Dear Mechanic Person

"Akio Ohtori - RIP Oppo" (akioohtori)
04/15/2019 at 11:27 • Filed to: project golf ball

As part of dropping off the Wagovan at a mechanic tomorrow, I’ve typed up a summary document for it. The hope here is that it’ll help the techs know what has been done, but at the same time I wonder if going at it with virgin eyes would be better? What does Oppo think? (Summary below)

Primary Symptom Summary:

At sustained, high throttle the engine loses power and begins to backfire though the intake. Hereby referred to as “the problem.”

Easiest way to replicate:

80% throttle, 5 th gear, on the highway. Long uphill sections make it happen faster. Full throttle briefly solves the problem… sometimes.

Related recent work:

Fuel system drained

Carburetor replaced/ converted (Weber DGEV 32/36)

Exhaust replaced

Fuel pump replaced

Fuel tank to hard line replaced

OE Fuel Filter deleted

In-engine compartment fuel filter added

Fuel return check valve replaced

Spark plug wires replaced

Spark plugs replaced

Distributor cap replaced

Distributor rotor replaced

Distributor replaced

Reluctor replaced

Ignition module replaced

Condenser checked (0.48uF) but not replaced (part NLA)

Ignition coil replaced

Valves Adjusted

Valve cover gasket replaced

Oil change

Air filter replaced/ upgraded

Fuel system checked

Return not plugged – 2.9 PSI

Return plugged – 3.9 PSI

Flow - ~ 10+ oz per 60 seconds

Block cleaned and re-terminated

Battery ground connector replaced

Exhaust system checked for obstruction (cat back, cat was not checked)

!!! UNKNOWN HEADER TYPE (MULTI-LINE BREAK?) !!!

Problem seems to be getting worse.

Problem went away completely after replacing the cap, rotor, wires, coil, plugs, and adjusting the valves, but came back after adjusting the timing. Changing the timing back did not restore “normal” functionality. At that time, the carburetor seemed to want to be ran much leaner and the idle was hunting. None of this made any sense, but led to the replacement of the distributor, which didn’t seem to help.

Manifold vacuum was checked and was steady at 20 in Hg at idle. Vacuum dropped considerably when the engine was revved, however.

Pulled the #3 plug on Friday (4/12) and plug look like it had been running very lean/ hot, with some blistering on the insulator.

Bypassing the crankcase ventilation solves the problem with bogging when the accelerator pump kicks in (known issue with a weber conversion) but doesn’t solve the problem.

As this problem started after I had the new exhaust put on, I this became my immediate suspicion. I took it back to the exhaust shop and they were happy with the tailpipe flow. Still we temporarily removed the exhaust, but not the OE CAT as it is built into the manifold, and the problem did not go away.

At this point I am fairly convinced that the problem is in the carburetor, but I am certainly open to suggestions.

DISCUSSION (14)

merged-5876237249235911857-hrw8uc > Akio Ohtori - RIP Oppo
04/15/2019 at 11:40

A fresh set of eyes is good, but it’s also good to know what has been attempted in the recent history of the vehicle. More info is good, they can choose to disregard whatever info they want. But should be a benefit to have the information in hand.

Highlander-Datsuns are Forever > Akio Ohtori - RIP Oppo
04/15/2019 at 11:54

Put the letter in a sealed envelope and tell them to open it when they have reached a high level of frustration or spent a certain amount of money.

razorbeamteam > Akio Ohtori - RIP Oppo
04/15/2019 at 11:55

Good luck to you, lets hope that whoever you take it to has some critical thinking skills. I did something similar on the rover and spent 30 mins with the mechanic under the hood explaining everything. 4 months later all they did was replace a bunch of parts that were working, swap the (+) and (-) on my coil (incorrectly) , and charge me $1,300. Hope you have a better time.

davesaddiction @ opposite-lock.com > Highlander-Datsuns are Forever
04/15/2019 at 12:02

I laughed.

HammerheadFistpunch > Akio Ohtori - RIP Oppo
04/15/2019 at 12:14

I’ve come to find that the best thing to do is explain how to replicate it and have them call you to talk about their diagnosis. Then you can explain your work and they don’t go into it expecting a certain fix to work.

TahoeSTi > Akio Ohtori - RIP Oppo
04/15/2019 at 12:53

Could be a bad new distro, I had to replace mine twice before a got one that worked...and endup going with one made in the USA which was $$$ but it works ..the others had bad pickups. But the problem was about the same, just i was pretty sure it was backfiring in the exhaust not the intake.

PartyPooper2012 > Akio Ohtori - RIP Oppo
04/15/2019 at 13:20

I had a le sabre with similar issue. It would drive just fine. Then something would happen (warm up more than normal? ) and it would start losing power. First you cant rev as high as you want. then revs get lower and lower range before it dies. Then cooled down and ran again.

No one could figure out what was wrong with it.

I hated that car. Only because no one could figure out what was wrong with it. It was not an issue i could replicate so mechanics and dealers told me everything seems fine with the car.... umm yeah... no. i got a beige camry after that and never looked back.

Good luck to you tho. you can replicate. Seems like some sort of electrical issue where metal expands and connection gets lost

Snuze: Needs another Swede > Akio Ohtori - RIP Oppo
04/15/2019 at 13:46

I actually like Highlander’s idea. Maybe not a sealed envelope, but I’d write 3 seperate pages and present it just like you did above. First one is just a description of the problem and how to replicate it, the second page a list of parts that have been replaced without context, and then the third page is the narrative (this is how it started, I replaced these things, it got better but then the problem came back, it so I tried this instead, etc.)

And that’s what I’d tell the shop, let the mechanic decide if they want to take it out for a spin and replicate the problem and try to diagnose it with a fresh set of eyes, or they want the additional context and information.

RacinBob > Akio Ohtori - RIP Oppo
04/15/2019 at 13:53

How far are you from LaCrosse? We have an outstanding ex Honda Tech who works at an independent shop. In fact he is going to do a comprehensive rebuild on my Alfa this week.

Granted, I think the carb makes the most sense. By the way, are you sure those are the correct plugs? I once put an extended tip set in by mistake and under high load, it would knock so bad it literally fell on its face. The reason was the steel threads were sticking into the combusion chamber and acting as a glow plug under high load. However it didn’t live very long so I doubt it is the source.

RacinBob > Akio Ohtori - RIP Oppo
04/15/2019 at 13:59

By the way, backfiring into the carb is what mine did too. I think you are way lean. You want to avoid that as rings and pistons get eaten by the lean monster.

RacinBob > Akio Ohtori - RIP Oppo
04/15/2019 at 14:08

Also, didn’t you say you were running a lot of advance? That will cause preignition too. Don’t worry, once found it will be obvious.

Our lemons car had a similar story, rough idle, and i t would stumble at throttle in acceleration. Being 25 year of fuel injected racing didn’t think much of it. We lost a set of pistons as a result.

We only found it because we did a dyno day and the guy took one look at the O2 mixture and shut it down, Crap got into the carb and leaned it out, I suggest somebody who knows webbers have a look at the carb.

AMGtech - now with more recalls! > Akio Ohtori - RIP Oppo
04/15/2019 at 14:17

I would find this extremely helpful.

Victorinoo > Akio Ohtori - RIP Oppo
04/15/2019 at 17:57

I had the same problem on a 1991 Jetta 1.8 fuel injected (not cis) . It was the ignition timing. The shop that did the timing belt did not set the ignition timing right. I suggested it to them and the told me they “adjusted it” and it did not help. I took it to another shop and they fixed it right away and timed it correctly.

MM54 > Akio Ohtori - RIP Oppo
04/15/2019 at 20:21

Best of luck! My bets are still condenser ( when hot) or the cat clogging :)