1999 Escalade power loss after running temp/heat up

[r.knighter]

Hello everyone. Thanks in advance for reading this thread. I'll do my best to articulate the issue (I'm not to mech savvy I'm afraid), and keep it as concise as possible.

Essentially, after driving at running temperature, I experience a sudden loss in power while revving, especially when accelerating from a stop, or when "gunning it" suddenly to pass or merge. The truck feels like it shutters and sputters as if it's running out of gas and can't power itself. But when I let off the gas, the problem vanishes and it coasts.

The first time it happened was after a 90 min drive with the cruise set to 60MPH on the highway. After the last few miles on city streets, I revved it a bit, hard off a light and it first felt as if the tranny was reluctant to shift gears. The problem didn't occur again for a while (several months) and when it arose again, it did in the way I described above. Recently, as the weather has heated up, it has gotten worse - shorter times to exhibit the issue, with rougher idling and shuttering, to the point where she just died while waiting to make a left!

My mechanic diagnosed the cats as being clogged. I took her to an exhaust specialist who said my cats were fine and the temps are in perfect range (after running for 15-25 mins). The exhaust shop mech said it could be my fuel injectors because he'd seen the issue before where guys had changed the cats and the problem came back!

So I went back to my mech while the problem was happening so he could pull off my muffler to rediagnose. Again, he said one of my cats was clogged. I decided to order new cats. He installed those and he was not happy with how the truck was running.

Then, he tried replacing the ignition coil and the ignition module with a good used one off of a GM Safari, but that showed no sign of improvement. He said that my fuel pump runs at 60psi when started and then drops to 50psi when the truck is running well and while the problem is happening, so he doesn't feel that is significant enough to cause the problem. He does not feel it is ignition related. He said the cams are at "-3 cam retard", but they should be between (I think he said) -1 and -2. The front 02 sensors read "extremely lean" when the problem persists, instead of switching between "lean to rich". He thinks it could be the fuel injectors or maybe the spider injector in the manifold.

He is stumped, and doesn't want me to spend any more money on the truck (replaced the fuel tank and transfer case which are now soild) until we know for sure where the source of the issue is. He said I could take the truck to a GM dealer and have them scan the computer for a few hours for tests and diagnostics, but at quite the expense. He did not charge me a dime for his labor on all of this latest visit.

Anybody have any ideas?

1999 Escalade, less than 110K miles.

Thanks!

 

[SunlitComet]

if you are getting lean indication and you pressure is dropping then you likely have pressure/flow issues. follow these test procedures to the key. http://www.sunlitcomet.com/pdf/auto...99 yukon-tahoe-5.7l-fuel-pressure-testing.pdf

if fuel pump, delphi unit only. if filter replace it. if regulator and/or injector issue and it has not been upgraded yet then replace the entire injection assembly with www.amazon.com/Delphi-FJ10566-Injector-Conversion-Assembly/dp/B000TYLIFS/. it is a much better unit and includes a better regulator as well. there are plenty of tests to do before just replacing parts. the back pressure could have been tested before replacing the cats.

 

[r.knighter]

Now, she's throwing a 300 code for random misfire!

 

[SunlitComet]

get a misfire history of the engine with the proper scan tool to find out which cylinders are acting up and how bad.

 

[r.knighter]

The miss code was due to a loose plug which has been tightened and they are replacing the fuel pump a dealer pump and cleaning some of the lines and injectors. Is a dealer pump the Delphi unit?

He said the gas looked "piss yellow", darker than normal. Could that be poor quality gas (though I put a tank of 94 in to help burn hotter for the injectors)?

 

[SunlitComet]

first off always remember that higher octane does nothing for cleaning really. wont make you burn hotter or whatever someone might have told you it does. also your pcm does not automatically change how the engine runs because of high octane. it must be reprogrammed for it. a bottle or two of techron or stp in a full tank is sufficient for minor cleaning. pressurized solvent by gm or their suppliers is the strongest cleaning. if a gm dealer it will be a delphi or delco pump which is good. a bunch of improvements to it have been made over the years. same with the the fuel injection body if they have to do that as well if the cleaning does not help. the delphi pump at amazon is about $150 and the new injector system is about $270 now. so what ever you can do your self would be saving you money. as for the gas it should be clear to a slight tint of yellowing. but not "dehydrated dude urinating" yellow. always stick with top tier gasoline like chevron, mobile, exxon, texaco. shell, 76. avoid the local no named pump, company house brands or commercial fuel depots.
there is a tsb out about this very thing in regards to the old style injectors originally installed at the factory. just to make sure it is gas pour some on a solid glass or glazed ceramic plate and watch the evaporation if gasoline all of it should disappear at the same rate.

 

[r.knighter]

Thanks. I'm picking it up tomorrow or Wednesday.

 

[r.knighter]

Running like a beaut so far... 40 min freeway and city drive in moderate heat!

 

[r.knighter]

Cel?

Still solid after 200 miles.

The CEL came on yesterday though. I started her up, she seemed a bit reluctant: she turned over, caught and started, then seemed like she was about to stall and die for two seconds and then she started right up like she changed her mind.

I thought maybe it was a cold start, because overnight it dropped to near 32F. I turned her off and she did the same thing again. The CEL came on. I drove around for several miles wondering if it would turn off. But it did not.

I pulled over and removed and retightened the gas cap, CEL stayed on. Then it turned off several miles later, and has been off for 25 miles or so.

That older "piss yellow" gas that went through the system was a mix of 94 and 87 from big national pumps (in Canada here, "Petro-Canada"). By older, I mean a few weeks at most. The last 200 miles has been 87 from Shell.

Now the CEL is off. So... ?

Hopefully it stays off. She ran like a champ the whole time it was on though.

 

[SunlitComet]

starting in 1998 the pcm on some emissions classifications started looking for the "driver forgot to install cap correctly" issue that happens to every one sometime or another. the light was likely flagging an evap system pressure leak as a result. it clears it self after testing good in three consecutively defined trips.