Mechanics

CAN'T DRIVE TRUCK OVER 50MPH. NO ACCELERATION AT ALL. AFTER A WHILE TRUCK STALLS. FUEL FILTER PROBLEM?

1999 Isuzu NPR • 78,000 miles

This morning I purchased a 1999 Isuzu NPR V8 350 in Ontario, CA for $6000.00. I test drove the vehicle and everything seemed just fine. I began my 6 hour drive back to Phoenix. As I increased speed upwards of 70-75mph the acceleration started to struggle. So, I kept my speed around 70-75 mph. My gas gauge was showing less than a quarter of a tank so I stopped to get fuel. As I pulled into the gas station the truck shut off! I coasted up to the gas pump but was just short. I tried starting the engine but it wouldn't start. It just gurgled and had some engine knock. After a 5 min wait I was able to start he truck and pull up to the pump. I filled the tank and got back on the highway. Things seemed to be the same as mentioned above until I was back down to about a quarter tank of fuel. My acceleration/power decreased and the engine shut off again as I exited the highway! I tried to start the truck again but no luck. After another 5 min wait I was able to start the truck again so I could pull up to the pump. I filled the tank and did some calculations. I only got 7.75 miles per gallon on one tank! That's horrible. As I began to drive again I could only get up to 50mph on the highway. Then after a short drive I began to loose acceleration/power again so I pulled over. I waited 10 minutes and tried to drive again. I only was able to drive about 8 miles at 50mph so I pulled over again and decided to have some dinner. Now I am going to go and try to drive it again after a 40 min wait. I will let you know what happens.

Could it be the fuel filter? The ERG valve? Clogged fuel lines? Exhaust flap getting stuck?

Any help you could provide would be greatly appreciated. Thank you. Marc
Avatar
Mgarrard
September 1, 2012.




There are a few possibilities and the fuel filter is might be partially clogged as the engine is struggling when you increae the speed.

Reduce the driving speed to see if there are any changes.
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KHLow2008
Sep 1, 2012.
After waiting 40 min last night I was able to drive the truck 50 miles back to my house without any problems. I didn't try any rapid accelerations or try to top out the speed for fear of having any problems. I just wanted to get home.

This morning I drove the truck to my job site and did not have the same problems I experienced last night. The only thing I noticed this morning was a knocking noise upon acceleration. It was coming from the driver side and sounded like it was coming from the exhaust/muffler area. This only happened one time.

Now I am sitting in the truck idling with the AC on and I can smell the fumes. The AC is on recycle so I shouldn't be smellin the gas fumes.

Hopefully this provides you with the information you are needing. Where should I begin with the trouble shooting process? Thank you again for your assistance as I just spent my hard earned $6000.00 and can't afford to spend another $1,000-3,000.00 on repairs.

Tiny
Mgarrard
Sep 1, 2012.
Let me add that just now when I got out of the truck I heard that knocking noise coming from the catalytic converter. Could this be my dilemma?

Tiny
Mgarrard
Sep 1, 2012.
It is possible the catalytic converter is bad and this can result in the knocking noise you are hearing. It can also cause the inability of high speed driving as knocking noise form the catalytic converter can mean it is dislodged internally and cause partial blockage of the exhaust system.

You would need to remove it to check. A viausl inspection might tell you something.

When the catalytic converter fails, it would usually throw a code. Is the MIL indicating and have you checked for trouble codes?

KHLow2008
Sep 1, 2012.
Yesterday (Tuesday) I drove the truck for the first time since arriving in Phoenix. The check engine light kicked on and stayed on the entire time I drove the truck. At stop lights the truck would go from idling as if the engine wasnt even running (which is great) to choking every 10 seconds or so. The choking made it feel like the truck was going stall. It had me in a panic everytime I came up to a light.

So, I stopped by O'Reilleys and had them check for a code. It said it was an issue related to the catalytic converter. I took the truck in to a muffler shop and they installed two new cats. The one cat was completely wasted inside and definitely needed to be replaced. After an hours wait. Voila. Two new cats and I was back on the road. I thought my problems were resolved! NOPE! Read on.

Once again the truck acted as if it wanted to stall at lights! Then as I was exiting the freeway, the truck decided to stall completely as I pulled up to the light. I couldnt restart the truck so I exited the truck and gave it 5 minutes. I went back to the truck and started it up. I drove straight to an Auto Zone. I spoke with one of the guys and described my problem. He said it could be a fuel filter, fuel pump, a sensor, a vacuum issue, etc. I purchased a fuel filter and I am going to start with that. While I am in there I am going to check the spark plugs as well.

Does anyone have any other suggestions or recommendations? Thank you for your help!

Tiny
Mgarrard
Sep 6, 2012.
Check the fuel pressure and if the idling was too low, have the throttle body and IAC cleaned.

Other than that your planned course of action should be sufficient for now.

KHLow2008
Sep 6, 2012.

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