rough start, sluggish acceleration and sudden loss of power
#1
rough start, sluggish acceleration and sudden loss of power
So over the past few days I’ve started having some running issues with my 86 NA 944.
I first noticed after I took it to the car wash. thought maybe using a high pressure water hose might have gotten it’s way into the engine bay because once I left I noticed in first and second gear my car would lose speed during acceleration abruptly (felt like someone was pressing on the brake) but instantly it would catch back up and continue on. No loss of electrical or any other power that I know of. It happened a few times and eventually smoothed itself out by the drive home. I figured the heat had gotten rid of any water.
This morning my car had a tough time starting up and wouldnt keep idle unless I held on the gas for multiple minutes for it to stay on. After, it would idle just fine but noticed it ran sluggish in early gears. No sudden loss of power like at the car wash though. After work it still had trouble keeping idle and was still sluggish in the lower gears, but was driving fine on the interstate. I’m only a few blocks from home and it starts doing the sudden decline of power when in first and second gear again...
Any idea what this could be? Where should I start and eliminate easy fixes first? DME, sensors, etc?
I’ve only owned the car for a few months so most things are more than likely original/in need of replacing anyways.
Thanks!
Justin
I first noticed after I took it to the car wash. thought maybe using a high pressure water hose might have gotten it’s way into the engine bay because once I left I noticed in first and second gear my car would lose speed during acceleration abruptly (felt like someone was pressing on the brake) but instantly it would catch back up and continue on. No loss of electrical or any other power that I know of. It happened a few times and eventually smoothed itself out by the drive home. I figured the heat had gotten rid of any water.
This morning my car had a tough time starting up and wouldnt keep idle unless I held on the gas for multiple minutes for it to stay on. After, it would idle just fine but noticed it ran sluggish in early gears. No sudden loss of power like at the car wash though. After work it still had trouble keeping idle and was still sluggish in the lower gears, but was driving fine on the interstate. I’m only a few blocks from home and it starts doing the sudden decline of power when in first and second gear again...
Any idea what this could be? Where should I start and eliminate easy fixes first? DME, sensors, etc?
I’ve only owned the car for a few months so most things are more than likely original/in need of replacing anyways.
Thanks!
Justin
#2
Rennlist Member
What kind of maintenance has been done on it in the past? Ignition system comes to mind, spark plugs, wires, cap and rotor. Then tps and idle control valve.
#4
previous owner installed water pump, timing belt, cap & rotor, and alternator but thats it to my knowledge
Im going to be testing the spark on the speed reference sensors as well as replacing the spark plugs first.
#5
#6
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Remove the distributor cap and do a thorough inspection. Maybe spray a little WD-40 in there and wipe out the excess. Be sure it goes back on properly. That's a free check. It could even be a bad plug wire.
There are a couple of other possibilities as well. Throttle position sensor - slim chance. Or the MAF sensor - slightly more probable.
Best of luck.
There are a couple of other possibilities as well. Throttle position sensor - slim chance. Or the MAF sensor - slightly more probable.
Best of luck.
#7
Remove the distributor cap and do a thorough inspection. Maybe spray a little WD-40 in there and wipe out the excess. Be sure it goes back on properly. That's a free check. It could even be a bad plug wire.
There are a couple of other possibilities as well. Throttle position sensor - slim chance. Or the MAF sensor - slightly more probable.
Best of luck.
There are a couple of other possibilities as well. Throttle position sensor - slim chance. Or the MAF sensor - slightly more probable.
Best of luck.
Few other findings. My battery was reading 11.9 but the car has been sitting for almost 2 weeks. Tested it autozone and came out fine, just needed a charge. Afterward it read 12.6 but still won’t start. I checked my ignition coil and I’m not getting any volts when I hook my multimeter to the black and green wires. I made sure the car ignition was on. Either I’m testing it wrong or it’s dead...
ive ordered a new one to test (can simply return if nothing changes) as well as spark plugs. The car really turns over with the intention of starting, but just can’t complete the process, I’m getting tach bounce
i still have to check my grounds and afm
Last edited by jwolfe; 02-17-2019 at 12:44 AM.
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#8
Nordschleife Master
If like you said, this happened immediately after a high-pressure car wash then it’s likely to be two things. Either the water jet knocked something loose or water got into the electrics. Even if you didn’t pressure wash the engine bay, still check all your underhood vacuum lines, electrical connections, spark plug wires, etc, are tight and dry everything off with a towel. A common failure point on these cars is water getting into the DME through corrosion under the battery, ie the battery tray area. Check for any pooling of water around the battery and for any dampness in the passenger footwell area, if you find anything you’ll have to remove and open up the DME and blow dry it out. Finally, disconnecting and cleaning ALL your grounds is good insurance for a number of spurious faults, it’s almost a routine maintenance item for our cars.
#9
Rennlist Member
If like you said, this happened immediately after a high-pressure car wash then it’s likely to be two things. Either the water jet knocked something loose or water got into the electrics. Even if you didn’t pressure wash the engine bay, still check all your underhood vacuum lines, electrical connections, spark plug wires, etc, are tight and dry everything off with a towel. A common failure point on these cars is water getting into the DME through corrosion under the battery, ie the battery tray area. Check for any pooling of water around the battery and for any dampness in the passenger footwell area, if you find anything you’ll have to remove and open up the DME and blow dry it out. Finally, disconnecting and cleaning ALL your grounds is good insurance for a number of spurious faults, it’s almost a routine maintenance item for our cars.
#10
Rennlist Member
Suggest removing AFM from J boot and crank engine and simultaneously spray fuel into inlet of J boot, if the engine fires, then the problem is in the fuel injection system.
Can remove fuel injector rail with injectors attached from intake manifold and place each injector in a cup. Crank engine for several seconds. Then evaluate amount of fuel collected in each cup. If no fuel in one cup, switch with one discharging into its cup. Crank engine and see the outcome.
This data should help isolate the problem if it is in the fuel injector system
Can remove fuel injector rail with injectors attached from intake manifold and place each injector in a cup. Crank engine for several seconds. Then evaluate amount of fuel collected in each cup. If no fuel in one cup, switch with one discharging into its cup. Crank engine and see the outcome.
This data should help isolate the problem if it is in the fuel injector system
#11
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checked today and the cap and rotor were recently replaced and look like new as well as the wires. Replaced temp sensor yesterday and also did nothing. Checked both my speed ref sensors and reading right around 1000 so those seem ok.
Few other findings. My battery was reading 11.9 but the car has been sitting for almost 2 weeks. Tested it autozone and came out fine, just needed a charge. Afterward it read 12.6 but still won’t start. I checked my ignition coil and I’m not getting any volts when I hook my multimeter to the black and green wires. I made sure the car ignition was on. Either I’m testing it wrong or it’s dead...
ive ordered a new one to test (can simply return if nothing changes) as well as spark plugs. The car really turns over with the intention of starting, but just can’t complete the process, I’m getting tach bounce
i still have to check my grounds and afm
Lots of good help offered up.
If you suspect the coil, there are a couple of easy tests. You need some basic equipment, though. 1) a test light (goes between a spark plug and the plug wire). It will light up at each electrical pulse. 2) an inductive timing light. Clamp the induction pick-up around a plug wire and pull the trigger on the timing light. This works best if you have a running engine, but is effectively the same as a test light. (Someone has to crank the engine over while someone looks for the light pulse).
In either case, if you get no light, you are not getting spark to the plug/wire.
Stole this from another thread - good basics. Pretty much everything applies to the 944, as well. Unlikely you've jumped timing. Though a compression test might be worth performing if the first few tests don't net results.
#12
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OK - I forgot the car runs (stated in the title). That makes the inductive timing light a very attractive test tool. Easy to move from plug wire to plug wire. Observe the frequency of the light pulse and its intensity from one cylinder to the next. Vary engine speed to be sure the pulses increase as engine speed increases. Significant differences are easily noted with this method.
#13
OK - I forgot the car runs (stated in the title). That makes the inductive timing light a very attractive test tool. Easy to move from plug wire to plug wire. Observe the frequency of the light pulse and its intensity from one cylinder to the next. Vary engine speed to be sure the pulses increase as engine speed increases. Significant differences are easily noted with this method.
since the problem arose the car will not start anymore. It started off with those sluggish moments and sudden loss of power in low gears (not complete loss of power, just for s split second) but it would start, now it doesn't anymore unless i hold the gas while i crank and keep its idle until it can hold on its own.
#14
If like you said, this happened immediately after a high-pressure car wash then it’s likely to be two things. Either the water jet knocked something loose or water got into the electrics. Even if you didn’t pressure wash the engine bay, still check all your underhood vacuum lines, electrical connections, spark plug wires, etc, are tight and dry everything off with a towel. A common failure point on these cars is water getting into the DME through corrosion under the battery, ie the battery tray area. Check for any pooling of water around the battery and for any dampness in the passenger footwell area, if you find anything you’ll have to remove and open up the DME and blow dry it out. Finally, disconnecting and cleaning ALL your grounds is good insurance for a number of spurious faults, it’s almost a routine maintenance item for our cars.