Car sputters under acceleration (Page 1/3)
Cliff Pennock AUG 16, 04:20 AM
I know there's a similar thread already but I don't want to hijack that thread and although the symptoms might be similar, I don't think the problem is similar.

This started two days ago. When I started my car for the first time in the morning, it started up fine as usual but when I tried to drive away, it immediately started to sputter. It didn't die, it just sputtered and hardly accelerated. Easing up on the throttle made the sputtering go away. Every time I applied a bit more throttle, it began to sputter. At higher RPMs, it goes away. It doesn't feel like a single cylinder cutting out, but more a whole rail. I'll try to make an audio recording today so you can hear what it sounds like. The engine doesn't backfire but I do smell gas when it happens.

Two things that might be related to the problem:

1) The evening before, I washed the (outside of the) car with a pressure washer. I didn't experience any problems in the two minute drive from the car wash to my house however. But it could still be related. But in the days since, it has been pretty hot up here (86F - 90F) so I would expect any water to have evaporated by now. Although we also had some rainfall in the evenings but rainfall has never caused any problems other than a squeaking belt for a few seconds.

2) My tachometer started acting up a few weeks ago. I have my digital dashboard installed so I'm not sure the jumping tach is caused by the car (like due to a broken tach filter) or because some electrical issue with the dashboard. I hadn't troubleshot the tachometer yet because I didn't notice anything different with how the car drove.
Mike in Sydney AUG 16, 05:45 AM
I was thinking fuel pressure until I saw the bit about pressure washing. Try pulling off the distributor cap and checking for moisture. Water can stay in there for a while. Second, check all of your ignition control module under the distributor. Also check your spark plug leads for cracks, etc. I had a similar problem on an old ford 6 cylinder once. A buddy told me to check the wires in the dark with the engine running. I did and saw a couple of wire arcing . My problem got better when I replaced the wires. If this doesn't solve your problem, you may want to check the fuel pressure when the engine is under load.

Mike

BTW, any chance you got water in the tank with the pressure washer?
Cliff Pennock AUG 16, 05:54 AM

quote
Originally posted by Mike in Sydney:

BTW, any chance you got water in the tank with the pressure washer?



No, I don't see how... My fuel cap is intact en the lid was closed.
fierosound AUG 16, 10:02 AM
TPS and MAP should be looked at.
Unplug connections and make sure they haven't corroded.



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[This message has been edited by fierosound (edited 08-16-2020).]

Cliff Pennock AUG 17, 03:31 AM

quote
Originally posted by fierosound:

TPS and MAP should be looked at.
Unplug connections and make sure they haven't corroded.




Wouldn't all those things cause the entire engine to cut out? I'm asking because it doesn't sound/feel like it's somehow not getting enough fuel, it sounds/feel like a few cylinders cutting out.
fierosound AUG 17, 10:17 AM

quote
Originally posted by Cliff Pennock:

It doesn't feel like a single cylinder cutting out, but more a whole rail. I'll try to make an audio recording today so you can hear what it sounds like. The engine doesn't backfire but I do smell gas when it happens .




quote
Originally posted by Cliff Pennock:

Wouldn't all those things cause the entire engine to cut out? I'm asking because it doesn't sound/feel like it's somehow not getting enough fuel, it sounds/feel like a few cylinders cutting out.




If we're talking a fuel problem, maybe some water got into the fuel injection harness connector under the MAP.
See in picture below. The one on my 87 GT is a wide flat connector unlike the one in this pic.
The injectors run in TWO banks and there are TWO fuses in the fuse box (one for each bank, can't hurt to put new ones in).

[This message has been edited by fierosound (edited 08-17-2020).]

cebix AUG 17, 12:21 PM
Stupid question but... did you pressure wash the engine?

I would check the coil and ignition module connections. I've had something similar happen to my duke when the tach started jumping around and it was sputtering unless I let off the gas. It was a loose signal connector to the coil. I've found they are very easily pulled off and the clips that hold them to the coil tend to break.
Cliff Pennock AUG 17, 12:54 PM

quote
Originally posted by cebix:

Stupid question but... did you pressure wash the engine?[quote]

No I didn't...

[quote]I would check the coil and ignition module connections. I've had something similar happen to my duke when the tach started jumping around and it was sputtering unless I let off the gas. It was a loose signal connector to the coil. I've found they are very easily pulled off and the clips that hold them to the coil tend to break.



I will check the connectors tomorrow.

Today I drove the car longer than a few minutes for the first time since this happened. When I just started it up, just touching the pedal would cause the engine to cut out. But with time, it does get better and after driving the car for a while it only happens during moderate acceleration. Easing up on the throttle and it will accelerate just fine. During kick-down, no problem either. But somewhere in between, it cuts out.

It's hard to explain. It's not at certain RPMs, it's also not at certain throttle positions. It's at certain acceleration.
Cliff Pennock AUG 17, 12:58 PM

quote
Originally posted by fierosound:

If we're talking a fuel problem, maybe some water got into the fuel injection harness connector under the MAP.
See in picture below. The one on my 87 GT is a wide flat connector unlike the one in this pic.
The injectors run in TWO banks and there are TWO fuses in the fuse box (one for each bank, can't hurt to put new ones in).




Thanks, will check that out tomorrow.
cmechmann AUG 17, 07:24 PM
If no condensation under the distributor cap, I would look for a shorting rotor(pencil like mark under the center contact tab) And listen to the coil to see if it sounds like it has a faint arcing in the E core. Both would show up more damp. Both will allow to reach up to a certain KV demand then short anything above that point. From the cap on out it would be random or all the time.