Barry Johnson

Hey all, my knowledge mainly lies with 928s, and my 951 had been sitting without an engine for about 3.5 years, and I've just now swapped in a good engine from another car.
I've got it all hooked up, running, boosting, but I have some problems...

My symptons seem to be characteristic of a bad TPS, and I did swap with another one I had lying around, but no good (I even brake-klean'd it and sprayed down the inside with contact cleaner/lube). Whats funny is that it acts exactly the same with or without the tps plugged in. However, this TPS could be worse off than the other one for all I know. I did ohm them both out and the idle stop does work properly on both, and I'm getting good voltage to the tps, but I've not yet checked the ohms for the potentiometer via the KLR plugs.

The car does have a stage-2 MAF kit with a Power Perfect controller (with a rough/fair starter map I made), has a Tial 38 with a Lindsey dual-port mbc, other non-related goodies, K26 (with minor shaft play), adjustable fuel regulator, and crappy chips.

I've done all the normal things you'd do when reviving a car that had been sitting (drain gas, flush fuel system, new oils, etc), and have rebuilt the connectors to the reference and speed sensors, boost leak test (I have a bad one somewhere around the air-oil separator), and I did use the wiring harness that was on this engine.

I've also spliced in a zeitronix zt-2 wideband unit and have been watching that like a hawk.

So, here's the dilema... Wine tour this weekend, and I haven't driven one of my own Porsches in about 4 years... I gotta go!
I need your help. If someone lives around Seattle or close to Edmonds (where the car is) that can have a look-over and let me know that it all looks good and see what their thoughts are, that would really be cool!
I've got a nice garage with most every tool you could need, and some spare parts for the car. Also, there are 3 other damn nice Porsches there too, as well as a couple high-hp twin turbo 300zx's if you like the Nissan stuff.
If you do come over, you'll be the first to see how to fit 12" wide wheels on a stock 951 too

I do have the barn-door setup that I'm currently fiddling with the put that on and see if I have a MAF problem, but I'm going to check the tps again.

Anyway, sorry for the long post but I wanted to put everything in one.
If you're in the area, call me at 425-280-8598 as I'll be downstairs in the garage.

Any advice is greatly appreciated!

Barry Johnson

Well, from the KLR, the tps reads 56x ohms at throttle shut, and goes up to 38xx ohms when at full throttle. At the DME, I get 2.2ohms with the throttle shut, and infinite when open. At the TPS, I get just under 5v, so everything I'm checking on the tps seems to be within spec... Damn.

I know the MAF is dirty, but not sure if that would cause it to run this bad. I will clean it though. Turns out the car won't run with the MAF unplugged like a normal car, so that test isn't happening. Unfortunately, I can't hook up the AFM setup any longer as the plug has been changed to accept the MAF style.

I'm going to ignore the idle stabilizer, because this is beyond an idle problem. I will note, that if I can get it to boost, it seems to run fine while its making boost. When it goes down to pulling vacuum, its a disaster.

I'm going to unplug the o2 sensor as well and see if I can get it to go default on me and if that does me any good.

I know it does have a very old fuel filter, but I had drained gas and flushed out the lines, and its burned through a good 3 gallons of good 92 octane by now, so I'm pretty sure I've removed all the bad gas. In the initial 5gals I put in after drain & flush, I put in some injector cleaner before the gas too.

Back to the car...

Jeff N.

So Barry...what's the specific problem? Not quite sure after reading your post.

BTW, yes a dirty MAF sensor will mess things up. And if you don't have the translation table right in the Power Perfect controller, that will mess things up.

Jeff
Bellevue WA

Barry Johnson

Well after gapping the ref sensor, it runs slightly better, but still much the same.

It idles around 1100, and when it drops below 1000, it leans out and starts to die, and then kicks itself back up. If I hold the throttle down to maybe 1800, it will stay there, then drop down to "idle", then come back up. It doesn't pop or miss and drop, its as if I was letting off the gas, and then back on again.

When in 1st, it seems to drive mainly ok with an afr around the 12s, dipping into 11s. Once I get into 2nd gear, it will hesitate to accelerate, almost as if I was brake-boosting, and then with enough throttle it will start moving. You hear the turbo spool, the mix gets way rich (9.9afr), and doesn't go any faster. Although, once you start to get going and it leans out to 10.5 or higher, then it acts like nothing happened...
Then, when I hit 3rd gear, any throttle at all and its rodeo time! It bucks very badly and will not accelerate at all.

So, thats whats going on now. I'm going to swap the fuel filter and then investigate plugs, but I'm running out of ideas... I'll also try the DME that came with that car instead of my chipped DME.

Barry Johnson

Car runs far worse with the dme that was for this engine. It immediately bogs with throttle, and has a hard time idling. Adjusting my 1v pot on the power perfect in either direction will cause it to die.

My map is a richer version of lindsey's lr001.lio they show on their site.

Cleaning the maf did help it run better, but very slightly.

Another thing I noticed, is that the engine's dme is 951.618.121.09 whereas the chipped dme from the car is xxx.02. Different dme!

All my notes for now...

Jeff N.

Barry, I'd set it back to stock. I have quite a bit of hands on experience with the Power Perfect unit (used to be sold by Pro-M racing out of michigan and had one for years on my BMW 535). Tuning it is a trick and the pots are only very very gross adjustments. I'd sort the wiring, put the AFM back in and put the stock chip / DME back and in get it running first.

Your AF ratios suggest the translation table is all off. Being that far off will hose you fuel and your timing.

Barry Johnson

The DME was for an 87-91 951, and since I am new to the power perfect and I have to have this car done by friday to make sure its good to go on the wine tour this weekend, I'm going to put the AFM back in and junk the MAF and PP POS until I have more time to tinker.

Good to know you have experience with the PP unit, I personally think the whole thing is pretty ghetto, especially the terrible software, of which I'm unable to find a newer version. Awesome.

Yeah, the a/f is all over the place, really, and for all I know the map that was on the PP unit before I made my own (which worked better with my dme) worked perfect with the newer dme.

But, its forcing me to get real intimate with the car, so thats good.

I'm going to head downstairs and wire up the AFM and put the 86 dme back in (the chipped one) and see how it reacts.

Jeff N.

The PP has it's uses but like I said, it takes a bit of work to get it right. And you're correct, the software leaves quite a bit to be desired.

Barry Johnson

My injectors are ohming at 1.5 vs the normal 4.5 of stock ones, and they are the green ones. I spoke with a local standalone expert and Wolf3D tuner, and it sounds like its heating up the transistor in the DME and causing a grounding problem, and therefore not closing the injectors, maybe at all. This could be my off-boost problem, but I'll know today (hopefully).
Either my injectors are all bad, or I have a wiring problem (90% sure of that) with the home-made wiring patch thats on there, with crimp connectors.

By the way, crimp connectors = electrician in a box. And no, I didn't do the wiring. I only use crimp connectors on my BMW

So i'm going to pull the leads off of the injectors and ohm right at them and verify their condition, and if they ohm out ok, then I'll get to rewire the loom.

I hope if nothing else that this thread helps someone else!

Barry Johnson

...injectors and wiring are fine...

I've rewired the connector in for the afm, and rigged up the j-boot to fit with a coupler to the turbo (my j-boot was snipped short at the end, I think for a larger turbo with some weird coupler previously), made sure everything was tight, double checked all the wires, disabled the power perfect and put that wiring back to stock, and now it runs on 3 cylinders...

Disconnecting the o2 sensor doesn't do much, unplugging the tps just makes it idle a tad lower (idle screw isn't correct I'm sure), and unplugging the afm connector does nothing. To its credit though, it runs better on 3 cylinders than it did with 4. Also swapped DME and KLR, and no change either.

3 days left, not looking good for wine tour

Barry Johnson

I spent all night with a voltmeter, checking everything, tearing harnesses apart, chasing wires, doing everything I could, and it was a freakin' fouled plug...

Amazing.

Car runs a lot better and is actually driveable with the stock AFM in place, however I still have a high idle around 1k, and my a/f seems to stay at 14.5-14.8 even in boost (scary).
So, now I have to do some more digging and see why I'm running so lean. Going to check the FQS in the DME and see what that reads at. My AFM hasn't ever been opened, so I doubt my CO adjustment is off...

Any advice on the lean condition? My DME does also have the europroducts chip and I have an adjustable fuel regulator that I haven't messed with either (no gauge on the rail).

Vac reads 15-16 at its idle too, if that helps.

Jeff N.

Progress! Check for intake / pressure/ vacuum leaks post AFM on your intake track. That could account for your high idle and a/f problems. Be sure to check the throttle body and all of the misc control hoses in the engine bay. Best way to locate is to pressurize the intake track with a compressor. Archives cover this well.

Vac is a bit low at idle, should be closer to 18 when warm, again a sign of possible leaks.

Can't comment on the chip, never heard of that one. If your FP is low, that could be a problem but I would try looking for leaks first; common problem and you need to rule it out.

Barry Johnson

Thanks Jeff, I was thinking the same things...
To get my J-boot to work, I've had to clamp a coupler on the end of it, and that could be leaking, however its just right in front of the turbo inlet, so not sure if that would matter much.

The only leak I had detected before was somewhere around the oil fill tube... I'm unfamiliar with it, so I'm not too sure where it would see vacuum, but I suppose the old soapy water trick would help... Maybe its the big vacuum plug on the brake booster.

I'll check the vac. lines again, and try and figure out where my speedo & odo signal went... And my heater controls...

Barry Johnson

Well, nothing new on the vacuum side, but my vac numbers are great so I'm not too worried about it.
Turns out that I had 2 fouled plugs, so once the new ones were in, it fired right up! The car was running in closed loop mode for some reason, and the o2 was unplugged to get it to fatten the mix up. Running 50psi at the rail, and it seems to like that. Nice mid-11s afr in boost, and re-aligned the balance shafts.

Ran great on the wine tour, made power, no vibrations, just no speed sensor and the heater fan speed control didn't want to work and idle is still a little high (950-1000).

Runs good! Thanks for the offer and input Jeff, its on the road now

FASTRNU

I'd love to come by and see your 12 inch rims,I'm working on a wheel project right now,maybe you can help