My 1985 928 hesitates between 1800 and 2200 rpm then takes off.

Asked by Dec 28, 2011 at 03:51 PM about the 1985 Porsche 928

Question type: Maintenance & Repair

Car hesitates on takeoff. Around 1800 rpms.  Idles fine.

25 Answers


first check for an intake vacuum leak check to make sure the vacuum advance on the distributor is still working then check your spark plugs if you have in the new platinum ones get rid of them 928s like the cheap regular plugs the best


Fuel pressure regulator

2 of 2 people found this helpful.

Has not happened to me. I agree with the previous 2 answers.


could be something as simple as a plugged fuel or air filter... or, those cars have the hot wire MAF sensor it could be on its way out the easiest way to check is to swap it with a known good one from another car sometimes they can be filled with crap from animals or just plain dirty. that year also uses a switch to tell the brain when the throttle is fully shut if that is not working it will cause weird things to happen

Best Answer

I have a question Paul. You seem very knowledgeable. I have a 1980 porsche 928. It idles and accelerates fine but off the line it does not have the power it should. It is the 4.7 euro which should have plenty. Any suggestions? Steve

2 of 2 people found this helpful.

Is it a auto or 5 speed


In the event that it is a auto trans the kick down switch that is under the gas pedal is probably not working and the car doesn't start in 1st gear making it feel like all the power isn't there 1way to find out is to bridge the wires the car should it 1st as soon as you touch the pedal but don't leave it that way also count the shift change from start W O T mike


It is a 5spd. Is the setup the same? Steve




I think that should be a timing issue To much advance well make it run great at higher speed but poor start up performance the vaccum advance in that Old distributor could be seized But hard to tell Cis fuel system have a number of other control that can produce this drivability problem and there is only a few tech welling to work on 928 and euro at that

1 of 1 people found this helpful.

Thanks for the info Michael. Finding that out about the euro.... Steve


hey steve i have that same problem with a 79 here (i have 8 928s) i have found that it has more to do with the warm up regulator in the cis. as the cars get older the WUR seems to lean out more and more making the car hard to start when cold and sluggish when driving. replacing the WUR is NOT required and may not even fix the problem if you do. the WUR has adjustments on it but you need a set of guages to get the right fuel presures to make it work right, it takes some messing around and time to get it just right they are very finicky there is a modification that you drill and tap the adjustment plunger to make it much easier to adjust i have done it many times are you close to me? i live close to london ontario canada or i can add you to my account and send you my number


The car is running really rich and to the point that it will not even stall, so it is not lean at all. You have 8 928s? Wow! Steve


hey steve check and make sure that the cold start injector isn't stuck on it should only shoot for a few seconds when you first start the car if its not that its prolly the WUR adjusted to rich you also have a fuel adjustment on the air sensor plate if that adjustment is out the idle usually hunts up and down the WUR is really easy to adjust richer you have to take it all apart to make it leaner someone may have already adjusted it wrong. all my 928s here have been rescued from the crusher all came to me non running most had been sitting for years its amazing how tough these old cars are i love all mine very much working on a 78 right now just got it a few months ago its a local car daily driven till it quit got it for $1400 its running and driving now just finishing up some of the details


Thanks Michael and Paul for the tips.


My backup light is not working and i am thinking it is the fuse. Did some research and the relay XXII would need to be replaced. On the 5 spd, bridge is at the manual transmission. What are they talking about? Thx


what year steve i will look it up in my manuals




ok steve i looked up reverse lights for an 80 the fuse should be number 9 it also powers the rear wiper and power mirrors if the wiper works then the fuse should be ok i would be really suspect of the fuse there is no relay just a switch to make the lights work if auto the switch is on the shift lever base if its standard the switch is in the trans there is a connection in the spare wheel well that should e checked and the ground goes out through the signal light grounds. check the fuses if you have aluminum ones get rid of them and clean and replace with all rass or copper fuses that usually cures 90% of the electrical probs if you need more msg me and i will pass you my home number


hey steve i assumed your car was a north american model and not an S or euro?


Haha. It is the euro 4.7 liter. Sorry. I should have specified.


ahhhhh lol ok so that fuse 9 just runs just the mirrors and rear lights not the wipers everything else is the same though again be very sure the fuse is passing power

1 of 1 people found this helpful.

Ok. Thanks again Paul.

Sounds like a centrifugal advance at the distrubutor. This is an ugly problem, have seen it before on a 1979 brown pontiac,


hey paul i have just bought my first 1981 928 with 43k original miles but the car has been sitting for a while.. it starts and runs well on cold start ups but when it reaching temp it seems to run rough/stumble/hesitate and also seems to misfire.. eventually it will just stall out and very hard to start after..... once it cools down it seems to start up fine again.. im aware of all this WUR info but my car doesnt seem to have this WUR soo im kind of confused..

3 of 3 people found this helpful.

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