1999 Chevy C2500 2WD pulling problems
 

Hey guys, I posted this over in another area with no response and think i maybe should have posted here based on the issues i'm having with my rig. Don't mean to "double post" but really need some advice as to what to do next.

I bought this truck in early June knowing i would have to invest a little money in it. Immediately, i replaced the battery, alternator, drive belt, upper/lower bj's, sway arm/link bushings and front shocks. Had some A/C issues and replaced the compressor, accumulator,orifice tube and recharged; also had to replace the dreaded air inlet door actuator. Although A/C runs fine, still having issues with the compressor clutch running constantly; i'm thinking the problem may be with the control head unit.

Now a new problem. We hooked on to our 27' Jayco (about 5000 lbs) and headed to the lake (approx. 110 miles one way). Immediately, i noticed the truck struggling to pull it. on the hwy, i couldn't get the tranny to stay in overdrive, as it wanted to constantly downshift (this was on flat roads). I basically drove to the lake at 58-63mph and 2500-2600 RPMs. The slightest grade (hills) had this truck struggling. The trip back home was no different. I did rule out that the trailer brakes were not sticking, nor were the truck's. Also, I did not have a check engine light on.

This truck has 3.73 gears w/ 17" wheels and 265/70 tires and 4L80 tranny. Other than a magnaflow exhaust, no modifications to engine chassis. Also, previous owner stated within the past 2 years, he had the dealer replace both converters, fuel pump and fuel psi regulator. Also, within the past year, he replaced the plugs, wires and cap/rotor.

Yesterday, I took the truck to a local mechanic and they had it all day; they ran a full diagnostic on it and drove it and said they couldn't find anything wrong. They asked to keep it over night to look at it again today. This afternoon, they informed me they still could not determine what is going on. I'm fixing to leave to go speak with them to determine what was performed and what my next step should be. The one thing they were sure about is that it is not related to the transmission. Will report back here when i know more. If anyone has any suggestions, i would surely appreciate hearing it. TIA, James

Isn't it supposed to NOT be in OD when towing? The OD is for cruising and simply does not have enough power to get (keep) going. All new trucks have the tow button on the shift lever to stop it from going in OD.....

did you remember to use tow/haul mode when you were hauling?

This model doesn't have the tow/haul function; it is the old body style with the 5.7. This engine/tranny/rear end shouldn't have any problems pulling this kind of weight in OD. I did have it out of OD in stop-n-go traffic, but in my opinion, on highway (and flat roads) it should be more than capable of this load; I sure hope i'm not wrong here because if i am, i made the wrong investment.

Something to add.... last night, my son informed me that when he borrowed my truck a few weeks to move his furniture, he said he felt the truck was struggling; he basically was pulling a 10' utility trailer with probably 800 lbs of furniture loaded on it. To me, this is an indication of a problem some where.

Also, i did speak with the mechanics after work yesterday and long story short, they are keeping my truck another day to determine if the catalytic converters may be plugged/restricted. As i stated above, the previous owner indicated the cats were changed out about 2 years ago; however, looking under the truck, it would appear only one was changed out. They asked that i call after lunch today and would update me on their findings. They also said the truck does drive kinda sluggishly and just doesn't have the pep a 350 should; maybe this does point to a restriction in the exhaust somewhere. We'll see. I appreciate the replies guys so keep them coming. I'll post when i hear back from the mechanics. thanks, james

Have you done a compression test ?
Using any Oil ?

oil is clean, not losing any and compression test good. Don't have the numbers though at this time. About to call and see if/what was found today and report back. thanks for replying.

HA ok, ya got me grabbing at straws here :D

Not a lot of things left, so...
You think it may be a/some Flat Cam Lobes ?
(of course that would have effected your compression readings)

Next, maybe focus on the Computer...timing...maybe ?

CW, thanks for helping me out here! First, i need to correct some information i posted earlier. Thursday evening, i left work to run over to shop. I spoke with both mechanics and revisited what they informed me they have done. I found out they did not do a compression test after all!! Also, they didn't have time to do anything to the truck that day. As they couldn't figure out what the problem was, i wasn't charged anything and i drove the truck home that evening.

Friday morning, took truck over to a muffler shop. We confirmed there wasn't any restrictions in the exhaust (or across the cats). Immediately afterwards, i went to Oreillys and purchased a gage/hose to perform my own compression test. I pulled all plugs, disconnected fuel relay and coil wire and hooked charger up to battery before i started testing. Readings looked good/uniform on cylinders 1,3 and 5; pressures came back at 160-165psi. I tested #7 several times and the compression was a constant 110psi. I squirted some oil through the plug hole and tested three times; compression increased to 120psi.

I moved to the other head and tested 2,4,6 and 8. #2 and #4 were at 110psi and #6 and #8 were 115psi and 105 psi respectively. Not good!! Based on these readings, I don't know if it is rings, cam and/or valve related. The truck doesn't smoke and isn't losing any oil. Also, I don't hear any valve or lifters acting up at idle, under acceleration or normal driving. Could it be a head gasket issue??

As my next step, I was contemplating sea-foaming in hopes of removing any carbon that might be preventing the valves from seating properly and checking again at some later point. CW and others, what are your thoughts?? I called some dealerships for pricing on a GM long block and I'm looking at $2200 to $2300; don't have the funds for this and sure am hoping it doesn't come down to this. Keep 'em coming guys, i really appreciate your input!! James

based on the compression test numbers I would do a cylinder leak down test. If that tests ok. I would measure the lobe lift for the valves. Is this a high mileage engine?

hello tech2. I bought the vehicle with approximately 149000 miles; it now has 152K and ready for oil change. I imagine this leak down test is something i can do at home with the gauge i bought yesterday and should be fairly simple; however, never have performed such a test.

This morning, i went to oreillys and bought can of seafoam. poured 1/3 can into brake booster line from intake (per the instructions), let sit 5 minutes and restarted. Instead of just letting it idle, took it down the road. Repeated this procedure a second time and now I am fixing to do a third and final time. Truck seems a little peppier from just "getting on it" but that may just be wishful thinking on my part. My plans today or tomorrow is to retest the 5 cylinders that are registering 105-115psi and see if there is any improvement. Would you guys agree or would this be meaningless.

(tech2) if or when i have the extra time, i will perform the tests you offered and i do appreciate your response. fixing to go drive it again...