Porsche Enthusiasts Club Forum

Hi All

I posted this on Rennlist, but hoping somebody can help me here.

I have had a problem starting the 944. It is an 8 V NA.

It did not seem to want to start, and when it did I had to tickle the accelerator to keep it running. Then it backfires and cuts out.

I pulled the reference sensors and checked according the Clark's Garage.
Resistances are ok.

I pulled the temp sensor and now she starts. Problem is the revs go high real quickly so after about 2 or 3 seconds I cut the ignition. Plug the temp sensor back in and I am back to the original problem.

Starting with the temp sensor removed the start is effortless, sounds smooth and runs ok with no backfires, or so it seems, just revs way too high. I recorded the start on my phone so I can see the tach reading is just over 3000 rpm.

Checked for obvious vacuum leaks but all of the vac lines have been replaced and reclamped with new clamps.

Any ideas what this can be?

I guess I have a faulty temp sensor, or the wires going to it. Would removing the temp sensor cause it to rev?

Thanks in advance.
James

Here is an update. But it is still not starting and running properly. I am on the verge of giving upon this car after spending an absolute fortune on it.

I have tested all of the following and followed the Clark's Garage instructions on the following pages:
TPS checks out ok by http://www.clarks-garage.com/shop-manual/fuel-06.htm

DME Temp sensor checks out ok by http://www.clarks-garage.com/shop-manua ... m#dme-temp

IACV opens and closes ok when 12 applied as per https://youtu.be/30Ctw8BoNog

AFM checks out ok by http://www.the944.com/afm.htm


I have removed all the new vac lines around the throttle, no change.

If anybody has any clue at all where to go next I would really appreciate it.

Thanks

New parts installed:
Fuel filter.
Fuel pump.
Fuel lines around above.
Fuel lines at from from hard line to fuel rail damper and regulator.
Ignition coil.
Spark plugs + properly gapped.
Rotor (not distributor as this looked fine).
Vacuum lines - All of them, Y pieces changes for T pieces.

Tested the following, all seem to check out ok:
TPS
AFM
IACV
DME Temp sensor
DME Relay - resoldered and tested ok.

Removed idle screw and cleaned in carb cleaner, cleaned throttle housing.

What am I missing?

ECU ?

From what I am reading up on, I am looking at IACV/ISV or a vac line in the wrong place.

Should the IACV/ISV be running/vibrating all he time on a NA? Not sure I have heard mine running at all.

Failing that I will do an fuel pressure test and move on in the next week.

Advice and encouragement still welcome.....

keep on keeping on James!

My ICV doesn't vibrate - not that I can tell anyway - I had asked this question just a week or so ago on my ICV thread. Don't start the engine - just turn ignition on - mine doesn't vibrate and others concurred.

What I would do is be sure that the hoses from the ICV are running in the correct direction i.e. to intake and j-boot. Mine idled very high & climbed when the hoses were swapped around. Swap yours and see what happens.

OK I have found an issue, well 2 in fact.............

IACV was vibrating a little when the ignition is on. You cannot hear it or notice it. I had to put my hand on it to feel it. Anyway I
decided to take it out and while I was in there re-check those hoses. Routing of hoses and for obvious leaks.

Well I found the short hose that goes from the valve to the manifold had in fact come off of the manifold, the clamp (which was obviously not tight enough) was laying on the balance shaft housing.

Well that accounts for vast amounts of air being sucked in and the revving.

The valve itself does attempt to move when voltage is applied. But it does not snap back and forth like I have seen on Youtube etc. It is more of a lazy vibration to the open position, then it seems to jam when attempting to close.

Looks like I may need a new one, or judging by the price more like a second hand one.
I may strip this one down first and see if I can get it going at all.

Thanks for the help so far, I will update soon.

Idle valve fixed.

I just opened it up, cleaned the contacts and generally all over.
Put it back together but realised that it is orientated in a certain way but I followed the top photo in this thread http://forums.pelicanparts.com/porsche- ... valve.html

O ring is fine, but I cleaned it and added a really tiny little spot of blue asket sealant to the edge of the aluminium casting the o ring is fitted to (this was just to hold it while I re-assembled).

Checked operation and it works great. Snaps open and when reversed it snaps closed.

Onto the next step.....

Hi, found your blog from the link in your post.
Great stuff there, really interesting reading. I have been thinking of doing something similar.

Thanks

DeLux

just had a quick read of your blog, nice work, just wondered why you did not send off the injectors for a proper clean at Mr Injector, would have been worth it after being sat around for all that time

Surely Mr Injector (and others like them) just clean the injector externally, then internally by flushing it through under controlled pulsing. Then reverse flush it the same. After that they just fit one of the overhaul kits they sell.

It really is not too difficult. If you are concerned over your injectors then they can provide printouts of the results, but a reasonably good clean and overhaul can be done at home.

Good News!!!!!

The engine starts effortlessly.
Slight smoke at the back but it started to clear as it warmed up. Problem is some smoke at the front.
Checked and it is a tiny oil leak getting on the exhaust manifold. I believe it is dripping from the oil cooler, so that is the next plan of action. But at least it starts and sounds really good.

Thanks

the oil cooler is a real pain you need an alignment tool