Mechanics

SHUTTERS AT SPEED

1990 Nissan Maxima • 220,000 miles

I have a 90 maxima just replaced all of the ignition system but occasionally the car will shutter violently at speed, like it is out of time or getting the wrong air fuel mixture, it will sometimes happen then backfire and begin to run smoothly again. Any help or advice on what the problem or problems could be?
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Cbaumann086
December 13, 2011.



Have it scanned for codes and check the timing.

Rivermikerat
Dec 13, 2011.
Well the timing belt broke a few years back and I think its a little out of time but adjusted as far out as possible on the distibutor but it hasnt seemed to have been a problem until just recently, its like it just starts missing badly and always smells like gas fumes as if running rich, could it be O2 sensor or MAF possibly please help, anything that could help on a limiteed budget.

Tiny
Cbaumann086
Dec 13, 2011.
Yes, possibly. Check the spark plugs and wires. Rent or borrow a compression gauge from a parts store like Autozone, O'Reilly's, etc and check compression. Also get a fuel pressure gauge and check the fuel pressure. What brand of gas do you use? When was the last time you ran a bottle of good quality fuel system cleaner, like Techron, through the tank?

Rivermikerat
Dec 13, 2011.
Well like I said the plugs a wires and cap and rotor and coil were replaced a month AGO, I have found thayt running the new ethanol enriched gas is not good for my car so I go out of my way to buy 100% gasoline and, I usually put some Lucas fuel system cleaner in atleast every other fill up. Another thing is, if the fuel pump is going bad could it over compensate and supply more than required by the car at the time. Ive owned and worked on a lot of vehicles and this one with this problem has me puzzled.

Tiny
Cbaumann086
Dec 13, 2011.
No. If the pump is going bad, it won't get enough fuel. Check the fuel pressure at the regulator. Pull the plugs and check their condition. Do they look wet with fuel? Check the quality of the spark being supplied to the plugs. They make a nice little "toy" that takes the place of the plug and clamps to a good ground so you can see the spark. It should be bright blue and audible.

When the timing belt was replaced, did whoever replaced it check the compression? Either way, do so again. You should see numbers of at least 120-140PSI, with no more than 15% variance from highest to lowest.

Rivermikerat
Dec 13, 2011.
The plugs are a little damp more with oil than fuel, I replaced the timing belt myself, and the car was cranked on for a while untill we realized it was the timing belt, so in theory the bottom end was turning w/o turning the cams, what could that imply. And one more quick question, if all cylinders test out the same, what would be the next step?

Tiny
Cbaumann086
Dec 13, 2011.
Cranking the engine repeatedly with a broken timing belt can cause bent valves. Which would require replacing them and performing a valve job. Compression check will tell us this.
Can you upload images of the oil slick plugs? Is it copious amounts of oil, or just a little? The oil could be interfering with the plugs supplying a strong spark.
Have it scanned for both hard and soft codes. We'll go from there with testing procedures for the O2 and MAF sensors, if I can find them.

Rivermikerat
Dec 13, 2011.