Massive Power Loss when Hot

waynenorcross

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Wow that's a lot of replies.

@07GtS197 IAT's hover around 90 on a cold day, go up to 130 sitting in traffic. But I had moments where the car was totally fine with IAT's at 95, and moments where she felt like 50hp with IAT's around 90.

@ttocs Texas, so still 100F. I did change the thermostat in April, when I swapped to a manual. Did the water pump gasket too, and consequently changed the coolant. Wouldn't I see rising temps if it was clogged up though? She's sitting steady at 204 at cruise and 210-218 with the fan on in traffic. It was a little brown earlier when I checked it, so that was a little concerning.

@JAD67428 I was hoping that was not the case. Out of desperation I got baited and bought some extreme cleaner for catalytic converters, so I'll see if that does something. There's no CEL for it though and the O2's SEEM to read a working cat. I don't have a thermometer to check though. Would explain the heat thing though, I would assume they close up more with more heat.

@waynenorcross yeah no CEL.


For a moment I was thinking of running open headers to see if that solves it (then it would definetly be the cats), but that seems unwise as the O2's are on the Y-pipe...any other ideas on testing that without buying a new Y-pipe?
Worked at Autozone for a year. Don't assume a new thermostat is not defective.
 

MyLittlePony

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Worked at Autozone for a year. Don't assume a new thermostat is not defective.

I would like to know why they call them “fail safe.” Seems like if they fail, they should fail open so I’m not overheating. I swear I’ve gone through more thermostats than tires! (Owned the car for 22 years).
 

ttocs

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don't assume a new anything from anywhere can't be defective no matter what is written on the box.
 

MyLittlePony

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One thing I’ve experienced, which I actually had to take to a professional to finally get a diagnosis... ...the MAF. I know you said you cleaned it, but if it’s failed, cleaning it won’t help. Because the part is expensive, I ended up using my 3.8 one for the v8 swap. It worked, but after 20 years (2014), 179k miles, it finally failed. You did not want to pull in front of anyone. It felt like driving a fully loaded semi or lawn mower with how bad it could accelerate. If yours is a 2003 3.8, there’s a possibility that it might be that.
 

ben37

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@cwgu3 I did not have access to an IR temp gauge, but I did remove the y pipe and checked the cats, the seem to flow fine. I also removed the rear O2 sensors (made a deliberate exhaust leak) to see if the rear cats are clogged, but it changed nothing on engine behavior. So I think I can rule out the cats at this point.

@lwarrior1016 damn. I have a code P1336. I had it for a while now but it started when I ran another strategy (fbgi0) on the quarterhorse, and decipha from efidynotuning.com said it was a hdr misfire initialization fault because it was configured for the v8 sensors, and also provided me with another bin that didn't show the code (which I stopped using for various other reasons). I haven't heard back from him about what specifically changed between the two bins he gave me, but I couldn't find anything. So there is a possibility it is the camshaft sensor that is acting up. Would certainly explain the irradical ignition behavior and all the other symptoms I am experiencing.

@waynenorcross I know, but wouldn't I see overheating then? Sensors read fine, and the temp pattern follows the regular behavior of a working thermostat. Also, wouldn't my motor have been seized up by now? I have ran her on the highway WOT for 10-15 minutes with this issue persisting (I know, not smart. But then again, tells me it's not a heat related issue).

@MyLittlePony I did clean it, yes, but I also have the direct MAF readings available from the quarterhorse. It reads correct for the driving condition and TPS value, comparing it to some logs from months ago, and what I experienced. So I am pretty sure the MAF is fine.
I also disconnected it for the heck of it, but the car struggled to idle really bad and I didn't run it for more than 10 seconds.


I'm feeling like lwarrior1016 might be on to something here. I'll go check out the wiring for that sensor later, maybe that has a nick in it. If not, I'll have to abandon this thread until I come back into the country in a couple months and have more time to throw parts at it/diagnose. I will post back once that happens. Thanks guys for all the help and suggestions so far!
 

waynenorcross

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@cwgu3 I did not have access to an IR temp gauge, but I did remove the y pipe and checked the cats, the seem to flow fine. I also removed the rear O2 sensors (made a deliberate exhaust leak) to see if the rear cats are clogged, but it changed nothing on engine behavior. So I think I can rule out the cats at this point.

@lwarrior1016 damn. I have a code P1336. I had it for a while now but it started when I ran another strategy (fbgi0) on the quarterhorse, and decipha from efidynotuning.com said it was a hdr misfire initialization fault because it was configured for the v8 sensors, and also provided me with another bin that didn't show the code (which I stopped using for various other reasons). I haven't heard back from him about what specifically changed between the two bins he gave me, but I couldn't find anything. So there is a possibility it is the camshaft sensor that is acting up. Would certainly explain the irradical ignition behavior and all the other symptoms I am experiencing.

@waynenorcross I know, but wouldn't I see overheating then? Sensors read fine, and the temp pattern follows the regular behavior of a working thermostat. Also, wouldn't my motor have been seized up by now? I have ran her on the highway WOT for 10-15 minutes with this issue persisting (I know, not smart. But then again, tells me it's not a heat related issue).

@MyLittlePony I did clean it, yes, but I also have the direct MAF readings available from the quarterhorse. It reads correct for the driving condition and TPS value, comparing it to some logs from months ago, and what I experienced. So I am pretty sure the MAF is fine.
I also disconnected it for the heck of it, but the car struggled to idle really bad and I didn't run it for more than 10 seconds.


I'm feeling like lwarrior1016 might be on to something here. I'll go check out the wiring for that sensor later, maybe that has a nick in it. If not, I'll have to abandon this thread until I come back into the country in a couple months and have more time to throw parts at it/diagnose. I will post back once that happens. Thanks guys for all the help and suggestions so far!
The thermostat needs to stay closed sometime for the radiator to do its thing. Sounds backwards. If it opens too soon and just stays open, the coolant isn't getting cooled. Then if the engine gets too hot, it could be going into "limp home mode". I will tell people when in doubt to put the thermostat in a pan with a thermometer. If it is a 180 ( recommended) you see it open when the water temp increases to 180. Then coil the water. Also, make sure it isn't in upside down. Working at Autozone was fun because you never knew what issue would come in the door next. Like the guy who came in asking why he had no power after installing a 500 pound stereo in his 100HP Civic
 

ben37

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@lwarrior1016 So I had a couple minutes to spare and I checked on my camshaft position sensor. One of the wires was stripped a bit and showed bare metal. I "replaced" the connector (I massaged some spade connectors with pliers) and cut out and replaced as much of the wiring as I could, and dusted off the sensor and the spinning thing. This is THE FIRST TIME since three weeks that I have seen ANY (persistent) improvement at all.

So now I am thinking - is my timing chain stretched? My camshaft position sensor out of sync? A retarded/advanced cam or spark would explain the occasional backfires on decel and loss of power, as well as the hesitation to start sometimes.

Another thing I read on some other forums is AC ripple from the alternator can confuse the sensors. I did stab my battery with a DMM set to AC voltage, and it settled at 0.06v. So there is some AC ripple, but I don't think this is enough to trip up sensors?

Now, as I don't have time anymore, I have to conclude this chapter for now. Once I get back I'm probably gonna hook up a scope to the battery and the sensors and see what is going on. But as for right now I'm happy about the little progress I made. I improved from massive traffic impedance to minor road hazard.
So that's a win. "Remember kids, keep lowering your standards until you achieve a goal" - Mike Finnegan, Roadkill

To clarify - I do not think it has to do with heat anymore. And absolutely not with the coolant temperature or the thermostat. It flows for sure. The same issue persists even with the engine coolant cooled down to a degree, and I am able to run the engine for extended periods of time without it seizing or puking coolant. The ECT readings are completely within check, and behave absolutely normal. I know this because I have run lots and lots of logs for all kinds of driving conditions and closely inspected them and compared them to known good logs.

I think the heat just coincides with something. It might be a sensor giving more erroneous data once it warms up, or a timing belt slacking more once it heats up, etc.
 

07GtS197

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I guess the extra load could be too much for the alternator which is either failing or putting out ac ripple.


Sent from my iPhone using Tapatalk
 

MyLittlePony

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Interesting. Back in 2004, my car got a CEL which indicated a problem with the cam positioning sensor. I can’t remember if it eventually overheated or if that was a separate problem within the same year, but I bought a new one and the problem fixed itself.

I would think that if exposed wiring were causing problems with the cam positioning sensor, you’d get a check engine light. I mean, clearly fixing it helped with something, so this is still a victory, I am just wondering why no CEL.
 

ben37

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Ok car is in storage now. I don’t think the alternator is failing outright because it still charges, but the diodes or so might be something that could be on the way out.

I’m thinking I’ll throw a camshaft position sensor and a crankshaft position sensor on it when I get back, they’re only $10 each on rockauto.

For the measurement of 0.06v, that was with a DMM, not a scope. If there is a lot of noise that is not sine shaped, it might not even pick it up, so I’m not totally ruling that out until I probe the heck out of the sensors.


Anyways, thanks guys for all the suggestions. I’ll post back in a couple months when I pull her out of storage.
 

lwarrior1016

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Don’t just do a cam sensor. Get a motorcraft synchronizer assembly, the whole thing. Swap that in there.
 

Benni614

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Honestly it Sounds like heat soak. Our car suffer from this another during hot summers. Usually the fan needs replacing and i went with a derale type fan 17in and wiring harness. This blows around 2400 cfm which is a lot fyi. As far as your hesitation it sounds like a bad iac. Or faulty one.
 

ben37

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Following this up for the archive:

Pulled car out of storage (changed oil and filter too), seems to run better than it did when I put it there. Still runs with lower power, but I'm not a major traffic hazard anymore.
Swapped IAC, got a little better and smoother.
Swapped cam synchro assembly and sensor (retarded the timing on the first two tries, but got it now - finding TDC is a pain) - little improvement, but still the same (or worse) sputter on acceleration. Had to turn the engine by hand a couple of times for alignment, it definitely has compression.

I can now press the gas slowly and she revvs all the way up, and she has more power now. When I press the gas too rapidly in neutral she sputters and stumbles, though it evens out a little when she starts to warm up. Does smell like excessive fuel now, and I burned through 1/4 tank in the 15 miles I have driven so far.

New injectors are in the mail now. I'll post back once they're installed, but if that doesn't fix it I need to get another car to go to school and save up for a new engine. Prob gonna do a v8 swap then. Go big or go home.

Thanks everybody for the advice. I hope I can conclude that thread in a couple of days.
 

ttocs

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Following this up for the archive:

Pulled car out of storage (changed oil and filter too), seems to run better than it did when I put it there. Still runs with lower power, but I'm not a major traffic hazard anymore.
Swapped IAC, got a little better and smoother.
Swapped cam synchro assembly and sensor (retarded the timing on the first two tries, but got it now - finding TDC is a pain) - little improvement, but still the same (or worse) sputter on acceleration. Had to turn the engine by hand a couple of times for alignment, it definitely has compression.

I can now press the gas slowly and she revvs all the way up, and she has more power now. When I press the gas too rapidly in neutral she sputters and stumbles, though it evens out a little when she starts to warm up. Does smell like excessive fuel now, and I burned through 1/4 tank in the 15 miles I have driven so far.

New injectors are in the mail now. I'll post back once they're installed, but if that doesn't fix it I need to get another car to go to school and save up for a new engine. Prob gonna do a v8 swap then. Go big or go home.

Thanks everybody for the advice. I hope I can conclude that thread in a couple of days.

test your tps for a dead spot in it and if the harness is a little loose on it replace it.
 

ben37

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Just checked it with Tuner Pro, reads perfectly smooth and accurate the whole way and even on quick taps
 

ttocs

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it will sound stupid but now go do that while you jiggle the harness going to it. I found a problem with my harness where it would lose contact and give my holley problems.
 

ben37

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Ok so I did as @ttocs asked, but nothing changed. TPS seems solid all around.

Changed the injectors, and now I have power...sometimes. She revvs, but still sputters if I give her too much gas. But it feels different now. Still, can't really get her past 4k rpm in 1st gear. She also bucks sometimes in the rev range.
I have also noticed that the exhaust sounds a little more throaty than I remember from back when I got the car. It must've been a gradual change, because I only noticed it after a friend who hadn't seen the car in a while pointed it out.

Interestingly though, I put on the original tune for the car (the factory default, configured for automatic transmission), and it ran a little smoother. But that's not driveable for me because the speedometer reads double, and it hangs the revvs like crazy when shifting. Still, the new tune ran perfectly fine for like 2 months when I first got it.

I'm at a loss once again, I just don't know what's wrong with the stupid car.

Cleaning the MAF rn, but I doubt that will change anything.
 

ttocs

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I would say to pull/inspect and replace the spark plugs as needed. At the very least they can tell you if its running rich/lean or not firing if that is an issue.
 

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