HELP no Power after valve job

mlfelch · 07-02-2001, 12:55 PM

I just finished a valve job, new vacuum line, plugs, rotor, tune up. Engine has good response to throttle while sitting but no response or power when driving.

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MiKey

Scott R · Scott R's Garage

Sounds like a coincidence. Your symptoms sound like a blocked catalyic converter. If you don't get any better ideas, I would go under and unbolt the exhaust lines, not too hard a job, and see if the problem goes away. Either that or your not getting correct fuel pressure, maybe vacum to the pressure regulators.

mlfelch · 07-02-2001, 01:01 PM

Thanks, I'll check it out!

p0r2chby · 07-02-2001, 01:05 PM

Go with the vacume, fuel pressure direction first. Plugged or clogged up cat? possible but these symptoms would probably would have been evident before the tune up work.

mlfelch · 07-02-2001, 01:12 PM

What are the chances that this could have anything to do with the oxygen sensor, I’m going to look anyway but it seems like I remember seeing it looking a little frail or pushed around.

p0r2chby · 07-02-2001, 01:15 PM

worth a look. The sensor feedback does adjust your fuel and timing.

porsche1987_944s · porsche1987_944s's Garage

double check base timing

kukunaokala · 07-02-2001, 07:19 PM

Most likely you missed something or the valve job was'nt the original problem. No power? fuel, air flow, compression or timing. Confirms these items then look for a bogus sensor. If you can get codes do that first. Hana pa'a (good luck), keep us posted and aloha. Neal

T86951 · 07-02-2001, 07:39 PM

I can unplug my oxygen sensor and there is no power difference at all, a little gas milage is all and I guess the emissions are a little better.

Look at fuel pressure or weak coil or plugged cat. Was it that way before the valve job?

[This message has been edited by T86951 (edited 07-02-2001).]

mlfelch · 07-03-2001, 12:25 PM

I'm gonna go back in tonight and re-check the compression then timing, crank to TDC, camshaft/pulley, distributor, cap and rotor to number one wire. Next I'll check the vacuum lines if nothing else works I'll loosen or remove the CAT. Hay I have another question. Does the air flow sensor housing dust cover have much pressure build up. Mine has a large slice in it. I repaired it as best I could. Calling it a dust cover implies no pressure. It's a boot connecting the air flow to the turbo, I think.

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MiKey

T86951 · 07-03-2001, 05:57 PM

Oh this is a 951? I have a na 944 daily driver and a 951 that I keep up and drive sometimes. You should have no leaks after the air flow senser. There is no pressure between the air flow sensor and the turbo but all air should go through the air flow sensor to give the computer correct information. Any hose problem after the air flow meter will cause big problems!

Pilot_951S · 07-03-2001, 07:24 PM

Sounds like the camshaft may be a couple of degrees off. Definitely check the timing.

mlfelch · 07-05-2001, 05:58 AM

Well, I went back to work on it and found a way to make it worse. Now while sitting still and I give full throttle the engine will run but it is choking really bad. As I rev up/down the engine it sounds ok but when I hold it at full throttle it just chokes. I reset the timing starting at the mark on the crankshaft, then I lined the dot on the pulley to the cam shaft cover. ( the pulley has a dot on each side, the one I used is on the inside and the first intake valve just closed. ) Then I set the distributor/rotor to point to the number one plug wire. I advanced it as needed. I also put new vacuum line and hoses and tighten them down. I did not remove the cat yet but now that I think about it I did have an exhaust leek around the manifold before I began work on the engine but it wasn't much.

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MiKey

Minhiriath · 07-06-2001, 11:38 AM

i had headwork done on my 924, and the fellow who put the car back together didn't tighten the header nuts all the way, which caused the exhaust manifold to crack, the car lost all power, i thought it was a plugged cat etc.

mlfelch · 07-06-2001, 12:03 PM

Thanks: I checked the torque on the head bolts again, They are ok. I can't think of what it's called but there are four single wires that connect just under the throttle body housing. I think it connects to a fuel/air adjustment. I took pic's during disassemble but the color didn't show up to well. If anyone can check the order it might help. Thanks again.

mlfelch · 07-09-2001, 07:51 AM

The pictures I took didn't come out clear enough for me to tell what color wires were connected to this location. It looks like from left to right was brown then white and then brown and white/green. The location is just under the throttle body to the right. It looks like a black block with four terminals coming off it. Please help is you can.
Thanks Mike