RE: 97 Blazer Loss Engine Power after warm up.
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 8:09:16 AM
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swartlkk
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From: Waterloo, NY
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Once you have reached closed loop status and before you start having problems, how does the truck accelerate at WOT?
I am just trying to get a handle on what is really going on here.
I've come almost full circle based on this latest information thinking that it may be fuel supply related, but that wouldn't explain the zero V output from the O2s as even extremely lean, the output should still be around .1V...
Engine load dependent is what it sounds like which could still point to a bad PCM... Have you had any luck finding a replacement PCM on the cheap?
*EDIT* - Well, I just did some ebay searching and found a few PCMs that will work, however I did forget about the passlock programming that will be in these PCMs. It isn't as simple as just swapping it in, but for $90+s&h, it should work nicely. Just verify that your PCM is the same PN and they should be able to program to your VIN for you.
< Message edited by swartlkk -- 2/4/2008 8:22:25 AM >
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 8:43:29 AM
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BrianSw
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It accelerates fine when in closed loop and before the problems start. Also accelerate good when cold and in open loop just after starting up in the morning. Even going uphill on a short drive. No luck on the PCM except some on Ebay. Kept my eyes on O2 signals and trims from the start this morning. Check my grounds to the PCM and O2s this weekend and they were good. Thinking I'm going to pull the O2 right before the cat and drive it home tonight that way after work.
Thing is they (O2s) after the loading problem starts go back to switching their full range when I pulled over and sat there at idle. Floored the gas really fast and I can watch them drop and fuel trims jump up. Engine's rpms pretty much don't get past 2000. Engine stumbles alot like not getting enough gas. Pretty much the same symtoms I had when I had a bad fuel pump. That was replaced.
Had replaced the pump twice within a 2 year period. Funny thing about all this is I didn't have this problem until I replaced the fuel pump last time along with the fuel pressure regulator. About a week after the pump was replaced I started having this problem. I would check my fuel pressure but my pressure gage lost that center pin in the connector along with the O ring. Need to but another one. How cheap these thing are made. Still can't see the pump being the problem as I don't think it would affect O2s on uphill load conditions when engine is warm.
Thing is with the cat I read others here having very similar problems and it turned out to be there cat. Even though they didn't monitor their O2s and trims to see what was happening.
Brian
< Message edited by BrianSw -- 2/4/2008 8:54:41 AM >
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 8:49:30 AM
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swartlkk
Posts: 15274
Joined: 5/1/2005
From: Waterloo, NY
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Does it depend on the fuel level? You could definitely rule out a fuel supply issue by driving around with the fuel pressure gauge on there, strapped someplace where you could watch it while driving.
I drove my old Intrepid around for a week without a hood and the fuel pressure gauge zip-tied to the windsheild wiper because I was having fuel issues with that. Ended up being a corroded wire under the car, but I only found that out after I had replaced the pump which helped, but it still stumbled at WOT. Ran a new wire from the relay all the way back and all of the problems went away.
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 9:08:31 AM
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BrianSw
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I am having alot of Fuel gage problems been pegging over to full alot and drops down slowly as I keep driving. Can't trust the thing as I never know really how much fuel I have in the tank. Sometimes it reads high 3/4 then low 1/4 and back to high. Don't know if it is the sending unit or the ground to it. I had to splice on a different connecter on my wiring harness to the new pump because of some kind of change GM did. I soldered the wires for a good connection and used heat shrink tubing on them and electrical tape to cover the connections. I'd really hate to drop that tank again. Took me 3 days to put in that pump. Had a real hard time getting the Filler hose lined up and another next to it again. About a whole day trying to put the tank back in place.
You think if the engine wasn't getting enough fuel on heavy loads going up hill for instance that O2s might drop in output and trims shoot up? Possibility pump is heating up and failing to provide enough fuel? Wish it would just heat up a real lot in the tank and blow this truck up so I could buy another one. Also, if during this Load problem when I pull over if I slowly give it gas the Rpms will cover over 2000 to 3000 or more. Only if I punch it down will it stumble and hang around 2000.
Brian
Edited: Wow!
Lunch break, went out to the car and started it up cold, put it in drive and floored it ( trying to burn some rubber). Computer in open loop, Car stumbled, O2s went way down and trims shot up. Drove it to the gas station put more gas in it. Got back to work and in the parking lot floored it again, same thing, O2s down, trims shoot up, lots of hesitation and loss of power. This is just barely hot doing this. Car running maybe 15 minutes total.
Before I use to just floor it in idle with no load and it wouldn't do anything like this. It does this even cold and in open loop as well as closed loop and slightly warm.
Pump maybe?
< Message edited by BrianSw -- 2/4/2008 9:54:34 AM >
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 9:50:07 AM
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swartlkk
Posts: 15274
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It is possible that the spliced connection is at fault as well... A heated wire will reduce the voltage available to the pump, reducing its ability to keep up with demand, possibly lowering the fuel pressure which would create a lean condition that the PCM cannot compensate for. This makes more sense with the conditions you are having. I just have never seen O2 voltages that low, that means that there is practically equal O2 levels outside as compared with inside.
Can you get to the fuel pump connector without completely dropping the tank? I know I couldn't with my big hands & forearms... LOL!
If you can, you might want to redo the connections that you made... I was going to suggest loading the circuit, but you are talking a 300Watt draw to get to 25AMP current. A resistor to put that kind of load on the system would cost a bunch and get quite hot!
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 9:52:08 AM
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BrianSw
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Lunch break, went out to the car and started it up cold, put it in drive and floored it ( trying to burn some rubber). Computer in open loop, Car stumbled, O2s went way down and trims shot up. Drove it to the gas station put more gas in it. Got back to work and in the parking lot floored it again, same thing, O2s down, trims shoot up, lots of hesitation and loss of power. This is just barely hot doing this. Car running maybe 15 minutes total.
Before I use to just floor it in idle with no load and it wouldn't do anything like this. It does this even cold and in open loop as well as closed loop and slightly warm.
Pump problem (wiring?) maybe?
I can get to the wires if I drop my spare and stick my head up there. I made sure I had extra length wires when I spliced them on so I can pull them out if I needed to get to them.
Brian
< Message edited by BrianSw -- 2/4/2008 9:58:27 AM >
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 10:01:40 AM
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swartlkk
Posts: 15274
Joined: 5/1/2005
From: Waterloo, NY
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That is probably the second or third thing I would try. Pull the connection and redo the wiring. Maybe try some 3M butt connectors first and see if that helps. If it doesn't, then it is likely that the pump is the cause. I have used 3M butt connectors on several fuel pump wiring repair jobs and they have always worked. You should be able to find the required sizes at Walmart of all places! LOL
The first thing would be to actually monitor the fuel pressure. That will be a definitive finger pointing at the true problem. If the pressure waivers, then it is a toss up between replacing the filter or redoing the wiring connections that were made.
< Message edited by swartlkk -- 2/4/2008 10:07:14 AM >
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 10:54:53 AM
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swartlkk
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Well, that may tell you one part of the story, but a plugged fuel filter could act the same way as a circuit problem in terms of the amp draw. Load is load at the fuse.
I guess the two easiest things to try first would be redo the electrical connection and replace the fuel filter. I have gotten bad fuel filters before.
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RE: 97 Blazer Loss Engine Power after warm up. - 2/4/2008 11:22:55 AM
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BrianSw
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Do you have any idea of what the current draw (amps) is on a fuel pump working normally?
Brian
< Message edited by BrianSw -- 2/4/2008 11:27:23 AM >
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RE: 97 Blazer Loss Engine Power after warm up. - 2/6/2008 8:41:57 AM
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BrianSw
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swartlkk,
Problem finally, finally, finally resolved!
After checking the resistance to the Fuel Pump motor several times before starting, then starting the car, then turning it off, checking resistance again I found it was changing alot. I was taking measurements from the wire lead under the hood (drivers side).
Check out my fuel pump relay it was OK, So I dropped my spare tire. Actually had to cut the wire cord to get it down really rusted and couldn't turn that thing on the rear bumper. I managed to pull the 4 pin connector off the fuel pump. The connector had water driping out of it and everything was green inside (corrosion). Lots of it. This is the new style connector I had to splice on because GM had problems with water getting into the old style one. Anyways I got a new one and put it on. Took the car for a very long ride and no problems with power loss. I could do burn rubber going up my steep inclined driveway even. This also fixed the problem with my fuel guage I was having (should have took that as a clue) pegging over full all the time. Whole thing for months of headaches was just this stupid connector. This all started happening less then one week after putting in the new pump and connector. There was a dry period durning the summer where the problem went away. But as soon as fall and wet weather came around it did it alot more (everyday). Bums me out I spent so much money replacing alot of parts that didn't need to be replaced.
Now I am still trying to get the computer to complete the cat and Evap tests so I can get it inspected. Taking for ever for this to complete. I run the driving test as GM states but still won't complete those to tests. Wonder how many times I have to keep performing them? Someone said I read somewhere it may take many drive cycles.
Thanks so much for your help.
Brian
< Message edited by BrianSw -- 2/6/2008 8:47:31 AM >
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RE: 97 Blazer Loss Engine Power after warm up. - 2/6/2008 9:09:05 AM
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swartlkk
Posts: 15274
Joined: 5/1/2005
From: Waterloo, NY
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Wow! Good deal!! Originally when you had replaced the pump, I had assumed that everything would be ok on that end and that is why the diagnosis lead where it did. But without knowing that you had spliced on a new connector in the back, I would never have thought that it would have been a connection problem at the pump.
With the new connector in place, I would put some dielectric grease in the connector before pushing it together to keep water out. But that is definitely odd that the new connector allowed water in like that...
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) and looks like my electrical tape is completely falling apart. I can't see much as I have no light and my spare is still in the way. I'll have to get to all that tonight after I try and make my way home again
. Still dogging police cars as my inspection is way expired because of all these problems (Sensor faults). Corrected now but can't get the car to complete it emmissions self tests it needs to make. 
. I went back under where my spare is and pulled off the 4 pin plug again. Found a small amount of water had still got inside (newly purchased and installed). I blew out the little bit of water there was. It was only a very small amount. Completely covered the new plug in dielectric grease (silicone). Plugged it back in and went for along drive. It still lost power when car driven for about 7 miles (going uphill and heavy acceleration). I'm don't think this plug to the fuel pump was or is the cause now. It may have been a slight addition to the problem but not the cause. 
. Decided to pull off the upper intake manifold (black plastic thing with throttle body). Wanted to check the spider assembly (injector pack) was secure. It was. The movement that it does is very little in the mounting bracket. Anyways I thought I'd pull the injector pack off the bracket and hook up the fuel lines to test for poppet valve leaks. Here come the really stupid part. When trying to put on the little nuts back on to hold the fuel lines down one slipped out of my hands and went down my #2 air intake port all the down to the valves. 
