Suburban can't take the heat

Hi guys,

I have a problem I have been struggling with for the last year. Over $2000+ and 2 months in the shop, nobody has a clue. I am desperate. Anyone with any ideas, please help. Here are the main symptoms:

- Engine stutters and sometime stalls ONLY in 3rd and 4th gear
- 1st and 2nd gear has NEVER given us a problem
- The outside temperature has to be above 75 degrees. The truck ran great all winter, but last week with the first warm day, acted up again
- There has to be a sizable load (6 adults, full tank of gas)
- gets much worse going up hills (again load)

Not sure if it is related but one time in the winter, the truck stopped blowing heat. If I turned off the fan, the system would "build up" heat but then as soon as I turned it back on, the heat would stay for maybe 30 seconds and then fizzle out back to cold air. This happened only on the coldest day of the year. The heat has been decent the rest of the time.

Last year they replaced the crankshaft position sensor like 4 times, then claimed it was the ECM, replaced that and it still acted up. Then they finally said it was some corrosion in the wiring harness. However by the time they got through with it, it got cold enough outside where it didn't act up any more.

I really need help

Thank you

Need to know year and engine.

Oh Right - sorry

2001 Suburban 1500

Let me know if there is anything else you need

as for the heating problem, it sounds as though it's low on coolant or the heater core needs to be flushed. draino works well. remove heater hoses at engine, drain coolant from heater core, pour draino down one hose till it comes out the other, let it sit 10-15 min, flush with water and hook em back up.

as for your other problem, i'd start with a tune-up. plugs and wires, pcv valve. all your issues are load related, usually ignition problems. Elec. resistance increases with heat.

probably needs a tune-up anyhow. use ac delco plugs and don't forget the dielectric grease.

swingline,

Thank you for your suggestions. I will definitely look into flushing the coolant system. Interesting you mention the tune up because that was the first thing we did last year. Replaced all plugs, 1 coil that supposedly tested bad, and cleaned the fuel injectors. This "fixed" it for a couple weeks, and then it came right back.

Couple questions though

- would the temp gauge not read abnormally high if the cooling system is having issues?

- right before the engine stalls, I can tell its about to do so because it just drags. Feels like someone threw a 500 lb of sandbags in the back, and then without fail, the first big hill and bam it chokes. Does this "extra weight" perception fall in line with the symptoms?

Thank you again!

Oh Right - sorry

2001 Suburban 1500

Let me know if there is anything else you need

Still need engine size.

Has the fuel pressure been checked?
Has the fuel filter been replaced?
Is the fuel pump original?

The best way to check a heater core is to get it up to operating temp and then with the motor running check both hoses going into and out of the heater core. If they are both hot it's ok. If ones cooler than the other it's not ok.

Hi guys,

I have a problem I have been struggling with for the last year. Over $2000+ and 2 months in the shop, nobody has a clue. I am desperate. Anyone with any ideas, please help. Here are the main symptoms:

- Engine stutters and sometime stalls ONLY in 3rd and 4th gear
- 1st and 2nd gear has NEVER given us a problem
- The outside temperature has to be above 75 degrees. The truck ran great all winter, but last week with the first warm day, acted up again
- There has to be a sizable load (6 adults, full tank of gas)
- gets much worse going up hills (again load)

Not sure if it is related but one time in the winter, the truck stopped blowing heat. If I turned off the fan, the system would "build up" heat but then as soon as I turned it back on, the heat would stay for maybe 30 seconds and then fizzle out back to cold air. This happened only on the coldest day of the year. The heat has been decent the rest of the time.

Last year they replaced the crankshaft position sensor like 4 times, then claimed it was the ECM, replaced that and it still acted up. Then they finally said it was some corrosion in the wiring harness. However by the time they got through with it, it got cold enough outside where it didn't act up any more.

I really need help

Thank you

as was asked by a fellow member what engine ????

also again as mentioned did they check the fuel pressures ?

with the loss of heat on a very cold day , my guess is you do not have sufficient coolant to prevent freezing. as the vehicle is driven on a very cold day the radiator will freeze then no heat also the temp guage may not read correctly.

I would not use DRAIN O in the engine system. there are other products available if the coolant system is damaged from mixing non dexcool coolants with GM APPROVED DEXCOOL.....