Injectors for a 88 3.2 engine
 

Hi, I’m having some injector issues. 3 are intermittent not firing occasionally but to be fair engine has been sitting for long time. I’ve had them all cleaned/ tested but can’t seems to stop intermittent issue. So is there a better updated injector recommended or do I just go std and best place to purchase pls?
Boydyrs

As far as a better, updated injector, others here can answer accurately I'm sure. Many have experimented, along with a few colossal failures but always something learned.

I used Buick 3.8 injectors in an 86 911 some years back with no issue whatsoever, but I later found that injector either discontinued or changed in some incompatible way.

More recently, I decided to go 'full modern' and get rid of my semi-ancient performance chip (Weltmeister) and old injectors. I contacted Sal Carceller who runs a 4 hole atomizing Bosch injector with his special chip. Mine's also an 85 model (M491), about 65k miles.

When you go to his injectors, you must change the chip; they've got a thing going on. <-Tech speak. Now you may be in love with pure stock - as I mostly am - but this combo had several advantages to consider.

In my experience, the modern injector you seek is a good portion of the upgrade. Squirting a stream of fuel vs an atomized puff give different starting/running/idling/throttle characteristics that others can quantify scientifically, but for me ALL of those improved. Oh, and not that I care too much, but the fuel mileage increased markedly. That alone indicates the uptick in efficient burning.

I know my car. We've grown familiar with each other. The chip + injector change was a leap in improved behavior all around. Far as cost, as I recall the package was less than the OEM old tech injectors alone. I actually pulled my old ones, had them 'rebuilt', and put them in a box, never installed but saved with my OEM chip when nostalgia or the values attached thereto warrant.

So, that's an option for you to consider. Others here may've found a compatible modern injector, and here's hoping they chime in. Otherwise, I'm seriously satisfied with my kit. Best to you.

Sal Carceller's injector kit is what you want. And if you really want a performance improvement, buy his MAF kit as well.

Can you post a link or contact details for Sal Carceller pls?
Thanks for reply.

http://forums.pelicanparts.com/porsche-911-technical-forum/888986-new-product-performance-chip-matched-injectors-3-2l-carrera.html?highlight=injector

Pelican username is scarceller. Great guy to work with. He'll get you squared away.

After much study I bought and fitted a set of Bosch 0280 155 931's and verified the AFR's as very safe on a dyno with my Wong chipped '88. They are a straight forward bolt in replacement but have a modern style 4 hole atomisation plate.

I'll do the same on my 3rd 3.2 if I buy another rather than having the standard injectors reconditioned like I did on my first one.

When you have injectors that are tested as good but you still have an intermittent problem then the injectors arebn't the problem. New injectors will just get you an intermittent issue with new components.
- Check the injector connection that is in front of the engine on the 'shelf' between the shock towers.
- Check the grounding strap to the driver's side intake manifold.
- Have the DME checked to make sure the injector drivers are working correctly.

Actually that's a good point that I didn't pick up in the original post. Just to take your point a little further, the injectors on a 3.2 are batch fire - even though they are wired separately for right and left banks - so if one works, the whole lot should work unless the injector harness is damaged or one of the recently reconditioned injectors has a intermittent problem. I would think both faults are highly unlikely.

I suspect the problem lies elsewhere.

However to check you would need to remove the electrical retaining clip off each injector plug and cut the zip ties on each injector lead, idle the engine and unplug each injector one by one until you find the lazy cylinder(s). Then do the same with the ignition leads. For those cylinders that aren't contributing, suggest you swap in a known good plug and lead as see if that corrects the misfire.

I reckon it more likely to be an ignition fault.

Which ones are giving issues? Injectors are connected in two banks in 3.2 (1+2+3 and 4+5+6).
If the problem is in one of the banks then it is most likely ECU or injector control wire from ECU, if they are not in one bank then it is probably some wiring issue in the injector harness.

Agree 100%, ANY oddball/intermittent issues with an untouched 30+ YO Motronic module warrants a check/rebuild/upgrade from a competent tech (like Ingo). A single trace that's cracked, one bad resistor, and you can chase your tail forever trying to buy parts to "fix" the issue...

That's my point, there is only one injector driver in the DME. If one or more injectors are working fine, it means the problem is not with the DME but has to be with the harness, connectors or the injectors.

Or the ignition system.

The harnesses can wear out and short as well. I've seen it on mine and a few others. Clip the cable ties securing the harness to the fuel rails and check the inside of any tight bends in the harness. You might find that the sleeving and wire insulation has been rubbed through.
Timmy2 built me a nice replacement.

Are you sure about that? For some reason I thought there were two drivers in the ECU. EDIT - I really am asking because I don't know.

Left bank and right bank fire alternately.

I haven't checked it myself but our favourite Pelcanites who are expert in 3.2 Motronic have posted this information in the past. I came across it when investigating the feasibility of upgrading to a modern ECU. A quick Google will uncover those posts if you're interested.

Also think of it this way, the 3.2 Motronic ECU has no capacity or sensor telling it where the engine is in it's 4 stroke cycle - ie Is a cylinder on compression or exhaust stroke? - as it only has crank position and speed sensors. Consequently there is no point in running multiple drivers or individual injector harnesses and the only feasible option is to batch fire.

Assuming you are talking about 3.2 injectors, I'm very happy to bet you a carton of my favorite beer if you really think you're correct.:)

I'm certain I read it in a reference document, but now that I think about it, it may have been about the 3.6 engines using a later version of Motronic. I'll see if I can find it.

Not so, the 84-89 injectors are batch mode they all fire at the exact same time. Not only that, they also fire every crank rev so they fire 2 times per stroke.

Each bank does go to a diffrent pin at the DME connector (pins 14 and 15) but internally these 2 pins get tied together within the DME and are then controlled from a single transistor.

Peter,

The 931 injector is a hi-impedance injector and the DME has a special injector offset (battery compensation) table. The table in the DME is for lo-imp injectors and way wrong for those 931 injectors.

Not saying they won't work, but the 931 injector does not properly match the injector model in the DME.

I know because in my solution I properly model injectors within the DME.

Just be sure all your AFRs are correct at idle, part throttle and WOT.

The lo-imp factory injector has a offset time of about 0.45milliseconds while most hi-imp injectors are in the 0.60 to 0.80ms nearly double the time.