HELP!! 964 C2 Tip Making me crazy!
03-19-2014, 07:36 PM
#1
Rennlist Member
Thread Starter
HELP!! 964 C2 Tip Making me crazy!
I have a 1991 964 C2 Cab with tip. It has 53,000 original miles. I am the 3rd owner and it has been babied all its life... basically kept in mint condition. It has a few frustratingly intermittent problems. They might be related, they might not?
Problem 1: Hard to start when cold - sometimes (I'm in so-cal so cold means 50F-70F). If I hold the throttle 1/2 way down it eventually starts with a laborious slow ramp-up to a pulsing idle between 800-1100 then eventually stabilizes. Other times is fires right up (at the same outside air temp) to a relatively smooth idle (for a 964).
Problem 2: Almost always hard to start when hot (engine is up to operating temperature). Holding the throttle half way in is the only way it will start.
Problem 3: When driving away after first start-up, is seems to be a little sluggish and resistant to acceleration - there is a slight hesitation. once it gets warm - in about 5-10 mins, it seems to run fine (good acceleration, no hesitation)... but then I come to a stop and when I accelerate to go, it just stays idles, fluctuates a little bit, gives a small muffled backfire, then after I quickly pulse the throttle a few times, teasing it into accelerating, then it reluctantly winds up and then seems to cruise ok once it's up and running. It never stalls, although it acts like it wants to, and comes close when I accelerate from a stop, as described.
Problem 4: Cruising with the throttle in the same position for a long period (same speed, same rpm, same throttle position) it flat out act like the ignition is shut off - if feels like the engine just dies... but when I tease the throttle again, it comes back to life and is normal again!
Here is what I HAVE done (and results):
1. Cleaned ISV - seemed to be better for about 2 or 3 trips, then back to the way it was.
2. Replaced the ISV with a new Bosch part from Pelican - seemed to be better for about 4 or 5 trips, then back to the way it was.
3. Thoroughly cleaned the air intake vane - no change.
4. Checked the OBD with Durametric software - no engine faults.
5. Replaced DME relay - no change.
6. Reset the DME (no hammer - just the de-power procedure) - no change.
7. Replaced battery (connections are perfect too) - no change.
8. Check adjustment and continuity of idle microswitch - no problem found.
9. Checked oil level - between the two marks (a little closer to the lower end).
10. Checked distributor drive belt - mod done and no problem found.
Here is what I have NOT done:
1. Replaced or rebuilt the DME
2. Replaced O2 sensor - (no check engine light or OBD fault observed)
3. Check coils - (assuming OK because when it runs - it runs very well)
4. Given it the Hammer (don't have access to one)
5. Pulled the remaining few hairs out of my head!!!! (but getting close!)
Any thoughts?
Problem 1: Hard to start when cold - sometimes (I'm in so-cal so cold means 50F-70F). If I hold the throttle 1/2 way down it eventually starts with a laborious slow ramp-up to a pulsing idle between 800-1100 then eventually stabilizes. Other times is fires right up (at the same outside air temp) to a relatively smooth idle (for a 964).
Problem 2: Almost always hard to start when hot (engine is up to operating temperature). Holding the throttle half way in is the only way it will start.
Problem 3: When driving away after first start-up, is seems to be a little sluggish and resistant to acceleration - there is a slight hesitation. once it gets warm - in about 5-10 mins, it seems to run fine (good acceleration, no hesitation)... but then I come to a stop and when I accelerate to go, it just stays idles, fluctuates a little bit, gives a small muffled backfire, then after I quickly pulse the throttle a few times, teasing it into accelerating, then it reluctantly winds up and then seems to cruise ok once it's up and running. It never stalls, although it acts like it wants to, and comes close when I accelerate from a stop, as described.
Problem 4: Cruising with the throttle in the same position for a long period (same speed, same rpm, same throttle position) it flat out act like the ignition is shut off - if feels like the engine just dies... but when I tease the throttle again, it comes back to life and is normal again!
Here is what I HAVE done (and results):
1. Cleaned ISV - seemed to be better for about 2 or 3 trips, then back to the way it was.
2. Replaced the ISV with a new Bosch part from Pelican - seemed to be better for about 4 or 5 trips, then back to the way it was.
3. Thoroughly cleaned the air intake vane - no change.
4. Checked the OBD with Durametric software - no engine faults.
5. Replaced DME relay - no change.
6. Reset the DME (no hammer - just the de-power procedure) - no change.
7. Replaced battery (connections are perfect too) - no change.
8. Check adjustment and continuity of idle microswitch - no problem found.
9. Checked oil level - between the two marks (a little closer to the lower end).
10. Checked distributor drive belt - mod done and no problem found.
Here is what I have NOT done:
1. Replaced or rebuilt the DME
2. Replaced O2 sensor - (no check engine light or OBD fault observed)
3. Check coils - (assuming OK because when it runs - it runs very well)
4. Given it the Hammer (don't have access to one)
5. Pulled the remaining few hairs out of my head!!!! (but getting close!)
Any thoughts?
03-19-2014, 07:52 PM
#2
Drifting
Did you check the Fuel Pressure Regulator? I had starting issues when my mine was on its way out. Remove the vacuum hose on the front of the FPR, any sign of fuel in this line is indication of a failing FPR.
03-19-2014, 10:49 PM
#4
My first thought was also fuel related, I would look at the fuel pump itself. The pump is actually lubricated by fuel, so it would function better the longer it runs. Also be a good time to replace the filter--easy job.
03-19-2014, 11:08 PM
#5
Instructor
sure sounds like a fuel pressure regulator to me. fuel vapor entering the intake manifold via the vacuum lines usually causes the backfire on a hot start. When it gets bad enough it will blow the intake manifold halves apart at the rubber junctions creating a huge vacuum leak and a no start situ.In addition to the FPR Id also be suspect of the plastic intake stacks and rubber boots, chances are on a 50k mile car its all original and could be the source of some vacuum leaks. Lots of little stuff being right is what makes these cars hum.
03-20-2014, 06:05 PM
#6
Rennlist Member
Thread Starter
OK thanks - I'll check the fuel pressure and residual pressure this weekend. Do you think it is related to the problem while driving, or is that a separate issue? It seems like the wiper arm in the MAF hits a bad spot and everything dies until I pump the throttle a few times. Is that symptomatic of a problem with the MAF, or fuel pressure?
