1994 XE Pickup Running Rough

[ChrisHarris]

I need help with my truck. My fuel mileage went from about 21mpg down to about 12mpg. This happened over a short period of time--about 6 weeks of slowly worse and worse running. It did not happen suddenly--so I don't think that the timing chain jumped a tooth.

1994 Nissan truck2.4L KA24E engine. 4cyl170,000 miles

It idles real rough. My fuel mileage went down to less than 1/2 what it should be. It runs okay, but the idle is awful. shaking the whole engine and truck. When it is cold, it runs. When it starts to warm up a bit, there is a period of time when it wants to die when I let off the gas pedal. I have to use gas and brake at the same time to keep it from dieing. After it warms up to temp, it idles real high (1500RPM) but it won't die anymore.

I changed the plugs. They were worn, but none of them was fouled. All had the same burn characteristics. Light tan color, just as it should be. About 40,000 miles on these plugs. The gap was worn to about .060" so, I knew they were worn, but they still looked good. I installed new plugs and gapped to spec at .044"

That didn't change anything. Still rough idle.

So, I pulled the air filter out. It's a little dirty, but not clogged. I took it completely out and wanted to see if that was causing the problem. No change. Still rough idle without an air filter. Put it back on.

Pulled the distributor cap to check the cap and rotor. Looks a little bit worn, but no carbon build up or flash anywhere. About 40,000 miles on this cap and rotor. Looks fine, so I put it back on.

Went outside at midnight and drove to a dark parking lot. Popped the hood and looked for arching plug wires. Don't see any voltage jumping around. Don't hear any of the tell-tale popping sound from bad plug wires. About 40,000 miles on these wires. Good high quality Beldon wires. Thats not the problem.

Okay, so not the plugs, wires, rotor, cap or air filter.

I'm thinking it could be a sensor. This truck has 4 sensorsThrottle positionAmbient air tempMass airflowOxygen sensor

BUT:I called the dealership and they said that if it was a sensor, then I'd see a CHECK ENGINE light on my dash panel. I don't see one. I know they all work, because they light up when you turn on the key. They go out when you start the truck.

The dealer said that if I have no CHECK ENGINE light, then it's not a sensor. He said it may be a clogged injector.

My friend is a mechanic at the power company (Excel Energy) and he is a top AAA certified mechanic. I called to pick his brain, but he's one of those guys who can't reason through a problem and use logic to figure it out. He says to hook it up to a computer and get it diagnosed. But, he's got access to the computers at work, so using them is no big deal to him. I don't have access to a diagnostic computer--so it IS a big deal to me. About $100. He did say that I could try a fuel injector cleaner called 44K. He said it's the best "over the counter" cleaner on the market.

I went to 3 different auto parts stores and they have the diagnostic computers, but they only go back to 1996. My truck is a 1994.

I don't want to take it to a shop. It'll cost me $150--$200 just to get it hooked up to a computer and diagnosed.

Can anybody offer any help? I'm out of work right now and I don't have a ton of money right now. I need to get it fixed because I'm wasting gas @ $3/gallon. It's costing me money. Money that I could be using for food, bills and job searches.

Thanks

[BungaloBill]

Hi Chris,

i just got rid of a 94 xe pickup and got a new 08 Titan.

I had the same problem. Took it to a mechanic and he figured it right away.

He took a can of ether starting fluid and sprayed on the intake manifold while the engine was running. the idle smoothed right out for about 5 seconds. he did it again and same thing happened. He said the intake manifold was leaking air at the gasket. Approximately $600 to repair.

Didn't want to spend the money so I put a wrench on the bolts and tightened them. Didn't fix it but gave me 60 to 70 percent improvement to the Idle.

Sold the truck about 6 months later.

Good luck with you problem