964 C2 Tip Engine Prob Making me crazy! HELP!!

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964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby flypfi on Wed Mar 19, 2014 3:39 pm

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, acts like it wants to die, 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 acts like the ignition is shut off - it 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 used 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?
Last edited by flypfi on Fri Mar 21, 2014 3:38 pm, edited 1 time in total.
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby Steve Grosekemper on Wed Mar 19, 2014 7:44 pm

Caleb,
It sounds like you have multiple problems.
First I would check fuel pump pressure and volume.
Then residual pressure.
Your starting issue could be from pressure bleeding down and boiling the fuel in the injection rail.


Good Luck
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby flypfi on Thu Mar 20, 2014 2:01 pm

Thanks Steve, I'll check the fuel pressure this weekend. If there is an issue with the pump or pressure regulator, do you think it could be related to the problem I'm having while driving as well?
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby LUCKY DAVE on Thu Mar 20, 2014 2:42 pm

Steve Grosekemper wrote:Caleb,
It sounds like you have multiple problems.
First I would check fuel pump pressure and volume.
Then residual pressure.
Your starting issue could be from pressure bleeding down and boiling the fuel in the injection rail.


Good Luck


Maybe a feeble/intermittent TPS as well?
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby flypfi on Thu Mar 20, 2014 3:11 pm

Thanks for your input Dave... Any simple way to test the TPS other than a simple R&R to see what happens?
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby LUCKY DAVE on Thu Mar 20, 2014 4:45 pm

If you had a 951 I could tell you exactly, but....
Steve?
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby Steve Grosekemper on Thu Mar 20, 2014 11:48 pm

Good call Dave. One of the problems could be a bad idle position contact.
951 and 964 are very different...
951 has one switch for idle, full load and throttle position.
964 has a throttle switch that you would expect with a long multi-pin plug. (Right side)
But the closed throttle position is sensed by a separate micro switch. (Left side)
It has a 2 pin plug like and injector plug.
Pull it off and check the signal with an ohm meter. Closed at idle; open just off idle.

But... If you have access to a durametrics tester you should go to input signals and activations.
That is where you can test, idle contact, WOT, load signal, AFM, and a host of other functions.
That would be my next move.
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby flypfi on Fri Mar 21, 2014 10:41 am

As posted at the start of this thread - I did check the adjustment and continuity of the idle position switch (all checked out perfect), but did not check the WoT switch (only because when it runs well, I'm not near the WoT contact). I suppose if the WoT microswitch is NO and shorted NC (or vice-versa) it could cause some problems? I was a little confused about the TPS - didn't think I had one - but now I understand the implication. So... do you think there could be a problem with the WoT, or should I continue down the fuel pressure path (I kind of like that possibility)?
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby flypfi on Fri Mar 21, 2014 12:16 pm

Steve - I do have the Durametrics software on my laptop, but the functionality is limited to fault codes and resets. Unless I am missing something, there must be different version because I don't see any tests for loads or input signals. Are you familiar with the laptop version of the program?
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby Steve Grosekemper on Sat Mar 22, 2014 10:21 am

Caleb
All durametric is on a laptop.
There is a pro version and a enthusiast version.
(Difference is in the cable-says Enthusiasts version)
The enthusiast version is limited to registered VIN numbers but not function.
From their website:
Question: What is the difference between the Enthusiast kit and the Professional kit?
Answer: In Durametric version 5, the difference is the number of cars the kit allows you to work on. The Enthusiast kits are limited to use on 3 cars - managed by VIN, not model. The Professional kit has no limit to the number of cars on which it can be used. With the introduction of Durametric version 6, the Professional kits alone gain the ability to perform Coding changes on supported control units.

So you should contact Durametrics and see what's up.
It should do everything you need to do on your registered car/VIN.
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby flypfi on Mon Mar 24, 2014 10:19 am

Durametrics said it has limited functionality on the 964's.
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby Steve Grosekemper on Mon Mar 24, 2014 12:36 pm

flypfi wrote:Durametrics said it has limited functionality on the 964's.


That's a bummer.
I usually just use the Hammer for 964's but know Durametrics works for many features.
I don't have a 964 in the shop right now to test my newer version of Durametrics.
Well if you finally hit a wall on your diagnostics you can bring it down to Black Forest and I will run a series of tests on all my factory 964 testers and see what we can find. (Hammer/PST-2)
I will make you a deal on time for testing and just give you a report on what I find so you can fix it yourself.

Let me know.
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby flypfi on Mon Mar 24, 2014 2:19 pm

Steve thank you very much - that is a great deal. The previous owner had BF do all of his maintenance so the car will feel right at home. I'll be traveling the next 10 days or so, but I'll reach out when I return... I will do the fuel pressure test this week (ran out of time over the weekend) before I leave so that will be one less thing to check.

Thanks again.

Caleb
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Re: 964 C2 Tip Engine Prob Making me crazy! HELP!!

Postby Steve Grosekemper on Mon Mar 24, 2014 6:04 pm

flypfi wrote:Steve thank you very much - that is a great deal. The previous owner had BF do all of his maintenance so the car will feel right at home. I'll be traveling the next 10 days or so, but I'll reach out when I return... I will do the fuel pressure test this week (ran out of time over the weekend) before I leave so that will be one less thing to check.

Thanks again.

Caleb


Sounds good Caleb,
I am preparing cars for the CFOS Time Trial and Club Race but should be available after the 7th.
Lets shoot for something that week.
Send me and email.
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