Need help diagnosing surge/stumble after Project Reset: Abandoned here by local expert

[redshiftquasars]

I wanted to share where I’m at after my **Project Reset** experience, because I think there’s value in documenting both the good faith going in and the current reality coming out.



I brought my **1971 FJ40** to **Mark’s Off Road** for a major reset because Mark has a strong reputation in the FJ40 world, and I trusted that experience. My truck came in with an **FJ135 engine**, **FJ145 original head/manifold**, and a **Weber carb**. It was actually running pretty well before the project.



The goal was to improve the setup by installing:

- a rebuilt **original carb** rebuilt bu Marks Off Road

- headers supplied by Mark’s Off Road

- a new intake manifold supplied by Mark’s Off Road



To be fair to Mark, I did hear back from him, and he said he did not remember the truck was still not really usable in its current state. He told me he would think about next steps, and I appreciate the callback. At the same time, that response also reinforced how alone I’ve felt in this process, because from my side this has been an unresolved and expensive problem for a while now. So while I’m glad the conversation has reopened, I’d be overstating it if I said I haven’t felt largely left to sit with the outcome on my own.

 

[redshiftquasars]

What makes this especially hard to swallow is that this has been roughly a $10k journey, and at the end of it I still don’t have a truly usable FJ40. This wasn’t some minor refinement issue — the truck came back with a drivability problem that affects basic takeoff in every gear. That’s a tough place to be after committing that level of money, trust, and time to a project that was supposed to reset the truck in the right direction. Adding to that frustration, I’ve only been provided invoices/accounting for about $5k of the work that was supposedly done.

 

[charliemeyer007]

How long ago did all this happen? If it has sat for years, the float/needle could be stuck or clogged, water in the gas..... A header and a intake manifold are almost bullet proof to install and run?

Drivability sounds like an accelerator pump issue. I once had a blob of some kind of glue/sealant bond the leather cup to the carb body - ran like crap, very twitchy with the gas pedal. Took the top of carb off, removed the leather cup and oiled it with neat's-foot oil reinstalled and back to running good.

 

[redshiftquasars]

For the sake of accuracy, Mark also supplied new fuel lines from the filter to the carb. Prior to these changes, the truck was running properly with the previous setup. That’s why I keep coming back to the fact that this drivability problem appeared after the new carb/intake/header/fuel line combination was installed, not before

 

[redshiftquasars]

I’m heading back to Palm Springs tomorrow (3/17/2026), where the ’71 FJ40 is currently sitting. If anyone has specific troubleshooting steps I should try on-site, or can recommend a competent person in the area who really understands these setups, I’d appreciate the help.*

**Project Reset gone wrong: FJ40 returned with drivability issues**

<Build - Project Reset - https://forum.ih8mud.com/threads/project-reset.1372858/>

Beware!!!!!!!

 

[redshiftquasars]

Part of why I trusted this process so deeply was because I was genuinely impressed by the history, experience, and stories Mark shared, including his connection to people like Marv Spector. That made me feel like I was putting the truck in the right hands. What makes the outcome so hard to accept is that after all of that confidence, and after spending this level of money, I’m still left with unresolved drivability issues and a truck that isn’t where it should be.

 

[procomsignathid]

What are the specific issues you're seeing? It's hard for us to help you diagnose w/o much information. Could be something simple, given the number of issues highlighted w/ the rig in that thread, seems like it should be in a better place now, may just be the kind of issues @charliemeyer007 suggested.

Either way, I'd suggest you get a vacuum gauge, check fuel filters, look in the carb window to see if there's fuel flowin', all the typical stuff.

 

[redshiftquasars]

this started with my FJ40 going through Mark’s Off Road for the original “Project Reset” thread here:**

<Build - Project Reset - https://forum.ih8mud.com/threads/project-reset.1372858/>



**What’s hard for me is not just the current surge/stumble issue — it’s that the truck went into that process to be improved, and I came out of it with a vehicle that now has a drivability problem it did not have before. I trusted the process because of Mark’s reputation and history, but the end result for me has been roughly $10k spent, incomplete accounting so far, and an FJ40 that still is not where it should be.**



**I’m trying to keep this factual:**

- the truck ran better before this round of changes

- after the carb/intake/header/fuel line work, it developed a surge/stumble on takeoff in every gear

- I’ve had to tow it to Palm Springs

- I’m still waiting on a concrete resolution path

 

[redshiftquasars]

What are the specific issues you're seeing? It's hard for us to help you diagnose w/o much information. Could be something simple, given the number of issues highlighted w/ the rig in that thread, seems like it should be in a better place now, may just be the kind of issues @charliemeyer007 suggested.

Either way, I'd suggest you get a vacuum gauge, check fuel filters, look in the carb window to see if there's fuel flowin', all the typical stuff.

I don’t think Mark has any of these tools otherwise he would do diagnosed what you are suggesting to find. Once I’m out there i will attempt to find what 10k of Marks Off road could not.

 

[procomsignathid]

Not sure what's goin on w your rig, but I had a had a similar experience after paying to have my carb rebuilt by a local shop in CO. On the drive home it starts stumbling, had to limp it home. I was pissed, but in the end... it wasn't their fault. I had a bad gas tank, crap was gettin into the carb (those cheap paper filters you buy at NAPA don't always do the trick), and so I took the the carb apart / cleaned it. Solved the issue until it happend again. Once I replaced the fuel tank, I was fine. (2.5 carb rebuilds later, but now Im good at it).

I'd take my truck back to that shop in a heartbeat... They did good work, I just had a bad component that I opted to defer replacement, and it bit me.

What Im saying it, it could be the truck was running fine, and there's crap in your fuel system, carb got clogged, any number of things. Honest mistakes happen. Looking at your rig in Mark's thread, a lot of stuff was corrected that was wrong, might be a simple carb clean that fixed things up.

 

[rkymtnflyfisher]

This sounds like it should be a phone call to Mark and talk through the issues directly, not low key try to smear him in a public forum that he is a major contributor to.

Did you ever follow up after the muffler shop to get the carb tuned?

Was the distributor swapped?

There wasn't any closure in the build thread you posted the link to.

 

[cstav86]

I had a similar carb issue with one of Mark's rebuilt carbs, but it was not HIS issue, it was the same as @procomsignathid . I had a new tank, but old metal fuel lines that were leaching junk into my carb.
First I'd call Mark, then check out your tank and fuel lines.

 

[Skreddy]

This sounds like it should be a phone call to Mark and talk through the issues directly, not low key try to smear him in a public forum that he is a major contributor to.

Did you ever follow up after the muffler shop to get the carb tuned?

Was the distributor swapped?

There wasn't any closure in the build thread you posted the link to.

I completely agree. Rereading that reset thread, I do see $10k of work. Rebuilt trans and t-case, rebuilt rearend, carb rebuild, stainless header, on and on. I’m not sure of his hourly rate but every 10 hours at $100 an hour is $1k; that seems like a light rate and doesn’t include 10% tax so….
I’d really like to start a cruiser shop of my own but all too common threads like this are exactly why I haven’t. I would highly doubt that anything Mark did is the “cause” of your issues and have my own assumptions, but it’s not my place to lay guesses. Why not resolve this with him instead of coming here with a vague, incomplete buyer beware story? Not to mention, not even mentioning @65swb45 so he can see and defend himself if needed….

 

[redshiftquasars]

That’s fair. I’m not trying to smear anyone, and if it’s coming across that way, I apologize. I’m genuinely trying to understand why a truck that drove better before this round of work now has a surge/stumble issue on takeoff in every gear. I did speak with Mark, and he said he does not know why it’s still behaving this way after all the work that was done, including the carb adjustment and timing work along with all the other work done in the Project Reset thread. I’ve thought about getting my original Weber back on it, but at this point I’d still like to see if this current carb setup can be made to work correctly given how much time, effort, and money have already gone into it.

 

[Skreddy]

Is it completely warmed up when you’re driving it? How old is the gas? What rpm’s are you shifting at?

There’s a very good chance that it ran “better before” because it was so out of tune it was masking issues. A lot of people find Weber carbs to be too rich, but if you had a big vacuum leak, it would counter that. The mismatched head and block could be part of it and now that it’s adjusted closer to where it should be, the deficiencies are more pronounced. Just putting a couple scenarios out there. There’s not enough info to give a solid internet diagnosis, especially if someone who knows these rigs really well and had his hands on it, isn’t offering anything up; or did have suggestions that weren’t followed.

 

[redshiftquasars]

Is it completely warmed up when you’re driving it? How old is the gas? What rpm’s are you shifting at?

There’s a very good chance that it ran “better before” because it was so out of tune it was masking issues. A lot of people find Weber carbs to be too rich, but if you had a big vacuum leak, it would counter that. The mismatched head and block could be part of it and now that it’s adjusted closer to where it should be, the deficiencies are more pronounced. Just putting a couple scenarios out there. There’s not enough info to give a solid internet diagnosis, especially if someone who knows these rigs really well and had his hands on it, isn’t offering anything up; or did have suggestions that weren’t followed.

That’s fair. I hear the concern, and I’m not trying to turn this into a smear thread. I’m frustrated, yes, but I also do want to get to the bottom of the actual issue. I’ll be with the truck today and can answer some of the more specific questions directly — whether it’s fully warmed up, age of the fuel, RPM range where the stumble shows up, and anything I can observe in the carb/fuel delivery. If this turns out to be something simple or unrelated to the work I’ll say that too. Right now I’m trying to separate frustration from diagnosis and get useful data.

 

[procomsignathid]

I agree with others that this reads much more like "buyer beware" than it does "help me fix my truck." Taking this in the most charitable way possible, I take it that you might not be experienced with carburation or mechanical stuff (that's fine, nobody was born with a wrench), and your data points boil down to "was running better before" + "running bad now" = "work done bad". That does not compute for the rest of us who have seen all sorts of interesting issues crop up, even after good work is done. It can be frustrating, but try to take things in stride.

Regarding money spent: I can tell you that shops around here would have charged way more than what Mark did for the work detailed in that thread. It's hard to find people as experienced as him, and even harder still finding folks like that who are willing to take on work. You won't find anyone here who feels Mark cheated you or cut corners, especially looking at the work done in that thread. I say you got a hell of a deal and your truck has better bones now than when you started. But you need to see it through, and that means either learning how to troubleshoot yourself or taking it somewhere who can help you.

Once you get your truck back, take notes on how its behaving, its responsiveness when you hit the gas, if you need choke to keep it alive, etc. Head to NAPA and get a vacuum gauge, see what vacuum you're running at idle, take the air cleaner off and do a visual inspection inspection of the carb when its idling, etc. Take a look at that fuel filter, see if you see crud in there. If you want help from folks here, details are important.

 

[peesalot]

NOPE, for as much as Mark posts on here, doesnt take comments on his posts, & always asks for you to hit the like button he should see this and make it right or explain why the truck doesnt run. The $ thing is well, 40's cost ALOT in many ways. As a matter of pride & backing up alot of talk I would think Mark will make it right or post some explanation of why it isnt running properly, he certainly has the knowledge, parts, & pride and experience. Your 40 was in good hands and if it isnt running correctly there will be a solid reason or something new since Mark had hands on, just my opinion.

 

[rlong]

Vintage cars and carburetors in particularly are simply not going to be as linear or black and white about operation and performance as one’s 2023 Camry. It is not unusual for a vehicle worked on by an expert, (or those of us with 30-40 years experience that play expert on the internet) to suddenly be “un-fixed” soon after “fixed”. Don’t hate the player; hate the game! (Or get out and buy a new 250 series or a Bronco!

 

[redshiftquasars]

Understood. That’s fair feedback. I hear the point that frustration alone isn’t diagnosis, and I’m going to treat it that way from here. I just stopped to put gas and checked the thread. Once I get started on the truck, I’m going to gather actual data: warm/cold behavior, fuel age, RPM range where the stumble shows up, choke behavior, fuel filter condition, vacuum reading, and what I can see in the carb at idle and on tip-in. I’ll post back with findings once I start digging into it.