Multipass

Hi, please help me diagnose why my '88 944 NA will not rev above 5K after it warms up, not even at idle.

When cold the engine revs all the way to redline, but after a few minutes of driving the engine sputters and stalls around 4.5 to 5k RPM. There is a pfft, pfft sound when this happens. At lower RMP it drives around fine with seemingly normal power.

Background: engine was put back together by a pro shop in Portland after a few years of sitting in my garage with the top end disassembled due to leaky head gasket. Car has new spark plugs, wires, ignition coil, air and fuel filters. Injectors were cleaned and balanced by a shop.

Thanks for your help!

Wipeout

Vacuum lines replaced? Was the AFM checked at all? Glad to see yet another Portlander here on RL!

Multipass

The vacuum lines were not changed, and the AFM not checked out. I'll replace the lines and check the AFM per: http://www.clarks-garage.com/pdf-manual/elect-22.pdf

Is there a list of all the little vacuum connections and Ts or maybe a kit I can buy?

Andy1212

Here ya go! Great thing to do for the money.

http://www.lindseyracing.com/LR/Part...ACUUMLINE.html

There seems to be a lot of Portland guys joining recently!

Multipass

Thanks, just ordered that kit

I'll report back if the problem persists.

Go Blazers.

Andy1212

Ha. B-Roooyyy!!!

Wipeout

If you can just get the Ts, I have TONS (two more cars worth) of the LR black silicone hose.

Wasn't planning on using all the rest, if that works for you.

Multipass

Thanks Darren, I'll let you know if I run out of lines, but I ordered the kit already

Wipeout

You won't run out of lines. Trust me.

Multipass

I still need help. I have replaced the vacuum lines, corrected two vacuum line connections on the TB, set the spark plug gap (came ungapped from the shop) and checked my timing.

In neutral the car revs over 5K, but is unstable and the revs jump around a lot. When driving, in gear the car still does not rev past 5K.

In the garage (not on the road), I checked the fuel pressure at different conditions and they were all within spec, per Clark's and Haynes. I also used the timing light to see that I had spark in each cylinder at revs over 5K. I also checked the AFM and that was fine too. I didn't go as far as removing the plastic cover on the AFM, as I am not sure how to reliably glue it back on.

While searching this forum, I read about exhaust back pressure possibly causing this problem, so I dropped the exhaust (all-original) and the cat looks fine from the back end. I even sucked air through it with a vacuum cleaner and nothing came out. I recently passed DEQ.

The car has about 150K miles and has a steady idle.

The car runs hot, but the fans keep it from going into the red, I don't know if this is related or not. The rev problem happens before the temp climbs much past normal.

The belts are tight, so the water pump is not slipping.

So that is it, I don't know what else to check. The frustration level is up there. Please, please help me diagnose the problem. Thank you in advance!

944S2NUT

Could it be an O2 sensor? My buddies Jetta did something similar. Shot in the dark.

drift a 944

Take off the plastic cover on the AFM and inspect the sliding contacts (I think they are 2 long U-shaped lines). They are like the old slot-cars where you have to shine up the copper contacts because they get smudged or worn and connection starts to get lost.

The same thing happened with my car as yours, so I used a small piece of very fine grit sand paper to shine up the contacts (be gentle) and then I sprayed some electrical contact cleaner over everything.

Has been working great now for 2 years so far since I did that. Good luck!

Multipass

I'll try the AFM cleaning first.

Elliott, what did you use to glue the cover back on? Clark's Garage mentiones that it is held on with a small bead of silicone, but I always thought that stuff is more of a sealant than a glue.

Thanks.

Wipeout

If you want to try a known working AFM before taking yours apart, I think the one from my early '85 would work as a test. The AFMs themselves are the same, I believe...

Multipass

Would a bad O2 sensor through a check engine light? I guess that is why I didn't suspect it.

Looking at O2 sensors for sale, there are the OEM and the cheaper generic 3 wire sensor. I don't mind soldering but are there instructions for installing the generic O2 sensor?