Strange engine stumble, 92 SE-R

jem1947 · 06-21-2010, 02:29 PM

I have an "aged", daily driver, '92 SE-R with a peculiar engine stumble. The car has 274k miles but cranks good & runs every day. But occasionally, and increasingly more often, it will stop running for a moment (1 to 4 seconds) then picks up & runs normal again. Originally it was mostly when the car was warming up but now occurs most any time.
What is stranger is that it often happens under two different conditions (not exclusively). On interstate roads when the car contacts a rise or drop in the pavement, as in new asphalt laid over existing, the car may shut down, sputter and then come back.
The other common case is again at higher speeds when I let off the accerator pedal and then when it is pressed again a stumble often happens.
Low end torgue driving has a stumble once in a while also.
The plugs are good but it may need plug wires but this seems too odd for somwthing like that.
Any suggestions are appreciated.
Thanks,
Jim

sr20bud · 06-21-2010, 03:10 PM

hmm could be a fueling or maf issue also pull your dizzy cap off and check the pick up points and rotor arm

skcusloa · 06-21-2010, 05:03 PM

wow, that is a great description, I wish half the people that described their problems could do that well

Here's what I'd do:

It sounds like either the spark or the fuel is getting cut when you are hitting a bump. Start your car up and start wiggling on stuff. Start with the wires that go to your distbutor/ignition system, then start pulling on the main harness near the firewall. If it doesn't stumble or anything, remove your bottom back seat and gently tap on the fuel tank/pump cover with something that won't damage it, wiggle the wires too. Some times fuel pumps will get dead spots in them, but they are generally reactivated by a bump not turned off.

A lot of times cars with that high of mileage will develop internal breaks in the wires, so whenever they are stretched or moved abruptly they'll lose connection. Most of the time it's from bad motor mounts and people will notice it when they floor the car, the motor moves, stretches the wires and something goes wrong.

Also look for any previous repairs that might have been done to the harness. That's the first thing I go for with any intermittent problem, I look at what's been messed with. 90 degree bends are also a common spot for breaks.

jem1947 · 06-21-2010, 06:35 PM

That sounds close to home regarding the motor mounts. I've noticed the motor seems to "rotate" (trans shifter moves) when I let off the accellerator while cruising. Another oddity is the pedal sticks sometimes after the coasting but breaks loose consistently although suddenly.
I'll take a look tonight or tomorrow.

Also, the maf may be a separate but present issue too with the morning ailments.

Thanks a heap!

Jim

llaprad1 · 09-06-2010, 10:59 AM

Have you noticed whether or not the amount of fuel in your tank is a variable?

I had a problem where my car felt like it was running out of gas at 1/4 tank if I made a sharp right turn.

It was a disconnect fuel return line in the tank.

Which could be possible because replacing a faulty fuel pump was an early TSB for most 2L B13s.