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1987 924s 5spd poor/no acceleration when hot

 
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HDMacaw  



Joined: 04 Jul 2011
Posts: 24
Location: Tennessee

PostPosted: Sun Aug 01, 2021 6:35 am    Post subject: 1987 924s 5spd poor/no acceleration when hot Reply with quote

Greetings all,
I was driving along just fine when my 924 lost all power. It didn't stall but I couldn't get more than about 1300rpm out of it.
The further I stepped on the pedal the more pooping and light backfiring came from the exhaust.
I managed to limp it 5 miles home at a whopping 20mph in 4th-5th gear.
I shut it off and it fired right back up but only will idle, any pressure on the accelerator and it starts popping and sputtering.
Next morning I go out to start checking things and I decided to try to start it. It fired right up, idled smooth as glass, and purred like a kitten.
I took it for a small ride and it ran like it's usual self.
Today I go up to town, it runs fine the whole time. I stop at the store come back out, it starts up fine but as soon as I step on the gas to back up same dead pedal issue.
I sat there for about an hour and let it cool down. It started, would get to about 2Krpm so I decided to limp it home again.
The hotter it got (normal op temp) the less RPM it would do and quickly it would do no more than about 1300rpm. After 2 hours in the driveway still the same 2Krpm max, and it's still a little warm.
Temp needle is sitting at the right edge of the box on the left side of gauge.
It's got a new fuel pump, filter, DME relay, and about 400 miles on a fresh tune-up and oil change.
The only more recent work was that I replaced the fuel sending unit and seal (I don't see how that would be related).

Any ideas or suggestions?

Thanks

Update: It's almost all the way cooled off and it's back to running normally now.
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HDMacaw  



Joined: 04 Jul 2011
Posts: 24
Location: Tennessee

PostPosted: Sun Aug 15, 2021 10:30 am    Post subject: Reply with quote

2 weeks and almost 600 views later and not one suggestion.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2541
Location: MI

PostPosted: Sun Aug 15, 2021 12:40 pm    Post subject: Reply with quote

I don’t know man sorry ;(

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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1277
Location: Washington DC area

PostPosted: Mon Aug 16, 2021 12:49 am    Post subject: Reply with quote

It sounds like it is not getting enough fuel when you open the throttle. Check that you get a large amount of fuel squirting out of the filter (disconnect before the fuel distributor) when you momentarily turn on the ignition. Be aware that you will need to catch the fuel or create a bigger problem. If it's only a dribble, you have a fuel pump or filter issue.
If that is all good, start looking into the fuel injection system.
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1979 924 NA race car
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1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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HDMacaw  



Joined: 04 Jul 2011
Posts: 24
Location: Tennessee

PostPosted: Mon Aug 16, 2021 12:54 pm    Post subject: Reply with quote

Fifty50Plus wrote:
It sounds like it is not getting enough fuel when you open the throttle. Check that you get a large amount of fuel squirting out of the filter (disconnect before the fuel distributor) when you momentarily turn on the ignition. Be aware that you will need to catch the fuel or create a bigger problem. If it's only a dribble, you have a fuel pump or filter issue.
If that is all good, start looking into the fuel injection system.


Thanks for the reply.
I replaced the fuel strainer, pump, and the filter last year.
I'll check the pressure though just to make sure the pump is still up to snuff.
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16again2009  



Joined: 04 Dec 2014
Posts: 68
Location: tulsa, ok

PostPosted: Thu Sep 30, 2021 2:46 am    Post subject: Reply with quote

Did you figure the problem out?
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1988 porsche 924s
5 speed
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HDMacaw  



Joined: 04 Jul 2011
Posts: 24
Location: Tennessee

PostPosted: Thu Sep 30, 2021 6:06 am    Post subject: Reply with quote

16again2009 wrote:
Did you figure the problem out?


Nope. Fuel pressure was good, and I replaced the DME temp sensor, tested the TPS, and MAF so far, all working as they should still the issue persisted.
The connectors of the speed sensor and the crank position sensor crumbled in my hand while I was cleaning up all the ground points under the hood so they need replacing now. The CPS came out easy enough but the speed sensor won't budge so it's sitting with some penetrating oil on it and hopefully it'll break loose soon.
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16again2009  



Joined: 04 Dec 2014
Posts: 68
Location: tulsa, ok

PostPosted: Mon Oct 11, 2021 2:14 am    Post subject: Reply with quote

there is a guy on the pelican forum that had sort of the same problem as you, but not exactly. It turned out to be his o2 sensor. You might check that. Just unplug it and see if it runs better.

.pelicanparts.com/porsche-924-944-968-technical-forum/1062112-flat-power-spot-3rd-gear-5.html
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1988 porsche 924s
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holcopa123  



Joined: 05 Nov 2021
Posts: 6

PostPosted: Thu Nov 18, 2021 6:33 am    Post subject: Reply with quote

I ran into a similar problem, but mine would just die. Something was going on with my DME when it would get hot. I replaced the DME with a known good one and it now runs fine. Try borrowing a known good DME and see if that works.
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924 timbo  



Joined: 18 Jul 2021
Posts: 5
Location: Buffalo

PostPosted: Mon Mar 14, 2022 1:03 am    Post subject: Reply with quote

Spark plug wires. I know that sounds crazy but I had a '84 VW gti that couldn't climb a hill and sprk plug wires fixed it.
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