94 3.0 MT surges between gear changes

[christw]

I think I've seen this problem on here before but can't recall any potential diagnosis other than problems with the charcoal canister that I already removed from the vacuum system.

Every once in a while my truck decides to surge up to 3k when I put the clutch in to shift after traveling upwards of 45 mph. It'll maintain 3k for a few seconds and bring itself back down to idle at about the same pace the revs drop after a start-up. Restarting the truck seems to solve the problem. Sometimes it just stops on its own after one or two shifts. This has only happened a handful of times these last few months so I don't have a whole lot more details.

I'd take it on a few more drives to get video but it was pissing coolant this morning and I've yet to go looking for the cause.

The following mostly unrelated parts have been replaced: clutch, driver side head, top end gaskets, rear main seal, oil pan gasket, battery, TPS, MAF, O2's, IAC, coil, plugs, wires, #4 injector

 

[Old-Black-88]

Sounds to me like a vaccum problem to me. Since you have been taking stuff off double check everything you touched. A line may have been nicked or left unplugged. I had a similar problem with my Lincoln. Now I have bigger problems since I took alot of the motor apart.

 

[black_demon69]

check accelerator peddle cable it could be sticking.

 

[racsan]

my 4.0 had a similar issue a few years back, ended up being a failed fuel rail gasket.

 

[christw]

I redid all the vacuum connections about two weeks ago when I did the #4 injector. The problem existed both before and after that. It'll do it when hot or cold and at about any speed and only when clutched. Seems totally random in when it shows up and how many gear changes it persists for. It acts normal if the clutch is engaged and returned to gear during the condition or if I wait out the revs (3-5 seconds). I really feel like my IAC is going nuts for a few seconds based on the sound and timing but I could always be wrong.