What to do with my engine....

[deschodt]

Almost immediately after I bought the car 16 years ago, the carb secondary was never opening and the local shop convinced me to go EFI with 320 parts and some DTA computer nobody carries anymore. After 15 ensuing years of excellent service, my engine is all of a sudden not running right anymore, ticking louder, running a bit rough and shakes more than normal. So much so that i can feel vibrations on the steering wheel (another issue, not sure where the contact happens but that is new also). the upgrade makes it a PITA to troubleshoot, to me..  I changed the plugs and also tested disconnecting plug wires one at a time, I notice a drop each time. So likely not ignition. Air is a given, that leaves fuel ? Nothing smokes nor are there shiny bits in the oil.  A few months back I tried to test the injectors with 4 little glass jars, found a suspect one - boxster injectors apparently -  and replaced it, and I could not see any other obvious issues... the problem I'm having is the engine is a friggin' Borg Cube with extra electrical plugs and connectors and hand made brackets for all the EFI, it's impossible for me to figure anything out, I even see a hose coming off the end of the fuel rail going.... nowhere (probably a pressure vent) and it's really impossible for me to know what's what and how to diagnose this is it's fuel... And quite frankly it's gonna be hard for anyone else since only one shop has a laptop old enough and the right software  to reprogram that DTA computer (or check it) and it's far away.  I would not drive the car there in its current rough state anyway. 

 

Part of me is getting annoyed at this rube goldberg deal and would not mind reverting to simpler carbs. I should also mention that my gas pedal travel was always crap on EFI anyway (all linkages are fabricated but it's all too short, very On Off).  I guess "current fix" aside, whatever it turns out to be, I am wondering if I should either go with a more accepted EFI computer and start over (but that's more rewiring), or go back to carbs and get some nice induction noise. I'm leaning towards carbs because I'm tired of all the wires and electronics in there, all over. Of course my distributor is long gone, I'd need a new intake manifold for carbs, a coil, figure out how all that stuff was originally done, redo the throttle linkage somehow, figure out what they did to the fuel tank for EFI gas return or whatever, no idea if all those parts are cost prohibitive or if that also affects my tach reading or fuel tank connections or what ? ... I really do not know which way to go, I'll go talk to shops, but I fear this problem is gonna require a decision because it is a black box right now...  Price wise I also have no idea what I'm looking at either, going back to carbs or change electronics seems pricey both ways...  If anyone has been there done that, feel free to clue me in a bit 😉 

Edited December 15, 2023 by deschodt

[tech71]

Wow,  not a lot of specific input right now but...

Have you considered other cause than your EFI? You did get 15 years out of it, Do a compression test... process of elimination and all that rot😉

 

27 minutes ago, deschodt said:

he local shop convinced me to go EFI with 320 parts and some DTA computer nobody carries anymore

Are we talking K-jet or L-jet here?

[deschodt]

Compression is next. It's possible... I did notice an oily plug last time.  If that's the problem it just punts the fuel delivery question down the line 😉 Will report tomorrow. 

DTA appears to be an ancestor of DTA Fast T2 ECU -  a management system that is ideal for 4-cylinder engines that do not require advanced features like continuously variable camshaft control, traction control, and so on.  An old ancestor. 

 

If I could summarize the original post, I guess I'm asking "considering all the crap I'd need to rebuy to go to carbs, do we think that's comparable/more/less than redoing the ECU with something more modern ? " - Of course if I have no compression somewhere that's moot for now! 

Edited December 15, 2023 by deschodt

[SydneyTii]

Might seem silly but how’s your engine mounts re the shaking ?

[Son of Marty]

I would remove the valve cover and inspect the valve train as one of the first steps in trouble shooting make sure everything is copasetic.

 

[resra]

59 minutes ago, SydneyTii said:

Might seem silly but how’s your engine mounts re the shaking ?

That was my thought too. Whatever is causing the excessive shake may have caused the motor mount to crack or give up to the point the engine tilted far enough for the oil pan to touch the center link? Hence you are feeling the vibes on your steering wheel?

[TobyB]

...you could start by lashing the valves...

 

t

takka takka takka

[PhilC]

EFi is simple stuff really. I changed my 1978 911 to EFi (and ITBs) all on my own with no previous experience. If it were me, as others have said, I would check that the engine is in good health first and if it is change the ECU to something more up to date. Much of the wiring will remain the same, just a case of matching it to the new ECU. 
Also, consider bike ITBs, generally cheaper than carbs and a more simple set up.

You have been challenged 

[jimk]

Post some pictures of the areas you have questions about.

[tzei]

What dta ecu u running? There are lots of download stuff at their web site and a forum for users. I have run DTA s60 ecu like 15 years and none of my problems have been with the ecu unit. And it has been tuned with more modern pc computers.

[popovm]

9 hours ago, TobyB said:

...you could start by lashing the valves...

 

t

takka takka takka

 

The ticking sound... @deschodt when's the last time you adjusted the valves? 

 

Edited December 15, 2023 by popovm

[Dudeland]

I am an EFI person, but I like to tinker. 

 

If you don't want to tinker.  Get a 32/36, and a megajolt which will allow you to reuse your crank trigger and out the door you go. But you will need to re-do your fuel system. If you want to tinker a little bit, a pair of DCOE's. 

 

If you want simple and well-supported, Holley offers a single-barrel EFI conversion that would work great on a stock setup.  This would allow you to keep the sensors, and fuel tank and rip out the rest. You will need a Hall effect sensor on the crank if you want to use it, otherwise a 123 or new bosch dizzy.  The two-barrel version is just a little too much for a stock setup. 

 

 

You will need to decide if you need to re&re the engine.  If that is the case, then you are greenfield, and carbs would be the call. 

 

 

 

 

 

 

 

 

 

 

[John76]

19 hours ago, deschodt said:

all of a sudden not running right

"All of a sudden" changes, especially shaking at idle, could be a vacuum leak. Check all your hoses. These tend to deteriorate over time, get brittle and fall off ... often in places you cannot easily see. Don't forget the brake booster and check valve.

Also check the fuel tank vent system. Remove the cap when idling to see if anything changes.

Noisy valves and low compression tend to be gradual changes over long periods of time...not suddenly.

Good luck,

John

[Mikesmalaga72]

Without all the technicals it all comes down to what you really want. Evaluate, rationalize then stay on plan with some enhancements if able to. Make it so. 

 

[deschodt]

Ok, PHEW....  
So I rechecked a few things within my reach and farmed out the rest. All in all, here is what was done, some by me, most by a pro.. Checked each cylinder exhaust temps with a cool FLIR add on to the iphone - no discrepancy,  retorqued cylinder head (all over, some too tight and too loose), adjusted valves (all over also, my bad on that one I did not think it had been this long), checked compression twice (145-150 on all 4!), inspected chain and other innards as possible, noted some piston slap noise at idle but was told "eh, they all do that forever, F-it", and also crucially I think :  he reconnected a loose vaccuum line that went from the EFI fuel accumulator (?)  I has spotted it but had no idea where it was suposed to connect to, he knew!  It is 80% better in terms of shaking and no more ticking. It's also much nicer in my head because now I know it's not a bottom end issue... There is still a buzz that is directly RPM related (not even in gear) in the steering wheel but I'm told that the engine is not touching any braces and the mounts are OK still and the infamous mount bracket not cracked. I'm told my steering column bearings are shot - wonder if that would remove some buzzing or transmit MORE ?  At the moment the mechanic suspects something out of balance between flywheel and rear wheels or exhaust possibly touchign but hard to tell, because he feels the vibe at 3500 rpm - me ? I feel it even out of gear jsut revving, wasn't there before but it's also less now. Could still be a slight injection imbalance... But anything is possible with a 5 speed shoehorned in there and the people who last did the clutch on it were not 02 specialists..  Still it's not dying, so I can start beating up on it and troubleshoot more.. Had a long chat about carbs - apparently he likes them for induction noise (not so much for mileage or driveability)  but said my EFI was actually VERY smooth and way more driveable,  making "stock" power (no more no less). Said the only tricky thing to revert to carbs would be finding my missing vacuum advance distributor but we can always send one of his spares to be rebuilt... Apparently carb inlet manifold is not hard to find, but he was not pushing to revert back now, he said "If" anything does break in the EFI - given the age of the ECU then yes, probably cheaper to swap back than figure this mess out, but I can just start gathering parts for the eventuality. I have a new valve cover too as mine did not survive the parts cleaner and I need to repaint it 😉

 

Edited December 22, 2023 by deschodt