Rough running 99 burban PLEASE HELP!!

**bferland** · 10-05-2008, 06:28 PM

Hello. We have a 99 Chaevy suburban 2500 7.4 ltr 454. Great truck! The only issue we are having is it is running rough. It has about 125,000 miles on her and we just bought her. My husband and I have noticed at mid range aceleration there is a delay in power. As well as at idle it seems like there is a miss. My husband changed the oil to synthetic and the plugs to stock AC DELCO from the Rapidfire. When I drove it today, at acceleration from a stoplight it would chug a little and have a hard time getting up to speed. No check engine light. It didn't do t all of the time, but most of the time. Once I got to my desired speed, it was fine. I am leaning more twards a vaccum leak or oxygen sensor or timing. To my knowledge you cannot "time" these trucks. I don't think it's the fuel pump because it is loud and consistant. Please any suggestions would be great! I really don't want to go through the expensive trial and error!! Thanks!

**mehoff400** · 10-05-2008, 06:46 PM

try changing your fuel filter sounds like its starving for fuel

**dwill3015** · 10-05-2008, 07:02 PM

Welcome to the site!

**Springthing** · 10-05-2008, 08:08 PM

to the site!

'99 Suburban 454 here as well. I'm going through the trial and error currently with an issue that is not quite the same as yours.

Good luck with finding what the issue is and getting it fixed!

**MrShorty** · 10-05-2008, 10:27 PM

Originally Posted by bferland

Hello. We have a 99 Chaevy suburban 2500 7.4 ltr 454. Great truck! The only issue we are having is it is running rough. It has about 125,000 miles on her and we just bought her. My husband and I have noticed at mid range aceleration there is a delay in power. As well as at idle it seems like there is a miss. My husband changed the oil to synthetic and the plugs to stock AC DELCO from the Rapidfire. When I drove it today, at acceleration from a stoplight it would chug a little and have a hard time getting up to speed. No check engine light. It didn't do t all of the time, but most of the time. Once I got to my desired speed, it was fine. I am leaning more twards a vaccum leak or oxygen sensor or timing. To my knowledge you cannot "time" these trucks. I don't think it's the fuel pump because it is loud and consistant. Please any suggestions would be great! I really don't want to go through the expensive trial and error!! Thanks!

I'd probably still put a scanner on it, even though the SES light isn't coming on. OBD-2 stores what are called "pending codes" which are faults the computer has seen, but not often enough or consistently enough to trigger the SES light. If there's something there, it might help.

I would also probably check fuel pressure to see if the problem is in the fuel system.

This summer, I had a similar problem in many ways that turned out to be a loose battery post. These newer trucks are so electrically intensive that it doesn't take much to cause a problem.

**tahoe freak** · 10-08-2008, 04:30 PM

Having the same problems. 99 Tahoe 4x4 350. Did you ever find the problem????

**Springthing** · 10-08-2008, 10:23 PM

Handful of these posts in the past few days... Maybe GM pushed a hidden button at HQ triggering a secret sensor in all our trucks causing these problems because profits are low lately.... Just a thought.

**tahoe freak** · 10-12-2008, 04:57 PM

I've had my cat's cut, fuel pump replaced, Fuel Pressure regulator replaced. Still didn't fix the problem. Did you come up with a solution?

**heaviechevie** · 10-12-2008, 05:58 PM

Check into injector problem. I know a friend of mine had the same problem with a mustang and those injectors were only good to about 100,000 miles. I just went thru a simular problem with my 86 K10 and found that the carb, cap and plugs were at fault. After replacing the cap and plugs I still had the "miss" and hesitation, I rebuilt the carb and now she's like new. I'd say injector maybe?

**bferland** · 10-13-2008, 08:53 PM

Well thank you for all of the great suggestions!! It turned out to be a BAD plug wire. The number five wire had a hole burnt in it. My husband said a very TINY hole burnt that was making the plug arch out on the heat shroud. ALSO, if you can beleive it, the truck was missing the ENTIRE PCV valve system on the right side of the motor that went from the valve cover to the intake. The hole to the valve cover was wide open! So needless to say, those issues fixed the problem. So a rough idle that is hard to diagnose, try a new PCV valve. For a missfireing problem, try a bad plug wire. The only way we found it was at the darkest part of night when the truck was running. When I put the truck in reverse, my husband heard a "ticking" noise and saw the slight spark from the plug wire. He said later the next day, after the truck was cool, he pulled that plug wire and really had to look hard. He found it though...A small burnt hole in the boot.

On to the new thing, if it's not one thing it's another! We now are hearing a howling noise almost like a train... from under the hood. Can't really pin point where it is comming from, but looks like more twards the front part of the motor assembly. We were told possibly the alternator. All of the gages are fine. Has anyone ever heard of a alternator howling when it is starting to go bad? There is no loss in battery charge and the voltage gauge is fine. Any help or suggestions on thisone would be great!!