, or just gain speed? I assume it was just a quick surge, and went back to normal on it's own?

Exactly, as if I got hit from the rear by a vehicle going much faster than me. It wasn't a slow, gradual surge... More like a quick bump. It didn't slow down at all. It happened and then went back to normal and it doesn't repeat for the rest of the drive.

85 FJ60
Chevy 5.7L TBI V8
H55F 5 speed transmission

 

[jgordon]

d'oh.

Notice that he has a 5.7 with TBI, so gotta think Chevy, not F motor. Did it slow down at all, or just gain speed? I assume it was just a quick surge, and went back to normal on it's own?

 

[iaintscared1969]

Got any codes set? What about recent fuel filter? Could have a bad connection on the 12v ign on connection or a bad ground for the harness. Check the TPS and see if it is reading consistant.

 

[greyface]

In troubleshooting this problem, I may be heading in the wrong direction altogether but while I was under the cruiser I found a quarter-sized hole in the muffler. The whole exhaust was rusted from the Y pipe to the tail pipe and all the welds in between were just shoddy. So, I had the entire thing replaced... Y pipe, muffler, and the cat-back. Like I said, I may be heading in the wrong direction but in the condition that the exhaust was in, it needed to be done. I still need to do what iaintscared1969 suggested and check the fuel filter, TPS, etc.

We'll see how this goes...

 

[elkiny]

surge

Hello Greyface,

I have an 85 FJ60, 2F w/H55F and I also have this exact problem. As a matter of fact I posted it a couple of weeks ago. In my case I actually hear a loud "thunk" at highway speeds mostly, but it has also done it in 3rd and 4th gear. Like you describe, its almost as is someone bumps you. It happens very seldom. I first noticed it after the H55 swap so I assumed it had something to do with the tranny, but I think its the carb or some other fuel component. If you figure it out please let me know, this has been driving me nuts. I changed out the fuel filter and it has not done it since, but like I said its intermittent.

Ramon....aka elkiny